REESE LIBRARY OF THK UNIVERSITY OF CALIFORNIA. ,190 Accession No. .Q 1.5.4.4... Cla&sNo. SELECT METHODS FOOD ANALYSIS HENRY LEFFMANN, A.M., M.D. ' i PKOFESSOK OF CHEMISTRY AND TOXICOLOGY IN THE WOMAN S MEDICAL COLLEGE OF PENNSYL- VANIA; PRESIDENT OF THH FACULTY OF THE WAGNER FREE INSTITUTE OF SCIENCE; VICE-PRESIDENT OF THE (BRITISH) S' CIETY OF PUBLIC ANALYSTS AND WILLIAM BEAM, A.M., M.D. FORMERLY CHII'F CHEMIST BALTIMORE AND OHIO RAILROAD WITH FIFTY-THREE ILLUSTRATIONS IN THE TEXT, FOUR FULL-PAGE PLATES, AND MANY TABLES PHILADELPHIA P. BLAKISTON'S SON & CO. 1012 WALNUT STREET 1901 V Copyright, 1901, BY P. BLAKISTON'S SON & CO. PRESS OF WM. F. FELL & Co.. I22O-24 SANSOM ST., PHILADELPHIA. PREFACE This book is intended to be a concise summary of analytic methods adapted to the needs of both practising analysts and advanced students in applied chemistry. A knowledge of the principles of chemistry and of ordinary laboratory manipula- tions is assumed, but some physical and chemical methods have been described in detail to assist in securing uniformity of operation. Much valuable matter relating to food analysis has been published in this country within the last decade, but most of it is scattered through official bulletins and reports that appear in limited editions and are distributed unsystematically. The bulletins of the United States Department of Agriculture and of the Association of Official Agricultural Chemists are now nearly all out of print and scarce. The present work contains a large amount of the data and processes given in those publi- cations, together with data from reports of some of the state agricultural experiment stations. The pages of The Analyst have been drawn upon largely, as also the works of A. H. Allen, H. Droop Richmond, and Charles A. Mitchell. The collection and arrangement of material were begun over a year ago, but were suddenly interrupted, and when resumed after considerable time, it was found necessary to in- corporate many new processes and analytic results. Dr. Beam having taken up residence in a distant part of the world, the duty of completing the book, as well as the proof-reading and indexing, devolved entirely upon the senior author. It 91544 VI PREFACE has been impracticable to keep Dr. Beam advised of changes or progress in the work or to submit any proof-sheets to him. The effects of food adulteration and the methods of control- ling it have not been given any consideration, it being con- sidered that these topics are not matters of concern for the analyst. Special attention has been given to the presentation of methods for detecting preservatives, artificial colors, and poisonous metals. The plates of leaves and starch granules were reproduced from Bulletin 13 of the United States Department of Agricul- ture, the originals being in many cases retouched by Dr. Beam. Several tables for general reference have been prepared. Effort has been made to maintain throughout the book uni- formity of nomenclature and method of statement in describ- ing analytic operations. Unless otherwise stated, all temperatures are centigrade and all readings of scale or arc positive. 715 WALNUT ST., PHILADELPHIA, PA. April, i go i. CONTENTS ANALYTIC METHODS PHYSICAL DATA: PAGE Specific Gravity Melting and Solidifying Points Boiling point Polarimetry Spectroscopy Microscopy, 9~35 ( HI MICAL DATA: Wa'er and Fixed Solids (Extract) Nitrogen Crude Fiber Ash Extraction with Miscible Solvents Extraction with Im- miscible Solvents Distillation and Sublimation Apparatus and Chemicals 36-67 APPLIED ANALYSIS GENERAL METHODS : poisonous Metals Colors Preservatives, 68-91 SPECIAL METHODS: Starch Flours and Meals Bread Leavening Materials Sugars Honey Candies and Confections, 92-140 Fats and Oils : lodin Number Volatile Acids Saponification Value Acid Value Solubility in Acetic Acid Thermal Reac- tion with Sulfuric Acid Specific Temperature Reaction Bromin Thermal Value Elaidin Test Index Soluble and Insoluble Acids Cholesterol and Phytosterol Acetyl Value Unsaponifiable Matter Analytic Data Special Tests, . . . 140-171 Olive Oil Cottonseed Oil Maize Oil Arachis Oil Sesame Oil Rape Oil Coconut Oil Cacao-butter Lard Butter- fat, 171-191 Milk and Milk Products: Milk Condensed Milk Butter- Cheese Fermented Milk Products, 192-250 Non-alcoholic Beverages: Tea Coffee Cacao, 251-282 Condiments and Spices : Vinegar Pepper Long Pepper Cayenne Pepper Ginger Nutmeg Mace Allspice Cinna- mon Cloves Mustard Vanilla Extract Lemon Juice and Sirup Catsup Table Accessories, 283-325 Vlll CONTENTS SPECIAL METHODS (Continued'] : PAGE Alcoholic Beverages; Cider Spirits Whiskey Brandy Gin Rum Malt Liquo's Wine Alcohol Tables Malt Extracts, . 326-360 Flesh Foods : Meats Meat-extracts, 360-369 Appendix : Addenda Specific Gravity of Water Conversion Table for Thermometric Degrees Elements, Symbols, and Atomic Weights, . 37-375 PLATES. REFERENCES. INDEX. CORRECTIONS Page 135 line 3 from bottom, insert 18 after " alcohol. " *3 8 " 5 5 delete the reference. " 237 " 14, insert "seepage 370." " 239 " 1 8, insert "see page 371." " 294 " 15, for "65 " read "6.5." ,- OF THE UNIVERSITY OF FOOD ANALYSIS ANALYTIC METHODS PHYSICAL DATA Specific Gravity. In food analysis, determination of specific gravity of solids is rarely made. Fats are usually tested in the melted condition. The following method for solid fats, due to Hager, is suita- ble for small amounts of material : The sample is melted and allowed to drop slowly from the height of about 3 centimeters into some cold alcohol in a dish. The globules thus obtained are placed in diluted alcohol at 15.5, the strength of which is so adjusted that the globules float in any part of the liquid. The specific gravity of the liquid is then determined ; it is, of course, the same as that of the globules. Many substances when cooled suddenly are liable to have abnormal density, hence it is preferable, as noted by A. H. Allen, to use frag- ments cut from a solid mass cooled under normal conditions and allowed to stand at least 24 hours. The specific gravity of a liquid is generally expressed by comparison with water. Confusion and inconvenience have arisen from the fact that results have been referred to water at different temperatures as unity. It is becoming customary to express, as is proper, the temperatures of observation and comparison, ^Jndicates a determination at 100 and com- 2 9 10 FOOD ANALYSIS parison with water at 1-5.5 as unity. It is best to compare the substance and the standard at the same temperature. Pyknonieter or Specific-gravity Bottle. This is a gener- ally applicable means of determining specific gravity, and is capable of furnishing good results. It is a bottle with a perforated stopper adjusted to hold a certain weight of water at a standard temperature, usually 15.5. -Bottles as sold are often inaccurate. The weight of water that a bottle holds should be carefully determined. E. R. Squibb devised a convenient form of pyknometer (Fig. i) which permits the determination to be made at any temper- SPECIFIC GRAVITY I I ature between o and 25, and compared with water at the same temperature. As received from the glass-blower, the chemically clean and tared bottle should hold 100 grams of recently-boiled distilled water at 20 at about 58 divisions of a scale of o to 100. In weighing the water into the bottle, the fine adjustment to o.ooi gram is made by very narrow strips of blotting-paper that will pass easily down the bore of the graduated stem and absorb minute quantities of the liquid. When the 100 grams are in the bottle, and the column stands between 50 and 65 divisions of the scale, the stopper is put in, a leaden ring is put on the neck, and the whole is immersed in a bath at o until the column of water in the stem ceases to fall. It should then read at zero of the scale, or not much above it, and the reading should be noted. If it reads below zero, the bottle is too large, and the stopper part of the stem must be ground farther into the bottle neck, until the reading, on new trial, brings the column a little above zero. The bottle is then put into a bath at 25 and kept there, with stirring of the bath, until the column ceases to rise, when it should read somewhere from 90 to 100 of the scale. Should it read above 100, while the lower limit is as far above the zero, the bottle is too small, and the end of the stopper must be ground off until the reading of the column is within the graduations at both ends of the scale. Squibb used the same bottle for many years. During the first two years the zero point rose, as happens in thermometers, but of late years the position has been constant. Sprengel Tube. This is a form of pyknometer with which the highest degree of accuracy is attainable, and is especially suitable for determinations at the boiling-point of water. It consists (Fig. 2) essentially of a thin glass U-tube terminating in two capillary ends bent at right angles and each provided with a ground cap. One of these capillary tubes must have a smaller caliber than the other not larger than 0.25 mm. 12 FOOD ANALYSIS The larger tube should bear a mark at m. The tube is filled by immersing b in the liquid under examination, connecting the smaller end with a large glass bulb, and applying suction to the latter by means of a rubber tube, as shown in figure 3. If now the rubber tube be closed, the glass tube will fill auto- matically. It is placed in water, the ends being allowed to project, and the water is brought to the proper temperature. A conical flask may be used to contain the water, the ends of the Sprengel tube being supported by the neck. The mouth FIG. 2. FIG. 3. of the flask should be loosely covered. As the liquid expands it will drop from the larger orifice. When this ceases, the liquid is adjusted to the mark at m. If beyond the point, a little may be extracted by means of a roll ol paper. The tube is then taken out of the bath, 'the caps adjusted, the whole thoroughly dried, allowed to cool, and weighed. The same operation having been performed with distilled water, the calculation of the specific gravity is made as usual. SPECIFIC GRAVITY \VistpJial Balance. This affords a convenient means of determining specific gravity. It consists of a delicate steel- yard provided with a counterpoised plummet. The latter, being immersed in the liquid, the equilibrium is restored by means of weights or riders, the value of which is directly expressed in figures for the specific gravity without calcula- tion. Thus, the rider A is of such a weight as to express the first decimal place, and will be represented by any of the figures from o to 9 according to its position on the beam. Similarly the riders A, B, and C furnish the figures for the FIG. 4. second, third, and fourth decimal places respectively. The weight A 2 is used in the case of liquids heavier than water. According to McGill, the best results are obtained by em- ploying plummets of different weights and density, adapted to the different characters (e. g., viscosity) of the liquids under examination. For viscous oils, the ratio of the weight of the plummet in air to the weight of the liquid displaced should be 4 rather than the usual ratio (2). The ordinary form of Westphal balance is untrustworthy, FOOD ANALYSIS but good instruments are made by some European manu- facturers. The principle of the hydrostatic balance may be applied by using a plummet (that sold with the Westphal balance will serve) with the ordinary analytic balance. Test-tubes weighted with mercury and sealed in the flame may also be used. The plummet is suspended to the hook of the balance by means of a fine platinum wire. The specific gravity of any liquid may be determined by noting the loss of weight of the FIG. 5. FIG. 6. plummet when immersed in the liquid and dividing this by the loss in pure water. If the determination be made at the boiling-point of water, the arrangements shown in figures 5 and 6 may be employed. The temperature of the liquid will not usually rise above 99. This may be done with a hydrometer or balance, if the cylin- der containing the liquid be kept for a sufficient time in boiling water. With the Sprengel tube high accuracy may be ob- SPECIFIC GRAVITY t 5 tained. The weight of the Sprengel tube and that of water contained at 15. 5 being known, the tube should be com- pletely filled with the oil, by immersing one of the orifices in the liquid and sucking at the other. The tube is placed in a conical flask containing water which is kept actively boiling, a porcelain crucible-cover being placed over the mouth of the flask. The oil expands and drops from the orifices. When this ceases, the oil adhering to the outside is removed by the cautious use of filter-paper, the tube removed, wiped dry, cooled, and weighed. The weight of the contents divided by the weight of water contained at 15.5 will give the specific gravity at the temperature attained compared with water at 15.5. When the amount of material is sufficient, the deter- mination may be made by use of the plummet, employing a cylindrical bath with two orifices. One of these is fitted with an upright tube for conveying the steam away from the neigh- borhood of the balance ; into the other a test-tube, 15 cm. in length and 2.5 cm. in diameter, fits tightly, the joint being made perfect by cork or india-rubber. The test-tube is filled with the substance to be tested, and the plummet immersed in it. The water in the outer vessel is then kept in constant ebullition, until a thermometer, with which the oil is repeat- edly stirred, indicates a constant temperature, when the plum- met is attached to the lever of the balance, and counterpoised. For temperatures higher than 100 glycerol or paraffin may be used, but considerable care is required in such cases. Hydrometers. These are much used for the determination of the specific gravity of liquids, but the indications are less reliable than by the methods described above. The instru- ments as furnished are rarely accurately graduated, and the zero point, at least, should be verified by immersing in distilled water at a standard temperature. Very sensitive hydrometers with slender stems, and carefully graduated, are made for use with milk. These are capable of furnishing good results. 1 6 FOOD ANALYSIS Care should be taken to make the reading at the top, center, or bottom of the meniscus according to the method used in the graduation of the instrument. Instruments intended for use with opaque liquids should be graduated to be read at the top of the meniscus. The actual specific gravity of any substance is the ratio of its density at a given temperature to that of water at the same temperature. Statements made upon any other basis than this may be converted into actual specific gravity by calculation from the table of density of water given in the appendix. Thus, a determination of specific gravity of 0.8000 at ^. may be converted into actual specific gravity (~^) as follows : Specific gravity of water at 15 = 0.99916. " " " 100 0.95866. 100 100 15 100 Therefore, 95866 : 99916 : : 0.8000 : 0.8337 (actual specific gravity at 100). Melting and Solidifying Points. The determination of these is often difficult. Many sub- stances, especially fats, assume conditions exhibiting abnormal melting-points, and also frequently solidify at a temperature very different from that at which they melt. If, in the prep- aration of any substance for determining its melting-point, it is necessary to make a previous fusion, the mass should be allowed to rest not less than 24 hours after solidification before making the experiment. Chemists disagree as to whether the melting-point should be considered to be that at which the substance begins to be liquid or that at which the liquid is perfectly clear. Ordinary thermometers are fre- quently inaccurate, the error amounting to a degree or more. No observations in which precision is required should be made with unverified instruments. The following method for determining melting-points is MELTING AND SOLIDIFYING POINTS suitable for many technical purposes. By substituting strong brine or glycerol for the water in the bath observations may be made at temperatures beyond the limits of o and 100 : The substance is heated to a temperature slightly above its fusing-point, drawn into a very narrow glass tube, and allowed to solidify for not less than 24 hours. The tube, open at both ends, is attached by a wire or rubber ring to a thermom- eter so that the part containing the substance is close to the bulb. The apparatus, immersed in water, is heated at a rate not exceeding 0.5 per minute until fusion takes place, when the tem- perature is noted. The tempera- ture is allowed to fall and the point at which the substance be- comes solid is also observed. To insure uniform and gradual heatjng, it is necessary to im- merse the vessel containing the thermometer and tube in an- other larger vessel filled with water. A. H. Allen suggests a flask of which the neck has been cut off, as shown in figure 7. A neater form of apparatus, from " Richter's Organic Chem- istry," is shown in figure 8 (p. 18). The two following methods are especially adapted to the examination of fats and waxes. The A. O. A. C. method dis- regards the abnormal condition of recently-solidified masses : A. 0. A. C. Method. A mixture of alcohol and water of the same specific gravity as the sample is prepared in the fol- lowing manner : Separate portions of distilled water and 95 per cent, alcohol are boiled for 10 minutes. The water is poured, while still hot, into the test-tube described below FIG. 7. FOOD ANALYSIS until it is nearly half full. The test-tube is nearly filled with the hot alcohol, which is carefully poured down the side of the inclined tube to avoid too much mixing. If the alcohol FIG. 8. FIG. 9. is added when water is cold, the mixture will contain air- bubbles and be unfit for use. The apparatus (Fig. 9) consists of: A thermometer reading easily and accurately to tenths of a degree ; a cathetometer MELTING AND SOLIDIFYING POINTS 1 9 for reading the thermometer (this may be substituted by an eyeglass if held steadily and properly adjusted) ; a thermom- eter ; a tall beaker 35 cm. high and 10 cm. in diameter ; a test-tube 30 cm. long and 3.5 cm. in diameter; a stand for supporting the apparatus ; some method of stirring the water in the beaker (for example, a rubber blowing-bulb and a glass tube extending to near the bottom of the beaker). The melted and filtered fat is allowed to fall from a drop- ping-tube from a height of from i 5 to 20 cm. on a smooth piece of ice floating in recently-boiled distilled water. Disks from i to 1.5 cm. in diameter, and weighing about 200 mg., are formed. Pressing the ice under the water the disks float on the surface, and are easily removed with a steel spatula, cooled in the ice-water before using. The test-tube contain- ing the alcohol and water is placed in a tall beaker containing water and ice, until cold. The disk of fat is then dropped into the tube from the spatula and at once sinks to the part of the tube where the density of the diluted alcohol is exactly equivalent to its own. The delicate thermometer is placed in the test-tube and lowered until the bulb is just above the disk. In order to secure an even temperature in all parts of the alcohol mixture in the vicinity of the disk, the thermom- eter is used as a stirrer. The disk having been placed in posi- tion, the water in the beaker is slowly heated and kept con- stantly stirred by means of the blowing apparatus already described. When the temperature of the alcohol-water mixture rises to about 6 below the melting-point, the disk of fat begins to shrivel and gradually rolls up into an irreg- ular mass. The thermometer is lowered until the fat particle is even with the center of the bulb. The bulb of the ther- mometer should be small, so as to indicate only the tempera- ture of the mixture near the fat. A gentle rotatory move- ment should be given to the thermometer bulb. The rise of temperature should be so regulated that the last 2 of incre- 2O FOOD ANALYSIS ment require about ten minutes. The mass of fat gradually approaches the form of a sphere, and when it is sensibly so the reading of the thermometer is taken. As soon as the temperature is taken the test-tube is removed from the bath and placed again in the cooler. A second tube, containing alcohol and water, is at once placed in the bath. The test- tube (ice-water having been used as a cooler) is of low enough temperature to cool the bath sufficiently. After the first de- termination, which should be only a trial, the temperature of the bath should be so regulated as to reach a maximum of about 1.5 above the melting-point of the fat under examina- tion. If the edge of the disk touches the sides of the tube a new trial should be made. Second and third results should show a near agreement. TITER-TEST. To eliminate error in determining melting- points of intimate mixtures, such as commercial fats and waxes, the titer-test, proposed by Delican, has been largely adopted. 100 grams of the fat are saponified, the fatty acids separated by addition of acid, freed from water, filtered into a porcelain dish, and allowed to solidify overnight under a desiccator. The mass is then carefully melted in an air-bath and sufficient poured into a test-tube 16 cm. long and 3.5 cm. in diameter to fill the tube a little more than half-full. The tube is then placed in a suitable flask, say of 2000 c.c. capacity, and a deli- cate thermometer, indicating one-fifth of a degree, inserted so that the bulb reaches the center of the mass. When a few crystals appear at the bottom of the tube, the mass is stirred by giving the thermometer a rotatory movement, first three times from right to left, then three times from left to right, and then continuously, by a quick circular movement of the thermometer, without allowing it to touch the side of the ves- sel, but taking care that all solidifying portions, as they form, are well stirred in. The liquid will gradually become cloudy throughout, and the thermometer must be observed carefully. BOILING-POINT 21 At first the temperature will fall, but will soon rise suddenly a few tenths of a degree and reach a maximum at which it remains stationary for a short time before it falls again. This point is called the " titer " or solidifying point. Boiling-point. For the determination of boiling-point the apparatus of M. Berthelot is convenient. Figure 10, from Traube's " Physico-Chemical Methods," shows the construction. The thermometer is inclosed in an outer tube, so that the portion of the scale to which the mercury rises is immersed in the vapor. If this be not done, a correction must be applied for the error produced by the cooling of the thermometer tube. The bulb of the thermome- ter does not reach into the liquid. A few fragments of pumice-stone or broken clay-pipe stems will pre- vent bumping. The exit-tube at the lower end of the wide tube connects with a condenser. The apparatus of O. Schumann (Fig. 1 1) is made entirely of glass and is constructed on the same principle. The barometric pressure must al- FIG. 10. ways be noted and allowance made for the variation from the standard pressure, 760 mm. The correction may be made by the following formula : B = B 1 -f 0.0375 (76o P) ; in which B is the boiling-point at normal pressure, B 1 the observed boiling-point, P the observed pressure in millimeters. FIG. II. 22 FOOD ANALYSIS i For an apparatus designed for special boiling-point observa- tions see under " Alcoholic Beverages." Polarimetry. Polarimeters are instruments used to measure the extent and direction of the rotation of the plane of polarized light. They consist essentially of a Nicol's prism as polarizer, a tube carrying the substance to be tested, and a second Nicol's prism, or analyzer, by which the extent of rotation is meas- ured. In all forms some condition of the field of vision is fixed upon as the zero point and the rotation of the analyzer or other manipulation necessary to restore this standard field affords the measurement of the rotation caused by the inter- posed substance. Several types of instrument have been devised, of which two are most important. In one form, de- vised by Soleil, white light is used and a colored field, known as the transition tint, is taken as the zero point. In the other type white light or monochromatic (yellow) light is used and the zero point determined by equalizing the brightness of the field. Instruments of the first form are unsatisfactory by reason of the difference in susceptibility in the eyes of differ- ent persons to color-contrasts. The instruments of the second type, commonly designated shadow instruments, are now much more generally employed ; they have been brought of late years to a high degree of accuracy and convenience. In the Laurent apparatus, 1 shown in figure 12, the mono- chromatic light passes through the collimating lens A and is polarized by the Nicol's prism B, which is so placed that it may be moved, on its axis, over a small arc by means of the lever C and clamped at any point ; by this the brightness of the field may be varied and the sensitiveness of the instrument in- creased or diminished as may be needed. The polarized beam then passes through a quartz plate of even thickness, cut ex- actly parallel to the optic axis, and placed so that it covers a POLARI METRY 23 semicircle of the field. At the other end of the apparatus is the analyzing prism E and the eye-piece F fixed to a graduated disk. This combination can be rotated upon its axis in a com- plete circle. Attached arms carry view-lenses for reading the angle of rotation, and the instrument is set at zero by an in- dependent adjustment by which the analyzing prism is rotated without disturbing the position of the graduated disk. Ver- niers are provided for close measurement. The monochro- FIG. 23. matic light must be obtained from a sodium flame, since the thickness of the quartz plate is adjusted to these rays. In use, the tube is filled with water, the instrument directed to the source of light, and the adjusting milled head turned until the disk is set at zero. The two portions of the field should now appear equally illuminated. If this is not the case, the position of the analyzer must be altered by means of the independent adjustment, the index remaining undisturbed at the zero point. The exact adjustment to zero is often tedious, FOOD ANALYSIS POLARIMETRY 25 and if desired a rough adjustment may be made, a number of readings taken and averaged, and the subsequent determina- tion corrected accordingly. The tube is filled with the liquid to be tested and again placed in the instrument. If optically active, the plane of the polarized light will be rotated and one-half of the field of observation will appear darker. The extent of rotation, which will depend upon the nature of the substance and its amount, is measured by rotating the analyzer to the right or left, as the case may be, until the halves of the field become equally illuminated. The recorded reading should be the average of a number of observations, correction being made, if necessary, for the true position of the zero. Greater sensitiveness is attained by dividing the field concentrically. This is accom- plished by fastening a small circle of quartz in the center of a glass diaphragm. An instrument of this form is now made by a Berlin firm. Most instruments are furnished with two scales, one express- ing angular degrees and the other percentage of cane-sugar. The latter registers 100 when a given quantity of the sugar has been dissolved in water and made up to 100 c.c. The normal weight is given elsewhere. The above form of Laurent instrument can be employed to measure the rotatory power of all classes of substances, but the forms next to be described give accurate indications only with substances which have the same dispersive power as quartz, unless monochromatic light be used. In the Schmidt and Hansch instrument (Fig. 13) the division of the field is obtained by a special construction of the polarizing prism and the restoration is accomplished by the adjustment of compen- sating quartz-wedges constructed so as to produce in the zero position no rotation. When an optically active substance is interposed in the path of the ray, one of the quartz-wedges must be moved to an extent sufficient to overcome this rota- 3 26 FOOD ANALYSIS tion in order to restore the standard field. The effect is de- pendent upon the fact that by this movement the thickness of the quartz is increased or diminished until it compensates for FIG. 14. the rotation produced by the solution. The extent of move- ment of the quartz is registered upon a linear scale, which is read by means of a lens and vernier. White light is employed POLARIMETRY in making the observations. A form of the Laurent instru- ment, with quartz-wedge compensation, and employing white light, is made. An instrument has been devised in which the field is divided vertically into three zones, the central one being a broad band. Duplicate Nicol prisms are so arranged that the lateral zones agree in tint, thus making stronger con- trast with the central zone (Fig. 13). It is often desirable, especially in the examination of sugars, to make the observation at a temperature above the normal. For this purpose the polarimeter of Chandler and Ricketts may be employed. (Fig. 14.) The observation tube is pro- vided with a thermometer and surrounded by water, which may be heated to the desired point. Landolt has described an improved form, in which the observation may be readily taken at low tem- peratures. For a temperature o the tube is surrounded by melting ice. A special feature of the apparatus is an arrange- ment by which the deposition of moisture on the end glasses is prevented. This is accom- plished by providing a closed space at each end in which a small amount of calcium chlorid is placed. The apparatus is shown in figure 15. Sources of Light. For white light oil, gas, or electric lamps are employed, of which numerous patterns are furnished. Sat- isfactory results may be obtained by the Welsbach lamp. H. W. Wiley recommends the use of the acetylene flame, especially for deeply colored solutions. For monochromatic light the lamp usually employed is a Bunsen burner with a ledge at the top for holding some FIG. 15. 28 FOOD ANALYSIS solid sodium compound. A fused mixture of sodium chlorid and phosphate is better than sodium chlorid alone. The fol- lowing is an excellent method for obtaining a steady, strong, yellow light : Strips of common filter-paper 5 cm. wide and about 50 cm. long are soaked in a strong solution of sodium chlorid and thiosulfate, dried, and rolled into a hollow cylin- der of such size as to fit firmly on the top of the Bunsen burner. The cylinder is kept from unrolling by a few turns of fine iron wire. The flame burns at the top of the cylinder, giving for the first few minutes a luminous cone, but soon becoming pure yellow. The cylinder becomes a friable charred mass, but if not disturbed may be used for some time continuously or at intervals. SPECIFIC ROTATORY POWER. The specific rotatory power of a substance is the amount of rotation, in angular degrees, produced by a solution containing one gram of the substance in I c.c. examined in a column one decimeter long. It is usually represented by the symbol [a] . Allen has suggested the letter S as more appropriate. To indicate the light employed in the observation, S D or Sj is used. D stands for light of wave length corresponding to the D line of the solar spectrum (sodium flame) and j (Jaune) for the transition tint, which in the case of sugar solutions furnishes results corre- sponding to the " mean yellow ray." It is usual also to indicate in the same symbol the temperature of observation ; thus, S. Under ordinary methods of observation the specific rota- tory power is represented by the following formula : c 100 a . ! i S D = ; m which S D is the specific rotatory power for the light of the sodium flame, a is the angular rotation observed, c is the concentration expressed in grams per 100 c.c. of liquid, / is the length of the tube in decimeters. POLARIMETRV 2Q Comparison of Scales of Various Instruments. Polarimeters are usually provided with a special scale, reading to 100 when a certain quantity of cane-sugar, called the normal weight, is dissolved in water and made up to 100 c.c. For the German instruments, which are largely used in the United States, this is 26.048 grams. The instruments made by Schmidt and Hansch are gradu- ated to read correct percentages when the normal weight of sugar is contained in 100 Mohr's cubic centimeters and ob- served in a 2 decimeters tube at 17.5. With the Laurent apparatus the normal weight of the sugar should be contained in 100 true cubic centimeters. The volume of 100 Mohr's cubic centimeters is that of 100 grams of water at 17.5 weighed in air with brass weights ; it is equal to 100.234 true cubic centimeters. For the normal weight of 26.048 grams in 100 Mohr's cubic centi- meters of solution, may be substituted 25.9872 grams in 100 true cubic centimeters at 17.5. At the session of the International Commission for Uniform Methods of Sugar Analysis held at Paris, July 24, 1900, it was agreed that the normal weight shall be fixed at 26 grams in 100 true c.c. at 20, weighed in air with brass weights (see under " Sucrose "). The following factors may be employed for the conversion of data obtained by different instruments : 2 division Schmidt and Hansch 0.3468 angular rotation D. D angular rotation D 2.8835 divisions Schmidt and Hansch. division Schmidt and Hansch 2.6048 divisions Wild (sugar scale). division Wild (sugar scale) 0.3840 division Schmidt and Hansch. division Wild (sugar scale) 0.1331 angular rotation D. D angular rotation D -75 II[ division Wild (sugar scale). division Laurent (sugar scale) 0.2167 angular rotation D. angular rotation D 4.6154 divisions Laurent (sugar scale). Correction for Precipitate. In some cases the volume of precipitate produced by the clarifying agents is considerable, FOOD ANALYSIS and a correction would be necessary. The error may be eliminated by Scheibler's method : A normal weight of the sample is dissolved in water or proper solvent, 'treated with the clarifying agent, the liquid made up to 100 c.c., shaken well, filtered, and a reading taken of the filtrate. A second portion of normal weight is treated in the same way except that it is made up to 200 c.c. be- fore filtration. Great care must be taken in the readings. The true reading is obtained by dividing the product of the two readings by their difference. Spectroscopy. In practical analysis the spec- troscope is mostly useful in detect- ing some of the .rarer elements in ashes and water-residues. For this purpose the direct vision in- strument shown in figure 16 is sufficient. It will often serve for the examination of absorption bands, but for precise research in distinguishing colors and specific absorptions a more elaborate in- strument, as shown in figure 17, will be needed. Those now manufactured have either a com- parison scale or the view-tube moves over a graduated arc so as to determine and record the position of any line or band. For the examination of ashes or water-residues the material is mixed with a few drops of hydrochloric acid, a portion of the mass taken up on a loop of clean platinum wire and held in a non-luminous flame, the spectrum being examined through the instrument. It is important that the first effects should FIG. 1 6. FLUORESCENCE 3 1 be noted, as some substances volatilize quickly. The platinum wire should be cleaned by dipping it in a little pure hydro- chloric acid and heating it in the gas flame until it imparts no color thereto. For the observation of absorption-bands of liquids, small flat bottles with ground and polished sides are used. These permit the observation of a thin or thick stratum as desired. Deeply colored solutions should not be used since large por- tions of the spectrum may be cut out by general absorption and the distinctive selective absorption be lost. FIG. 17. For some purposes the microspectroscope will be needed, but its use is practically limited to medico-legal work. Fluorescence. This may be detected satisfactorily in the manner described by A. H. Allen : A test-tube or cylindrical beaker is nearly filled with a perfectly clear solution of the substance, set upon a dark surface, and observed from above. Another plan is to make a streak of the liquid on a piece of black glass or pol- ished black marble and examine this in a good white light. Tests can also be made by directing a ray of white light from 32 FOOD ANALYSIS any source through the side of a beaker containing the liquid and looking at it from above. In all the methods the liquid must be perfectly clear or misleading reflection-effects are pro- duced. Microscopy. For preliminary examination of food samples a hand lens is useful, but the practical analysis involves the use of the compound microscope. A good instrument can now be ob- tained at comparatively small cost. It should be supplied with at least two objectives, one of quite low power, about 13 mm. focus (j in.), and one of rather high power, 5 mm. focus (i in.). For some examinations, especially for the detection of bacteria, an immersion-lens is needed. This is costly and requires special care in manipulation. The useful- ness of a microscope is much enhanced by the attachment of a sub-stage achromatic condenser and adjustable diaphragm. Polarizing apparatus is needed especially for differentiation of starches. The instrument shown in figure 18 is of American con- struction, is of moderate price, and arranged to receive all accessories. The triple nose-piece, though not necessary, is convenient. For the better differentiation of objects submitted to ex- amination under the microscope, clearing and staining agents are used. In many cases details of structure are brought out sharply by using a dense liquid as a mounting fluid. The following is a list of the important apparatus and reagents : Slides and cover-glasses. Agate mortar, 2.5 cm. outside diameter, and a somewhat larger glass triturating mortar are useful for preparing mate- rials. The pestles of agate mortars are usually inconveniently short, and are much improved by being mounted in a wooden handle. MICROSCOPE 33 Dissecting needles are easily made by sawing off the metal portion of an ordinary penholder close to the wood and forc- ing the eye-end of a sewing needle under the ferule which has FIG. 18. been thus formed. Figure 19 shows a neat form of a needle- holder furnished by the instrument makers. FIG. 19. 34 FOOD ANALYSIS Small forceps and sharp scissors will be needed. Capped bottles provided with pipets, as shown in figure 20, are convenient for holding reagents. Watch-glasses are used for immersing specimens in liquids ; still better are the Syracuse glasses, shown in figure 21. The best form of these has a ground-glass surface for entering memoranda. Water. Distilled water is best, but any clear, colorless water not containing much mineral or organic matter will answer. FIG. 20. FIG. 21. GlyceroL A pure article is easily obtained. Alcohol. The commercial 95 per cent, form is used for hardening tissues, but for ordinary microscopic work, a 70 per cent, solution will suffice. Methyl alcohol in the purified form now obtainable may be substituted in many instances for common alcohol. Ether, chloroform, benzene, and carbon disnlfid are occasion- ally used for their solvent action, especially to remove oils, waxes, and resins. For these extractions it will often be most satisfactory to operate in a small continuous extraction MICROSCOPE 35 apparatus, with repeated washings, as described under " Ex- traction," and drying the material at a gentle heat to get rid of all the solvent, which would interfere with the action of watery solutions or glycerol. CJdoral hydrate solution, a saturated solution in water. Chloral hydrate and iodin solution, a portion of the above solution to which a trace of iodin has been added. Potassium iodid and iodin solution, potassium, 0.4 gram ; iodin, o.i gram; water, 20 c.c. Zinc chloriodid and iodin solution : Dissolve 5 grams of zinc chlorid and 1.6 gram of potassium iodid in 17 c.c. of water and saturate with iodin. Sodium hydroxid, 5 per cent, solution. In some instances a strong solution is employed, which is best prepared when required. Acid pliloroglucol. This is best prepared when needed by dissolving a few milligrams in I c.c. of alcohol and adding a drop of hydrochloric acid. 36 FOOD ANALYSIS CHEMICAL DATA Water and Fixed Solids (Extract). Water is usually determined with sufficient accuracy, pro- vided other volatile bodies are not present, by heating the material (in the case of solids it should be finely divided) in a flat dish on the water-bath or in the water-oven until it ceases to lose weight. The residue constitutes the fixed solids or extract. Flat platinum dishes from 4 to 8. cm. in diameter and 0.5 cm. high are well adapted to this work. They should rest on porcelain or asbestos rings when being heated. Nickel dishes are often applicable, especially the broad shallow cruci- ble covers made in dish form. Dishes of glass, porcelain, and aluminum are less suitable. In many cases drying will be much facilitated by using an absorbent material such as pure quartz sand, powdered asbestos, or pumice-stone. These materials should be extracted with dilute hydrochloric acid, well washed, and well dried before use. The quantity used should be rapidly weighed, preferably in the dish in which the operation is to be carried out. It is advisable to cover the dish with a nearly flat, thin watch-glass in all the weighings. By a few trials a glass can be selected which fits fairly close to the rim of the dish and restricts evaporation or absorp- tion of water. It is often convenient to weigh a small stir- ring-rod with the dish and absorbent. In many cases liquid can be measured directly into the dish, the residue being recorded in grains per 100 c.c. or other suitable ratio. Sirupy and gelatinous liquids or those containing much solid matter, especially if this be somewhat difficult to dry, may often be more satisfactorily treated by diluting a weighed portion with several times its weight of water, evaporating a measured or weighed amount of the dilute liquid, and calcu- lating the amount of residue in the original substance. \\A1KR AND FIXED SOLIDS 37 The ordinary water-bath and water-oven need no descrip- tion. The temperature of materials heated on the former is usually much less than 100 ; in the latter, slightly below 1 00. By using strong brine a somewhat higher temperature may be obtained. In the case of very hygroscopic or easily FIG. 22. decomposable bodies it may be necessary to dry in a current of hydrogen or at reduced pressure. Figure 22 shows a drying oven for use with a current of hydrogen. The apparatus was designed by Caldwell for determining moisture, ether-extract, and crude fiber as pre- scribed by the A. O. A. C., the three data being determined on the same sample. 38 FOOD ANALYSIS The bath is made of copper and is 24 cm. long, 15 high, and 8.5 broad. It stands in a piece of sheet-copper bent at right angles along the sides, as shown in the end view ; on one side this vertical part need not be over I cm. high, just enough to project a little up the side of the bath, which rests snugly against it ; along the other side it projects upward, at a little distance from the side of the bath, about 15 mm., and to about the height of 4 cm. ; opposite each of the tubes of the bath a slot is cut in this vertical part, which serves then as a shoulder against which the glass tube rests when in place, to keep it from slipping down and out of position. The tube for containing the substance has at the zone a three small projections on the inner surface, which support a perforated platinum disk of rather heavy platinum foil carry- ing the asbestos filter. This tube is 13 cm. long and 23 mm. inner diameter, and weighs, with its closed stoppers, about 30 grams. The filter is readily made in the same manner as the Gooch filter, the tube being first fitted to a suction flask by an en- largement of one of the holes of the rubber cork, or, better still, by slipping a short piece of rubber tube over it, of such thickness that it will fit tightly in the mouth of a suction flask provided with lateral tube for connection with the suction. A thin welt of asbestos is sufficient ; if it is too thick, the gas and ether will not flow through readily. About 2 grams of the substance are put in this tube, pre- viously weighed with the stoppers b and c, and the weight of the substance accurately determined by weighing tube and contents. The stoppers are removed, a band of thin asbestos paper is wound around the end d of the tube, a little behind the slight shoulder at the rim, as many times as may be necessary to make a snug fit, when this tube is slid down into the copper tube in the bath, thus preventing circulation of air between the glass and the copper tubes that would retard the WATR AND FIXED SOLIDS 39 heating of the former ; the stopper e is put in the lower end of the tube for connection with the hydrogen supply, and the stopper / in the upper end ; this latter stopper is connected by rubber tube with a glass tube slipping easily through one of the holes of a rubber cork closing a small flask containing a little sulfuric acid, into which this tube just dips ; when as many tubes as are to be charged are thus arranged in place and the hydrogen is turned on, the even flow of the current through the whole number is secured by raising or lowering a very little the several tubes through which the outflow passes, so as to get a little more back pressure for one, or a little less for another, as may be found necessary. When the drying is supposed to be completed, the tubes are weighed again with their closed stoppers, and so on. For ether-extraction the unstoppered tube with contents is put directly into the extractor. Carr and Osborne have made an extended series of inves- tigations as to the determination of water, and find that more accurate results may be obtained if the operation be conducted under a diminished pressure at a temperature not exceeding 70 C. Under these conditions it was found possible to dehydrate levulose completely, without decomposition. The oven is made of a section of metal tubing, from 15 to 20 cm. in diameter and 30 to 40 cm. long. One end is closed air- tight by a brass end-piece, brazed or attached by a screw. The other end is detachable and is made air-tight by ground surfaces and a soft washer. On the upper longitudinal surfaces are apertures for the insertion of a vacuum-gauge and for attachment to a vacuum-apparatus, thermostat and thermometer. The aperture for admission of air or hydrogen is best placed at the fixed end. The oven may be heated by a single burner, but a series of small jets extending along the entire length of the oven is preferable. The flame should not be allowed to strike the cylinder directly ; the latter 4O FOOD ANALYSIS should be protected by sheet asbestos. The temperature of the oven can be kept practically constant by means of the gas regulator, or by attention to the lamp. The method of operating is as follows : Clean pumice-stone of two grades of fineness is used, one that just passes through a i mm. mesh and one that passes through a 6 mm. mesh. These are digested with hot 2 per cent, sulfuric acid, washed by decantation until the wash-water is free from acid, placed, wet, in a sand crucible and heated to redness. When the water is expelled, the material may either be placed hot into a desiccator or directly into the drying dishes. In loading the dishes, place a thin layer of the dust over the bottom of the dish to prevent the material to be dried from coming in con- tact with the metal ; over this layer place the larger particles, nearly filling the dish. If the stone has been well washed, no harm may result from placing the dish and stone over the flame for a moment before transferring to the desiccator pre- paratory to weighing. If the material to be dried is dense, it is diluted until the specific gravity is in the neighborhood of 1.08 by dissolving a weighed quantity in a weighed quantity of water. (Alcohol may be substituted in material not precipitable thereby.) Of this, 2 to 3 grams may be distributed over the stone in a dish the area of which is in the neighborhood of 20 sq. cm., or one gram for each 7 sq. cm. of area. The material is distributed uniformly over the pumice by means of a pipet weighing- bottle (weighing direct upon pumice will not answer), ascer- taining the weight taken by difference. The dishes are placed in the vacuum-oven, which should be maintained at a pressure of not more than 125 mm. of mer- cury. The form of the oven is not material if the moisture escapes freely by passing a slow current of dried air beneath the shelf supporting the dishes. The temperature must not exceed about 70. All weighings must be taken with the 41 dish covered by a close-fitting plate. The open dish must not be exposed to the air longer than absolutely necessaiv. Weighings may be made at intervals of two or three hours. In the laboratory of the United States Geological Survey 3 a sheet-iron or nickel basin about 10 cm. in diameter and 3 cm. deep is set upon an iron plate which is heated directly by the burner. A platinum or pipe-clay triangle rests in the basin and supports the dish containing the liquid to be evaporated. It is stated that almost any liquid can be evaporated in this way without sputtering. The temperature, however, is liable to be too high for many organic solutions. C. C. Parsons has obtained good results in the drying of sensitive organic substances by the following method : A perfectly neutral petroleum oil, free from animal or vegeta- ble oils and mineral substances, sp. gr. 0.920, flash test 224, fire test 260, boiling-point about 288, is heated to about 1 20 for some time and preserved in a well-stoppered vessel. A quantity of oil about six times that of the weight of the substance to be dried is heated in an evaporating dish in a drying oven to a temperature of 115, and then weighed. The weighed portion of the substance is put into the oil ; if it be very moist, it is added in small portions. Slight efferves- cence will usually occur, and the mass should be kept in the drying oven for a short time after effervescence has ceased. The evaporating dish containing the oil and substance is weighed ; the loss is moisture. The whole operation may be completed in less than half an hour. Nitrogen. TOTAL NITROGEN. The Kjeldahl-Gunning method is the most satisfactory. The reagents and operation are as follows : Potassium Sn/fatc. A coarsely powdered form free from nitrates and chlorids should be selected. 4-2 FOOD ANALYSIS Strong Sulfuric Acid. This should have a sp. gr. 1.84 and be free from nitrates and ammonium. Standard Acid. - Sulfuric or hydrochloric acid, the strength of which has been accurately determined by barium chlorid or silver nitrate as required. Standard Alkali. . Ammonium hydroxid, sodium hy- droxid, or barium hydroxid, the strength of which in relation to the standard acid must be accurately determined. Strong Sodium Hydroxid Solution. 500 grams should be added to 5 c - c - of water, the mixture allowed to stand until the undissolved matter settles, the clear liquor decanted and kept in a stoppered bottle. It will be an advantage to determine approximately the quantity of this solution required to neutralize 20 c.c. of the strong sulfuric acid. Indicator. Cochineal solution is recommended by the A. O. A. C, but methyl-orange is quite satisfactory. Phenol- phthalein is not well adapted to titration of ammonium com- pounds. (See under " Indicators.") Digestion Flasks. Pear-shaped round-bottomed flasks of hard, moderately thick, well-annealed glass, about 22 cm. long, maximum diameter of 6 cm., tapering gradually to a long neck, 2 cm. in diameter at the narrowest part, and slightly flared at the mouth. Distillation Flasks. Ordinary flasks of about 550 c.c. ca- pacity. A copper flask, such as sometimes used in the manu- facture of oxygen, may be substituted. Combined Digestion and Distillation Flasks. Hard, well- annealed, round-bottomed glass flasks with a bulb 12.5 cm. long and 9 cm. in diameter, the neck cylindrical, I 5 cm. long and 3 cm. in diameter, flared slightly at the mouth. Condenser and Receiver. A tube of about I cm. caliber passes through a rubber stopper and is cut off obliquely at the lower end. This tube has a bulb about 4 cm. diameter, the exit tube of which is constructed so as to prevent any NITROGEN 43 liquid that may be thrown into the bulb passing into the con- densing tube. The condensing tube is led through a cooling apparatus and is joined to another bulb-tube, the lower end of which dips below the standard acid in the receiving flask. FIG. 23. FIG. 24. The condensing-tube should be block-tin, circumference about 3.5 cm., and at least 50 cm. should be in contact with the cooling water. The delivery tube should slope down toward the flask and may be connected flush with the con- dcMiser tube by a close-fitting rubber tube, but it will be better 44 FOOD ANALYSIS if the tin tube is enlarged so as to receive the glass for a couple of centimeters. The lower end of the condensing tube is extended by means of a glass tube and rubber con- nected or by the attachment shown in figure 23 so as to lead the distilled liquid into the acid in the receiver. Many operators arrange to allow the lower end of the delivery tube to dip below the level of the liquid in the receiver. If this be done, the tube must be provided with a bulb to avoid the danger of suction if the boiling happens to be interrupted. About 20 c.c. of standard acid is placed in the receiver. A special arrangement is shown in figure 23. The sodium hydroxid solution is introduced through the stopcock, and the distillation carried on by a current of steam obtained from the metal vessel which is shown provided with a water-level indicator, a safety-pipe, and a delivery-pipe. The indicator is not necessary if care be taken to keep the boiler filled with water. The safety-pipe should pass nearly to the bottom of the boiler. If obstruction occurs in the distilling or con- densing apparatus, hot water maybe thrown out of the boiler, hence provision must be made to avoid damage from this cause. The distilling-flask does not need to be directly heated. Figure 24 shows a compact apparatus devised by H. Comer for these distillations, but applicable also to other similar operations. For other distilling apparatus see under " Distillation." Process. 0.7 to 3.5 grams, according to the proportion of nitrogen, are placed in a digestion flask. Then 10 grams of powdered potassium sulfate and 15 to 25 c.c. (ordinarily about 20 c.c.) of the strong sulfuric acid are added and the diges- tion conducted as follows : The flask is placed in an inclined position and heated below the boiling-point of the acid for from five to fifteen minutes, or until frothing has ceased. Ex- cessive frothing may be prevented by the addition of a small NITROGEN 45 piece of paraffin. The heat is raised until the acid boils briskly. No further attention is required until the liquid has become clear and colorless, or not deeper than a pale straw. A small, short-stemmed funnel may be placed in the mouth of the flask to restrict the circulation of air. The flask is then removed from the flame, allowed to cool, diluted with 100 c.c. of water if the smaller form of flask has been used, the liquid transferred to the distilling flask, and the digestion flask rinsed with two portions of water, 50 c.c. each, which are also transferred to the distilling flask. With the larger form of flask the dilution is made at once by the cau- tious addition of 200 c.c of water. Granulated zinc, pumice- stone, or 0.5 gram of zinc dust is added. 50 c.c. of the strong sodium hydroxid solution, or sufficient to make the reaction strongly alkaline, should be slowly poured down the side ot the flask so as not to mix at once with the acid solution. It is convenient to add to the acid liquid a few drops of phehol- phthalein solution, which will indicate when the liquid be- comes alkaline, but it must be borne in mind that strong alkaline solutions destroy this indicator. Connect the flask with the condenser, mix the contents by shaking, and distil until all ammonia has passed into the standard acid. The first 150 c.c. of the distillate will generally contain all the am- monia, and should require from 40 minutes to 90 minutes. The distillate is titrated with standard alkali and the amount of acid which has been neutralized by the distillate calculated as ammonia or its equivalent in nitrogen. If nitrates be present in the material to be analyzed, the following modification in the process must be made : The weighed material is well mixed with 35 c.c. of sulfuric acid containing 2 per cent., by weight, of salicylic acid, and the mass shaken frequently during ten minutes ; 5 grams of sodium thiosulfate are added and 10 grams of potassium sul- fate. The mixture is heated very gently until frothing ceases, 46 FOOD ANALYSIS and then according to the usual method. The ammonia in the distillate will include that derived from the nitrogen of the nitrates. ALBUMINOID NITROGEN. Stutzer's method for this deter- mination requires a special reagent, as follows : Copper Hydroxid Mixture. 100 grams of copper sulfate are dissolved in 5000 c.c. of water, 25 c.c. of glycerol added, and then a dilute solution of sodium hydroxid until the liquid is alkaline. The mass is filtered, the precipitate is mixed well with water containing 5 c.c. of glycerol per 1000 c.c. and washed until the washings are no longer alkaline. It is then rubbed up with a mixture of 90 per cent, water and 10 per cent, glycerol in sufficient quantity to obtain a uniform magma that can be measured with a pipet. The quantity of copper hydroxid per c.c. should be determined. It should be kept in a well-closed bottle. Analytic Method. A suitable amount of the material, gen- erally about 0.7 gram, is heated with 100 c.c. of water to 1 00, and a quantity of the copper hydroxid mixture containing about 0.5 gram of solid*added, stirred well, allowed to cool, filtered, washed well with cold water, and the filter and pre- cipitate treated by the Kjeldahl-Gunning method. Substances rich in starch are best subjected to about ten minutes' warming in the water-bath instead of direct boiling. With substances containing much soluble phosphates a few cubic centimeters of alum solution should be well stirred in before adding the copper hydroxid. Crude Fiber. The A. O. A. C. method, used by many American chemists, is substantially as follows : 2 grams of the substance, well extracted with ordinary ether (see under " Extraction " ), are mixed in a 500 c.c. flask with 200 c.c. of boiling water con- taining 1.25 per cent, of sulfuric acid, the flask is connected ASH 47 with an inverted condenser, the tube of which passes only a short distance below the rubber stopper of the flask. The liquid is brought to the boiling-point as rapidly as possible and maintained there for 30 minutes. A blast of air conducted into the flask may serve to reduce the frothing of the liquid. The mass is filtered, washed thoroughly with boiling water until the washings are no longer acid ; the undissolvep! sub- stance rinsed back into the same flask with the aid of 200 c.c. of boiling water containing 1.25 per cent, sodium hydroxid, nearly free from sodium carbonate ; again brought to the boiling-point rapidly and maintained there for 30 minutes as directed above. The liquid is filtered by means of a Gooch crucible ; washed with boiling water until the washings are neutral to phenolphthalein ; dried at 110; weighed and incin- erated completely. The loss of weight is crude fiber. The filters used for the first filtration may be linen, glass, wool, asbestos, or any form that secures clear and reasonably rapid filtration. Hardened filters may also serve. The sul- furic acid and sodium hydroxid are nearly N , and are to be made up of the specified strength, determined by titration. Many analysts use stronger solutions. O. Hehner uses 5 per cent, acid and alkali. It would be convenient if normal sulfuric acid and normal sodium hydroxid were adopted as standards. Crude fiber should not be called cellulose. Ash. The ash of food materials may usually be determined by heating several grams in a platinum or porcelain crucible at a low red heat. Higher temperature may cause loss of volatile salts e. ., chlorids. If a white ash cannot be obtained thus, the material should be heated only to a temperature sufficient to produce charring, the charred mass thoroughly extracted with water, and the insoluble matter collected on a filter, 48 . FOOD ANALYSIS which may then be returned to the crucible and ashed. To this residue the filtrate containing the soluble matter is now added, the liquid evaporated to dryness, heated to low red- ness, cooled, and weighed. A muffle, heated by gas, will often be very useful in the incineration of organic bodies. A light draught of air should be maintained during the operation. Ash Soluble in Water. The ash obtained above is treated with boiling water, the solution filtered through an ashless filter, and the filter and contents again ignited and weighed. The soluble ash is determined by difference. If desired, the filtrate may be filtered to dryness, heated just below redness, and weighed. The method first mentioned is the most con- venient. Alkalinity of Soluble Ash. This is determined by titrating the soluble ash with standard acid, using methyl-orange as indicator. The alkalinity is usually expressed in terms of potassium oxid. Ash Insoluble in Acid. The residue insoluble in water is treated with hydrochloric acid and the portion undissolved is well washed on the filter with water, dried, ignited, and weighed. The ash of fats is conveniently determined by the following method : A weighed quantity is melted in a platinum dish, and a small filter, free from ash, is folded in four, placed upright in the melted fat, and lighted. The fat is quickly burnt off. The following is a compilation of various methods proposed for the determina- tion of the ash of sugars, molasses, honeys, etc., given by the A. O. A. C. : (i) 5 to 10 grams of the material are heated in a platinum dish of from 50 to ico c.c. capacity at 100 until the water is expelled, and then-slowly over a flame until intumescence ceases. The dish is placed in a muffle and heated at low redness until a white ash is obtained. If the substance contain iron or any other metal capable of uniting with platinum, a dish of some other material must be used. For soluble ash the ash obtained as above is digested with water, filtered through a Gooch crucible, washed with hot water, and the residue dried at 100 and weighed. The difference of weights equals the soluble ash. KXTKACTION WITH MISCIHLK SOLVEN I > 49 (2) To 25 grams of molasses or 50 grains of sugar, 50 mg. of /inc oxid are added, and the mass incorporated thoroughly by adding dilute alcohol and mix- ing. It is then dried and ignited as above. The weight of zinc oxid is deducted from the weight of the ash. (3) The mass is carbonized at low heat, the soluble salts dissolved with hot water, the resiilual mass burned, the solution of soluble salts added, and evapo- rated to dryness at 100, ignited gently, cooled in a desiccator, and weighed. (4) The sample is saturated with sulfuric acid, dried, ignited gently, then burnt in a muffle at low redness. One-tenth of the weight of the ash is deducted to calculate the percentage. Extraction with Miscible Solvents. Cold extraction may be made by macerating a weighed portion of the material in a measured volume of the solvent in a vessel closed so as to prevent appreciable evaporation, decanting or filtering an aliquot portion of the liquid, evap- orating and weighing the residue. The time of macera- tion and the method of evaporation must be adapted to each case. The percolation method of producing a con- centrated solution is not well suited to the operations of food analysis. For thorough extraction, especially with difficultly soluble materials and volatile solvents, the continuous extraction ap- paratus devised by Szombathy, 4 but commonly called the Soxhlet tube, is most suitable. The general construction and arrangement are so well known as not to require detailed description. The apparatus, as shown on page 50, is provided with a globular metal condenser, but the ordinary spiral condenser or Cribb's form may be employed. The material may be placed in a fat-free paper thimble and covered with a plug of cotton to prevent loss of fine particles. In place of the cotton plug a Gooch crucible may be used, as shown in the cut. The top of the thimble should be a short distance below, and the top of the crucible a short distance above, the bend of the siphon. The thimble should be supported by a section of 5 FOOD ANALYSIS LJ glass tubing, I to 2 cm. long, with rounded edges ; the edge on which the thimble rests should be a little uneven to pre- vent a close joint, which would hinder the siphoning of some of the liquid. Another method is to use a glass tube open at both ends, the material to be extracted being held in position by loose plugs of cotton placed above and below. To obtain good results with ether it is essential that it be as nearly as pos- sible free from alcohol and water. The method of purification recommended by the A. O. A. C. is as follows : Commercial ether is washed with two or three successive portions of distilled water and solid sodium hydroxid added until most of the water has been ex- tracted. Carefully-cleaned metallic so- dium, cut into small pieces, is added until there is no further evolution of hydrogen. The ether thus dehydrated must be kept over metallic sodium, and should be only lightly stoppered in order to allow any accumulated hydrogen to escape. Light petroleum, commonly known as benzin and gasolin, and often by other trade-names, may be used for ex- traction purposes. It should be purified FIG. 25. by redistillation, selecting the portions which come over below 50. Other solvents are employed in special cases. Benzene, chloroform, carbon disulfid, and acetone are now obtainable TIG. 26. FOOD ANALYSIS of high purity, but are liable to contain some moisture, which can be removed by treatment with plaster- of-Paris. Knorr's extraction apparatus substitutes mercury seals for corks and ground joints. Several other improvements in the details of the Soxhlet apparatus are made, as shown in figure 26. The condenser is a tube with a series of bulbs, and is fused to the hood which holds the material to be extracted. The rubber stopper which supports the outside of the con- denser should be put on before the junction is made. A shows a section of the flask and lower part of the hood in position. 5 is a siphon for preventing the accumulation of solvent between the hood and the neck of the flask. The junction between the hood and the flask is sealed by mercury. The flask is held by a rubber band which passes under it and over two hooks on the hood. Figure 28 shows a tube for holding the mate- rial ; D is a perforated platinum plate. At / are nipples for holding the tube upon the rim of the flask. A convenient arrangement of the siphon is also shown in figure 28 ; the siphon, being within the apparatus, is protected from breakage. With Knorr's apparatus little leakage occurs even with the most volatile solvents. For the recovery of the solvent the apparatus shown in figure 27 is used, in which A is the flask containing the liquid. C may be a ground joint ; the joints of A and B are sealed with mercury. It must not be overlooked that mercury seals exposed con- stantly to the air of badly ventilated rooms may cause chronic mercurial poisoning. Wiley's extraction apparatus is shown in figure 29. V FIG. 28. EXTRACTION WITH IMMISCIBLE SOLVENTS 53 The outer vessel is a stout glass tube. The inner vessel is of nickel-plated metal in a series of double cones ; the flat plate at the top fits tightly on the ground surface of the glass vessel. Cold water is passed continually through the interior of the metal vessel, by which the solvent is constantly con- densed, and drops upon the material to be treated, which is contained in a porcelain or platinum bucket, with a detach- able perforated bottom, through which the extract drops into a vase-like receiver resting in the outer vessels. This is not shown in the cut, and will not be required if the estimation be made by the indirect method. Extraction with Immiscible Solvents. Solvents not miscible with water are em- ployed for extracting substances by shaking the solvent thoroughly with the aqueous solution, allowing the liquids to separate, and removing one of them. The process is most conveniently performed in a stop- pered separator. The principal difficulty is the liability of some liquids to form emulsions which separate only after long standing. Separation may sometimes be hastened by cooling the mixture or by adding more of the solvent. One of the most satisfactory methods when operating upon small amounts of liquid is to whirl the mixture for a short time in a high-speed centrifuge. Figure 30 shows an apparatus devised by O. Forster for use with solvents lighter than water. The cylinder A should hold about 1000 c.c. Two openings are not necessary, since both tubes may pass through the cork, but the arrangement shown is more convenient. 600 c.c. of FIG. 29. 54 FOOD ANALYSIS the solution are placed in the cylinder, 300 c.c. of solvent added and the mixtures well shaken. The rest of the appa- ratus is then attached. The flask B has a capacity of 200 to 300 c.c.; the solvent in it is heated by a water-bath. The vapor passes by a into b, the condensed liquid flows to the bottom of A and rises through the solution ; the upper layer returns through c into B. The tube c should not extend into the liquid in B. A small quantity of aqueous liquid may collect at inter- vals in B and should be removed. Distillation and Sublimation. Retorts and alembics are now but little used, but are serviceable in some cases. With glass vessels the irregular percussive boiling, commonly called "bumping," is liable to break the vessel or to spurt portions of the undistilled liquid into the condensing appara- tus. Bumping may usually be pre- vented by the addition of a few frag- ments of pumice, clay pipe, or plati- num foil. Dry pumice floats on most liquids. It may be made to sink either by soaking it in water for a day or so or by heating the fragment to redness and quench- ing it in the liquid. With inflammable liquids, the latter method must be used cautiously. A special device to prevent bumping is described by W. H. Hess and A. B. Prescott : 5 A capillary tube is cut of such length that it cannot lie on the bottom of the distilling vessel, and projects some distance above the level of the liquid. One end is sealed and the tube FIG. 30. DISTILLATION AND SUBLIMATION 55 is placed with open end resting about the center of the bot- tom of the vessel. In special apparatus, a flask with a short platinum wire fused into the bottom is preferred. As a protection against spurting, bulb-tubes are used, as shown on page 43. Condensing apparatus is made in considerable variety ; practically, glass and block-tin are the only available materials for tubes. Glass tubes are liable to crack at the point at FIG. 31. which the cooling action begins. To avoid leakage and the contact of hot vapors with corks or rubber tubes, the con- nections should be as few as possible. Arrangements of dis- tilling apparatus are shown in the section on nitrogen determ- ination and other convenient forms in figures 31 and 32. In the former a block-tin worm passes through a copper tank containing the cooling water. The upward inclination of the FOOD ANALYSIS neck of the retort causes any material that is thrown into it to return to the boiling liquid. This is a convenient appara- tus for the so-called ammonia process in water analysis. FIG. 32. Figure 32 shows an improved form of distilling apparatus devised by R. S. Weston. The condenser tube is of copper or japanned galvanized iron. The details of construction and DISTILLATION AND SUBLIMATION 57 B arrangement are sufficiently indicated in the drawing. The apparatus is shown as arranged for water analysis. When Kjeldahl distillations are being made the lower end of the block-tin tube should be extended by means of a bulbed glass tube, as noted elsewhere. Safety bulbs may also be placed between the flask and condensing tube in such a way as to avoid rubber-tube connections. Materials are added by means of long-stemmed funnels. Weston uses a Bunsen burner, but it is probable that the low temperature burner would be satisfac- tory in many cases. Figure 33 shows Cribb's condenser, which may be attached to any distilling apparatus. The distillation tube is at- tached at A. The walls are double ; condensation occurs in the space between them, and the distillate flows out by the tube E. The cooling water flows through F to the bottom of the inner space, over- flows at J into the catch-basin below, es- caping by G. The stopper 7 serves to steady the tube F, and should have several large notches cut in it to allow the water to escape freely. It is usually necessary to wrap a piece of muslin around the outside of the apparatus to cause the overflow- ing water to run properly. The condenser may be made of glass, block-tin, or tinned copper. Experience shows that the apparatus will be more satisfactoiy if some of the dimen- sions are changed from those indicated in the figure, which is taken from Cribb's paper. The annular space should be larger, especially at the bottom ; the catch-basin must be roomy, and G should have a caliber at least three times that of F. The catch -basin is held in place by rubber tubing. FIG. 33. So FOOD ANALYSIS The condenser is supported by a strong clamp. L is for attachment of an air-pump for distillation under diminished pressure. For forms and arrangements of reflux or inverted con- densers see under " Extraction." Distillation of small amounts of material may be made with the ordinary extractor, terminating the operation before the distillate reaches the level of the bend of the siphon. Distillation under reduced pressure or in a current of indif- ferent gas may be carried out in the apparatus devised by L. T. Thorne, 6 which, in a form improved by F. C. Axtell, is FIG. 34. shown in figure 34. This consists of a distilling-flask, a condenser, an upright receiver, and a small receiving-flask. It is convenient to have several of the last. The distilling- flask is furnished with a tap-funnel. Its mouth is best closed with a good cork which has been well softened. .A ther- mometer may be passed through this. The condenser and upright receiver are joined by fusion and the latter has three stopcocks, the upper and lower being of ordinary form, the middle one a three-way cock. All stopcocks and joints must be well ground. DISTILLATION AND SUBLIMATION The operation is as follows : A little powdered pumice- stone is placed in the distilling-flask and the cork with the thermometer placed in position. The tube at the upper extremity of the receiver is connected with the air-pump, a strong vessel, having a capacity of several liters, being inter- posed between the pump and the apparatus to obviate the effect of sudden variations of pressure. The funnel-tap on the distil ling-flask is closed, the upper stopcock is opened and the lower one is closed, and the middle one opened so as to exhaust the receiving-flask. The liquid is then introduced into the distilling flask through the tap-funnel, and after the foaming due to the liberation of air by the pumice-stone has subsided, distillation is begun. When the first fraction or a sufficient quantity has collected in the upright receiver, the upper cock is closed, the lower one opened, and the liquid allowed to run into the receiving-flask. The lower cock is closed and the middle one turned so as to admit air to the flask, which is then disconnected and another substituted. The cocks are then set for the beginning of another distilla- tion. Axtell finds that powdered pumice, used as indicated, entirely prevents bumping. For lubrication of glass stopcocks, the following mixtures, devised by F. C. Phillips, are useful : Pure rubber, 70 parts Pure rubber, 70 parts Spermaceti, 25 " or Unbleached beeswax, . 30 " Vaselin, 5 " The rubber must be fresh and pure ; rubber scraps will not answer. It should be melted in a covered vessel, the other materials added, and the mixture well stirred while hot, care being taken not to scorch it. It must not be exposed to air longer than is necessary during heating, and should be kept in well-closed bottles. These mixtures may be removed from 60 FOOD ANALYSIS the parts of the apparatus which are not easy of access by the use of a little strong nitric acid, which loosens the lubri- cant so that it may be washed out with water. Fractional distillation may be performed with the Thorne- Axtell apparatus. Special bulb-tubes have been devised for attachment to ordinary flasks so that the vapor may be par- tially condensed and succeeding portions washed with the liquid which runs back continuously into the flask. Among these are the Le Bel-Heninger and Glynsky tubes. The former bears from two to six bu-lbs. The upper part has an inclined side tube for connection with the receiver and an opening through which the thermometer can be passed. Each of the bulbs is connected with the one just below by a side tube. At the constricted part of each bulb a small thimble of platinum, copper, or nickel gauze rests. The vapor con- denses in the cups and washes the vapor subsequently formed. The liquid runs off from each bulb, back to the flask. The flame should be regulated so as to keep all the cups full, and cause the distillate to fall from the end of the tube in separate drops. In the Glynsky bulb hollow glass balls replace the gauze. It must be borne in mind that the present United States revenue-law requires all distilling apparatus to be registered, no matter for what purpose it is used. Heavy penalties are imposed for using non-registered stills. No fee is imposed for registry, which is made on blanks furnished by the Col- lector of Internal Revenue. SUBLIMATION may be performed in a narrow test-tube or watch-glasses with concavities facing, the upper glass being slightly small so that it may fit well. A gentle heat is ap- plied to the lower dish. By substituting a beaker containing water for the upper watch-glass a better cooling effect will be obtained. APPARATUS AND CHEMICALS 6l Apparatus and Chemicals. These can now be obtained generally of good quality at almost all times and places, but a few suggestions may be of value. Centrifuge. Centrifugal apparatus is of much advantage in laboratory work. The slow-speed machines made for milk analysis are of limited application ; much better results are obtained by the high-speed apparatus of the type shown in figure 35. In operating such machines, the load on the revolving arms must be balanced or the center of gravity will not coincide with the center of revolution, and an ob- jectionable vibration will be produced. The machine should be attached to a firm table or shelf and kept properly oiled and protected from dust. The tubes usually furnished are narrowed at the bottom, and, as solid material is apt to be packed closely by the centrifugal action, it is sometimes difficult to dislodge it, but care should be taken to get all such ma- terial out of the tube so as not to con- taminate the substance used in a subse- quent experiment. If it be desired to use vessels not narrowed at the base, small glass tubes closed by cork at one end may be substituted. In this case, however, the lower end of the tube-holder should be packed with cotton to such a height that the cork cannot be driven into a part of the tube narrow enough to hold it tightly. If this precaution be neglected, the rotation will push the glass tube so far into the tube-holder that it may be impos- sible to draw it out without leaving the cork. Glassware suitable for most laboratory work is now made FIG. 35. 62 FOOD ANALYSIS in the United States, but the Bohemian and Jena glass still shows important merit which will lead to preference for it in many cases. For the cleaning of glass and porcelain, especi- ally when working with fatty matters, the commercial triso- dium phosphate is of much use. Vessels cleaned with it must be well rinsed. A bath of so-called battery fluid (potassium dichromate or sodium dichromate, or, better, the crude chromic acid sold for the purpose, 250 grams ; water, 2000 c.c.; sul- furic acid, 300 c.c.) will make an efficient cleaning solution for all non-metallic articles. These should be cleansed with soap, sodium phosphate, or sodium carbonate to get rid of the organic matter, rinsed, and then soaked in the liquid overnight. The solution gives off no fumes and its color guards against imperfect rinsing. It is of little value when it has become brown or green, but may be freshened by adding crude chromic and sulfuric acids. As the liquid is very corrosive, all waste from it should be washed down the drain-pipes with a free flow of water. Strong sulfuric acid is used by some chemists, especially for cleaning greasy apparatus. Organic matters such as corks and tubes should, of course, not be put in these cleaning solutions. For heating beakers and flat-bottomed flasks the hot-plate is much used, but the thin cast-iron plates commonly fur- nished are unsatisfactory. A better form is a rolled plate at least I cm. thick. Nickel wire-gauze is a good substitute for the common wire-gauze. The Chaddock burner, made of non-corrodible materials, is now obtainable, and is adapted to use in the fume-box. Electric heating apparatus has been brought to considerable efficiency, and will in time supplant all present methods, but the installation and operation are as yet costly. An incandescent lamp may be arranged as a heating apparatus, and is especially satisfactory in extractions and distillations with inflammable materials. The low-tempera- ture burner shown in figure 36 is convenient in many opera- APPARATUS AND CHEMICALS 63 tions. As sold, the inlet pipe is too short and the rubber connection becomes hot. The inlet should be lengthened by a piece of metal pipe (standard l /% inch gas-pipe is suitable) about 10 cm. long. In default of this, the joint may be kept cool by wrapping around it a piece of muslin, the ends of which dip in a vessel containing water. Filter-papers are furnished in great variety, adapted to all purposes. The so-called hardened filters are serviceable in several operations, such as determination of crude fiber, insolu- ble matter, and extraction with volatile solvents, for with care the wet precipitate can be scraped off without removing an appreciable amount of the filter-paper. Glass rods slightly flattened or bent at the middle to a very obtuse angle are convenient because they are not liable to roll off of beakers or funnels. Reagents, especially those used only in small amounts, are most conveni- ently kept in capped bottles, each with small glass tube or pipet, the tube be- ing just long enough to reach above FIG. 36. the top of the bottle. In this way none of the solution will get in contact with the neck of the bottle. Solids should be kept in hood-stoppered bottles,- i. e., those in which the flat top of the stopper is close to the bottle, so as to give less chance for deposit of dust. All chemicals in general use should be kept in closed cases, ammo- nium hydroxid and ammonium carbonate being separate from the common acids. The stock bottles for acids and standard solutions should be protected from dust by placing over the stopper of each, an inverted tumbler large enough to rest on the top of the body of the bottle. Platinum ware requires care to prevent staining and crack- ing. Substances containing any of the easily -reducible metals 64 FOOD ANALYSIS must not be heated in contact with platinum ; even iron com- pounds in the presence of reducing agents e. g., filter-paper will do harm. Sudden cooling of platinum should be avoided, as it tends to make the metal brittle. After being heated to redness the metal, when cold, should be lightly rubbed with very fine sea-sand (not river-sand nor powered quartz or pumice), by which the metal will be burnished and its texture preserved. The platinum-pointed forceps should be treated in the same way. Platinum dishes may often be cleaned by rubbing them with sodium amalgam, decomposing this by immersion in water, and driving the mercury off by heating to redness. Some stains may be removed by melted potassium acid sulfate. Nickel dishes may be substituted for platinum in cases in which only gentle heating is required, but nickel is apt to be injured by direct heating with gas. All the largely used chemicals are obtainable of good qual- ity, as a rule, but in important investigations tests for purity and strength should be applied. The following notes will be sufficient. Alcohol. Ethyl alcohol, commonly called " grain alcohol," contains in its strongest commercial form about 95 per cent, of ethyl hydroxid, notable quantities of esters, aldehydes, fusel oil, and traces of acid. For some purposes e. g., mak- ing standard solutions of alkali it must be purified by redis- tillation over sodium hydroxid. The absolute alcohol sold by dealers usually contains some water. The presence of water in alcohol may be detected by the evolution of acety- lene when a little calcium carbid is added. This may also be employed for removing small amounts of water, the liquid being then redistilled, but hydrogen sulfid, hydrogen phos- phid, and ammonium compounds may be thus introduced. Anhydrous copper sulfate is turned blue by alcohol containing water. APPARATUS AND CHEMICALS 65 Methyl alcohol. Crude wood-alcohol is of limited use in laboratory work. It contains much acetone. A purified article is now furnished, under the trade name " Columbian Spirit," which is about 98 per cent, methyl hydroxid and is free from notable amounts of impurities. It may be used with economy as a substitute for ethyl alcohol in many cases. It is more volatile, but traces of strong-smelling foreign matters may cause the odor to persist longer than with refined alcohol. Ether. Commercial ether contains notable amounts of al- cohol and water, but much purer samples can be obtained from dealers in laboratory supplies. A method for preparing ether for extraction purposes is given on page 50. Chloroform, benzene, w& petroleum spirit are usually obtaina- ble of good quality, except that all are liable to contain water, which is sometimes objectionable. It may be removed by use of anhydrous calcium sulfate or anhydrous copper sulfate and redistillation. Commercial chloroform is liable to decomposi- tion, t>y which it becomes acrid. All volatile solvents are liable to contain appreciable amounts of non-volatile materials. Sodium hydroxid. Several brands sold for household use are suitable for ordinary purposes, such as making standard alkali or in the Kjeldahl-Gunning process. Potassium liydroxid. Purified grades should be used. Sand and asbestos intended for moisture and extract deter- mination must be selected with care, and dried thoroughly be- fore weighing. Common sand contains much material other than quartz ; asbestos fiber is often of inferior quality. Electrolytic Method for Standard Solutions. The preparation of standard solutions by electrolysis has been investigated by R. K. Meade, 7 who finds the following method accurate : 12.487 grams of pure crystallized copper sulfate are dis- solved in about 750 c.c. of hot water in a 1000 c.c. beaker. 66 FOOD ANALYSIS When the solution is cold, a cylinder of thin copper foil a little more than three times the diameter of the beaker is rolled so that the ends lap. The negative wire is slipped through holes in the lap and fastened. The beaker is covered by a per- forated watch-glass, through which a platinum wire for the positive pole passes. A current of 1.5 to 2 amperes is sent through the solution for at least 8 hours. The terminals are then well rinsed, also any copper that may have dropped, the liquid decanted into the flask, made up to mark, and mixed. The solution is decinormal. Normal and half-normal can also be prepared in this manner. In the preparation of standard solutions it must be borne in mind that graduated apparatus is not only often inaccurate, but the systems of standardizing it are not wholly uniform. It is to be regretted that some of the dealers in reagents have not established a system of supplying standard solutions of certain reagents of absolutely uniform strength. Indicators. For ordinary laboratory work litmus, phenol- phthalein, and methyl-orange are usually preferred. Litmus. Litmus solution is now little used. It is prepared by treating the commercial material with water and filtering the solution after sufficient color has dissolved. It must be kept in an open bottle. Intermediate litmus-paper, which is convenient for ascertaining the reaction of liquids, is prepared as follows : A clear, fresh solution of litmus is divided into two equal portions ; one of these is rendered purple-red (not bright red) by the cautious addition of dilute nitric acid ; the other portion is then added and strips of good filter-paper soaked in the liquid and dried quickly. This paper will be affected by ordinary acid or alkaline solutions. It should be kept in the dark, protected from dust. Plienolplithalein. A solution of I gram in 100 c.c. of good (methyl or ethyl) alcohol is sufficient and keeps well. APPARATUS AND CHEMICALS 6/ Methyl-orange. A solution of o. I gram in water will be satisfactory. In titrating with methyl-orange very little of the indicator should be used. Cochineal. Many prefer this indicator for titrating ara- moniun hydroxid. The following description is given by the A. O. A. C. in connection with the Kjeldahl-Gunning process : 3 grams of powdered cochineal are macerated for several days, with occasional shaking, in alcohol of about 20 per cent., and the solution filtered. APPLIED ANALYSIS GENERAL METHODS POISONOUS METALS The elements included under this title are mercury, arsenic, lead, tin, copper, and zinc. Some very poisonous elements are not likely to be encountered in foods, and therefore are not considered in this connection. A. H. Allen 8 has devised a general process for the de- tection of poisonous metals. A convenient quantity of the substance, say 25 grams, is mixed in a porcelain crucible by degrees with sufficient strong sulfuric acid to moisten the mass thoroughly without making it fluid. About 2 c.c. will generally be required. Liquid material should be evapo- rated to dryness or nearly so at a low temperature before being treated with the acid. The crucible is heated for a short time on the water-bath, after which the temperature is gradually raised to a point below that required to volatilize the sulfuric acid, and maintained until the action seems to be complete. It is not necessary to carry on this part of the process until the carbon is burnt off. The crucible is allowed to cool, about I c.c. of strong nitric acid added, and the heating con- tinued until red fumes are evolved. Recently ignited mag- nesia, in the proportion of 0.5 gram for each cubic centi- meter of the acid used, is incorporated with the mass and the mixture burned off at a dull red heat, preferably in a muffle. After cooling, the ash is moistened with nitric acid, again burned off, and the process repeated until all the carbon is consumed. The residue is treated with 0.5 c.c. of sulfuric 68 POISONOUS METALS 6 9 acid, heated until fumes are evolved, cooled, boiled with water, diluted without filtration to about 100 c.c., saturated with hydrogen sulfid, the solution filtered and examined according to the following scheme : AQUEOUS SOLUTION may contain zinc, iron and earthy phosphates. Add bromin water to destroy hydrogen sulfid, coti- ' vert iron into the ferric state, boil, then add excess of ammonium hydroxid, boil again, and filter. PRECIPITATE AND RESIDUE may contain lead sulfid, stannic oxid, copper sulfid, or calcium sulfate. Fuse in porcelain cru- cible for 10 minutes with 2 grams of mixed potassium and sodium carbonate's and i gram of sulfur. When cool, boil with water and filter. PRECIPI- FILTRATE if blue, contains RESIDUE. Boil with strong hy- FILTRATE. TATE may con- tain iron nickel. Divide into two por- tions : drochloric acid as long as hy- drogen sulfid is evolved, add a few drops of bromin water Acidu- late with acetic and phos- to complete the oxidation of acid. A phates. the copper sulfid, and filter yellow if necessary. To the filtrate precipi- add excess of ammonium hy- tate of droxid, when a blue color- stannic ation will be indicative of sulfid in- copper. Acidulate the liquid d i cates with acetic acid and divide tin. into two portions : I. Heat to boil- ing and add II. If zinc found in I, I. Add potas- sium chro- II. Add potas- sium ferro- i pot assiu m for its deter- mate. A cyanid. A ferrocyanid. White pre- m i na t i on, acidulate yellow pre- cipitate in- brownish precipitate cipitate or the ammoni- dicates lead. or colora- turbidity in- acal solution tion indi- dicates zinc. strongly cates copper. with acetic acid, filter, if n ecessary, and precipi- tate the zinc from the fil- trate by hy- drogen sul- fid. Any nickel pres- ent will also be precipi- tated. Allen's scheme does not include chromium, which may be present as a constituent of lead chromate and will be found almost entirely in the precipitate and residue insoluble in water. For its detection a portion of this or of the original ash may be fused with sodium carbonate and potassium chlorate, the yellow melt containing chromate dissolved in 70 FOOD ANALYSIS the smallest possible quantity of water and slightly acidulated with hydrochloric acid. The liquid is then added to a test- tube containing a small amount of hydrogen dioxid overlaid with a little ether. In the presence of a chromate the water will acquire a blue color, which on slight shaking will pass into the ethereal layer. When tin is known to be present, the amount may be found , by treating the precipitate of stannic sulfid with strong nitric acid, igniting the metastannic acid formed, and weighing the resultant stannic acid. For the detection of tin it is recom- mended to treat the stannic sulfid with hydrochloric acid and bromin water and boil the filtered liquid with iron wire to reduce to the stannous condition. The liquid is diluted and decanted from the undissolved iron and any precipitated material, and the tin detected by adding a drop of mercuric chlorid solution, which will produce a white or gray turbidity according to the amount of tin present. Copper may be estimated colorimetrically by means of ammonium hydroxid or potassium ferrocyanid. According to Bodmer and Moor, for very small amounts the ferrocyanid method is the most accurate. Paul and Cownley estimate copper as follows : The sample is carbonized in a platinum dish and extracted with a little hydrochloric acid ; the insolu- ble residue is ignited with a little nitric acid, hydrochloric acid added, and the resulting mixture added to the original extract. The solution is then concentrated to about 30 or 40 c.c., placed in a weighed platinum dish, and the copper depos- ited with pure zinc. If the deposit is not of true copper color, it is dissolved in a little nitric acid and the copper determined colorimetrically. Zinc. Wiley determines the amount of zinc in evaporated fruits as follows : The sample is placed in a large platinum dish and heated slowly until dry and in incipient combustion. The flame is removed and the combustion allowed to proceed, POISONOUS METALS /I the lamp being applied from time to time, in case the burning ceases. The mass, when burned out, consists of ash and char. It is ground to fine powder and extracted with hydrochloric or nitric acid, the residual char is burned to whiteness at a low temperature, the ash extracted with acid, the soluble portion added to the first extract, and the whole filtered. A drop of methyl-orange solution is placed in the liquid and ammonium hydroxid added until it is only faintly acid. The iron is pre- cipitated by adding 50 c.c. of a solution of ammonium acetate, 250 grams to the liter, and raising the temperature to about 80. The precipitate is separated by filtration, washed in water at 80 until free from chlorid, the filtrate saturated with hydrogen sulfid, allowed to stand until the zinc sulfid settles, and poured on a close filter. It is often necessary to return the filtrate several times before it becomes limpid. The collected precipitate is washed with a saturated solution of hydrogen sulfid containing a little acetic acid. The precipi- tate and filter are transferred to a crucible, dried, ignited, and the oxid weighed. Arsenic, if present in amount sufficient to be of sanitary significance, may be detected by Reinsch's test, a liberal amount of hydrochloric acid being used, since arsenates do not otherwise respond to the test. Some water strongly acid- ulated with hydrochloric acid is placed in a test-tube, about half a square centimeter of bright copper foil added, and the liquid boiled gently for a few minutes. If the copper remains bright, showing that the reagents contain no arsenic, the material to be tested is added and the liquid again boiled for several minutes. If arsenic be present, a steel-gray stain will appear on the copper. The slip is removed, washed with dis- tilled water, dried by pressure between filter-paper, placed at the closed end of a narrow glass which has been previously dried by heating nearly to redness. The tube is gently heated at the point at which the copper rests. The arsenic will be 72 FOOD ANALYSIS converted into arsenous oxid, which will collect on the cooler portions of the tube in octahedral crystals. Reinsch's test cannot be applied in the presence of active oxidizing agents, such as chromates, chlorates, or nitrates. Gutzeit's test, which is more delicate, is as follows : Place in a tall test-tube about a gram of pure zinc, 5 c.c. of diluted sulfuric acid (6 per cent.), and I c.c. of the sample. The mouth of the test-tube is covered with a tightly-fitting cap of three thicknesses of filter-paper. A drop of strong solution of silver nitrate is placed on the upper paper and the tube allowed to stand for 10 minutes in the dark. If arsenic be present, a bright yellow stain will appear on the filter-paper, which, on the addition of water, becomes black or brown. A blank test should always be made to establish the purity of the reagents. Sulfids (which may be detected by substituting lead acetate for the silver nitrate in the above test) must be oxidized to sulfates before applying the test. The test is delicate. A less rigorous one may be made by substituting a drop of a saturated solution of mercuric chlorid for the silver nitrate. If no yellow coloration appears after 10 minutes, the sample may be considered free from arsenic. The purity of the reagents must be carefully ascertained before applying any of these methods. COLORS At present, the colors used in food-articles are mostly synthetic products, commonly called " anilins," but largely derived from other coal-tar materials. Natural organic colors annatto, cochineal, turmeric, indigo, saffron, and chlorophyl are used to a limited extent, but the mineral colors, such as lead chromate and ferric oxid, are rarely employed. The National Association of Confectioners of the United COLORS 73 States has published a list of forbidden and permitted colors, and many manufacturers are following the suggestions therein made. A summary of this list is herewith presented. The nomenclature of the colors is much confused, but the list has a suggestive value. FORBIDDEN All colors containing appreciable amounts of mercury, lead, copper, arsenic, antimony, tin, zinc, chromium, cadmium, and barium. PONCEAU 3RB Ponceau B extra, Fast Ponceau B, New Red L, Scarlet EC, Imperial Scarlet, Old Scarlet, Biebrich Scarlet. CROCEIN SCARLET 36 Ponceau 4RB. COCHENILLE RED A Crocein Scarlet 46 and G, Brilliant Scarlet, Brilliant Ponceau 4R, Ponceau 4R, Ponceau Brilliant 4R, New Coccin Scarlet. CROCEIN SCARLET 76 Crocein Scarlet 8B, Ponceau 6RB. CROCEIN SCARLET O Extra. SAFRANIN Safranin T, Safranin extra G, Safranin G extra, GGSS, Safranin GOOO, Safranin FF extra, No. O, Safranin cone, Safranin AG extra, Safranin AGT extra, Anilin pink. GUM GUTTA. PICRIC ACID. MARTIUS YELLOW Naphthylamin yellow, Jaune d'or, Man- chester yellow, Naphthalene yellow, Naphthol yellow. ACME YELLOW Chrysoin, Chryseolin yellow T, Gold yellow, Resorcin yellow, Acid yellow RS, Tropeolin O, Jaune II. VICTORIA YELLOW Victoria Orange, Anilin Orange, Dinitro- cresol, Saffron Substitute, Golden yellow. ORANGE II Orange II, Orange P, Orange extra, Orange A, Orange G, Acid Orange, Gold Orange, Mandarin G extra, 7 74 FOOD ANALYSIS /9-Naphthol orange, Tropeolin OOO 2, Mandarin, Chry- saurin. METANIL YELLOW Orange MN, Tropeolin G, Victoria yel- low (O double cone.), Jaime G, Metanil extra. SUDAN I Carminnaphthe. ORANGE IV Orange IV, Orange N, Orange GS ; New yel- low, Acid yellow D, Tropeolin OO, Fast yellow, Diphen- ylorange, Diphenylamin Orange, Anilin yellow. NAPHTHOL GREEN B. METHYLENE BLUE BBG Methylene Blue BB, in powder extra, Methylene Blue DBB, extra, Methylene Blue BB, (Crystalline), Ethylene Blue, Methylene Blue BB. BISMARCK BROWN Bismarck brown G, Manchester brown, Phenylene brown, Vesuvin, Anilin brown, Leather brown, Cinnamon brown, Canelle, English brown, Gold brown. VESUVIN B Manchester brown EE, Manchester brown PS, Bismarck brown, Bismarck brown T. FAST BROWN G Acid brown. CHRYSOIDIN Chrysoidin G, Chrysoidin R, Chrysoidin J, Chrysoidin Y. PERMITTED ULTRAMARINE BLUE. ULTRAMARINE VIOLET. MANGANESE BROWN. CHOCOLATE BROWN and colors of a similar nature have as their basis natural or precipitated ferric oxid which in an impure condition may have small quantities of arsenic in its composition. It is possible with proper care to secure raw material entirely free from this objectionable element and no ferric oxid containing any traces of arsenic should be used in the preparation of color. ULTRAMARINE GREEN. COLORS 7 5 COCHINEAL CARMIN. CARTHAMIC ACID (from saffron). RED WOOD. ARTIFICIAL ALIZARIN AND PURPURIN. CHERRY AND BEET JUICES. EOSIN Eosin A, Eosin G extra, Eosin GGF, Eosin JJJ, Eosin JJJJ extra, Eosin extra, Eosin KS, Eosin DH, Eosin JJF. ERYTHROSIN Erythrosin D, Erythrosin B, Pyrosin B, Prim- rose Soluble, Eosin J, Dianthin B. ROSE BENGALE Rose Bengale N, Rose Bengale AT, Rose Bengale G. PHLOXIN Phloxin TA, Eosin blue, Cyanosin, Eosin 10 B. BORDEAUX AND PONCEAU reds resulting from the action of Naphtholsulfonic acids on diazoxylenes. PONCEAU 2 R Ponceau G, Ponceau GR, Ponceau R, < Brilliant Ponceau G, Ponceau J. BORDEAUX B Fast Red B, Bordeaux BL, Bordeaux G, Bordeaux R extra, Cerasin, Rouge B. PONCEAU GG Brilliant Ponceau GG, Ponceau JJ. FUCHSIN S Acid Magenta, Rubin S, and Fuchsin. ARCHIL SUBSTITUTE Naphthion red. ORANGE I Orange No. I, Naphthol orange, a- Naphthol orange, Tropeolin OOO I. CONGO RED. AZORUBIN S Azorubin, Azorubin A, Azoacidrubin, Fast red C, Carmoisin, Brilliant Carmoisin O. FAST RED D Fast red EB, Fast red NS, Amaranth, Azo- acidrubin BB, Bordeaux DH, Bordeaux S, Naphthol red S, Naphthol red O, Victoria ruby, Wool red (extra). FAST RED Fast red E, Fast red S, Acid Carmoisin S. 7 6 FOOD ANALYSIS PONCEAU 4 GB Crocein Orange, Brilliant Orange G, Orange GRX, Pyrotin Orange, Orange ENL. METANITRAZOTIN. ANNATTO. SAFFRON. SAFFLOWER. TURMERIC. NAPHTHOL YELLOW S Citronin A, Sulphur yellow S, Anilin yellow S, Anilin yellow, Succinin, Saffron yellow, Solid / yellow, Acid yellow S. BRILLIANT YELLOW (Schoelkopf ). PONCEAU 4 GB Crocein Orange, Brilliant Orange G, Orange GRX, Pyrotin Orange, Orange ENL. FAST YELLOW Fast yellow G, Fast yellow (greenish), Fast yellow S, Acid yellow, New yellow L. FAST YELLOW R. AZARIN S. ORANGE Orange GT, Orange RN, Brilliant Orange O, Orange N. SPINACH GREEN. CHINESE GREEN. MALACHITE GREEN Malachite green B, Benzaldehyde green, New Victoria green, New green, Solid green crystals, Solid green O, Diamond green, Diamond green B, Fast green, Bitter Almond-oil green. DINITROSORESORCIN Solid green O, in paste, Dark green, Chlorin, Russia green, Alsace green, Fast green, Resorcinol green. INDIGO. LITMUS. ARCHIL BLUE. COLORS 77 GENTIAN BLUE 6 B Spirit Blue, Spirit Blue PCS, Opal Blue, Hessian Blue, Light Blue. COUPIER'S Blue Fast blue R and B, Solid blue RR and B, Indigin DF, Indulin soluble in alcohol, Indophenin extra, Blue CB (soluble in alcohol), Nigrosin (soluble in alcohol). IN GENERAL such blue colors as are derived from Triphenyl- rosanilin or from Diphenylamin. PARIS VIOLET Methyl violet B & BB, Methyl violet V 3, Pyoktanin, Malbery blue. WOOL BLACK. NAPHTHOL BLACK P. AZOBLUE. MAUVEIN Rosolan, Violet paste, Chrome violet, Anilin violet, Anilin purple, Perkins violet, Indisin, Phenamin, Purpurin, Tyralin, Tyrian purple, Lydin. CARAMEL. LICORICE. CHRYSAMIN R. The identification of individual colors in mixture with foods or beverages is usually difficult, often impossible, with methods at present available. It is possible in many cases to distin- guish between artificial and natural colors ; for example, to determine whether a sample of wine owes its color to a coal- tar derivative or to the coloring-matter of the grape. Special methods for determining such points will be given in connec- tion with examination of articles that are liable to be artifi- cially colored. The following general test, known as Arata's wool-test, is very serviceable. White wool or woolen cloth is cleaned by boiling for a few minutes, in water containing 0.5 per cent, of sodium hydroxid and washed with clean water until all alkali is removed. A convenient quantity of the substance to be tested (e. g., about 100 grams ot wine or /8 FOOD ANALYSIS fruit juice) is mixed with one per cent, of potassium acid sul- fate, heated to boiling, the washed wool manipulated in the liquid for a few minutes, washed well in boiling water, and dried. The natural coloring-matters of wines and fruits leave the wool uncolored or give merely a pink or brown tint, which is changed to green by ammonium hydroxid and not restored by washing with water ; but with many artificial colors the wool is dyed to a color which is either not changed by ammonium hydroxid or, if changed, is restored by wash- ing in water. When dyes intended for food-coloring are to be examined in bulk, the following methods are advantageous : A small quantity of the sample (o. I to 0.25 gram) is heated on platinum foil. Nitro-colors show more or less deflagra- tion at first. Sulfonated colors form a fusible residue, in which the carbon burns with difficulty. It will be advanta- geous to add some oxidizing agent (potassium nitrate, potas- sium chlorate, or sodium nitrate). It is not necessary to burn off all the carbon. The mass is allowed to cool, boiled up with water acidulated with hydrochloric acid (this may cause the evolution of a little hydrogen sulfid), and barium chlorid added. A copious white precipitate will occur if the color is a sulfonated one. For detection of arsenic the Reinsch test may be applied or the color may be examined for all the important poisonous metals by the scheme given on page 69. Identification of colors may sometimes be accomplished by the scheme on pages 80, 81, and 82, which is A. G. Green's adaptation of Weingartner's tables. It is reproduced without modification of spelling or nomenclature from A. H. Allen's " Commercial Organic Analysis," edited by J. M. Matthews. 9 The reagents required are as follows : Tannin solution : Tannin, I gram ; sodium acetate, I gram ; water, 10 c.c. COLORS 79 Zinc dust. Dilute hydroMoric acid : Hydrochloric acid, 5 c.c. ; water, 15 c.c. Ammonium hydroxid solution. Chromic acid solution : Chromic acid, I gram ; water, looc.c. Chromic-sulfuric acid solution : Chromic acid, I gram ; strong sulfuric acid, 2.5 c.c. ; water, 100 c.c. Strong sodium hydroxid solution: Sodium hydroxid, 33 grams ; water, 67 c.c. Dilute sodium hydroxid solution: Sodium hydroxid, 5 grams ; water, 95 c.c. Alcohol. 70 per cent. In applying the scheme a primary division is made into dyes soluble and insoluble in water. The former are divided by means of the tannin solution into the so-called basic and acid groups. The dyes which in aqueous solution are precipi- tated by tannin solution are termed basic dyes. The reduction with zinc dust is best made by adding a little of the zinc dust to the hot dyestuff solution contained in a test-tube, agitating, and adding dilute hydrochloric acid drop by drop until decolorized. Excess of acid should be care- fully avoided. When the color acid is quite insoluble, the reduction is made with zinc dust and ammonium hydroxid. The reduced solution is decanted upon a small filter ; if the color does not return in a few minutes, the paper is moistened with chromic add solution. In the case of acid colors the chromic-sulfuric acid solution should.be used. As some dyes do not show their color in presence of free acids, the paper should be exposed to the fumes of strong ammonium hy- droxid solution before deciding as to whether the color will return. Tests adapted to the recognition of colors in particular foods will be described in connection with such foods. 80 FOOD ANALYSIS 12! s o X I C3T3 K S *>$$ " ^ Or^ 111 " *s * a fci-gl g .a I Tl| ^ I <06 zin , th '2 2 m If =-s ; 7-* t& -i-+:i "S r &SS l . S|| I E 2SlH=^l 111 l COLORS 8l !ls ./: lift; IlII 5 ! IH-Ili -c^S il iiS ties 3 ! 11 be aqueo dyestuff shaken w 2S i aa^ligfl g ii ii piiisi|iii| e^J. 5>-r-^^ =Oo8 o III |j| . l lliplilli 5111 82 FOOD ANALYSIS gjj 3 1 .si QO W 9) 3 rrt ^ ^ j2j "^ fl .2 3 S O '3 . ^ g t eg 2 "S *3 OJ I 8 02 IS II "5 ^ M 1 "3 5-0 d 3 5 f s I 1 R 8 0) g The alkaline solu dust and ammc on niter-paper. Q OJ *S O> m O 'S ^^1S -Sag 51 -a S fl**^CQS w Q>>'- : ^ 5 : S ' .2o2 S g o o -3 |3 s >.^.sn n o bo Il|jjlll|l PRESERVATIVES 8 3 PRESERVATIVES The decomposition of food is prevented by sterilization or by addition of antiseptics. Numerous food-preservatives are now in use. Some e. g., common salt, niter, acetic acid, and wood smoke have been known from early times and are still in vogue. Among the more important of the newer forms are salicylic acid, benzoic acid, sodium benzoate, beta-naphthol, saccharin, abrastol, formaldehyde, fluorids, silicofluorids, sul- fites, boric acid, and borax. Other forms, principally synthetic coal-tar derivatives, have been suggested and, to a limited extent, used. Most acids are antiseptic. Each of the substances above enumerated has special adap- tabilities ; some of them are widely applicable, and hence are largely used. Most of the permissible food-preservatives are not distinctly germicidal and must remain in the food if con- tinued preservation is desired. Salicylic acid may be obtained from natural sources, but the artificial product made from phenol is almost always used. It is apt to contain injurious by-products. The commercial article is a white crystalline powder, soluble in about 500 parts by weight of cold water, and more freely soluble in a solution of borax and in alcohol, ether, or petroleum spirit. The last two liquids extract it from an acidified watery solution. It distils in a current of steam. Its most characteristic reaction is the violet color produced with ferric chlorid. Sodium benzoate, now largely prepared from the artificial acid, derived from toluene, is usually sold as a granular white powder which has a slight aromatic odor and a nauseous taste. The latter is of some advantage, since it prevents too liberal use in food articles. It is freely soluble in water and has marked antiseptic qualities. In the United States, sodium benzoate is the most common preservative for catsups, jams, jellies, mince-meat, and preserves. 84 FOOD ANALYSIS Benzole acid is not frequently used in food articles, but some of it may be formed from sodium benzoate by the action of acids or acid salts in the food. It is necessary, however, to insure the liberation of the benzoic acid when testing for it by the addition of sulfuric acid. Saccharin. Commercial saccharin is somewhat variable in composition. It is a white, crystalline, intensely sweet powder, soluble in 1000 parts of cold and 100 parts of boil- ing water. It is more soluble in alcohol, glycerol, and ether, and very slightly soluble in chloroform, benzene, and petro- leum spirit. Ether removes it from its aqueous solutions. Pure saccharin is slightly volatile at 100 and leaves no ash, but impurities may be present in the form of sodium salts, and considerable ash, principally sodium sulfate, may be left upon ignition. $-naphthol is a white crystalline powder, slightly soluble in water, freely in alcohol, ether, chloroform, benzene, fats, and alkaline solutions. It is wholly volatile on ignition. It is liable to contain small amounts of the more toxic isomeric form, a-naphthol. The so-called hydronaphthol is substanti- ally the same as /9-naphthol. Abrastol or asaprol (calcium /3-naphthol-a-monosulfonate) is a colorless or light reddish powder freely soluble in water or alcohol. Formaldehyde is a gas freely soluble in water, from which solution a polymeric modification is easily obtained as a white solid, volatilized only at a temperature above the boiling- point of water. Formaldehyde is principally sold as a 40 per cent, watery solution designated by the copyrighted name " formalin." More dilute solutions are .sold under a variety of fanciful and misleading names. The 40 per cent, solution is a colorless liquid with a slight and not disagreeable odor and a faint acid reaction, the last property being probably due to small amounts of formic or acetic acid produced by oxida- PRESERVATIVES 8 5 * tion. When this solution is boiled, the formaldehyde distils readily with the steam ; but if the fresh distillate be evapo- rated at a lower temperature, as, for example, on a shallow dish placed over boiling water, a large part is converted into the solid form. All the modifications of formaldehyde have active reducing qualities and exhibit strong tendency to com- bine with proteids so as to form insoluble bodies. A small percentage of formaldehyde, for example, will cause a gelatin solution to solidify so that the mass cannot be melted at any temperature below that of destructive decomposition. In the preservation of food the commercial formalin is almost ex- clusively used. Sulfites. The acid salts are more active than the neutral form and are more used. Calcium sulfite is also frequently employed. Sulfites are white solids freely soluble in water and glycerol, but not appreciably in alcohol, or the solvents immiscible with water. Their antiseptic action being strongly exerted upon yeast, they have been used largely to control or prevent alcoholic fermentation. The detection of sulfites being based upon the recognition of the sulfurous acid derived from them, a specific description of each will not be needed. Boric acid and borax. The observations of R. T. Thomson have shown that, at least with milk, a mixture of these sub- stances is more efficient than either alone, and the two are very frequently sold in mixture under trade names, such as " Preservaline " and " Rex Magnus." They are also used separately, boric acid being the more common. Both are white powders soluble in water ; borax is practically insolu- ble in alcohol, boric acid freely soluble. Both are non-volatile at a red heat, but a watery solution of boric acid cannot be evaporated without considerable of the acid passing off with the steam. Borax has an alkaline reaction ; boric acid is acid to litmus, but turns turmeric paper brown when its solu- tion is evaporated on it. From a solution of boric acid in 86 FOOD ANALYSIS methyl alcohol the whole of the acid may be obtained by distillation, which is utilized in the determination. When boric acid is heated with glycerol, tritenyl borate is produced as a thick sirup miscible in all proportions with cold water and decomposed by hot water. By evaporation it can be obtained in the form of a transparent, glassy, brittle mass which absorbs water readily. A preparation made by dis- solving borax in glycerol has also been offered as a preserva- tive, but is little used. These glycerol preparations have been sold under various names, such as " boroglyceride " and "glyceride of boric acid." Fluorids, borofluorids, and silicofluorids. Of these, the sodium and potassium compounds have been principally used, being among the few forms soluble in water. They are white powders, not volatile at a red heat. Detection of Preservatives. Owing to the difference in the chemical character of preservatives and of the food articles in which they are used, few general methods can be given ; the examination must be conducted with reference to the material likely to be present. The following are suggestions in this direction : In meats, boric acid ; in milk and milk prod- ucts, formaldehyde and boric acid, occasionally salicylic acid. In jams, jellies, mince-meat, and table delicacies, benzoic and salicylic acids or their salts ; occasionally boric acid. In cider and some other fruit juices, salicylic acid and sulfites. In fer- mented beverages and malt extracts, salicylic acid, sulfites, fluorids, silicofluorids, borofluorids ; abrastol may be employed, but the data in regard to it are limited. Saccharin is likely to be present in beers, wines, and sweetened articles. Benzoic and salicylic acids and their salts may often be de- tected by shaking the material with a mixture of equal parts of ether and petroleum spirit. A little sulfuric acid should be added if the material is not already distinctly acid. If the extrac- PRESERVATIVES 87 tion be repeated with several portions of the solvent, an approxi- mate quantitative determination may be made. The shaking must be vigorous, so as to bring the solvent in contact with all parts of the sample. In many cases this will produce an emul- sion which separates very slowly. The application of the cen- trifugal method will be useful in this case. The addition of more of the solvent and the cooling of the material is also advised. The following descriptions are adapted especially to the conditions under which the different preservatives are likely to be found. As they are all somewhat soluble in water, solid or semi-solid materials may be exhausted with water and the liquid concentrated at a low temperature. In many cases the sample may be strained through muslin and the tests applied to the filtrate. The volatility of some preservatives, especially in a current of steam, is occasionally serviceable. Formaldehyde may be thus obtained from milk. Benzoic acid and saccharin may be separated by mixing about 200 grams of the sample with 5 c.c. of a 20 per cent, solution of phosphoric acid, and distilling nearly to dryness. The benzoic acid distils, while the saccha- rin remains in the flask. A current of steam passing through the distilling flask is still more efficient. Salicylic acid. This is usually detected by extraction with an immiscible solvent as noted above. 25 to 50 c.c. of the sample are rendered feebly acid with a few drops of sulfuric acid and shaken vigorously with about an equal bulk of a mixture of equal parts of ether and petroleum spirit, the liquids are allowed to separate, as much as possible of the solvent is drawn off, filtered, and evaporated at a gentle heat. When salicylic acid has been added as a preservative, distinct needle-like crystals will be usually seen. A few drops of water should be added and then a drop of ferric chlorid solu- tion. The reaction of salicylic acid is distinct. When a crys- talline deposit cannot be obtained, a larger quantity of the 88 FOOD ANALYSIS sample may be concentrated at a gentle heat and extracted as above. Saccharin. A suitable amount of the sample (50 or 100 c.c.) is acidified with dilute (25 per cent.) sulfuric acid and extracted with a mixture of equal parts of petroleum spirit boiling below 60 and ether. The solvent is evaporated at a gentle heat. The presence of saccharin in the residue may be detected by the taste. 2 c.c. of a saturated solution of sodium hydroxid are added and the dish heated until the residue dries and the mass fuses, and maintained thus for half an hour. The saccharin is converted into salicylic acid, which may be detected in the residue by acidulating it with sulfuric acid and applying the ferric chlorid test. If salicylic acid be present originally in the sample, the residue from the petroleum spirit and ether solution is dissolved in 50 c.c. of dilute hydrochloric acid, bromin water added in excess, the liquid shaken well, and filtered. Salicylic acid is completely removed as a brominated derivative. The filtrate is made strongly alkaline with sodium hydroxid, evaporated, and fused as described above. Benzole acid and benzoates. E. Mohler's method : l About 100 grams of the sample are made alkaline with sodium hydroxid and evaporated to a paste, which is then acidified with hydrochloric acid, mixed with sand, and extracted with ether. The ether is evaporated spontaneously, the residue moistened with 2 c.c. of sulfuric acid, heated until acid vapors escape (at about 240), and a few decigrams of sodium nitrate added in small portions, until the liquid becomes color- less. The liquid is poured into excess of ammonium hydroxid and a drop of ammonium sulfid solution added. Benzoic acid is indicated by a yellow, changing to reddish-brown. Peter's method : 1 1 The material is made slightly acid and extracted with chloroform, which is then evaporated sponta- neously. The vessel containing the residue is placed in PRESERVATIVES 89 melting ice, 2 c.c. of sulfuric acid added, and stirred until the residue is dissolved. Barium dioxid is dusted into the mass, with constant stirring, until the liquid begins to foam, when 3 c.c. of hydrogen dioxid (3 per cent.) are added drop by drop. The dish is then removed from the cold bath, the contents diluted with water to convenient bulk, and filtered. The acid filtrate is extracted with chloroform. The benzoic acid will have been converted into salicylic acid by the process and the latter may be detected by ferric chlorid. Boric acid and borax. These may be detected in many food-articles, especially milk and milk products, by the follow- ing test: A few drops of the sample or of a solution obtained by shaking some of it in water are mixed with a drop of strong hydrochloric acid and a drop of strong alcoholic solu- tion of turmeric, evaporated to dryness at a gentle heat, and a drop of ammonium hydroxid added to the residue when cold. A dull green stain shows that boric acid is present. Boric acid is a normal constituent of wine, and hence a qualitative test in such case is of no value. The following approximate quantitative test is recommended by W. D. Bige- low : A series of solutions containing amounts of boric acid from o.ooi to 0.020 gram in dilute hydrochloric acid (i part of strong acid to I 5 parts of water) is prepared. A drop of each solution is evaporated on a piece of turmeric paper 2 cm. square and the color noted, care being taken that the drops are uniform. 50 c.c. of the wine are made slightly alkaline with calcium hydroxid solution, evaporated to dryness, and burned to an ash. 3 c.c. of water are added to the ash and then half-strength hydrochloric acid drop by drop until the liquid is acid. The solution is then made up to 5 c.c. with hydrochloric acid one-sixth the strength of the strong acid, the mass mixed, and a drop tested on a piece of turmeric paper and compared with the standards. If stronger than a 90 FOOD ANALYSIS standard which is of characteristic tint, the liquid should be diluted with the I to i 5 hydrochloric acid and again tested. Fluorids. 100 grams of the sample are made slightly alka- line with ammonium carbonate, heated to boiling, a few centi- meters of calcium chlorid solution added, and heating con- tinued for 5 minutes. The precipitate is collected, washed, dried, transferred to a platinum crucible, and ignited. When the mass is cold, a few drops of strong sulfuric acid are added, and the crucible covered with a piece of glass partly protected on the lower side by paraffin. The bottom of the crucible is then heated for an hour at a temperature between 75 and 80. The glass is etched if fluorids are present. Borofluorids and silicofluorids. 200 grams of the sample are made alkaline with calcium hydroxid solution, evaporated to dryness, incinerated, and the ash extracted with sufficient acetic acid to decompose carbonates. The residue is col- lected on a filter, washed, again extracted with acetic acid, and filtered. The filtrate contains any boric acid that may be present and is tested for this substance as directed on page 89. The insoluble residue contains the calcium silicate and calcium fluorid. The filter and residue are ashed, a portion of the mass mixed with a little precipitated silica and 2 c.c. of sulfuric acid, and placed in a short test-tube to which is attached a small U-tube containing a few drops of water. The test-tube is heated cautiously in a water-bath ; any sili- con fluorid that may be formed from fluorin present will pro- duce a gelatinous deposit in the U-tube. If boric acid has been found in the filtrate noted above, it may be assumed that any fluorin is in the form of borofluorid ; but if boric acid is not present, the other portion of the ash from the filter and residue is treated with sulfuric acid without previous addition of silica. If gelatinous silicic acid be formed, the compound was originally silicofluorid. Formaldehyde. The tests for formaldehyde have been PRESERVATIVES 9! mostly adapted to its detection in milk. It is not likely to be used as a general food-preservative. It may be obtained pure by distillation of the sample, especially in a current of steam. An investigation by N. Leonard, H. M. Smith, and H. D. Richmond showed that with ordinary aqueous solu- tions about 30 per cent, of the formaldehyde has passed over when 20 per cent, of the liquid has been distilled, and nearly 50 per cent, when 40 per cent, of the liquid has been dis- tilled. For methods of detecting formaldehyde see under Milk." For detection of sulfites see under " Alcoholic Beverages." fi-naphthol. Several allied antiseptics of this type may be detected by the following method : 200 grams of the sample are acidified with sulfuric acid and distilled with open steam until i 50 c.c. of distillate are obtained. This liquid is shaken with 20 c.c. of chloroform, the latter withdrawn, rendered alkaline with potassium hydroxid, and heated almost to boiling for a Tew minutes. Color changes occur as follows : Salol, light red. Phenol, light red, to brown, to colorless. 3 naphthol, deep blue, to green, to brown. A portion of the distillate may be tested as follows : 25 c.c. are made faintly alkaline with ammonium hydroxid, then faintly acid with nitric acid, and a drop of strong sodium nitrate solution added. /3-naphthol develops a rose-color. The reaction is rather uncertain, and appears to be affected by light. SPECIAL METHODS STARCH Detection. The reaction with iodin affords a delicate method for detect- ing starch. The color is shown by the undissolved material, but it is more satisfactory to dissolve it by boiling with water, allowing the solution to cool and adding the iodin, preferably as potassium iodid-iodin solution (p. 35). If the proportion of starch be large, an almost black precipitate will be formed. The depth of color will be some indication of the amount present, but exact determinations cannot be made by this method. In the undissolved condition, starch may be recognized under the microscope and its botanical source usually deter- mined. A magnifying power of from 200 to 300 diameters will be required. The characteristics of the granules are seen more vividly by mounting them in a dense medium such as chloral hydrate solution or glycerol (p. 35) and arranging the reflecting mirror so as to throw an oblique light upon the object. By this means distinct markings, termed the hilum and concentric rings, are recognized. If the chloral-hydrate iodin solution (p. 35) be employed for mounting, or if a drop of the potassium iodid-iodin solution be introduced under the cover of a glycerol or water mounting, the granules will become blue. With polarized light, many starches show on the dark field i. e., with crossed Nicols dark bands radiating from the hilum in four directions, giving the appearance of a Maltese cross. For this examination the object is mounted uncolored in one of the denser media and the light thrown directly from below. 92 STARCH 93 By inserting a selenite plate between the object and the lower Nicol, colors will be produced with many starches. Muter employed a selenite giving a green field, but red and red-violet fields are also suitable. The successful application of these optic methods requires good apparatus and considerable prac- tice. A careful study of starch-granules of authentic origin should always be made before deciding as to the nature of any specimen. A synopsis of the characters of the principal starches is pre- sented in the annexed tables. A micron (o.ooi millimeter) may be converted into thousandths of an inch by multiplying by 0.03937. The factor 0.04 will be near enough for most cases. The classification is essentially that of Muter, the basis being the predominating form of the granule, the distinctness and position of the hilum and markings, the appearance under polarized light, with or without selenite plate. Muter indi- cated five groups, each group designated by the name of an important type of starch, as follows : POTATO GROUP. Oval or ovate granules, showing hilum and concentric rings clearly, cross and colors usually distinct. LEGUME GROUP. Round or oval granules, hilum marked, rings faint, but rendered visible in cases by chromic acid solu- tion, cross and colors feeble. WHEAT GROUP. Round or oval granules, hilum and rings generally invisible, feebly-marked cross and colors. SAGO GROUP. Truncated granules, hilum distinct, faint rings, cross and colors fairly marked. RICE GROUP. Polygonal granules, hilum distinct, rings faint, cross and colors usually faint. In the^ description of individual starches, the term " eccen- tric " denotes that the hilum is not in the apparent center of the granule. The form of the granule is usually given as oval, spherical, polygonal, etc., terms which are strictly appli- cable to surfaces and not to solids. It will be understood, 94 FOOD ANALYSIS therefore, that such terms refer to the apparent cross-section of the granule as it is usually viewed. The dimensions given must be regarded as general ; granules not included within the limits will often be found. Polarized light is affected to some extent by almost all starch granules, if very close ob- servation be made. SIZE IN GENERAL CHARACTER WITH Po LARIZER. MICRONS. OF GRANULES. Without Selenite. With Selenite. Potato, . . . Canna, . . . 60-100 45-135 Smaller granules round, large ones ovate ; hi- lum a spot, eccentric ; rings numerous and complete. Irregular ovate ; hilum annular, eccentric ; Well-marked cross. Well-marked cross. Well-marked colors. Well-marked colors. Maranta, Natal arrow- root, . . . . Turmeric, . . Ginger, . . . Mother-cloves, Banana, . . . 10-70 35-40 30-60 40 20-66 40-80 rings incomplete, narrow and regular. Ovate ; hilum eccen- tric, circular or linear, often cracked ; rings numerous, not very distinct ; sometimes a projection at one end. Ovate to circular, ir- regular projections ; hilum eccentric, cracked ; rings dis- tinct. Ovate, often much nar- rowed at one end ; hilum eccentric, dot- like ; rings indistinct. Ovate, many with a projection on one end ; hilum and rings scarcely visible. Ovate ; hilum a dis- ! tinct spot, eccentric ; rings visible. Ovate but often very ! narrow in proportion to length; hilum a spot, eccentric ; rings distinct. Well-marked cross. Well-marked colors. Well-marked cross. Well-marked colors. Well-marked cross. Well-marked colors Faint cross. Faint colors. Well-marked cross. Well-marked colors. Faint cross. Faint colors. STARCH 95 SOURCE. SIZE IN MICRONS. GENERAL CHARACTER OF GRANULES. WITH POLARIZER. Without Selenite. With Selenite. Bean, .... 35 tinct, nearly cen- tral ; rings invisible. 9 6 FOOD ANALYSIS SOURCE. SIZE IN MICRONS. GENERAL CHARACTER OF GRANULES. WITH POLARIZER. Without Selenite. With Selenite. Rice, .... 5-10 Pentagonal, hexagonal, Cross distinct, Colors distinct. occasionally triangu- well marked. lar with sharp angles ; hilum distinct under high power. Buckwheat, . 5-20 Polygonal, angles Cross distinct. Colors distinct. somewhat rounded ; hilum central, spot or star ; granules often compound. Oat, .... 5-30 Mostly polygonal, a Faint cross. Faint colors. few spherical ; hilum and rings visible only * with high power ; often compound. Maize, . . . 5-20 Round to polygonal, Faint cross. Faint colors. angles usually round- ed ; hilum central, crack or star; rings nearly invisible. Pepper, . . o-5-5 Polygonal, very small, Cross with high Color with high sometimes showing power. power. Brownian movement, sometimes united into large irregular masses; hilum only seen with high power. (See plates in Appendix. ) Determination. The exact quantitative determination of starch is difficult. The proposed methods have been carefully investigated by H. W. Wiley and W. H. Krug, who have shown that in the presence of vegetable tissue containing pentosans or similar carbohydrates the diastase method is alone trustworthy. The first method is applicable to the examination of commercial starches. HYDROCHLORIC ACID METHOD. 3 grams of the substance are treated with about 50 c.c. of cold water for an hour, with frequent stirring ; the residue is collected on a filter and washed with sufficient water to make a total of 250 c.c. This STARCH 97 liquid contains the soluble carbohydrates. The undissolved residue is heated for 2^ hours with 2.5 per cent, hydro- chloric acid (200 c.c. water and 20 c.c. hydrochloric acid, sp. gr. I.. 125) in a flask provided with a reflux condenser, cooled, neutralized with sodium carbonate, made up to 250 c.c., filtered, and the dextrose determined in an aliquot portion of the filtrate. The weight of dextrose multiplied by 0.9 gives the weight of starch. DIASTASE METHOD. 3 grams of the finely-powdered sub- stance are extracted on a hardened filter with five successive portions of 10 c.c. of ether, washed with 150 c.c. of a 10 per cent, alcohol, and then with a little strong alcohol. The residue is mixed in a beaker with 50 c.c. of water. The beaker is immersed in boiling water, the contents stirred constantly until all the starch is gelatinized, cooled to 55, and 30 c.c. of malt-extract added. The liquid is maintained at 55 until a microscopic examination of the residue shows no starch with iodin. It is cooled and made up directly to 250 c.c. and filtered. 200 c.c. of the filtrate are placed in a flask with 20 c.c. of a 25 per cent, solution of hydrochloric acid (sp. gr. 1.125), connected with a reflux condenser, and heated in boiling water for 2^/ 2 hours. It is nearly neutralized, while hot, with sodium, carbonate, made up to 500 c.c., mixed, poured through a dry filter, and the dextrose determined in an aliquot part. Convert the dextrose into starch by the factor 0.9. Preparation of Malt Extract. 10 grams of fresh, finely ground malt are macerated overnight at about 25 with 200 c.c. of water, filtered, the amount of dextrose in a given quantity of the filtrate after boiling with acid determined as in the starch determination, and the proper correction noted. If diastase be used, a correction will be unnecessary. A good' diastase is now easily obtainable. Commercial malt extracts are liable to be destitute of diastatic power. 9 98 FOOD ANALYSIS In the application of the diastatic method, the material must be ground very fine and the preliminary extraction with ether must not be omitted. In many cases it will be more convenient to make the extraction in the continuous extractor. If a large tube be used, several samples may be treated at once by tying each in filter-paper. The centrifugal apparatus may also be used. The fine material is shaken up with ether in the proper tubes, whirled for a short time, the ether poured off, fresh ether added and again whirled, and the operation re- peated until the necessary amount of solvent has been used. The liquid may be poured off closely each time. FLOURS AND MEALS Meal is coarsely ground, flour is finely ground material. Most of the forms used as foods are derived from plants be- longing to the order Graminece, but buckwheat, banana, and potato are not of this class. The distinction between the different flours and meals is based in part on the microscopic characters of the starches as indicated under that head, but chemical tests are in some cases available. The proteids of wheat flour have been studied by T. B. Osborne and E. B. Voorhees. The most important are gliadin and glutenin. Gliadin, which constitutes nearly half the proteid matter of the grain, is soluble in dilute alcohol. Glutenin is insoluble in water, dilute saline solutions, and dilute alcohol. Gluten is composed of gliadin and glutenin in nearly equal proportions. The gliadin forms the sticky substance of the gluten, while the glutenin imparts to it its solidity. Gluten can not well be formed from its constituents by the action of pure. water, as gliadin is quite soluble in that menstruum and thus is easily removed. The mineral salts of the wheat, however, form with distilled water a medium in which the gliadin is scarcely soluble, and under these circumstances the gluten is produced. The commercial value of wheat flour depends upon its STARCH 99 color and texture and upon quantity and quality of gluten. The latter differs much in different varieties and in the same variety grown in different localities. In whole- wheat flour containing about 10 per cent, of gluten the quantities of the chief proteids are about as follows : Globulin, 0.70 Albumin, 0.40 Proteose, O-3O Gliadin, 4.25 Glutenin, ' 4.35 Good wheat flour will yield from 20 to 40 per cent, moist gluten and 10 to 18 per cent, gluten dried at 100. Rye flour contains gliadin, but no glutenin. COMPOSITION OF CEREAL GRAINS WEIGHT OF IOO KERNELS IN GRAMS. MOIST- URE. 6.25 ETHER N. EXTRACT. CRUDE FIBER. ASH. CAR- BOHY- DRATES OTHER THAN CRUDE FIBER. Typical unhulled barley, 10.85 II. O 2.25 385 2.5 69-55 Typical American 38.0 10 75 IO.O 4.25 1.75 1.5 71.75 Typical wheat, . . . 3-85 10 6 12.25 1-75 2.4 1-75 71-25 Sweet corn, 19 sam- ples (Richardson), 8-44 11.48 8.57 2.82 1.97 66.72 Typical American buckwheat 3-0 12.0 10.75 2.0 10.75 1-75 62.75 Typical rye, .... 25 10-5 12.25 1.5 2.1 1.9 71-75 Typical unhulled oats, 3-0 IO.O 12. 4-5 I2.O 3-4 58.0 Tvpical rice, un- 'hulled, 3.0 10.5 7-5 1.6 9.O 4.0 67-4 Typical rice, hulled, but unpolished, . . 2-5 12.0 8.0 2.0 1.0 I.O 76.0 Typical rice, pol- ished . . 2.2 12-4 7-5 0.4 0.4 0.5 78.8 Typical rye 2-5 10.5 12.25 2.1 1.9 Typical wheat, . . . 3-85 10.6 12.25 1-75 2-4 i-75 71-25 A detailed description of the proteid and other constituents of cereal grains has been published by the United States De- partment of Agriculture. The annexed table has been taken 100 FOOD ANALYSIS from this. The proteids are calculated by multiplying the nitrogen by the factor 6.25, but the investigations by T. B. Osborne, R. H. Chittenden, and E. B. Voorhees indicate that the following factors would be better: Maize, 6.23 ; barley, rye, and wheat, each 5.68 ; oats, 6.10. The proteids of rice and buckwheat have not been fully studied. A recalculation of the proteids by corrected factors will change the proportions of the carbohydrates, since these were determined by difference. Wheat Flour. Good wheat flour is a fine white powder with a very faint yellow tinge. Several tests are recognized for its examination, among which are the following : Color Test. The sample may be compared with one of known quality by laying out heaps of equal size, say, 3 cm. by 8 cm., and 0.5 cm. deep. If this be done on a colorless glass plate, the examination may be made with both white and colored background, and the plate may subsequently be immersed in water (not over 35) so that the colors produced on wetting may also be observed. Dougking Test. This consists in making a dough with I 5 grams of the sample and 10 c.c. of water and comparing color, firmness, elasticity, and compactness. Gluten Test. 10 grams of the sample are mixed with suf- ficient water to make a stiff dough and allowed to stand for one hour. The mass is kneaded in a piece of linen in running water until the washings are clear. The fresh gluten thus obtained should have a faint yellow tinge, be tough and of such consistency that it can be pulled out into threads. Gray and red glutens indicate inferior samples. Good gluten swells at 150 and assumes the appearance of bread. ADULTERATIONS. Flour may be mixed with mineral matters to increase weight, with alum or copper sulfate to improve its appearance, or with cheaper flours or starches. It may also contain seeds of weeds, may be damp or decom- posed, or may contain fungi. STARCH 101 In examining for these adulterations, determinations of ash, crude fiber, ether extract, and total nitrogen are of consider- able value. The following table gives some data on these points, but the limits must not be rigidly interpreted. The figures, except the first column, have been calculated on the water-free substance : COMPOSITION OF FLOURS MOISTURE. Max. Min. ASH. Max. Min. 6.25 N. Max. Min. FIBER. Max. Min. ETHER EXTRACT. Max. Min. N-FREE EXTRACT. Max. Min. Wheat, . . . Rye Barlev 15.0 9.0 I4.O 12.0 15 o 10 o 0.8 0.3 i-5 0.5 20 i o 15.0 8.0 u.o 6.0 12 O 85 I.O O.I 0.6 0.4 06 03 2.0 0.5 i.o 0.9 2O O5 90.0 82.0 92.0 88.0 92 o 87 o Buckwheat, Rice .... 18.0 12.5 15.0 10 o 1.5 0.8 o 6 0.3 9-5 5-0 10 o 70 0.6 0.3 04 o i 2.0 0.8 06 03 93.0 84.0 90 o 85 o Oat (meal), . Maize (meal), Graham, . . . 10.0 6.0 18.0 8.0 15.0 u.o 2.4 2.0 4-5 i-o 2.2 1.8 18.0 14.0 11.5 8.0 15.0 10.0 1.4 0.7 3-5 0.7 2.4 2.O 9-5 6.5 6.0 2.5 2.2 1.9 76.0 72.0 80.0 63.0 72.0 70.0 ALUM. Logwood Method. An alkaline solution of logwood is pre- pared as follows : Haifa gram of fine logwood chips, preferably freshly cut from the log, is macerated for 10 hours in 1 5 c.c. of alcohol ; 10 c.c. of the solution are poured off and mixed with 150 c.c. of water and 10 c.c. of a saturated solution of am- monium carbonate. To make the test, 50 grams of the flour are made into a thin paste with water, a few drops of the log- wood solution (freshly prepared) added, and the mixture allowed to stand several hours. Alum produces a lavender- blue lake. Cliloroform Method. 200 grams of flour are shaken in a separatory funnel with a sufficient amount of chloroform, allowed to stand overnight, and the materials which subside carefully removed through the stopcock. This material may be further purified by shaking a second time with a little chlo- roform and then transferred to a watch-glass and the chloro- IO2 FOOD ANALYSIS form evaporated. The residue is treated with water, the solu- tion separated from the insoluble portion and allowed to evaporate, when the crystals of alum will be observed. The crystals may be dissolved in water and tested for sulfates, aluminum, potassium, and ammonium. The residue insoluble in water should be examined under the microscope for mineral matters. The steps in the treatment of the residue insoluble in chloroform will be assisted by the use of a centrifuge. Copper sulfate can be detected by the ferrocyanid method as described under BREAD. Ergot in Rye Flour. A preliminary test may be made to determine if the flour has been damaged by fungi. Vogel advises that the sample be stained with anilin violet and exam- ined with the microscope. Any starch granules that have been injured by fungus will be deeply stained. M. Gruber's test : A little of the flour is moistened with water on a microscope-slide, a cover-glass placed on, and the mass heated to the boiling-point on a hot plate or water-bath. After cooling it is examined with a power of 1 20 diameters. Ergot will be recognized by its high refracting power, furrows, and color deep violet on the edge, greenish-yellow within. A second examination with a power of about 300 diameters will enable any doubtful particles to be recognized. Chemical Tests. 20 grams of the sample are digested with boiling alcohol as long as any color is extracted. The solu- tion is treated with I c.c. of sulfuric acid (i 13). In the presence of ergot the solution will be red, and if it be diluted with a large volume of water, the color may be extracted from separate portions by means of chloroform, ether, petro- leum spirit, or amyl alcohol. 10 grams of the sample are macerated for about 30 minutes with a mixture of 20 c.c. of ether and 10 drops of dilute sulfuric acid (i 15); the liquid filtered, washed with ether until the filtrate amounts to 1 5 c.c. This is shaken with 5 STARCH IO3 drops of a saturated solution of sodium bicarbonate. The chlorophyl remains in the ether ; the sodium bicarbonate so- lution remains clear if the flour be from sound grain, but takes on a deep violet color if ergot be present. A. Miller examined a sample of flour containing not more than o. i per cent, of ergot, which imparted to the alcoholic extract a clear rose coloration as pronounced as if the propor- tion had been I per cent. The flour contained bluish-green particles of husk of unknown origin, which assumed a red- dish tint on treatment with acidulated alcohol, and imparted the same color to the alcoholic extract. The difference in shade between the color produced by this flour and one con- taining ergot was only distinguishable in concentrated solu- tions, when the former was rose-red, the latter brick-red. Mixed Flours. The following data are taken, with but few changes, from the contributions of Bigelow and Sweetser and Kraemer : Gluten obtained from a mixture of wheat and rye flours is dark and viscous, without homogeneity ; from a mixture of wheat and barley flours, dark, non-viscous, and dirty reddish- brown ; from a mixture of wheat and oats, dark yellow ; from a mixture of wheat and maize, yellowish and non-elastic ; from a mixture of wheat and leguminous flour it varies from a grayish-red, in the case of vetch or beans, to green, in the case of peas, and has the characteristic odor and taste of leguminous products. The ash of leguminous flour is deli- quescent, high in chlorids, and turns turmeric paper brown ; cereal ash is the reverse. The aqueous extract of the legu- minous flour is acid ; that of cereal flour is faintly alkaline. If the filtrate from the gluten determination of flour contain- ing leguminous flour be made alkaline with ammonium hy- droxid, allowed to stand overnight, and the clear liquid de- canted, dilute sulfuric acid will precipitate legumin. IO4 FOOD ANALYSIS For the detection of potato flour a portion of the sample is rubbed in a mortar until a stiff paste is obtained, thinned with more water, filtered, and the clear filtrate tested with a drop of a dilute solution of iodin. Potato flour produces a deep blue, while with pure wheat flour the result is yellow or light orange. If a mixture of cereal and potato flours be dried, spread in a thin layer on a glazed black surface, and examined with a lens, the potato is indicated by bright and glassy par- ticles in the otherwise dull white substance. Vogel extracts the flour with 70 per cent, of alcohol, to which 5 per cent, of hydrochloric acid has been added. The extract is colorless if the flour consist only of wheat or rye, pale yellow if adulterated with barley or oats, orange yellow with pea flour, purple red if made from mildewed wheat, and blood red if made from ergotized wheat. Rice in Buckwheat Flour. When pure buckwheat is mixed with water into a thin paste, the addition of calcium hydroxid produces a dark green, which becomes red when acidified with hydrochloric acid. Rice flour gives a yellow color with potas- sium hydroxid and white with hydrochloric acid. A mixture of buckwheat and rice flours made into paste is changed to a light green color by potassium hydroxid and becomes flesh- colored when acidified with hydrochloric acid. Wheat in Rye Flour. A. Kleeburg has advised the follow- ing test : A pinch of the sample is mixed on a small glass plate (a microscope-slide will serve) with water at about 45 in sufficient quantity that the particles of flour still float. The mixture is spread over a considerable part of the glass and a similar glass laid upon it so that about one-fourth of each glass protrudes at the ends. The two glasses are pressed together, the exuded liquid wiped off, and the glasses rubbed on each other several times. If wheat flour be present, white spots will be observed, which will form threads on being rolled ; these are short and thin if the proportion of wheat be STARCH IO5 small, and thicker and longer with larger amounts. An ad- mixture of 5 per cent, of wheat flour with rye is said to be thus recognizable. Maize in Wheat Flour. H. Kraemer has devised the follow- ing test, which, he states, will detect 5 per cent, of maize in wheat flour : I gram of the sample is mixed with I 5 c.c. of good glycerol and heated to boiling for a few minutes. An odor recalling that of popcorn indicates maize. It is alleged that cheap flours have been adulterated with sawdust. G. A. Le Roy applied the following test for detect- ing this addition : A small amount of the sample is gently warmed with the acid solution of phloroglucol (page 35). Ordinary wood-fiber quickly acquires a bright red tint, while bran particles are but slightly affected. BREAD Bread is made by baking the mass obtained by kneading flour with water. This gives the so-called unleavened bread, but it is usual to add a little common salt to the water and make the dough light by inflating it with carbon dioxid. This may be done by the use of baking powder, or by mixing the flour with water containing carbonic acid under pressure (aer- ated bread), but commonly yeast is added to the dough and the mixture, called the " sponge," allowed to stand for some hours and then baked. The slight fermentation which occurs liberates carbon dioxid. The chemical composition of bread is approximately that of the flour from which it is made. The moisture usually ranges from 30 to 40 per cent., and will depend, among other condi- tions, upon the quantity and quality of the gluten, and the size and shape of the loaf. On the size and shape will also depend the relative proportion of crust to crumb, the latter containing about twice as much moisture as the former. The addition of potato flour or rice flour will enable a bread to be 10 io6 FOOD ANALYSIS prepared containing a much larger proportion of water than usual. The addition of about I per cent, of mashed potatoes to the dough is said to render the bread white without any notable increase in the amount of moisture retained. The proportion of fat in bread, as determined by the ether extract, is apt to be less than that of the original flour, owing to decomposition of the fat in the crust, by heat, and also to the inclosure of the fat particles in such a way as to render them difficult of extraction. On the other hand, the propor- tion of fatty matter may be increased by the use of milk or by the material used to grease the pans. When bread is raised by yeast, some solid matter is lost by the fermentation. According to Lawes and Gilbert, this is prob- ably less than ^ of I per cent., and appears to be due to the decomposition of the sugar. The unchanged starch is not appreciably altered during the short time that the yeast acts. The ash of bread will be higher than that of the flour if salt or baking powder has been added. ORIG- INAL SUB- IN THE DRY SUBSTANCE. STANCE Carbo- Moist- ure. Pro- teids, NX Ether Ex- tract. Crude Fiber. Ash. Salt. hy- drates. exclud- 5-70. ing Fiber. Vienna, average of 10 sam- ples. ?g 71 13 21 I Tl O Q7 I Q$ O Q3 8^ I Home-made, average of 2 y*' i J'^O * 1 3 * yl yy vy ' yj W O samples, 33-02 10.8 2. 9 I 0.36 i-55 0.84 84.75 Graham, average of 9 sam- ples \A g 12 ci 3 13 I 74. 2.2Q I. O7 82.06 Rye, average of 7 samples, oH- >,+y 2-79 w^ 1.5 84.36 Quaker, average of 3 sam- ples, 36.16 11.17 !-75 0.41 1.68 0.92 85.41 Miscellaneous, average of 9 samples, ..... 34-41 10.59 2.21 0.46 i-53 0.76 85.66 BREAD ID/ The table on page 106 represents the average composition of various breads of commerce according to analyses made in the laboratory of the United States Department of Agricul- ture. The loaves weighed approximately one pound each. Trade names are given in most cases. ADULTERATIONS. These may consist in the use of damaged flour, of flours other than that purporting to be present, presence of excess of water, or addition of alum or copper sulfate to improve appearance. ALUM. ^The bread is moistened with water and some of the alkaline logwood solution (see p. 101). If alum be present, the bread will become lavender-blue in an hour or two. Pure bread assumes a light red-brown tint. The blue color, however, is not proof of the presence of alum unless it is permanent at the temperature of boiling water. Blyth's test for alum is as follows : 1 50 grams of the material are macerated for two days in 2 liters of water. The solution is strained through muslin and evaporated at a gentle heat to small volume ; a strip of gelatin immersed in this liquid, and then in the alkaline logwood solution, will acquire the laven- der color if alum is present to the extent of 0.03 per cent. These tests are not applicable to sour bread. J. Vander- planken recommends the following modification to meet the difficulty : I 5 grams of the sample are triturated to a paste with water and some pure sodium chlorid and 10 drops of a freshly-prepared solution of logwood in alcohol, and then 5 grams of pure potassium carbonate are added. The mass is well mixed, washed with 100 c.c. of water into a beaker, and is allowed to settle. In a few minutes the liquid becomes reddish-violet if alum is absent, grayish-blue to deep blue when it is present. The quantitative estimation of the alum is made as follows : The ash from 100 grams or more of the bread is boiled with hydrochloric acid and the solution filtered. The filtrate is 108 FOOD ANALYSIS boiled and added to a concentrated solution of sodium hy- droxid, the mixture being again boiled and filtered while hot. A little disodium acid phosphate is added to the filtrate, which is then slightly acidulated with hydrochloric acid and finally made feebly alkaline by addition of ammonium hydroxid. The precipitate of aluminum phosphate is filtered, washed, ignited, and weighed. Flour contains a small proportion of aluminum, which, in the ash, is probably in the form of silicate. The amount of silica is approximately equal to that of alum equiva- lent to the aluminum normally present. It is the practice, therefore, to determine the silica and subtract it from the amount of alum calculated from the aluminum phosphate found. The remainder, multiplied by 4.48 or 3.73, will give the potassium alum or ammonium alum respectively. Copper sulfate may be detected by the brown produced when a thin slice of bread is immersed in a dilute solution of potassium ferrocyanid. Foreign flours may be sought for by the microscope, but the starch granules are often so altered by heat as to render their identification impossible. The following adulterants are said to be employed abroad, but their use does not appear to have been attempted in this country : Soap is said to be used to render the bread light and soft. It is said to be added in solution containing emulsified oil. Terra alba and gypsum have been found ; they are readily detected in the ash. Stannous chlorid is a common constituent of ginger cake, to which it is added, with potassium carbonate, in order. to give the product the color ordinarily produced by honey or mo- lasses. It is said to render a product made of poor flour and molasses of the same color as that produced by a good flour and honey. Tin may be detected as described on page 69. LEAVENING MATERIALS LEAVENING MATERIALS The yeast cakes sold for leavening purposes are usually mixtures of common yeast with potato starch. The study of yeast is practically limited to those connected with the fermentation industries. Cream of tartar and baking soda are commonly employed as leavening agents. Baking Soda, Sodium Acid Carbonate, is not subject to serious adulteration. Cream of Tartar, Acid Potassium Tartrate, is frequently adulterated with starch, alum, acid calcium phosphate, calcium sulfate, and potassium acid sulfate. Many samples will be found to contain no tartrate, but merely a mixture of starch, calcium phosphate, and alum. A. H. Allen has devised the following method for the ex- amination of commercial cream of tartar : 1. 88 1 grams of the dried material are dissolved in hot water and titrated with * sodium hydroxid arid phenolphthalein. If tartaric acid and acid sulfates are not present, each c.c. will represent I per cent, of acid potassium tartrate. i. 88 1 grams of dried material are ignited for 10 minutes, the residue boiled with water, filtered, and washed. The filtrate is titrated with ^ hydrochloric acid and methyl-orange. With pure tartrate the amount of acid consumed will be the same as that of the alkali in the first experiment. Each cubic centimeter of deficiency is equivalent to 0.36 per cent. calcium sulfate, or 0.72 per cent, acid potassium sulfate. If the amount of acid be more than equivalent to that of the alkali used in the former experiment, it suggests the presence of neutral tartrate, each cubic centimeter of excess represent- ing 0.6 per cent, thereof. The amount of sulfate can be de- termined by precipitating with barium chlorid in the usual way. The residue is ignited, dissolved in 20 c.c. of io acid, filtered I 10 FOOD ANALYSIS from any insoluble residue, and the filtrate titrated with ^ alkali. Each c.c. corresponds to 0.5 per cent, of calcium tartrate, or 0.36 per cent, of anhydrous calcium sulfate. The cream of tartar substitutes commonly sold contain starch, alum, and calcium phosphate. The presence of starch FIG. 37. and its source can easily be determined by the iodin test and microscopic examination. Quantitative examination of such samples will be conducted as described under " Baking Pow- ders." Baking Powders. These contain acid sodium carbonate, some acid salt, e. g., acid potassium tartrate, acid calcium LEAVENING MATERIALS 1 1 i phosphate, or alum, with inert material, starch or flour, to prevent caking. Many powders contain both alum and acid calcium phosphate. The following methods for examining baking powders were published by C. A. Crampton : 1 2 The value of baking powder depends on the gas liberated when it is mixed with water. The determination may be made by the apparatus arranged by A. E. Knorr. 13 (Fig. 37.) The flask A holds the weighed portion of sample. The condenser D, attached by a ground joint, serves to condense the steam formed when the liquid in A is boiled. ~B contains either recently-boiled water or dilute sulfuric acid, according to whether the available carbon dioxid or total carbonates are to be determined. It has a soda-lime .tube attached by a ground-joint to pre- vent admission of carbon dioxid from the current of air which is drawn through the apparatus during the operation. The junction of this portion with the flask should be by ground or fused joint. The evolved gas is dried in E by sulfuric acid and absorbed in F. Available carbon dioxid, which gives the leavening power, is determined as follows : The flask A is dried thoroughly, a weighing tube is charged with about 2 grams of the powder, accurately weighed, the contents emptied into the flask, and the tube weighed again. The exact amount of powder taken is thus known. Recently-boiled water is put into B, the apparatus connected tightly, and the water allowed to flow in slowly from B, the aspirator attached to G being put in operation. When the effervescence in A has ceased, the liquid in it is boiled for a few seconds, the lamp removed, and aspiration through G continued for 15 minutes. The absorption apparatus F is weighed, and the increase represents carbon dioxid. Total carbonates are determined by substi- tuting 10 c.c. dilute sulfuric acid for the water in B. Starch. 5 grams are mixed in a flask with 200 c.c. of I 12 FOOD ANALYSIS 4 per cent, hydrochloric acid. A condensing tube about I meter long is attached by means of a cork (an inverted con- denser may be used) and the liquid boiled for 4 hours. The contents are cooled, rendered slightly alkaline by sodium hy- droxid, and the dextrose determined as given under " Sugars," and multiplied by 0.9. For powders not containing appreciable amounts of alum, direct washing with water, and drying the residue, will often give determinations of sufficient accuracy. Since the residual liquid in properly-made baking powders is alkaline, due to slight excess of baking powder, the diastase method for starch may be applicable. The liquid should be filtered and the insoluble residue well washed. The aluminum hydroxid may interfere with this method. If flour be used as filler, which may be ascertained by inspection, the starch found may be roughly calculated to flour by the tables on page 99. Aluminum and Phosphates. K. P. McElroy 1 4 devised the following method : 5 grams are charred in a platinum basin, mixed with strong nitric acid, and filtered into a 500 c.c. flask. The residue is washed slightly, the filter and residue returned to the basin, burned to whiteness, mixed with sodium carbon- ate, fused, and cooled. Nitric acid is added, the liquid evapo- rated to dryness, again acidified with nitric acid, and the whole mass washed into the 500 c.c. flask. The liquid is made up to the mark and filtered through a dry filter, 100 c.c. of the filtrate are nearly neutralized with ammonium hydroxid, am- monium nitrate and ammonium molybdate solution added, the mass digested at a low heat for a few hours, and filtered. The filtrate contains the aluminum, which may be precipitated as hydroxid by adding ammonium hydroxid. The precipitate is dissolved in ammonium hydroxid and the phosphate deter- mined in the usual way. Calcium. 5 grams are mixed in a 500 c.c. flask with 50 c.c. of water and 30 c.c. of strong hydrochloric acid, the SUGARS I I 3 mixture made up to the mark, shaken well, and allowed to settle. 50 c.c. are collected through a dry filter, nearly neu- tralized by ammonium hydroxid, acetic acid added in small amount, then ammonium acetate, and the liquid boiled. If any precipitate forms it should be removed. The clear liquid is precipitated by ammonium oxalate. Sulfates. 0.5 gram of the sample are digested with strong hydrochloric acid until everything has dissolved, the liquid is diluted considerably, brought to boiling, and precipitated with barium chlorid, taking care not to use a large excess. The precipitate is weighed in the usual manner. Ammonium Compounds, These may be determined by the Kjeldahl-Gunning method applied to the water filtered from a known weight of the powder. The best commercial baking powders yield about 12 per cent, by weight of gas. 10 grams would, therefore, yield 1.2 grams, occupying at ordinary temperature about 600 c.c., which will be much increased in baking. Many powders yield much less gas. SUGARS Detection. Most of the tests for sugars depend on their reducing effect, except the phenylhydrazin, fermentation, and optic tests. Su- crose possesses less reducing action than other common sugars, does not give any precipitate with phenylhydrazin, and is not directly fermentable. By the action of dilute acids or inver- tase (yeast-enzym) it is converted into equal parts of dextrose and levulose, a change commonly termed " inversion," the mix- ture being known as "invert-sugar." This responds to all the above tests. Cobalt Nitrate Test. Wiley has experimented with this method and has obtained satisfactory results. He describes it as follows : 114 FOOD ANALYSIS 5 c.c. of a 5 per cent, solution of cobaltous nitrate are well mixed with 15 c.c. of sugar solution, and 2 c.c. of a 50 per cent, solution of sodium hydroxid added. Sucrose gives an amethyst-violet solution, which is made somewhat more blue by boiling, but regains its color on cooling. Dextrose gives a turquoise-blue, which in the course of two hours passes into a pale green. A slight flocculent precipitate is noticed in the tube containing dextrose. Maltose and lactose act very much as dextrose, but in the end do not give so fine a green color. If the solution containing dextrose, lactose, or maltose be boiled, the original color is destroyed and a yellow-green color takes its place. In mixtures of dextrose and sucrose the sucrose coloration predominates one part of sucrose in nine parts of dextrose can be distinguished. Impurities such as gum arabic or dextrin should be removed by alcohol or lead subacetate before the application of the test. Dextrin may also be thrown out by treatment of the solution with barium hydroxid and ammoniacal lead acetate. The reaction may be applied to the detection of cane-sugar in wines after they are thoroughly decolorized by means of lead acetate and bone-black. Sucrose may be detected in fresh or condensed milk after the disturbing matters have been thrown out by lead acetate. Sucrose may be detected in honey. Phenylhydrazin Test. Phenylhydrazin hydrochlorid is usu- ally employed. The commercial article is often contaminated with anilin hydrochlorid. It may be purified by solution in hot water, precipitation by strong hydrochloric acid, and recrys- tallization from hot water. For the test, o. I gram of the sample, about 0.2 gram phenyl- hydrazin hydrochlorid, and 0.3 gram of sodium acetate are dissolved in 5 c.c. of water and heated on the water-bath for some time. Sucrose forms no precipitate, but with many sugars crystalline compounds called osazones separate. Dextrosazone and levulosasone have similar properties, crys- SUGARS I I 5 tallizing in needles melting at 204 205. They reduce Fehl- ing's solution, and when dissolved in acetic acid are slightly levorotatory. Maltosazone crystallizes in tables, which melt, with decom- position, at 206. It is levorotatory. Lactosazone crystallizes in prisms of melting-point 200. Sucrose forms no osazone. After inversion it yields a mix- ture of dextrosazone and levulosazone. Lactose, after boiling with sulfuric acid, yields a mixture of dextrosazone and galactosazone. The latter is distinguished by its melting-point, 193, from dextrosazone. Starch and dextrin, after hydrolysis, yield dextrosazone and maltosazone. The application of these reactions to the quantitative deter- mination of sugars has met with partial success. Determination. . The preparation of sucrose for use as a standard in polar- imetry and reduction-tests has been the subject of formal action at the third session of the International Commission for Uni- form Methods of Sugar Analysis, Paris, July 24, IQOO. 15 Purest commercial sugar is selected and dissolved by satu- ration in hot water, and ethyl alcohol added sufficient to pre- cipitate the sugar. The precipitate is whirled in a centrifuge and washed with alcohol. The material obtained is put through the whole process a second time, and the washed material is dried on pure bibulous paper and kept in stoppered glass ves- sels. It still contains moisture, which must be determined and allowed for in making standard solutions. The temperature of the water is not given. Blotting-paper is mentioned in the text, but folds of pure filter-paper seem best, as commercial blotting-paper is of uncertain composition. For the standardization of solutions for the determination of sucrose and invert-sugar, 2.5 grams of pure sucrose should Il6 FOOD ANALYSIS be dissolved in a mixture of 75 c.c. of water and 5 c.c. of hydrochloric acid (sp. gr. 1.188 at 15), inverted according to the method on page 1 24, the acid neutralized with sodium carbonate, and the solution diluted to one liter. 2.5 grams of sucrose yield 2.6316 grams of invert-sugar. The number of cubic centimeters of sugar solution used, multiplied by 0.00263, will give the weight of invert-sugar required to re- duce completely 10 c.c. of the test solution under the con- ditions of the experiment. CHEMICAL METHODS. The following standard reagents are generally employed : SOXHLET'S MODIFIED COPPER SOLUTION (A. o. A. c.). Copper sulfate solution. 34.639 grams of pure crystallized copper sulfate are dissolved in sufficient water to make 500 c.c. Alkaline tartrate solution. 173 grams of pure potassium sodium tartrate and 50 grams of sodium hydroxid are dis- solved in sufficient water to make 100 c.c. A convenient method is to use 100 c.c. of a solution containing 500 grams of sodium hydroxid in one liter. Potassium acid tartrate, now obtainable of very good quality, may be used instead of potas- sium sodium tartrate, in which case the proportion required will be 133 grams of potassium acid tartrate and 80 grams of sodium hydroxid made up to 500 c.c. The copper and alka- line tartrate solutions must be kept separate in well-stoppered bottles and mixed only when needed. APPROXIMATE VOLUMETRIC METHOD FOR RAPID WORK. 5 c.c. of each of the solutions are placed in a large test-tube, 10 c.c. of distilled water added, the liquid heated to 'boiling, and small portions of the solution to be tested gradually added until the copper has been completely precipitated, boiling to complete the reaction after each addition. When the end reaction is nearly reached and the amount of sugar solution can no longer be judged by the color of the solution, a small SUGARS 117 portion of the liquid is removed by means of a filtering-tube, placed in a porcelain crucible or on a testing plate, acidified with dilute acetic acid, and tested for copper by solution of potassium ferrocyanid. The sugar solution should be of such strength as will require from 15 to 20 c.c. to complete the reduction, and the number of additions of solution should be as few as possible. It is best to verify the first experiment by a second, based on the approximation which the first gives. Boiling for 2 minutes should be required for complete precipitation when the full amount of sugar solution has been added in one portion. The factor for calculation varies with the minute details of manipulation ; every operator must determine the individual factor by using a known amount of the form of sugar that is to be determined and maintaining conditions as uniform as pos- sible. Figure 38 shows filter-tubes suitable for obtaining a small quantity of the liquid. Wiley's tube (A) is a thick-walled glass tube about 4 cm. long on one of which a flange has been made, over which a piece of fine linen is tied. Knorr's tube (B) is much nar- rower, and has a perforated platinum disk sealed into the lower end. The tube is dipped into water containing suspended asbestos, and by aspiration a thin felt is formed over the lower surface of the platinum disk. The tube, thus prepared, is dipped into the boiling copper solution and by aspiration a drop is drawn into the tube. The Wiley filter requires that the liquid be poured from the tube when it is to be tested, but with the Knorr tube the asbestos is wiped off, the liquid expelled through the platinum, and the drop is tested for copper as noted. FIG. 38. I 1 8 FOOD ANALYSIS Another method is to remove a drop of the boiling solution by means of a rod and place it on a piece of pure filter-paper. The precipitate remains in the center of the moistened spot. A drop of potassium ferrocyanid solution, acidulated with acetic acid, is then placed near it ; as the spot spreads, a brown stain will appear where the liquids meet, if copper still be in solution. POTASSIUM COPPER CYANID METHOD. This method, devised by Gerrard, has been investigated by A. H. Allen, who has pointed out the conditions necessary to insure accuracy, and regards it as superior to other reduction methods. When potassium cyanid is added in sufficient amount to copper sulfate, a potassium copper cyanid is formed. This compound is not decomposed by sodium hydroxid or hydrogen sulfid. By operating on a solution containing an excess of copper sulfate, the reduction will take place with this excess only, and the end of the reaction is indicated by the disappearance of the blue tint of the liquid. The cuprous oxid remains in solution, but as it reoxidizes very slowly, a brief exposure to air does not interfere so much as in some other methods. The following description is con- densed from A. H. Allen's " Chemistry of Urine " : 5 c.c. of each of the solutions described on page 116 are accurately measured into a porcelain basin, 40 c.c. of water added, the liquid heated to boiling and maintained so during the entire manipulation. A solution of potassium cyanid (5 grams in 100 c.c. of water) is added gradually until only a tinge of blue remains. An excess of cyanid must be avoided. Additional measures of 5 c.c. each of the copper sulfate and alkaline tartrate solutions are now added, and when the liquid begins to boil the solution of sugar to be tested is dropped in rapidly. The end reaction is sharp when pure solutions ot sugar are used. The amount of reagent used is decolorized by 0.05 gram of invert-sugar corresponding to 0.0475 su- crose. SUGARS 119 The potassium cyanid must be of good quality ; the com- mercial article contains cyanate, carbonate, and sodium com- pounds. The solution of potassium copper cyanid keeps for some weeks ; hence if several determinations are to be made, a small stock of solution may be prepared by using ten times the amounts directed above, adding 300 c.c. of water, decol- orizing with potassium cyanid at the boiling-point, and dilut- ing the liquid to 500 c.c. when cold. 50 c.c. of this liquid are mixed with 5 c.c. each of the reagent solutions and the titration proceeded with. SOXH LET'S EXACT METHOD. An approximate determination of the reducing sugars in the sample is made by one of the titration methods and a solution is prepared which contains nearly, but not more than, 1 per cent, of these sugars. 50 c.c. of copper sulfate solution and 50 c.c. of alkaline tartrate solution are mixed, added to a volume of the solution of the sample estimated to be suffi- cient for the complete precipitation of the copper, boiled for 2 minutes, some of the solution filtered rapidly, and the filtrate tested for copper. The process is repeated until two proportions of the solution of the sample are determined which differ by o. I c.c., one giving complete reduction and the other leaving a small amount of copper in solution. The mean of these volumes is the amount of solution required for the volume of Fehling's solution taken. Under these conditions, which must be rigidly observed, the volume of solution used will contain 0.475 gram of dextrose or 0.494 gram of invert-sugar. As the weight of the sample which is in this amount of solution is known, the percentage of either sugar may be calculated by simple proportion. ALLIHN'S METHOD FOR DEXTROSE. Copper sulfate solution. 34.639 grams of pure crystallized copper sulfate are dissolved in water and made up to 500 c.c. Alkaline tartrate solution. 173 grams of pure potassium 120 FOOD ANALYSIS sodium tartrate and 125 grams of potassium hydroxid are dissolved in water and made up to 500 c.c. The substance to be tested is dissolved in water in such proportion that the solution shall not contain more than I per cent, of dextrose. 30 c.c. of each of the reagent solutions and 60 c.c. of water are mixed and heated to boiling, 25 c.c. of the solution to be examined are added, the boiling con- tinued for 2 minutes, and the liquid immediately filtered with- out dilution, as directed in connection with the reduction or electrolytic methods of determination of copper. The precipitated cuprous oxid is usually converted into free copper and weighed as such. Two methods may be employed for re- duction : by hydrogen or by electrolysis. Reduction by Hydrogen. The cuprous oxid is collected on an asbestos filter. This is ar- ranged most conveniently in a special filtering tube, which is shown in figure 38 a. The wider part is about 8 cm. long and 1.5 cm. in diameter, the narrower portion about 5 cm. long and 0.5 cm. in caliber. A perforated platinum disk is sealed in just above the point FIG! 38 a. f narrowing. The asbestos is placed on this disk, washed free from loose fibers, dried well and the tube weighed. The filtering tube is attached to an exhaustion apparatus by passing narrower portion through the cork, and a small funnel is fitted tightly in the top of the tube. The object of this funnel is to prevent the precipitate -collect- ing on the upper part of the tube. The lower end of the funnel should project several centimeters below the bottom of the cork through which it passes. The filtering apparatus must be arranged prior to the pre- cipitation, so that the cuprous oxid may be filtered without delay. The precipitate is transferred as rapidly as possible SUGARS 121 to the filter, well washed with hot water, alcohol, and ether successively, dried, and the cuprous oxid reduced by gentle heating in a current of dry hydrogen. When the reduction is complete, the heat is withdrawn, but the flow of hydrogen is continued until the tube is cold. It is then detached and weighed. The amount of sugar is determined by reference to the following table. Quantities of copper intermediate between those given in the table may be converted into the equivalent in sugar by allowing for each o.ooi of copper, 0.0005 of dextrose for figures in the first column, 0.00055 for figures in the second column, and 0.0006 in the third column. EQUIVALENTS FOR ALLIHN'S METHOD COPPER. DEXTROSE. COPPER. DEXTROSE. COPPER. DEXTROSE. q.oio 0.0061 0.170 0.0869 0.330 0.1731 0.020 O.OIIO 0.180 0.0921 0.340 0.1787 0.030 0.0160 0.190 0.0973 0.350 0.1843 0.040 0.0209 0.200 o. 1026 0.360 0.1900 0.050 0.0259 0.210 0.1079 0.370 0.1957 0.060 0.0308 0.220 0.1132 0.380 0.2014 0.070 0.0358 0.230 0.1185 0.390 0.2071 0.080 0.0408 0.240 0.1239 0.400 0.2129 0.090 0.0459 0.250 0.1292 0.410 0.2187 o. 100 0.0509 0.260 0.1346 0.420 0.2245 o. no 0.0560 0.270 o. 1400 0.430 0.2304 O. I 2O 0.0611 0.280 0-1455 0.440 0.2363 0.130 0.0662 0.290 0.1510 0.450 0.2422 0.140 0.0713 0.300 0.1565 0.460 0.2481 o. 150 0.0765 0.310 0.1620 0.463 0.2499 o. 1 60 0.0817 0.320 0.1675 0.465 0.2511 Reduction of Copper by Electrolysis. The filtration is per- formed in a Gooch crucible with an asbestos-felt film and the beaker in which the precipitation was made is well washed with hot water, the washings being passed through the filter, but it is not necessary to transfer all the precipitate. When the asbestos film is completely washed, it is transferred with the adhering oxid to the beaker ; any oxid remaining in the 1 1 122 FOOD ANALYSIS crucible is washed into the beaker by use of 2 c.c. nitric acid (sp. gr. 1.42), added with a pipet. The crucible is rinsed with a spray of water, the rinsings being collected in the beaker. The liquid is heated until all the copper is in solu- tion, filtered, the filter washed until the filtrate amounts to at least 100 c.c., and electrolyzed. FIG. 39. Electrolytic apparatus has been constructed in a great variety of forms. When the operation is carried out frequently, it is best to have an electrolytic table. A platinum basin holding not less than 100 c.c. is used. A cylindrical form with flat bottom is convenient. It should rest on a bright copper plate, which is connected with the negative pole of the electrical SUGARS 123 supply. The positive pole should be also platinum, either a spiral wire, cylinder, or flat foil. Many operators use a funnel- shaped perforated terminal for the negative pole ; as shown in figure 39. In this case a beaker or casserole will be a suitable container, the positive terminal being placed within the negative. Four cells of a gravity battery will suffice for a single de- composition, and will operate two, but more slowly. It is usual to arrange the apparatus so that the operation may be continued during the night. When the electricity is taken from the general supply of the laboratory, it is usually neces- sary to interpose resistance and to have some means of meas- uring the current-flow. This is sometimes done with a gas evolution cell and incandescent lamp, but an ammeter and adjustable rheostat is better. (See page 66.) OPTIC METHODS. The general principles of polarimetry have been explained elsewhere. For the decolorization and clarification of solu- tions, the following standard reagents are employed : Lead subacetate. Solution of lead acetate is boiled with excess of lead monoxid for 30 minutes, filtered, and brought to a specific gravity of 1.250. Solid lead subacetate may be used in preparing the solution. Alumina- cream. A cold saturated solution of alum is divided into two unequal portions ; a slight excess of ammo- nium hydroxid is added to the larger portion and the remain- der is added until a faintly acid reaction is obtained. For sugars and molasses the normal weight for the instrument is weighed out, washed into a 100 c.c. flask, and water added to make about 80 c.c. When the material has dissolved as far as possible, lead subacetate is added until all precipitable matter has separated. (With mo- lasses sufficient acetic acid should be added to convert the lead subacetate into acetate.) The flask is filled to the mark, 124 FOOD ANALYSIS using, if necessary, a little ether spray to break bubbles, the solution filtered with a dry filter, the first 1 5 c.c. re- jected, and the reading taken on the remainder of the filtrate. If the liquid is very dark, some dry finely-powdered pure bone-black should be used instead of paper and the first 40 c.c. of filtrate rejected. All observations should be made as nearly as possible at the temperature for which the instrument is adjusted. A change of 5 in the interval between filling the flask and making the reading will cause, by change of volume, an error of about o. I per cent, in samples containing 90 per cent, of sucrose and an error of about 0.5 per cent, in samples containing 50 per cent, of sucrose. With juices or other dilute materials, weighing may be omitted, and 100 c.c. of the sample placed in a flask marked IOO c.c. and 1 10 c.c., the clarifying reagents added, the flask filled to the 110 c.c. mark, filtered as above,' and a reading taken. The following formula may be employed for calcu- lating results : Percentage of sucrose = l ' 1 X readi "g on su E ar scale x normal weight for instrument 100 X specific gravity of sample A. O. A. C. INVERSION METHOD. A clear solution is made according to one of the methods given above. 50 c.c. of the filtrate are placed in a flask marked at 50 and 55 c.c., 5 c.c. of pure fuming hydrochloric acid added, and the liquids well mixed. The flask is heated in water until the thermometer, with the bulb as near the center of the solution as possible, marks 68. About 15 minutes should be required for this heating. The flask 'is then removed, cooled quickly to room temperature, and polarized, noting the temperature. If the sample originally contained invert-sugar, the second polarization should be made at ap- proximately the same temperature as the first. The calcula- tion of the amount of sucrose is made by adding the two readings if they are on opposite sides of the zero, or subtract- SUGARS I 2 5 ing them if they are on the same side, and dividing the result in either case by 143 less half the observation temperature in centigrade degrees. The rule, therefore, may be expressed by the following formula : g _ a6 a being the first and b the second reading, which are added when of opposite signs and subtracted when of like signs ; that is, the algebraic difference is taken, in either case. With dark-colored materials it will often be advantageous to add an excess of alumina cream. Alumina cream alone will often suffice for clarification. When lead subacetate is used with liquids containing levu- lose, it is necessary to render the filtrate acid in order to break up a compound which the levulose forms with the lead. GERMAN OFFICIAL METHOD. 26.048 grams of the sample are dissolved in a sugar flask and the solution made up to 100 c.c. ; 50 c.c. of this solution are transferred by means of a pipet to a flask graduated at 50 and 55 c.c., enough lead subacetate solution added for clarification, the volume made up to the 55 c.c. mark, and the liquid thor- oughly shaken and filtered. The filtrate is then polarized, the reading being corrected for the extra 5 c.c. The liquid ad- hering to the pipet is washed into the 100 c.c. flask containing the remaining 50 c.c. (13.024 grams), 5 c.c. of concentrated hydrochloric acid (38 per cent., specific gravity i.iSSat 15) added, and the flask placed in a water-bath the temperature of which is 70. The contents of the flask should reach a tem- perature of 67-7O in two or three minutes, when the tem- perature should be maintained within this limit for exactly five minutes, keeping the temperature as nearly 69 as possible. (See international agreement, page 29, as to standard weight of sugar.) 126 FOOD ANALYSIS SUCROSE Under the term sucrose all forms of table sugar are in- cluded. These are, principally, the sugar-cane, SaccJiarum officinarum L. ; beet, Beta vulgaris L. ; sorghum, Sorghum saccharatum Persoon ; sugar maple, Acer saccharinum L. In the crude state there is a noticeable difference in these varieties, but so far as is known, the sucrose is identical in all cases. Adulterations are rarely encountered. The addition of glucose, especially to the lower grades, formerly extensively practised, now rarely occurs. The difference in the grades depends largely upon the extent to which the molasses and mineral matter have been removed. Maple sugar is sold in the crude condition and is often adulterated. The usual examination of commercial sugar is determina- tion of the amount of water, ash, sucrose, and reducing sugar. Water and ash are determined as on page 48. In the best grades of sugar these together will often not amount to more than o. I per cent. In the lower grades ash may be 3 percent., and water between loand 15 percent. The higher proportions of ash are found in beet-sugar. The estimation of sucrose is most conveniently made by the polarimeter. The direct reading is usually sufficient, but the result may be checked by inversion, and reading at ordinary temperature and at 86. The best grades will give a direct reading closely approximating 100 per cent. In some cases the direct read- ing will slightly exceed 100, due to a small proportion of raffinose. The lower grades of sugar contain some invert- sugar and the proportion of sucrose may be even below 80 per cent. Maple sugar usually contains about 85 per cent, of sucrose. COLORING-MATTERS. Granulated and loaf sugars often con- tain ultramarine blue, added to improve color. It may be separated by dissolving a considerable quantity of the sample SUGARS 1 27 iii water, allowing the coloring-matter to subside, and washing it with water several times by decantation. Ultramarine blue is decomposed by hydrochloric acid, the color discharged, and hydrogen sulfid liberated. Tin chlorid is sometimes employed in order to give sugar a bright, lasting, yellow color. The color appears to be the result of action on the sucrose. As a rule, the finished product contains but traces of tin, the greater portion being removed with the molasses. The so-called Demerara sugar is prepared in this way. Demerara sugar is frequently imitated by the addition of artificial coloring, usually to beet- sugar. To separate such added coloring-matter Cassel rec- ommends the following method : About i oo grams of the sample are shaken with alcohol of 90 per cent. This will often remove the color in a single washing. In some cases it is advisable to use alcohol of 75 or 80 per cent. The solution is filtered from the sugar, evaporated to dryness, the color again taken up with alcohol, and a skein of silk or wool (preferably slightly mordanted with aluminum acetate) treated with the solution, warmed for some time, and subsequently well washed with water. The skein will be dyed of a more or less yellow color in the pres- ence of artificial dye. A sample containing only such color- ing-matter as is natural to sugar, even by repeated washing with alcohol of 90 per cent., does not leave absolutely color- less crystals, and does not give a solution capable of perma- nently dyeing silk or wool. It is probable that the wool test described on page 77 might be successfully applied to a solution in water. See also Crampton and Simon's test for caramel, page 130. The occasional occurrence of saccharin as a substitute for sugar in confections, fruit juices, jams, and similar articles must not be overlooked. The detection of saccharin is given in the section on " Preservatives." The possibility of commercial 128 FOOD ANALYSIS glucose and invert-sugar containing arsenic and lead derived from the sulfuric acid must also be borne in mind. MOLASSES AND SIRUP Molasses is the uncrystallizable sirup produced in the manufacture of sugar. It properly differs from treacle in that it comes from sugar in the process of making, while treacle is obtained in the process of refining, but the two terms are usu- ally employed synonymously. Treacle, often called refiner's molasses, may contain 35 per cent, or more of sucrose, which is prevented from crystallizing by the associated substances. Ordinary table-molasses is made from cane, sorghum, or maple. Molasses from raw cane-sugar contains considerable invert-sugar, from which beet-root molasses is comparatively free. The latter, however, contains raffinose and a great variety of other bodies ; the proportion of salts being some- times 1 5 per cent. These impurities render it unfit for table use. Beet-sugar partially or wholly refined is free from these ingredients and may be used in the preparation of table sirups. Maple sirup is molasses from the maple. Much so-called maple sirup or " mapleine " is made by addition of extract of hickory-bark to sucrose or glucose sirup. This use of ex- tract of hickory-bark has been patented in the United States. Molasses and maple sirup are often adulterated by the addi- tion of glucose sirup. The product is usually sold as molasses, but is sometimes designated " mixed goods " or " table sirup." Glucose sirup produces a good body and light color, and many samples consist almost entirely of this material, flavored by the addition of a small proportion of the lowest grades of refuse molasses. The addition of glucose to molasses is readily detected by means of the polariscope. The normal or one-half normal quantity for the instrument is dissolved in water, clarified, and made up to 100 c.c., as described on page 123, and the read- SUGARS ing taken. A portion of this solution is inverted, as described on page 124, and two readings taken, one at or near the same temperature as the direct reading, and a second at 86 (see page 125). Pure molasses generally gives on direct reading at a temperature of 20 a deviation corresponding to 40 or 50 on the cane-sugar scale. After inversion, the reading at the same temperature will be 10 or 20, and at a temperature of 86 will be zero or near it. Sirups made by the solution of sucrose in water will usually give a rather higher direct reading, but after inversion the results will be the same as with molasses. In the presence of any consid- erable quantity of glucose the direct reading is nearly always above 60 and may rise to 1 20 or more. After inversion, the sample remains strongly dextrorotatory even at 86. Dark molasses is often bleached. Bone-black is sometimes used, but ozone, hydrogen dioxicl, sulfurous acid, sulfites, and sulfuric acid have been employed. One method consists in the addition of zinc dust and sodium sulfite, the zinc being subsequently removed by the addition of oxalic acid. The bleached molasses is liable, therefore, to contain either zinc or oxalic acid. As noted above, some samples of sugar are prepared by the use of stannous chlorid ; the latter may pass into the mo- lasses in such proportion as to be dangerous. Copper is occa- sionally present, derived from the apparatus of the refinery. For the detection of metallic impurities in molasses, not less than 50 grams should be ashed and examined as described on page 69. CARAMEL is a dark brown mass, soluble in water and weak alcoholic liquids, obtained by heating sucrose to about 200. It is largely used as a coloring-matter in foods and beverages. It is now occasionally adulterated or imitated by artificial coal-tar colors. Arata's wool test will serve in many cases to detect these. Caramel as a coloring agent is most 12 130 FOOD ANALYSIS easily recognized by a method due to Crampton and Simons : The liquid is well shaken with a small quantity of fuller's earth and filtered. Coloring matters from charred or un- charred wood are not removed, but if caramel be present the filtrate will be noticeably paler than the original liquid. See also under " Alcoholic Beverages." GLUCOSE Commercial glucose consists principally of dextrose with considerable maltose and gallisin and some dextrin. In trade the term " glucose " is restricted to the sirup ; the solid is called " grape-sugar." Inferior qualities of glucose may con- tain sulfurous or sulfuric acid, calcium sulfate, arsenic, and lead. A large number of cases of poisoning caused by beer made from arsenical glucose and invert-sugar occurred in England in 1900. The following are analyses of commercial glucoses, presum- ably all from maize-starch. 1 6 Nos. i and 2 are by Moritz and Morris ; 3 and 4 by L. Stern. In Stern's analyses some fig- ure has been determined by difference, probably that given as " unfermentable bodies," in which the gallisin and nitrogen- ous matters are included. The nature and effects of these accessory bodies are uncertain, but the figures show that commercial glucoses will differ in reducing power and optic activity. No. i. No. 2. No. 3. No. 4. Dextrose, 50.58 47-71 70.0 67.4 Maltose, H-I9 12.29 5- 1 II - Dextrin, . 1.76 2.98 Gallisin, 15-59 l S-9 Nitrogenous matters, ....... 1.18 o.8l Unfermentable bodies, 14.08 4.3 Ash, 1.44 1.39 0.2 1.6 Water, 16.49 20.77 9-9 I 5-7 101.23 101.85 100.0 100.0 The examination of glucose samples may be conducted as follows : SUGARS I 3 I Arsenic may be detected by Reinsch's test; lead by the routine method given on page 71. The amount of free acid is determined by titration of a known weight with standard alkali, using phenolphthalein as indicator. Sulfurous acid may be detected by adding some of the samples to dilute hydrochloric acid, with a few fragments of zinc in a test-tube, and covering the mouth of the tube with a piece of filter- paper containing some lead acetate. A spot of lead sulfid indicates reducible sulfur compounds. Calcium sulphate or other mineral matter may be determined by the weight and composition of the ash. LACTOSE Commercial lactose is usually obtained from the whey of cows' milk. Inferior qualities contain notable amounts of nitrogenous matter, mineral substances, bacteria, and spores of fungi. Pure lactose is a white crystalline powder, not very soluble in water and feebly sweet. When crystallized by evaporation at low temperature, it retains one molecule of water, but this is easily removed. The freshly made solution in water has a dextrorotatory power much greater than normal ; upon standing for 24 hours, or immediately upon boiling, it acquires its normal rotatory action. This phe- nomenon, known as " birotation," must not be overlooked in examining samples of lactose or concentrated milk-products. Lactose has high reducing power, especially upon alkaline copper solutions. Under the influence of some common organisms it is rapidly converted into lactic acid ; by special methods it may be converted into ethyl alcohol. For qualitative tests for lactose see page 1 14. Quantitative determinations are made either with a polarimeter or an alkaline copper solution. The details of these methods are given in connection with the analyses of milk. The examina- tion of commercial samples should be directed to the deter- mination of the amount of nitrogen, ash, lead, copper, and 132 FOOD ANALYSIS zinc. The sample should not be acid, nor contain any appre- ciable amount of matter insoluble in water. MAPLE SIRUP AND. MAPLE SUGAR These are substantially sucrose with minute amounts of special flavors. Sucrose from other sources may, therefore, be added in large amounts without being detected by any direct method. It is claimed, however, by some analysts that the amount of ash of a sample may be a guide, since a good sucrose contains but a small amount of mineral matter. Suf- ficient data are not yet at hand to decide upon this point. Adulteration with glucose solution maybe detected by polari- metric examination before and after inversion, as directed in connection with examination of sucrose. Pure maple sirup is converted into invert-sugar and shows a decided change from positive to negative, while glucose is not affected. The following results, given by A. W. Ogden, 1 7 will illustrate this method : Maple sirups f r e e from glucose : Maple sugars : Maple sirups containing glucose : c i POLARIME Direct. :TER READING. After Inversion. 22.2 -21. 9 -I 7 .6 2O. O 28.8 -28.3 29-3 18.9 45- 6 37-7 61.2 PERCENTAGE SUCROSE. 56.0 60.6 57-7 62.4 85-9 87.6 88.5 \1 ' 59-6 56 7 u 61.7 f I . 84 i (1: 88.0 88.4 - 1 ? 80.0 . . . IOO O . 06 4 J 4, - Q7-4 HONEY Honey is the nectar of flowers and other saccharine exuda- tions of plants collected and stored by the hive bee, Apis mellifica. Similar material is produced by other species of bees and by some wasps and ants. HONEY 133 Honey consists principally of dextrose and levulose with small proportions of mineral and flavoring matters and often formic acid. In some cases siruill amounts of sucrose and mannitose and a considerable proportion of carbohydrates of the dextrin class are present. Microscopic examination will usually show pollen, portions of insects' wings, and spores of fungi. Crystallized dextrose is occasionally present. The color of honey varies from light amber-yellow to brownish-black, according to the source and time and man- ner of storage. White clover honey is nearly colorless. Strained honey is that freed from comb. The proportion of water ranges within the limits of 12 and 22 per cent, the ash is rarely over 0.3 per cent. The re- ducing bodies calculated as dextrose usually amount to from 60 to 75 per cent. If sucrose be present in but small amount in the nectar of the flowers, it may be entirely inverted in the bee or after deposition in the hive, the resulting honey being quite free. The maximum proportion which may be present in pure honey is as yet unknown. Some authorities have pro- posed 5 per cent., others are disposed to allow a much higher proportion, but it is probable that the lower limit will rarely be exceeded in pure samples. Honey contains no true dextrin, but many samples yield, with strong alcohol, precipitates of carbohydrate intermediate between starch and sugar, the proportion being as high as 40 per cent, or more in the case of honey of coniferous origin. Honey is mostly levorotatory. Using the normal sugar- weight and measured on the sucrose scale at a temperature of 20 it will show a deviation of 2 to 14, but the following table shows some dextrorotatory results from samples of undoubted purity. They were probably derived, in part, from the black cherry, and also from the honey-dew of a neighboring pine forest. Other observers have noted dextro- rotation in honey of coniferous origin. 34 FOOD ANALYSIS POLARIZATION. REDUCING TEMPERA- TURE, C. SUCROSE. CARBO- HYDRATE CAL- CULATED AS DEXTROSE. WATER. ASH. Direct. After Inversion. 8.2 2.8 29.0 5-0 64.52 17.00 0.12 7.2 3-3 29.0 3-1 66.45 18-33 O. IO 5-i 2.4 30.0 2.1 63.42 18.65 0.19 7-3 2.6 29-5 3-6 58.42 16.72 0.2O 0.6 2.2 29.0 2.2 64. 10 19.60 0.25 ADULTERATIONS. Bees are often fed with cane-sugar, which is partially inverted by them, but the product is inferior in flavor to true honey. Ogden gives the following results of polarimetric examination of honey in the comb obtained in this way : Direct, i8 .5- Temperature, 25.2. After inversion, 9.0. Temperature, 24. The common adulterants of strained honey are invert-sugar and glucose sirup. It is usually impossible to detect with certainty the addition of invert-sugar. An ash higher than 0.3 per cent., containing a notable quantity of calcium sul- fate, may point to invert-sugar or to glucose sirup. Samples are frequently encountered which give a direct polarimetric reading of 14 to 20 on the cane-sugar scale, and, after inversion, slightly higher figures ; these in most cases probably contain added invert-sugar, but it is not possible at present to establish this point. The direct addition of sucrose to honey is not usual, but has been practised in some cases. Its presence in considerable quantity will be indicated by the high right-handed rotation, decidedly reduced on inversion. A sample of so-called "hoarhound honey" examined in the chemical laboratory of the United States Department of Agriculture was found to consist mainly of a solution of sucrose with some alcohol. The analytic results were as follows : HONEY 135 POLARIZATION. TEMPERA- TURE, C. SUCROSE. REDUCING BODIES CAL- CULATED AS DEXTROSE. WATER, PER CENT. ASH, PER CENT. Direct. After Inversion. 78.90 2. 4 24.6 5 8.I 7.92 23.12 0.03 A common method of adulteration consists in pouring glucose sirup over honeycomb from which the honey has been drained, and allowing the mixture to stand until it has acquired a honey flavor. Such samples give a high positive polarimetric reading, but little affected by inversion with acid. The following are some results of examination of honey con- taining glucose : WATER. ASH. POLARIZATION. REDt BODIES AS DE> CING CALC. .TROSE. SUCROSE. SOLIDS NOT DETER- MINED. Direct. oc. After inv. c. Before inv. After inv. By Polar. Reduc. 16.93 22.45 i5-4i 1907 O.2I 0.31 3 74-50 74.00 89.50 24-65 26.38 2t-5 24-5 21-5 23-0 25-5 60.18 57-40 51-99 40.0 57.60 65-23 61.33 59-85 57 oo 64-35 64.85 3-99 16.50 5-84 0.00 1.09 2-33 16.15 6.43 0.00 15-42 25-39 0.50 19-53 15-52 73-80 67.50 16.90 23-50 24.0 21.6 22.6 25.0 Dextrin is a constant constituent of commercial glucose sir-up, and the attempt has been made to detect the latter by the formation of a precipitate when the sample is diluted with alcohol. It has been shown, however, that many samples of honey contain a considerable material precipitable by ethyl alcohol, amounting in some instances to 50 per cent. Accord- ing to Beckmann, better results may be obtained by the use of methyl alcohol. Pure honey, both the ordinary form and the dextrorotatory variety, that might be regarded as adul- terated with glucose, was found to yield, when largely diluted 136 FOOD ANALYSIS with methyl alcohol, only a slight flocculent precipitate, which did not adhere to the walls of the vessel. Glucose sirup yielded a precipitate of dextrin amounting to about 31 per cent., which produced with a solution of iodin in potassium iodid the red characteristic of erythrodextrin. The reaction is also obtained by direct addition of the iodin solution to honey containing glucose sirup. The quantitative determina- tion is made by diluting 8 grams of the sample with 8 c.c. of water and diluting the mixture to 100 c.c. with methyl alcohol. The precipitate is filtered off, washed with methyl alcohol, dissolved in water, and the solution evaporated on the water-bath with repeated addition of methyl alcohol until quite dry. Adulteration with solid glucose (so-called grape-sugar) cannot be detected by this method, since in the preparation of this the conversion is carried beyond the point at which dextrin is formed. Methyl alcohol produces only a slight turbidity. Beckmann has also proposed the following test for solid glucose and glucose sirup : 5 c.c. of the honey solution (20 grams in 100 c.c. of water) are mixed with 3 c.c. of a 2 per cent, solution of barium hydroxid, 17 c.c. of methyl alcohol added, and the mixture shaken. Pure honey remains clear, but in the presence of dextrin, glucose, or glucose sirup a considerable precipitate is formed. The test was applied quantitatively by increasing the amount taken to 50 grams, the methyl alcohol added rapidly to avoid deposition on the glass, the liquid well shaken once, the precipitate collected on a tared asbestos filter, washed with methyl alcohol and ether, and dried at 55-6o. Excessive shaking was avoided in order to prevent the action of air on precipitate. It was found that the quicker the working, the more accurate the results. In some cases it was found necessary to determine the sulfates and phosphates and to correct the results accordingly. The mean results in test analyses, calculated to I gram of the HONEY 137 material taken, were: Dextrin, 0.916 gram; glucose sirup, 0.455 gram; solid glucose, 0.158 gram. Admixture of dextrorotatory conifer honey to the extent of 90 per cent, was not found to increase the amount of precipitate, but, on the contrary, to diminish it slightly. The following are results obtained on samples of natural honey rich in dextrinous bodies. Sp. is the specific rotatory power for yellow light : Apple honey, . . . Sp. = 12.2. Precipitate by ethyl alcohol 23.7 per cent. Barium precipitate 5 c.c. 10 per cent, solution gave 0.0044 gram. " " 5 c.c. 20 per cent. " " 0.0072 " Umbellifer honey, . Sp. =-. 4.6. Precipitate by ethyl alcohol 29.1 per cent. Barium precipitate 5 c.c. 10 per cent, solution gave 0.0148 gram. " " 5 c.c. 20 per cent. " " 0.023 " Conifer honey, . . . Sp. = 16.9. Precipitate by ethyl alcohol 41.9 per cent. Barium precipitate 5 c.c. 10 per cent, solution gave 0.0132 gram. " " 5 c.c. 20 per cent. " *' 0.0248 gram. It appears from these data that even under unfavorable cir- cumstances it is possible to recognize the addition of from 5 to 10 per cent, of ordinary dextrin, 10 to 20 per cent, of glucose sirup, and 30 to 40 per cent, of solid glucose to conifer containing as much as 40 per cent, of natural dex- trinous matter. With ordinary samples, such as the apple honey just noted, adulteration would be much more easily detected. Molasses is said to have been added to honey, but its use is infrequent. The ash of molasses is high and con- tains considerable chlorids. Beckmann suggests its detection by the production of a precipitate on addition of a solution of lead subacetate in methyl alcohol, the formation of which is attributed to the presence of raffinose. 5 grams of the solu- tion are mixed with 22.5 c.c. of methyl alcohol and 5 c.c. of a solution of the honey (which should not contain more than 25 per cent.) are added. If the honey be pure, the solution will remain clear, but in the presence of molasses a precipitate 138 FOOD ANALYSIS will be formed. The amount of precipitate varies according to the particular sample of molasses present, but Beckmann claims that it will usually be possible to detect as low as 10 per cent. Konig and Karsch 18 have proposed the following method for detection of glucose : 40 grams of the sample are made up to 40 c.c. with water, well mixed, 20 c.c. placed in a 250 c.c. flask, and absolute alcohol added, by very small portions at a time, with constant shaking, until the flask is filled to the mark. The mixture is allowed to stand for several days with occasional shaking. The solution is again shaken well and quickly filtered. 100 c.c. of the filtrate are evaporated to remove alcohol, but not to dryness, the residue made up to 20 c.c. by addition of lead subacetate and water, and the solution examined in the polarimeter. The precipitate produced by alcohol is washed several times with 90 per cent, alcohol and then dissolved off the filter with water, evaporated on the water-bath, dried in the water-oven, and weighed. The following are some of the results obtained : PERCENTAGE OF REDUC- POLARIMETRIC READING. ING CARBOHYDRATES Before Treatment After Treatment PRECIPITATED BY with Alcohol. with Alcohol. ALCOHOL. Pure honey, 6.4 8.5 3.2 12.4 13.4 1.7 16.7 17.0 . . . ii. 7 n-7 3-3 9.2 13.2 ... 7-7 9-9 9-7 9-9 12-5 7-5 6 - 2 34-0 Honey containing 75 per cent, glucose, 25.5 2.4 20.6 CANDIES AND CONFECTIONS These terms include many articles, including complex mixtures, the composition of which is secret. The main ingredient is usually sucrose, but invert-sugar, dextrose, CANDIES AND CONFECTIONS 139 starch, mucilaginous substances, gelatin, colors, and flavors are largely employed. Among the objectionable ingredients are paraffin, clay, calcium sulfate, mineral colors, fusel oil, and metal foil. Preservatives are usually unnecessary. The use of mineral colors has declined much of late years, owing to the cheapness and superior brilliancy of artificial organic dyes, but some of the chocolate confections contain consider- able amounts of brown ferric hydroxid. The plain candies, such as rock candy, molasses candy, and candy toys are usually only crystallized or melted sucrose with flavors and colors. Actual experiment by manufacturing confectioners has furnished the following data for proportion of color : One part of auramin will color 30,000 parts of melted sucrose to the deepest yellow required. One part of eosin or fluores- cein will give the average tint to 28,000 parts of "cream goods" (such as used in high-class "mixtures") or 21,000 parts of clear and hard candies, or 12,000 to 24,000 parts of some other types. These figures are for "solid" coloring that is, the whole mass is dyed ; when merely surface-coloring is done, the quantity needed is about I part to 50,000. The ash of candies and confections is generally below one per cent. The flavors are often artificial. A brand called " Rock and Rye Drops" is .often flavored with fusel oil. The colors employed are numerous and constantly chang- ing. At present various eosins (e. g. y rhodamin B, rose bengale, erythrosin) are much used for red, fluorescein and auramin for yellow, malachite green and sulfonated allies for green. Natural chlorophyl is sometimes used. Bismarck brown is apt to be employed in chocolate colors, although disapproved by the National Confectioners' Association. Its list will furnish suggestions as to the color likely to be present in any sample. Analytic Methods. The examination of candies will be I4O FOOD ANALYSIS usually limited to identification of the coloring-matters and detection of starch, clay, calcium sulfate, paraffin, and poison- ous metals. Determination of sucrose, invert-sugar, dextrose, and gum are difficult and of no practical interest. A weighed portion of the sample is stirred in cold water until all soluble matter is taken up, the liquid is filtered in a Gooch crucible, the residue washed with cold water, trans- ferred to the crucible, dried at a low heat, weighed, burnt off, and again weighed. The figures for insoluble residue and ash will be obtained. The aqueous solution will usually contain the coloring and some of the flavoring material ; the former may often be identified by the tests given on pages 80 to 82. Many flavoring agents may be recognized by odor. Starch may be detected by iodin. Any notable amount of gelatin or albumin will be indicated by the Kjeldahl method. Clay, calcium sulfate, and iron oxid will be found in the ash. FATS AND OILS The methods for determining melting and solidifying points and specific gravity of fats and oils have been fully described in the introductory part. Some comparative data are given in this section, together with methods applied almost exclu- sively to this class of food-products. Specific gravity determined at temperatures other than 15.5 may be reduced to this by a correction of 0.00064 for each degree. This figure is derived from results obtained by A. H. Allen. The specific gravity of fats and oils changes by time. The following table, due to Thomson and Ballen- tyne, shows this fact ; the figures are for |^ : FRESH. ONE MONTH. THREE MONTHS. Six MONTHS. Olive, 0.9168 0.9187 0.9208 0.9246 Cottonseed, .... 0.9225 0.9237 0.9261 0.9320 Arachis, 0.9209 0.9213 0.9233 0.9267 Rape, . 0.9168 0.9183 0.9188 0.9207 FATS AND OILS 14! Color-tests. Many color-tests for oils and fats have been proposed. The reactions are in many cases dependent on accessory materials and may fail when the sample has been pro- duced under unusual conditions or subjected to special treat- ment. Thus, cottonseed oil by heating loses susceptibility to several color-tests, while lard derived from animals fed liberally on cottonseed products will give distinctly the cotton- seed oil reactions. Special color-tests applicable to particular oils or fats will be described in connection with these. The following general reactions are much used : SULFURIC ACID TEST. A drop or two of strong sulfuric acid is placed in the center of about 20 drops of oil, allowed to rest a few moments, the color change noted, the mixture stirred, and the effect again noted. The charring action which often obscures the reaction may be avoided by dissolving a drop of the oil in 20 drops of carbon disulfid and agitating this with the sulfuric acid. NITRIC ACID TEST. O. Bach's method is to agitate 5 c.c. of the sample with 5 c.c. of nitric acid, sp. gr. 1.30. The color reaction is noted, the mixture immersed in boiling water for 5 minutes, and the condition again noted. As the reaction on heating may be violent, care must be taken that no injury be done. Massie's method is to agitate 10 grams with 5 c.c. of nitric acid, sp. gr. 1.40, and note the color at the end of one hour. J. Lewkowitsch states that an acid of specific gravity 1.375 gives often the best results. In some cases the mixture should stand 24 hours before the final observation is made. Mixtures of strong sulfuric acid and strong nitric acid have been used, but the results are interesting specially in the case of certain fish oils. The following data, compiled by A. H. Allen, 19 will illus- trate the value of these color-tests : 142 FOOD ANALYSIS OLIVE. COTTON- SEED. SESAME. ARACHIS. RAPE. SULFURIC ACID. Before stirring, . After stirring, . Yellow- green or brown. Brown or green. Red-br-.wn. Dark red- brown. Yellow to orange. Green or brown. Yellow with red rings. Brown. NITRIC ACID. Bach's test : After agitation. After heating, After 1 2 hours' Pale- green. Orange- yellow. Yellow- brown. Red-brown. White. Brown- yellow. Pale rose Brown- yellow. Pale rose. Orange- yellow. standing, . Massie's test, . Solid. Yellow- Buttery. Orange-red Liquid. Yellow- Solid. Pale red. Solid Orange. Time for solidifica- green. orange. tion (minutes), . 60 105 105 200 lodin Number. This, also called iodin value, is the per- centage of iodin absorbed under specified conditions. Baron Hiibl discovered that a solution of iodin and mercuric chlorid was more uniform in action than iodin alone, and this solution, commonly known as Hiibl's reagent, is usually employed. The following reagents are used in the process : Iodin solution. 25 grams of iodin are dissolved in 500 c.c. of 95 per cent, alcohol. Mercuric chlorid solution. 25 grams of mercuric chlorid solution are dissolved in 500 c.c. of 95 per cent, alcohol and the solution filtered, if necessary. Starch solution. A solution of 5 grams of starch in 200 c.c. of water. Potassium io did solution. 15 grams in 100 c.c. of water. Potassium dichromate solution. 3.874 grams of pure potas- sium dichromate in 1000 c.c. of water. For use, equal parts of the iodin and mercuric chlorid solutions are mixed and allowed to stand at least 12 hours. FATS AND OILS 143 \ The strength of the thiosulfate solution is determined as follows : 20 c.c. of potassium dichromate solution, 10 c.c. of potassium iodid solution, and 5 c.c. of strong hydrochloric acid are mixed in a glass-stoppered flask, and the solution of sodium thiosulfate is allowed to flow in from a buretuntil the yellow color of the mixture has almost disappeared. A few drops of starch solution are then put in and the addition of the thiosulfate continued until the blue color just appears. The number of cubic centimeters of thiosulfate solution used, multiplied by 5, is equivalent to I gram of iodin. Not more than I gram of fat is weighed in a glass-stoppered flask holding about 300 c.c., and 10 c.c. of chloroform are added. After complete solution 30 c.c. of the iodin solution are added and the flask is placed in the dark for three hours, with occasional shaking. 100 c.c. of water and 20 c.c. of potassium iodid solution are added to the contents of the flask. Any iodin which may be noticed upon the stopper of the flask should be washed back into the flask with the potassium iodid solution. The excess of iodin is now titrated with the sodium thiosulfate solution, which is run in gradually, with constant shaking, until the yellow color of the solution has almost disappeared. A few drops of starch-paste are added, and the titration continued until the blue color has entirely disappeared. Toward the end of the reaction the flask should be closed and violently shaken, so that iodin remaining in the chloroform may be taken up by the potassium iodid solution. A sufficient quantity of sodium thiosulfate solution should be added to prevent a reappearance of any blue color in the flask for five minutes. At the time of adding the iodin solution to the fats, two flasks of the same size as those used for the determination should be employed for conducting the operation without fat. In every other respect the performance of the blank experi- 144 FOOD ANALYSIS ments should be just as described. These blank experiments must be made each time the iodin solution is used. IODIN NUMBER OF LIQUID ACIDS. This determination is sometimes of value for detection of admixture of vegetable oils with animal. oils. The separation of the oleic and other liquid fatty acids is best made by the method of J. Muter and L. De Koningh, as follows : 3 grams of the fat are mixed with 50 c.c. of alcohol and a fragment of potassium hydroxid in a flask furnished with a long tube. The mixture is boiled until saponification is com- plete, when a drop of phenolphthalein solution is added and acetic acid until the solution is slightly acid. Alcoholic solution of potassium hydroxid is added drop by drop until a faint permanent pink tint is obtained, when the liquid is poured slowly, with constant stirring, into a beaker containing a boil- ing solution of 3 grams of neutral lead acetate in 200 c.c. of water. The solution is rapidly cooled and stirred at the same time, and, when cold, the clear liquid is poured off. The precipitate is well washed with boiling water by decantation, transferred to a stoppered bottle, mixed with 1 20 c.c. of ether, and allowed to remain 12 hours. Wallenstein and Finck use a Drechsel gas-washing flask having the tube shortened about two-thirds, to contain the ethereal solution, and pass a current of hydrogen through it for about a minute. In the case of white fats the liquid is said to remain colorless at the end of 12 hours, but if free access of air is permitted, a dark-yellow solution is produced by oxidation. Lead oleate, hypogeate, linolate, or ricinolate will be dissolved by the ether, 'leaving lead laurate, myristate, palmitate, stearate, and arachidate undissolved. Lead erucate is sparingly soluble in cold ether, but readily in hot. The contents of the bottle are filtered through a covered filter into a Muter separating-tube (Fig. 40), 40 c.c. of dilute hydrochloric acid (1:4) added, and the tube shaken until the clearing of the ethereal solution shows FATS AND OILS that the decomposition of the lead soaps is complete. The aqueous liquid, containing lead chlorid and excess of hydro- chloric acid, is run off through the bottom tap, water added, and agitated with the ether and the process of washing by agitation repeated until the removal of the acid is complete. Water is then added to the zero mark and sufficient ether to bring the ether to a definite volume (e. g,, 200 c.c.). An aliquot portion of this (e. g., 50 c.c.) is then removed through the side tap and the residue weighed after evaporation of the ether in a current of carbon dioxid. Another aliquot portion of the ethereal solution should be dis- tilled to a small bulk (avoiding complete evap- oration), alcohol added, and the solution titrated with decinormal sodium hydroxid and phenolphthalein or methyl-orange, from which the fatty acids may be calculated from the result, or their mean combining weight deduced therefrom. A third aliquot part of the ethereal solution should be evaporated at about 60 in a flask traversed by a rapid stream of dry carbon dioxid. When every trace of ether is removed, 50 c.c. of the iodin-mercur- ic chlorid solution (p. 142) should be added, the stopper inserted, and the liquid kept in absolute darkness for 12 hours, after which an excess of potassium iodid solution is added and 250 c.c. of water, and the excess of iodin ascertained with thiosulfate solution in the usual way. From the result the iodin number is calculated. Volatile Acids. This method was first suggested by Otto Hehner and A. Angell, but was systematized by E. Reichert, and hence is generally called the Reichert process. In this form it is carried out by saponifying 2.5 grams of the fat, 13 FIG. 40. 146 FOOD ANALYSIS adding excess of sulfuric acid, distilling a definite portion of the liquid, and titrating the distillate with N alkali. The num- ber of cubic centimeters of this solution required to overcome the acidity of the distillate is called the Reichert number. E. Meissl suggested the use of 5 grams, and the number so obtained is called the Reichert-Meissl number. Alcoholic solution of potassium hydroxid was originally used for sap- onification, but most chemists now use the solution devised by Leffmann and Beam, namely, sodium hydroxid in glycerol. The reagents and operation are as follows : Glycerol-soda. 100 grams of pure sodium hydroxid are dissolved in 100 c.c. of distilled water and allowed to stand until clear. 20 c.c. of this solution are mixed with 180 c.c. of pure concentrated glycerol. The mixture can be conveni- ently kept in a capped bottle holding a 10 c.c. pipet, with a wide outlet. Sulfuric Acid. 20 c.c. of pure concentrated sulfuric acid, made up with distilled water to 100 c.c. Sodium Hydroxid. An approximately decinormal, accu- rately standardized, solution of sodium hydroxid. Indicator. An alcoholic solution of phenolphthalein or aqueous solution of methyl-orange. A 300 c.c. flask is washed thoroughly, rinsed with alco- hol and then with ether, and thoroughly dried by heat- ing in the water-oven. After cooling, it is allowed to stand for about 15 minutes and weighed. A pipet, gradu- ated to 5.75 c.c., is heated to about 60 and filled to the mark with the well-mixed fat, which is then run into the flask. After standing for about 15 minutes the flask and con- tents are weighed. 20 c.c. of the glycerol-soda are added and the flask heated over the Bunsen burner. The mixture may foam somewhat ; this may be controlled, and the opera- tion hastened by shaking the flask. When all the water has been driven off, the liquid will cease to boil, and if the heat FATS AND OILS 147 and agitation be continued for a few moments, complete sap- onification will be effected, the mass becoming clear. The whole operation, exclusive of weighing the fat, requires about five minutes. The flask is withdrawn from the heat and the soap dissolved in 135 c.c. of water. The first portions of water should be added drop by drop, and the flask shaken between each addition in order to avoid foaming. When the soap is dissolved, 5 c.c. of the dilute sulfuric acid are added, FIG. 41. a piece of pumice dropped in, and the liquid distilled until 110 c.c. have been collected. The condensing tube should be of glass, and the distillation conducted at such a rate that the above amount of distillate is collected in 30 minutes. The distillate is usually clear ; if not, it should be thor- oughly mixed, filtered through a dry filter, and 100 c.c. of the filtrate taken. A little of the indicator is added to the distillate, and the standard alkali run in from a buret until neutralization is attained. If only 100 c.c. of the distillate 148 FOOD ANALYSIS have been used for the titration, the number of cubic centi- meters of alkali should be increased by one-tenth. The distilling apparatus shown in figure 43 is that recom- mended by the A. O. A. C. (and since adopted in Great Britain), and the directions for preparing the flask are also from the same source, but when it is intended merely to dis- tinguish butter from oleomargarin, it will be sufficient to measure into a flask 3 or 6 c.c. of the clear fat, and operate upon this directly in an ordinary distilling apparatus. A blank experiment should be made to determine the amount of standard alkali required by the materials employed. With a good quality of glycerol, this will not exceed 0.5 c.c. Most fats give distillates containing but little acid. Saponification Value. Koettstorfer Number. This is the number of milligrams of potassium hydroxid required for the saponification of I gram of fat. Its use was suggested by M. Berthelot, and it was applied to the examination of butter by J. Koettstorfer. If the saponification value be divided by 10, the result will be the percentage of alkali required for saponification. The reagents and process are as follows : Alcoholic potassium hydroxid. 40 grams of good potassium hydroxid are dissolved in sufficient 95 per cent, alcohol to make 1000 c.c. of alcohol. The solution should be clear and not darker than light yellow. Alcohol that becomes brown is unfit for use. Purified methyl alcohol may be substituted for ethyl alcohol. Sodium hydroxid may be substituted for potassium hydroxid. The saponification value of sodium hydroxid may be converted into the standard number by multiplying by 1.4025. Half-normal hydrochloric acid accurately standardized. Phenolphthalein solution. The process is as follows : About 1.5 grams of the sample FATS AND OILS 149 are accurately weighed into a small flask, 25 c.c. of the alcoholic alkali added, and the mass saponified. The same amount of the alkaline solution must be used in all compara- tive experiments, and it must be accurately measured. The flask is heated under an inverted condenser or, more simply, with a tube about 50 cm. long and 0.5 cm. caliber passing through the cork. The flask is heated on the water-bath for 30 minutes, being occasionally given a rotatory motion. The alcohol should not boil actively. A drop of the indicator solution is added, the liquid allowed to cool somewhat, the flask being closed, and then titrated with the standard acid. A blank test should be made, which will eliminate some of the errors of experiment. The number of cubic centimeters used for titration of the saponified mass, subtracted from the number used in the blank experiment, will give the acid corresponding to the alkali which has been neutralized by the fat. From this, the amount of alkali can be determined and calculated by simple proportion to I gram of fat. Flasks of the same kind of glass should be used in com- parative experiments, as some of the cheaper forms of glass are notably affected by alkali. A special form of saponifica- tion flask and method of heating used by the A. O. A. C. are shown in figure 42. The flask is arranged so that the cork can be tied down. A. H. Allen suggested the use of the figure representing the grams of fat saponified by 1000 c.c. of normal alkali. This would render the method independent of the alkali employed, but the suggestion has not been generally approved. FIG. 42. I 5O FOOD ANALYSIS The datum was called by Allen saponification equivalent. It may be obtained in any case by dividing 56100 by the saponi- fication number. Similarly, the saponification number may be obtained by dividing 56100 by the saponification equiva- lent. Acid Value. This is the amount of free fatty acids pres- ent in the sample. The reagents and process are as follows : Sodium hydroxid solution. Decinormal solution of sodium hydroxid. Neutral alcolwl. Alcohol (95 per cent.) carefully neutral- ized by addition of a drop or two of phenolphthalein solution, and running in the alkali solution until the color-change occurs. 10 grams of the sample are placed in a bottle pro- vided with a glass stopper, about 50 c.c. of the neutral alco- hol and I c.c. of the indicator added, and the mass heated to boiling by immersing the bottle in hot water. The bottle is then stoppered and well agitated and the liquid titrated with standard alkali, the bottle being vigorously shaken after each addition until a faint pink coloration persists for a minute or two. On long standing the alkali acts upon the fat itself. I c.c. of decinormal alkali is equivalent to 0.0256 gram of palmitic acid, 0.0284 gram of stearic acid, or 0.0282 gram of oleic acid. As the acid present may not be known, it is usual to express the result as the milligrams of potassium hydroxid required to neutralize I gram of fat. This is called the acid number. When sodium hydroxid is used for titra- tion, the acid number may be calculated by multiplying the quantity of sodium hydroxid required for I gram of sample by 1.4. Solubility in Acetic Acid. Valenta's Test. Fats and oils are arranged by Valenta into three classes, according to their solubility in acetic acid. Equal volumes of the oil and acid are placed in a test-tube, thoroughly mixed, and, if no solution takes place, warmed. FATS AND OILS !$! Class i. Completely soluble at ordinary temperature : Olive kernel oil ; castor oil. Class 2. Completely soluble or nearly so at temperatures ranging from 23 up to the boiling-point of glacial acetic acid : Palm oil ; coconut oil ; olive oil ; cacao-butter ; sesame oil ; cottonseed oil ; arachis oil ; beef tallow ; butter, etc. Class 3. Not completely dissolved even at the boiling- point of glacial acetic acid : Oils obtained from the seeds of the Crucifera ; rape-seed oil ; mustard-seed oil ; hedge-mus- tard oil. For the practical application of the test the method of W. A. Chattaway, T. M. Pearmain, and C. G. Moor is satisfac- tory : 2.75 grams of the sample are weighed in a short, rather thick tube with a well-fitting stopper, 3 c.c. of acetic acid (99.5 per cent.) are added, the tube closed, placed in a beaker of warm water, and the heat increased until, after well shaking the tube, the contents become quite clear. The source of heat is then removed, and the test-tube so placed that it is in the center of the beaker of heated water, and, by means of a thermometer attached to the tube by a rubber band, the whole is allowed to rest until the change from brilliancy to turbidity takes place. The change is very definite, and can be repeated as often as is wished, with a maximum error of about 0.25. Thermal Reaction with Sulfuric Acid. Maumen6's Test Maumene found that on mixing sulfuric acid with drying oils a higher temperature is produced than with non- drying oils. With the same sample the temperature will depend upon the acid. The strength of acid employed should be determined by titration, since the specific gravity of the acid of 96 per cent, and of 99 per cent, is practically identical. L. Archbutt recommends the following method of operating : 50 grams of the sample, weighed closely, are 152 FOOD ANALYSIS placed in a beaker "of 200 c.c. capacity, and, together with the bottle of acid, placed in a vessel of water until both have acquired the temperature of the water, the thermometer hav- ing been placed in the oil. The beaker is removed from the water, wiped outside, and placed in a nest of cardboard having hollow sides stuffed with cotton. (A large beaker, lined with cotton, may also be used.) The temperature having been noted, 10 c.c. of acid are rapidly withdrawn from the bottle, which is immediately closed, the acid is allowed to flow into the oil while it is being stirred with the thermometer, and the stirring is continued until no further rise of temperature is observed. The stirring must be so managed as to effect as perfect admixture of the oil and acid as possible, thereby in- suring an even development of heat throughout the mixture. The best results are obtained with an acid about 97 per cent. It is desirable to keep on hand a stock of oil of known purity, and to test some of this with each set of samples examined. Specific Temperature Reaction. The discrepancies ob- served in Maumene's method may be largely eliminated by that devised by R. T. Thomson and H. Ballentyne, which is to compare the rise of temperature with oil and with an equal volume of water under similar conditions. The number ob- tained by dividing the oil figure by the water figure is multi- plied by 100 to eliminate decimals, and the datum so obtained is called the specific temperature reaction. Bromin Thermal Value. O. Hehner and C. A. Mitchell ascertained that the heat evolved in the reaction of bromin with unsaturated fatty bodies furnishes more definite data than does sulfuric acid. As the action of bromin upon some oils is violent, it is moderated by the use of a diluent such as chloroform or glacial acetic acid. The latter has the advan- tage, owing to its high boiling-point, of allowing a wider range of temperature. The procedure is as follows : The FATS AND OILS 153 bromin, oil, and diluent are all brought to the same tempera- ture. I gram of the oil is dissolved in 10 c.c. of chloroform in a vacuum-jacketed test-tube. Exactly I c.c. of bromin (measured by means of a pipet, connected at the upper end with a narrow tube filled with caustic lime, and having an as- bestos plug at each end) is added and the rise of temperature determined by a thermometer graduated into fifths. Acids are dissolved in glacial acetic acid instead of chloroform. A definite relation exists between the iodin number and the heat produced by bromin. In Hehner and Mitchell's experi- ments it was found that if the rise of temperature in degrees was multiplied by 5.5, a close approximation to the iodin number was always obtained, except with rape and linseed oils, but each observer must ascertain the factor applying to particular cases. H. W. Wiley has made this method more accurate and more easy of application. A solution of bromin in four parts by volume of chloroform or carbon tetrachlorid is em- ployed. This is to be made up in quantity sufficient for one day's use, and kept in the dark. Dissolving the sample in similar solvents is an additional convenience. 10 grams of the sample, in sufficient chloroform or carbon tetrachlorid to make 50 c.c. of solution, will suffice for nine determinations. At least four determinations should be made. The apparatus is shown in figure 43. The tube for holding the reagent and thermometer is about 40 cm. in length, and 1.5 cm. internal diameter. It is conveniently held in a drying jar, being fitted air-tight by a rubber stopper. Air is withdrawn from the jacketing jar through the side tubulure. The bromin solu- tion is contained in a stout-walled Erlenmeyer flask with a side tubulure provided with a rubber bulb. Through the stopper passes a pipet, and the flask may be rendered air- tight by gentle pressure on the stopper. The thermometer should be graduated to 0.2 and be read to a tenth by a lens. 14 154 FOOD ANALYSIS The operation should be conducted in a room at uniform temperature. The solutions and apparatus are allowed to stand until all FIG. 43. reach a uniform temperature. 5 c.c. of the solution of the sample are placed in the inner tube by means of the pipet, without allowing any of the solution to run down the walls FATS AND OILS 155 of the tube, the thermometer is inserted, and the bromin so- lution is forced up into the pipet by compressing the rubber bulb until the liquid has passed the mark on the stem. The top of the pipet is closed by the finger, the stopper of the flask loosened, and the liquid allowed to run out until it reaches the mark, when it is transferred to the mixing tube and allowed to flow directly into the solution of fat, but it is now not necessary to prevent the liquid running down the side of the tube. The empty pipet is returned to the flask and the thermometer is observed at once by means of a lens since the bromination is practically instantaneous, the mercury reaching its maximum height in about a minute after the pipet is with- drawn. When the mercury begins to fall, air is admitted to the jacketing space, the mixing tube is withdrawn, its con- tents emptied, and the tube held inverted until the residual bromin vapor escapes. The tube may be cleaned by wiping it with a long test-tube cleaner or may be used again without cleaning, after standing inverted for half an hour. Traces of brominated oil which may remain upon the side of the tube do not interfere unless they obscure the thermometer. By the above manipulation the thermometer soon returns to the room temperature, and a second determination may be made in half an hour. As noted by Hehner and Mitchell, each analytic system must be separately standardized and the factor for calculating the iodin absorption determined. It is important not to stir or churn the mixture of oil and bromin further than is pro- duced by the running in of the solution itself. Carbon tetra- chlorid is the preferable solvent, but the rise of temperature is slightly higher with chloroform. A. H. Gill and I. Hatch have proposed to facilitate the comparison of tests made with different apparatus by employ- ing a standardizing material, and recommend sublimed cam- phor for this purpose. 7. 5 grams of the camphor are dis- 156 FOOD ANALYSIS solved in carbon tetrachlorid, the solution made up to 25 c.c., and portions of 5 c.c. each brominated. The temperature increase obtained with various oils is divided by the rise ob- served with camphor, giving a specific temperature increase, analogous to that suggested by Thomson & Ballantyne (see p. 152). By dividing the iodin value of an oil by the specific temperature increase, a figure will be obtained by which the iodin value may be approximately calculated. Klaidin Test. i c.c. of mercury is dissolved in 12 c.c. of cold nitric acid of 1.42 specific gravity. 2 c.c. of the freshly -made deep green solution are shaken in a wide- mouthed stoppered bottle with 50 c.c. of the sample to be tested and the agitation repeated every ten minutes during two hours. When treated in this manner, oils consisting of nearly pure olein or of mixtures of olein with solid esters, such as palmitin and stearin, give a more or less solid product. Olive oil is remarkable for the canary or lemon-yellow and great firmness of the mass formed. After 24 hours the hard- ness of the product is such that it is impervious to a glass rod, and sometimes rings when struck ; but this character is also possessed by the elaidins yielded by the arachis and lard oils. In making the test, it is important to note the time re- quired to obtain a "solid" product, which will not move on shaking the bottle, as well as the ultimate consistency. The temperature should be kept nearly constant, or erratic results may be obtained. The behavior of the more important oils, when tested in the foregoing manner, is described by A. H. Allen as fol- lows : A hard mass is yielded, among others, by olive, almond, lard, and sometimes arachis oils. A product of the consistency of butter is given by mustard, and sometimes by arachis and rape oils. A pasty or buttery mass which separates from a fluid portion FATS AND OILS 157 is yielded by rape, sesame, cottonseed, sunflower, and some- times mustard oils. Liquid products are yielded by linseed, hempseed, walnut, and other drying oils. The results of the elaidin test must be accepted with cau- tion, since it is affected by many conditions, such as tempera- ture, shape of the containing vessel, and the mode of prepa- ration of the nitrous acid. The extent to which the sample has been exposed to light and air is a still more important factor ; it has been shown that olive oil after exposure to sun- light for two weeks may fail to respond to the test. Index of Refraction. This datum differs notably in differ- ent oils, but it is not of much value in detecting adulteration unless considerable of the adulterant be present. Several in- struments have been devised for making refraction determina- tion ; the familiar ones are the refractometer of Abbe, the oleorefractometer of Amagat and Jean, and the butyrorefrac- tometer of Zeiss. The oleorefractometer consists essentially of a collimator, a view-telescope, and a vessel to contain the oil. The last is provided with parallel glass slides, and in the center is a vessel with two plate glass sides, inclined to each other at an angle of 107. An arbitrary scale is placed in the focus of the eye-piece, and the reading is made by means of a semicircular stop in the collimator, the image of which is thrown on the scale and divides the field into a dark and a light portion. If the outer vessel and inner prism be filled with the same oil, the light which passes through will not be refracted, and con- sequently no alteration of the position of the image will take place. If, however, the inner prism be filled with a different oil, refraction will take place and the line dividing the field will be displaced to the right or left. The instrument is fur- nished with a standard oil, said to be sheepsfoot oil, for use in the outer vessel. Instead of this, the oil may be compared with a sample of the same kind known to be pure. 158 FOOD ANALYSIS The butyrorefractometer has been strongly recommended for the examination of butter. It is equally adapted for the examination of fats and oils, and maybe used for the determ- ination of the index of refraction as well. Drying Property. Livache's Test. The so-called drying of oils (a process of oxidation) is hastened by admixture with finely divided lead. This is prepared by precipitating lead acetate by zinc, washing the precipitate rapidly with water, alcohol, and ether in succession, and drying at very low pres- sure. (Probably drying in nitrogen gas would be preferable.) I gram of the dried lead is mixed on a watch-glass with not more than 0.7 gram of the sample by dropping the latter so that it is distributed over the mass of the lead. The glass is allowed to stand at room temperature exposed to light, but reasonably protected from dust. Drying oils absorb the maximum quantity of oxygen after from 1 8 hours to 3 days, but non-drying oils do not begin to gain weight until after 4 or 5 days. Fat-acids, except those from cottonseed oil, behave the same as the fats. Livache's results are given in the following table. The figures show the percentage of increase in weight after the time specified. A drying oil (linseed) is added for comparison with the food oils. The figure for maize oil is given by Vulte and Gibson. OIL. 2 DAYS. 7 DAYS. 10 DAYS. Olive, o 1.7 Cottonseed, 5.9 Maize, 5- Arachis, . o 1.8 Sesame, o 2.4 Rape, o 2.9 Linseed, ..... 14.3 Soluble and Insoluble Acids. This method, due to O. Hehner and A. Angell, has been much modified by other in- vestigators. The proportion of acids insoluble in water is often called the Hehner value. The following method, de- FATS AND OILS I 59 scribed by A. H. Allen, is somewhat different from that rec- ommended by the A. O. A. C, but will serve for practical purposes, it being understood that blank tests and tests with standard oils should be made for comparison : About 5 grams of the sample, accurately weighed, are placed in a saponifica- tion flask, 50 c.c. of a solution of 40 grams of sodium hy- droxid to 1000 c.c. of strong alcohol added, the flask closed, and the mixture heated in a steam-bath until complete saponi- fication has occurred. The flask is cooled, the soap solution acidulated with sulfuric acid, the aqueous liquid separated from the layer of fatty acids, and the latter several times boiled with a considerable quantity of water in a flask fur- nished with a reflux condenser. The liquids resulting from these operations are separated from the insoluble fatty acids, which it is desirable to boil again with a moderate quantity of water, while driving a current of steam through the flask in which they are contained, collecting the distillate, and treating it like the washings. The acidulated aqueous liquid first sep- arated from the layer of fatty acids is then distilled to a small bulk, and the distillate exactly neutralized with standard so- dium hydroxid, using phenolphthalcin as an indicator. The first washings from the insoluble fatty acids are then added to the contents of the distilling flask, and the liquid again dis- tilled to a small bulk, the process being repeated with the succeeding washings. The different distillates should be titrated separately with decinormal alkali and phenolphthalein, so that the progress and completion of the washing may be followed, and some information obtained as to the nature and relative proportions of the lower fatty acids present. The neutralized distillates should be united and evaporated gently to dryness, and the residue dried at 100 until the weight is constant. It consists of the sodium salts of the acids that passed over in the distillation. If the number of cubic centimeters of N sodium hydroxid employed for neu- l6o FOOD ANALYSIS tralization be multiplied by 0.22, and the product be sub- tracted from the weight of the dry residue, the difference will be weight of the volatile acids. When coconut oil and palmnut oil are treated in this man- ner, the distillate will be found to contain lauric acid, which, though almost insoluble in water, is volatile in a current of steam. It may be separated from the more soluble volatile fatty acids by filtering the distillate. Cholesterol and Phytosterol. Most vegetable oils, with the notable exception of olive oil and palm oil, contain a small proportion of phytosterol. Animal oils and olive oil, on the other hand, contain cholesterol, and it is thought to be possible to distinguish a vegetable oil from one of animal origin by the isolation and identification of one or the other of these bodies. A method for the extraction of cholesterol and phytosterol is that of A. Foster & R. Riechelmann : 50 grams of the fat are twice boiled, for about 30 minutes at a time, with 75 c.c. of 95 per cent, alcohol in a flask fitted with a reflux condenser, the flask being meanwhile well shaken. The alcoholic solution is mixed with 15 c.c. of 30 per cent, sodium hydroxid solution, and boiled on the water- bath in a flask fitted with a condensation tube until about one- fourth of the alcohol is evaporated. The fluid is then evap- orated nearly to dryness in a porcelain basin and the residue shaken with ether. The ethereal solution is evaporated to dryness, the residue treated with a little ether, filtered, evap- orated, and the residue crystallized from 95 per cent, alcohol. Von Raumer determines the amount of crude cholesterol and phytosterol in fats as follows : 50 grams of the oil are saponified with alcoholic potassium hydroxid. The resulting soap is evaporated to dryness, reduced to powder, and ex- tracted with 50 to 75 c.c. of ether in a Soxhlet apparatus, plugs of fat-free cotton being placed above and below the layer of soap. The residue is saponified again with 10 c.c. FATS AND OILS l6l of half normal alkali, evaporated to dryness with sand, and re-extracted as before during two hours. When the work is carefully done, the second saponification and extraction is un- necessary. The following amounts of residue were obtained from 100 grams of oil : Cottonseed oil, 0.719 gram ; sesame oil, 1.314 grams to 1.325 grams ; lard, 0.217 gram. Pure cholesterol can easily be distinguished from phyto- sterol by the form and grouping of the crystals. If both bodies are present, the mixture crystallizes in one form only, the crystals either approximating to the form of phytosterol or, if cholesterol be present in the greater quantity, differing from the pure crystals of either body. Clwlesterol is insoluble in water, sparingly soluble in cold alcohol, but dissolves readily in ether, chloroform, petro- leum spirit, and carbon disulfid. It crystallizes in anhydrous needles of melting-point 147, but from its hot alcoholic solution it is deposited in laminae composed of extremely thin rhombic plates, often showing reentering angles. A delicate test for cholesterol is that of Hager, as modified by Salkow- ski : A few centigrams of cholesterol are dissolved in 2 c.c. of chloroform, an equal volume of sulfuric acid is added, and the mixture shaken. The chloroform solution immedi- ately becomes blood-red, afterward cherry-red and purple ; this last tint remains for several days. The sulfuric acid layer under the chloroform shows a strong green fluorescence. On pouring a few drops of the purple chloroform layer into a porcelain basin, the red color changes rapidly to blue, green, and finally to yellow. On diluting the purple chloroform solution with more chloroform, it becomes nearly colorless, or acquires an intense blue ; if it now be shaken again with the sulfuric acid layer, the former coloration appears. These changes of color are due to traces of water in the chloro- form. 1 62 FOOD ANALYSIS Phytosterol resembles cholesterol, but differs from it in crys- talline form and in melting-point. From a hot alcoholic solu- tion phytosterol crystallizes in solid needles grouped in tufts. Under the microscope these appear as long solid needles arranged in star or bunch-like groups. Like the cholesterol crystals, these contain a molecule of water, but they melt at 132 to 134. (Bomer gives a mean melting-point of 137, but this figure requires confirmation.) The solution of phytosterol in chloroform gives the same reaction with sulfuric acid as does cholesterol, but there is the slight difference that the coloration obtained with the former passes after a few days into a bluish-red, whereas the choles- terol solution remains more of a cherry-red. Acetyl Value. This determination, originally suggested by Benedikt, is most conveniently carried out by the method of J. Lewkowitsch 20 : 10 grams of the sample are boiled for two hours with an equal volume of acetic anhydrid in a flask provided with an inverted condenser ; the mass is then trans- ferred to a larger beaker, diluted with several hundred cubic centimeters of water, and boiled for 30 minutes, with a slow current of carbon dioxid passed through by means of a tube drawn out at the lower end to a fine opening. This prevents bumping. On cooling, two layers are formed. The water- layer is drawn off by a siphon and the other portion washed three times by boiling with convenient measures of water. Prolonged washing should be avoided. The acetylated prod- uct is freed from water by filtration through a dry filter in a water-oven at 100. 5 grams of the substance are saponified as noted on page 148, the alcohol is evaporated, and the soap dissolved in water. The subsequent operations may now be completed by two methods, " distillation " or "filtration." The latter is the shorter and more convenient. Distillation Method. The liquid is made up to a volume of FATS AND OILS 163 several hundred cubic centimeters in a flask fitted with an arrangement for passing in steam or for adding water from time to time. Sufficient dilute sulfuric acid (i part of acid to 10 of water) is added to make the liquid slightly acid, and distillation is carried on until about 700 c.c. are collected. The distillate is filtered and titrated with decinormal alkali. Phenolphthalein is recommended as an indicator, but probably methyl-orange will serve as well. The number of cubic cen- timeters of solution required to neutralize the distillate, mul- tiplied by 5.61 and the product divided by the weight of the acetylated material, gives the acetyl number. Filtration Method. The solution of the saponified acetyl- ated substance is mixed with sufficient standard sulfuric acid just sufficient to neutralize the alkali added for saponification, and the mixture warmed gently. The acids will separate as an oily layer. The layer is removed, washed with boiling water until the washings are not acid, titrated with decinormal alkali, and the acetyl number calculated as above. The acetyl number is the number of milligrams of potas- sium hydroxid required for neutralizing the acetic acid ob- tained from i gram of the acetylated substance. In this process cholesterol and phytosterol are included in the acetylization. Substances yielding volatile acids give an acetyl number too high ; this condition will affect the distillation method more than the filtration method. To eliminate most of this error, the percentage of volatile acid should be determined and the figures obtained deducted from the acetyl number. The water used in both methods should be freed as far as possible from carbon dioxid. Even the water used in pro- ducing the open steam should be brought to active boiling before the steam is let into the flask. Waters rich in car- bonate are especially objectionable. A slight excess of sul- furic acid causes the insoluble acids to separate better, but 164 FOOD ANALYSIS this must, of course, be known accurately and allowance made for it. It is possible that the data elucidated by H. D. Richmond with regard to the rate of distillation of acids of the acetic series could be applied to the distillation method with advan- tage, but a special investigation will be needed to determine the point. Viscosity. Practical determinations of viscosity are com- parative only and are of little value unless uniform methods are employed. Many forms of viscosimeter have been de- vised. The only form we can recommend for general use is the torsion viscosimeter devised by O. S. Doolittle. A de- scription of the instrument and its use is unnecessary, as it is made according to standard patterns and full working direc- tions are furnished with it. W. C. Blasdale investigated the relative viscosities of solu- tions of soap from different grades of olive oils and found the figures of much value. He used the torsion viscosimeter. The preparation of the solution is as follows : 1 5 grams of the sample are saponified with a mixture of 10 c.c. of alcohol and 30 c.c. of water containing 7.5 grams of potassium hy- droxid. The mass is washed into a large dish, heated until the alcohol is removed, diluted to 500 c.c. at 20, and the viscosity determined. The result is expressed by Blasdale in the number of grams of sugar that it would be necessary to add to a liter of water to get the same readings. With some oils it would be necessary to dilute the solution to 1000 c.c. Blasdale's results were as follows : OILS. VISCOSITY. Olive (California), 573-655 Cottonseed, 280 Arachis, 220 Sesame, 4' 5 Rape 670 Sweet almond, 645 FATS AND OILS i6 5 Mustard-seed oils give high viscosity figures, and a mixture of these with cottonseed oil in some proportions would escape recognition by this test. Unsaponifiable Matter. Most fats and oils contain ap- preciable amounts of unsaponifiable substances, but the determination of them is of value principally in detecting adulteration with mineral oil and paraffin. In many cases saponification and solution of the soap in water will not suffice for separation, and the routine method devised by A. H. Allen must be followed : 5 grams of the sample are saponified, the solution freed from alcohol if any has been used, and transferred to a stoppered separator (Fig. 44) of 200 c.c. capacity, the exit tube of which is cut off obliquely. The mass is diluted with water to about 80 c.c., 60 c.c. of ether added, the vessel closed, well shaken, and allowed to rest. Separation does not always occur readily, but may often be induced by cooling the contents, by adding a little sodium hydroxid solution, more ether, or a few cubic centimeters of alcohol and rotating the mass gently. The aqueous liquid is run FIG. 44. out, a few drops of sodium hydroxid solution and 10 c.c. of water are added, gently agitated, and run off. This treatment is repeated, after which the ether is run off in a tared flask, the aqueous liquid is agitated with a fresh por- tion of ether, which is washed and poured into the tared vessel as before. This process is again performed, when it will be complete. The ethereal solution will often be fluorescent. The greater portion of the ether should be distilled off in a recovering apparatus and the rest evaporated in the water- bath. If the mass retains globules of water, the flask should be held horizontally and rotated rapidly so as to spread the l UN1V_ V J 1 66 FOOD ANALYSIS residue in a thin layer. When no more water is visible and the odor of ether is very slight, the flask is placed on its side in the water-oven for I 5 minutes, cooled, and weighed. Long heating should be avoided, as some hydrocarbons are sensibly volatile at 100. Spermaceti and waxes yield in this process a large percentage of unsaponifiable matter, hence it is not available for the detection of paraffin in such sub- stances. In ordinary cases the distribution of the bodies will be as follows. Many resins will pass into the water in the form of sodium salts : IN THE ETHER : IN THE WATER : Hydrocarbons. Sodium salts. Mineral oils. Glycerol. Paraffin. Sodium hydroxid. Neutral resins. Coloring-matters from palm oil. Phytosterol. Cholesterol. ANALYTIC DATA. The data, commonly termed " con- stants," obtained by the processes described in the preceding pages, are subject to uncertainty, owing to the want of abso- lute standards. Fats and oils, especially the latter, being mixtures of several ingredients, will vary with conditions of growth of the animals or plants yielding them, methods of extracting and refining, exposure to light, heat, and air, and, doubtless, from unrecognized causes. Samples prepared in the laboratory do not necessarily serve as standards for com- mercial products. Errors of observation from defective ap- paratus, especially inaccurate thermometers, are by no means uncommon. The data for specific gravity and for melting and solidifying points given in the following tables have been compiled from the best accessible sources, and will give a general idea of the range of figures in commercial samples : FATS AND OILS i6 7 SPECIFIC GRAVITIES OF FATS AND OILS AND OF ACIDS DERIVED FROM THEM OILS. Olive, .......... 0.914-0.918 Cottonseed, ....... 0.922-0.930 0.8725 Maize, .......... 0.916-0.926 0.8711 Coconut, ......... 0.925 (at 18; 0.868-0.874 Arachis, ........ 0.916-0.922 Sesame, ......... 0.921-0.924 Rape, .......... 0.913-0.917 Cacao-butter, . ...... 0.945-0.976 0.857 Lard, . . ........ 0.931-0.938 0.859-0.864 Tallow, ......... 0.893-0.898 Butter-fat, ........ 0.926-0.940 0.909-0.914 Coconut olein, ...... 0.926 0.907 ACIDS. (iooP.) 0.875 0.882 0.844 0.847 0.875-0.879 0.837-0.840 0.870 MELTING AND SOLIDIFYING POINTS OF FATS AND OILS. MELTING-POINTS AND TITER-TESTS OF ACIDS The liter-tests were determined by J. Lewkowitsch. OIL OR FAT. ACIDS. Melting- point. Olive, Cottonseed, . . . Maize, Coconut, 20 to 28 Arachis, Sesame, Rape, Cacao-butter, . . . 30 to 34 Lard 28 to 45 Butter-fat, ... . 29 to 35 Beef tallow, . . . .361049 Mutton tallow, . . . 36 to 49 Solidifying- point. Melting-point. Titer-test. 4 to 2 24 to 27 16.9 to 26.4 I to IO 35 to 40 32.2 to 37.6 not above IO 18 to 20 14 to 23 24 to 27 21.2 to 25.2 5 28 to 33 28.1 to 29.2 4 to 6 23 to 31 21.2 to 23.8 6 to 10 18 to 22 11.7 to 13.6 20 to 27 48 to 52 48.0 t048.2 27 to 44 35 to 47 41.4 to 42.0 20 to 30 36 to 46 (insol.) 33 ^ 48 43 to 47 37.9 1046.2 33 to 48 46 to 54 40.1 1048.3 IODIN NUMBERS OF FATTY ACIDS OIL OR FAT. MIXED ACIDS. LIQUID ACIDS. Olive, 86-90 Cottonseed, Ill-li6 147 Maize 113-125 140 Arachis, 95-103 128 Sesame, 109-112 Rape, 99-105 Coconut, 8.5-9 54 Cacao-butter, 3 2 -5~39 Butter-fat, 28-31 Lard, 64-81 104 i68 FOOD ANALYSIS Q ^i - . t, U %<'v M OS <^- t^ CO ON ON s"-b f 1 1 ON 00 1 CO J id ^ w "^ CO Q ON HH H u_ 00 K 00 ^ ON K N ON i . oo 10 CO s w J o 4 2 2 ^ I I CO M vq |u OO O 13 "73 xt- 13 H 13 1 & 13 I 1 * s Cfl 1 00 S3 tfl vo vo I l< CO ^ 1 u <; 5 t^ rh filS ! CO VO CO VO 7 i-O ^H & 00 VO O (-H Sgilf q ^ t-O ^ vq VO ^l^jS 1 ^? 2 s 5* CO vo 6 * H *--' , pj fc " ^ IO t^ t^ 00 OJ ill 1 ! J CO 4 g I 1 VO 1 < u " J^ O ^ ^ ^ ON OO n co j. H j ON ON 0\ ON vo O co ON fc < C^ (.^ ^_, c^ o^ r^ i 1 l-O J, 1 oo I 7 VO VO 01 i vo 00 ON oo ON 00 tx rf ON 20.2 20.3 20.3 20.4 20.5 20.6 20.7 20.8 20.9 20.9 21.0 21. 1 21.2 22 21.2 21.3 21-3 21.4 21-5 21.6 21.7 21.8 21.9 21.9 22.0 22.1 22.2 23 22.2 22.3 22.3 22.4 22.5 22.6 22.7 22.8 22.8 22.9 23.0 23.1 23.2 24 23.2 23-3 23-3 23-4 23-5 23.6 23.6 23-7 2 3 .8 23-9 24.0 24.1 24.2 25 24.1 24.2 24-3 24.4 24-5 24.6 24.6 24.7 2 4 .8 24.9 25.0 25.1 25.2 26 25-1 25.2 25.2 25-3 25-4 25-5 25.6 25.7 2 5 .8 25-9 26.0 26.1 26.2 27 26.1 26.2 26.2 26.3 26.4 26.5 26.6 26.7 26.8 26.9 27.0 27.1 27-3 28 27.0 27.1 27.2 27-3 27.4 27-5 27.6 27.7 2 7 .8 27.9 28.0 28.1 28.3 29 28.0 28.1 28.2 28.3 28.4 28.5 28.6 28.7 28.8 28.9 29.0 29.1 29-3 30 29.0 29.1 29.1 29.2 29-3 29.4 29.6 29.7 29.8 29.9 30.0 3 O.I 30-3 31 29.9 30.0 3 O.I 30.2 30-3 30-4 30-5 30.6 30.8 3-9 3 I.O 31.2 31.3 32 30.9 31.0 31-1 31.2 3*-3 31.4 3i-5 31.6 31-7 3i-9 32.0 3 2.2 32-3 33 31-8 31-9 32.0 32.1 32-3 32.4 32-5 32.6 32.7 32.9 33- 33-2 33-3 34 32.7 32.9 33-o 33-i 33-2 33-3 33-5 33.6 33-7 33-9 34-o 34-2 34-3 35 33-6 33-8 33-9 34-o 34-2 34-3 34-5 34-6 34-7 34-9 35-o 35-2 35-3 C. 10 i^mm^^m 10.5 ii. i n.6 12.2 12.7 13-3 13-8 14.4 *S- 15-5 16.1 16.6 MILK AND MILK PRODUCTS 201 More accurate determination can be made by the methods detailed in the introductory part (page 41), the most suitable being the Sprengel tube. According to H. D. Richmond, the pyknometer is less suitable for rigidly accurate work, on ac- count of the tendency of the cream to separate before the mass has acquired the standard temperature. Total Solids. This determination may often be made with sufficient accuracy for practical purposes by evaporating a measured volume (e. g., 3 or 5 c.c.) in a shallow nickel 63 64 65 66 67 68 69 70 71 72 .z^aaH 73 74 75 21.3 21.4 21-5 21.6 21.7 21.8 22.0 22.1 22.2 22.3 22.4 22.5 22.6 22.3 22.4 22.5 22.6 22.7 22.8 23.0 23.1 23-2 23-3 23.4 23-5 23-7 23-3 23-4 23-5 23.6 23-7 23-8 24.0 24.1 24.2 24-3 24.4 24.6 24.7 24-3 24.4 24-5 24.6 24.7 24.9 25.0 25-1 25.2 25-3 25-5 25.6 25-7 25-3 25-4 25-5 25.6 25-7 25-9 26.O 26.1 26.2 26.4 26.5 26.6 26.8 26.3 26.5 26.6 26.7 26.8 27.0 27.1 27.2 27-3 27.4 27.5 27.7 2 7 .8 27.4 27-5 27.6 27.7 27.8 28.0 28.1 28.2 28-3 28.4 28.6 28.7 28.9 28.4 28.5 28.6 28.7 28.8 29.0 29.1 29.2 29.4 29-5 29.7 29.8 29.9 29.4 29-5 29.6 29.8 29.9 30.1 30.2 30-3 30-4 30-5 30-7 3-9 31.0 30-4 30-5 30-7 30.8 30.9 3I-I 31.2 31-3 31-5 31-6 31.8 31-9 32.1 31-4 3i-5 3i-7 31-8 32.0 32.2 32.2 32.4 32.5 32.6 32.8 33-o 33-i 32.5 32-6 32.7 32.9 33-o 33-2 33-3 33-4 33-6 33-7 339 34-o 34-2 33-5 33-6 33-8 33-9 34-0 34-2 34-3 34-5 34-6 34-7 34-9 35-i 35-2 34-5 34-6 34-8 .34-9 35-0 35-2 35-3 35-5 35-6 35-8 36.0 36.1 36.3 35-5 35-6 35-8 35-9 36.1 36.2 36.4 36.5 36.7 36.8 37-o 37-2 37-3 17.2 17.7 18.3 i8.8 19.4 20 20.5 21. 1 21.6 22.2 22.7 23-3 23.8 18 2O2 FOOD ANALYSIS dish from 5 to 8 cm. in diameter. Nickel crucible-covers are suitable. When greater accuracy is required, and especially when the ash is to be determined, platinum dishes must be used. Satisfactory results may be secured by the following simple method : A flat platinum dish, 3.5 cm. in diameter, with sides o. 5 cm. high, is provided with a thin flat watch- glass cover that fits rather closely. The total weight of the cover and dish is noted. 2 or 3 c.c. of the sample are run into the dish from the pipet, the watch-glass placed on, and the weight taken as rapidly as possible. The glass prevents appreciable loss from evaporation during an ordinary weighing. The cover is removed, the dish heated on the water-bath or in the water-oven, and weighed from time to time (with cover on it) until the weight is sensibly constant. The percentage of residue can be easily calculated. About three hours may be required to secure constant weight. The following are the methods adopted by the A. O. A. C. : 1. Heat to constant weight at the temperature of boiling water from I to 2 grams of milk in a tared flat dish of not less than 5 cm. diameter. If desired, from 15 to 20 grams of pure dry sand may be previously placed in the dish. 2. Babcock Asbestos Method. Provide a hollow cylinder of perforated sheet metal 60 mm. long and 20 mm. in diameter, closed 5 mm. from one end by a disk of the same material. The perforations should be about 0.7 mm. in diameter and 0.7 mm. apart. Fill the cylinder loosely with from 1.5 to 2.5 grams of freshly ignited woolly asbestos free from fine or. brittle material. Cool in a desiccator and weigh. Introduce a weighed quantity of milk (about 4 grams) and dry at 100 to constant weight. The residue may be employed for the determination of the fat. Ash. The residue from the determination of total solids is heated cautiously over the Bunsen burner, until a white ash is left. The result obtained in this manner is apt to be slightly MILK AND MILK PRODUCTS low from loss of sodium chlorid. This may be avoided by heating the residue sufficiently to char it, extracting the sol- uble matter with a few cubic centimeters of water, and filtering (using paper extracted with hydrofluoric acid). The filter is added to the residue, the whole ashed, the filtrate then added, and the liquid evaporated carefully to dry ness. The ash of normal milk is about 0.7 per cent, and faintly alkaline. A marked degree of alkalinity and effervescence with hydro- chloric acid will suggest the addition of a carbonate. The method of the A. O. A. C. is as follows : In a weighed dish put 20 c.c. of milk from a weighing bottle ; add 6 c.c. of nitric acid, evaporate to dryness, and burn at a low red heat till the ash is free from carbon. Fat. Many methods for fat determination have been devised. The following will suffice for all practical work : . Adams' Method. This consists essentially in spreading the milk over absorbent paper, drying, and extracting the fat in an extraction apparatus ; the milk is distributed in an extremely thin layer, and by a selective action of the paper the larger portion of the fat is left on the surface. A paper, manufac- tured especially for this purpose by Schleicher & Schuell, is obtainable in strips of suitable size. Each of these yields to ether only from o.ooi to 0.002 gram of extract. The procedure recommended by the A. O. A. C. is as fol- lows : Coils made of thick filter-paper, cut into strips 6.25 by 62.5 cm., are thoroughly extracted with ether and alcohol, or the weight of the extract corrected by a constant obtained for the paper. From a weighing bottle about 5 grams of the milk are transferred to the coil by means of a pipet, care being taken to keep dry the end of the coil held in the fingers. The coil is placed, dry end down, on a piece of glass and dried at the temperature of boiling water for one hour, preferably in an atmosphere of hydrogen ; it is then 2O4 FOOD ANALYSIS transferred to an extraction apparatus and extracted with ab- solute ether or petroleum spirit of boiling-point about 45. The extracted fat is dried in hydrogen and weighed. The above procedure is very satisfactory, but the drying in hydrogen may usually be omitted. After the coil has received at least ten or twelve washings, the flask is detached, the ether removed by distillation, and the fat dried by heating in an air-oven at about 105, and occasionally blowing air through the flask. After cooling, the flask is wiped with a piece of silk, allowed to stand ten minutes, and weighed. H. D. Richmond states that to perform a rigidly accurate determination attention to the following points is necessary : The ether must be anhydrous (drying over calcium chlorid and distilling is sufficient). Schleicher & Schuell's fat-free papers should be used, and one should be extracted without any milk on it, as a tare for the others. Four or five hours' extraction is necessary, and the coils should be well dried before extraction is begun. Thimble-shaped cases made of fat-free paper are now r obtainable and are convenient for holding the absorbent material on which the milk is spread. The fine texture pre- vents undissolved matter escaping. A case may be used repeatedly. Sour milk must be thinned with ammonium hydroxid before taking the portion for analysis. BabcocK s extraction method is also recommended by the A. O. A. C. The cylinder containing the residue from the determination of total solids (page 202) is placed in the extraction tube and extracted with ether in the usual way. The ether is evaporated and the fat weighed, or the extracted cylinder may be dried at 100 and the fat determined by the loss in weight. As before, a higher degree of accuracy is secured by performing the drying operation in hydrogen. Werner-Schmid Method. This is suitable for sour milk. 10 c.c. of the milk are measured into a long test-tube of 50 MILK AND MILK PRODUCTS 205 c.c. capacity, and 10 c.c. of strong hydrochloric acid added, or the milk may be weighed in a small beaker and washed into the tube with the acid. After mixing, the liquid is boiled I y 2 minutes, or the tube may be corked and heated in the water-bath from 5 to 10 minutes, until the liquid turns dark brown. It must not be allowed to turn black. The tube and contents are cooled in water, 30 c.c. of well-washed ether added, shaken, and allowed to stand until the line of acid and ether is distinct. The cork is taken out, and a double-tube arrangement, like that of the ordinary wash-bottle, inserted. The stopper of this should be of cork and not of rubber, since it is difficult to slide the glass tube in rubber, and there is a possi- bility, also, of the ether acting on the rubber and dissolving it. The lower end of the exit-tube is adjusted so as to rest immediately above the junction of the two liquids. The ethereal solution of the fat is then blown out and received in a weighed flask. Two more portions of ether, 10 c.c. each, are shaken with the acid liquid, blown out, and added to the first. The ether is then distilled off and FIG. 45. the fat dried and weighed as above. Centrifugal Methods. Among the processes for the rapid determination of fat, those employing centrifugal action have been found most convenient. The following method, devised by H. Leffmann and W. Beam in 1889, has proved satisfac- tory on the score of accuracy, simplicity, and ease of manipu- lation. The distinctive feature is the use of fusel oil, the effect of which is to produce a greater difference in surface tension between the fat and the liquid in which it is sus- pended, and thus promote its readier separation. This effect 206 FOOD ANALYSIS has been found to be heightened by the presence of a small amount of hydrochloric acid. The test-bottles have a capacity of about 30 c.c. and are provided with a graduated neck, each division of which repre- sents o. I per cent, by weight of butter fat. 15 c.c. of the milk are measured into the bottle, 3 c.c. of a mixture of equal parts of amyl alcohol and strong hydro- chloric acid added, mixed, the bottle filled nearly to the neck with concentrated sulfuric acid, and the liquids mixed by holding the bottle by the neck and giving it a gyratory mo- tion. The neck is now filled to about the zero point with a mixture of sulfuric acid and water prepared at the time. It is then placed in the centrifugal machine, which is so arranged that when at rest the bottles are in a vertical position. If only one test is to be made, the equilibrium of the machine is maintained by means of a test-bottle, or bottles, filled with a mixture of equal parts of sulfuric acid and water. After rota- tion for from one to two minutes, the fat will collect in the neck of the bottle and the percentage may be read off. It is convenient to use a pair of dividers in making the reading. The legs of these are placed at the upper and lower limits respectively of the fat, allowance being made for the menis- cus ; one leg is then placed at the zero point and the reading made with the other. Experience by analysts in various parts of the world has shown that with properly graduated bottles the results are reliable. As a rule, they do not differ more than o. I of I per cent, from those obtained by the Adams process, and are generally even closer. For accurate work, the factor for correcting the reading on each of the bottles should be determined by comparison with the figures obtained by the Adams or other standard process. Cream is to be diluted to exactly ten times its volume, the specific gravity taken, and the liquid treated as a milk. Since in the graduation of the test-bottles a specific gravity MILK AND MILK PRODUCTS 2O? of 1.030 is assumed, the reading must be increased in pro- portion. A more accurate result may be obtained. by weighing in the test-bottle about 2 c.c. of the cream and diluting to about 15 c.c. The reading obtained is to be multiplied by 15.45 and divided by the weight in grams of cream taken. The mixture of fusel oil and hydrochloric acid seems to be- come less satisfactory when long kept. It is best, therefore, not to make up large amounts at once. The mixture should be clear and not very dark in color. It is best kept in a bottle provided with a pipet which can be filled to the mark by dipping. Rigid accuracy in the measurement is not needed. Calculation Methods. Several investigators have proposed formulae by which when any two of the data, specific gravity, fat, and total solids, are known, the third can be calculated. These vary according to the method of analysis employed. That of O. Hehner and H. D. Richmond, as corrected by Richmond, was deduced from results by the Adams method of fat extraction, and has been found to be the most satisfactory. It is as follows : T = 0.25 G -j- 1.2 F -f 0.14; in which T is the total solids, G the last two figures of the specific gravity (water being 1000), and F the fat. A table based upon this formula is annexed (p. 208). A formula has been devised by Richmond by which the lactose and proteids may be calculated (approximately), the specific gravity, fat, total solids, and ash being known. Thus : P = 2.8 T + 2.5 A 3.33 F 0.7 -- in which Pis the proteids, Tthe total solids, A the ash, .Fthe fat, D specific gravity (water at 15.5 being taken as i), and G i ooo D i ooo. 2 3 208 FOOD ANALYSIS r^ O PJ to r^ O t^Q\O M CS Tf cxo 4 00 CO M PJ P) M P< PI PI PI PI PJ PJ PJ to vO 00 ON O PJ' PJ' PJ' pi -< rOrJ-vovOOO Pj' pj PJ" PJ' P) fOvOOO M ro Q\O w ro^ pj ro fO ro ro rt-vo O\H4 O\O -i rO ON vO ONO HH CO rj- rf CN vO tooo O ON O PJ M" pj PJ' to t^ O . 00 ON d 6 o' MQMMMMMMPJ MILK AND MILK PRODUCTS The difference between the total solids and the fat, proteids, and ash gives the lactose. In this formula it has been assumed that everything that is not fat, proteids, nor ash is milk-sugar ; an assumption which is not strictly correct, and which intro- duces a small error. Another error is introduced by the fact that the ash in milk is not the same as the salts existing in the milk. The errors between the proteids and lactose found and calculated vary between 0.4. Total Proteids. For practical purposes the total pro- teids are best estimated by calculation from the total nitrogen obtained by the Kjeldahl-Gunning method. Milk contains, however, a sensible proportion of non-proteid nitrogen. Ac- cording to Munk, this may range, in cows' milk, from 0.022 to 0.034 per cent., and from 0.014 to 0.026 per cent, in human milk. According to these figures, the average pro- teid nitrogen in cows' milk would be 94 per cent., and in human milk 91 per cent., of the total nitrogen. The determination of total nitrogen as recommended by the A. O. A. C. is to place in the digestion flask a known weight (about 5 grams) of the sample and proceed, without evaporation, as described on page 44. The factor used to convert nitrogen to proteids is 6.25. Ritthausen Method. This method depends on precipitation by copper sulfate and sodium hydroxid. It is applicable only to fully developed milks ; the proteids of colostrum and whey are only partially precipitated. The reagents are given on page 1 16. 10 grams of milk are placed in a beaker, diluted with 100 c.c. of distilled water, 5 c.c. of copper sulfate solution added, and thoroughly mixed. The sodium hydroxid solu- tion is then added drop by drop, with constant stirring, until the precipitate settles quickly and the liquid is neutral, or at most very feebly acid. An excess of alkali will prevent the precipitation of some of the proteids. 210 FOOD ANALYSIS The reaction should be tested on a drop of the clear liquid, withdrawing it by means of a rod, taking care not to include any solid particles. When the operation is correctly per- formed, the precipitate, which includes the fat, settles quickly, and carries down all of the copper. It is washed by decanta- tion with about 100 c.c. of water, and collected on a filter (previously dried at 130 and weighed in a weighing bottle). The portions adhering to the sides of the beaker are dis- lodged with the aid of a rubber-tipped rod. The contents of the filter are washed with water until 250 c.c. are collected, which are mixed and reserved for the determination of the sugar as described below. The water in the precipitate is removed by washing once with strong alcohol, and the fat by six or eight washings with ether. An extraction apparatus may be used for this purpose. The washings being received in a weighed flask, the determination of the fat may be made by evaporating the ether, with the usual precautions. The residue on the filter, which consists of the proteids in association with copper hydroxid, is washed with absolute alcohol, which renders it more granular, and then dried at 130 in the air-bath. It is weighed in a weighing bottle, transferred to a porcelain crucible, incinerated, and the resi- due again weighed. The weight of the filter and contents, less that of the filter and residue after ignition, gives the weight of the proteids. The results by this method are slightly high, since copper hydroxid does not become com- pletely converted into copper oxid at 130. Casein and Albumin. The most accurate separation of casein and albumin is made by Sebelein's method, as follows : 20 c.c. of the sample are mixed with 40 c.c. of a saturated solution of magnesium sulfate and powered magnesium sul- fate stirred in until no more will dissolve. The precipitate of casein and fat, including the trace of globulin, is allowed to settle, filtered, and washed several times with a saturated MILK AND MILK PRODUCTS 211 solution of magnesium sulfate. The filtrate and washings are saved for the determination of albumin. The filter and contents are transferred to a flask and the nitrogen deter- mined by the method described above. The nitrogen so found, multiplied by 6.38, gives the casein. The filtrate and washings from the determination of casein are mixed, the albumin precipitated by Almen's tannin reagent, filtered, and the nitrogen in the precipitate determined as above. The same factor is used. A/men's reagent is prepared by dissolving 4 grams of tan- nin in 190 c.c. of 50 per cent, alcohol and adding 8 c.c. of acetic acid of 25 per cent. H. D. Richmond and L. K. Boseley have modified the Ritt- hausen process by diluting the milk to 200 c.c., adding a little phenolphthalein, and neutralizing any acidity by the cautious addition of dilute sodium hydroxid solution, then adding from 2.0 to 2.5 c.c. of the copper sulfate solution. The precipitate is allowed to settle, washed, and estimated as above. This modification was found to give good results with all milk products except whey, which contains albumoses pro- duced by the action of rennet. In a mixture of milk and whey in about equal parts, Richmond and Boseley found about 0.3 per cent, of albumoses not precipitated by the copper sul- fate nor by magnesium sulfate, but precipitable, along with the albumin, by a solution of tannin. The separation may be effected by diluting the filtrate from the magnesium sulfate precipitation, acidifying slightly with acetic acid, and boiling, when the albumin will be coagulated and precipitated. The albumoses may be separated by filtering the solution and pre- cipitating with tannin solution. The precipitated proteids are best estimated by determining the nitrogen in the moist pre- cipitate. The separation of the proteids may be effected, though less accurately, by the use of acetic acid, as recommended by 212 FOOD ANALYSIS Hoppe-Seyler and Ritthausen. The following methods have been provisionally adopted by the A. O. A. C. : 1. Provisional Method for the Determination of Casein in Cows' Milk. The determination should be made when the milk is fresh. When it is not practicable to make the deter- mination within 24 hours, add one part of formaldehyde to .2500 parts of milk and keep in a cool place. 10 grams of the sample are diluted with about 90 c.c. of water at between 40 and 42 and 1.5 c.c. of a solution containing 10 per cent, of acetic acid by weight, allowed to stand for five minutes, washed three times by decantation, pouring the washings through a filter, and the precipitate transferred completely to the filter. If the filtrate is not clear at first, it will generally become so in two or three filtrations, after which the washing can be completed. The nitrogen in the washed precipitate and filter is determined by the Kjeldahl-Gunning method. The nitrogen, multiplied by 6.25, gives the casein. In working with milk which has been kept with preserva- tives, the acetic acid should be added in small portions, a few drops at a time with stirring, and the addition continued until the liquid above the precipitate becomes clear or nearly so. 2. Provisional Method for the Determination of Albumin in Milk. The filtrate obtained in the above operation is neutral- ized with sodium hydroxid, 0.3 c.c. of the 10 per cent, solu- tion of acetic acid added, and the mixture heated for 1 5 minutes. The precipitate is collected on a filter, washed, and the nitrogen determined. We have found the following method satisfactory, avoiding the difficulty of washing the precipitate : 10 c.c. of the milk are mixed with saturated magnesium sulfate solution and the powdered salt added to saturation. The mixture is washed into a graduated measure with a small amount of the saturated solution, made up to 100 c.c. with the same solution, mixed, and allowed to stand until the separation takes place. As MILK AND MILK PRODUCTS 213 much as possible of the clear portion is drawn off with a pipet and passed through a dry filter. An aliquot portion of the filtrate is taken, the albumin precipitated by a solution of tannin, and the nitrogen in the precipitate determined as above. The casein is found by subtracting the figure for albumin from that for total proteids. Lactose. Soxhlet's method, adopted by the A. O. A. C., is as follows : 25 c.c. of the sample in a 500 c.c. flask are diluted with 400 c.c. of water and 10 c.c. of copper sulfate solution (34.639 grams crystallized copper sulfate in 500 c.c.) and 8.8 c.c. ^ sodium hydroxid solution added. (The mix- ture should still have an acid reaction and contain copper in solution. If this is not the case, the experiment must be repeated, using a little less of the alkali.) The flask is filled to the mark with water, shaken, and the liquid passed through a dry filter. 50 c.c. of the mixed copper reagent (page 116) are heated to brisk boiling in a 300 c.c. beaker, 100 c.c. of the filtrate obtained as above added, and boiling continued for six minutes ; the liquid then promptly filtered, and treated ac- cording to methods given on pages 120 to 122. The amount of lactose is calculated from the copper obtained by the table on page 214. The figures for weights of copper between any two data given in the table may be calculated with sufficient accuracy for practical purposes by allowing 0.0608 gram of lactose for each o.ooi gram of copper. Lactose may be determined by the polarimeter after re- moval of the fat and proteids, which is best effected, as recom- mended by H. W. Wiley, by a mercuric nitrate solution, pre- pared by dissolving mercury in twice its weight of nitric acid of 1.42 sp gr. and adding to the solution five volumes of water. 60 c.c. of the milk are placed in a 100 c.c. flask and 10 c.c. of the mercuric solution added. The flask is filled to the 214 FOOD ANALYSIS mark with water, well shaken, and the liquid filtered through a dry filter. The filtrate, which will be perfectly clear, may be examined at once in the polarimeter. Several readings should be made and the average taken. COPPER. LACTOSE. COPPER. LACTOSE. COPPER. LACTOSE. 0. 100 0.072 0.205 0.151 0.305 0.228 0.105 0.075 0.210 0.154 0.310 0.232 O.I 10 0.079 0.215 0.158 0.315 0.236 0.115 0.083 O.22O 0.162 0.320 0.240 0.120 0086 0.225 0.165 0.325 0.244 O.I25 0.090 0.230 0.169 0-33 0.248 0.130 0.094 0.235 0.173 0-335 0.252 0.135 0.097 0.240 0.177 0.340 0.256 0.140 O.IOI 0.245 0.181 0-345 0.260 0.145 0.105 0.250 0.185 0.350 0.264 0.150 0.109 0.255 0.189 0-355 0.268 0-155 0. 112 0.260 0.192 0.360 0.272 o. 1 60 0.116 0.265 0.196 0.365 0.276 0.165 0.120 0.270 O.2OO 0.370 0.280 0.170 o. 124 0.275 0.204 0-375 0.285 0.175 0.128 0.280 O.2O8 0.380 0.289 0.180 0.132 0.285 0.212 0.385 0.293 0.185 0.134 0.290 0.216 0.390 0.298 0.190 0.139 0.295 O.22I 0-395 0.302 0.195 0.141 0.300 8.224 0.400 0.306 O.2OO 0.147 It is to be noted that the actual volume of the sugar-con- taining solution is 100 c.c., less the space occupied by the precipitated proteids and fat. The volume of fat is found by multiplying the weight in grams by 1.075 and the proteids by multiplying the weight by 0.8. P. Vieth recommends adding mercuric solution in the pro- portion of 3 c.c. to 100 c.c. of the milk, when the whey will oc- cupy the same volume as the original milk, less that of the MILK AND MILK PRODUCTS 215 fat, since, for all practical purposes, 3 c.c. may be taken as the volume of the albuminoids precipitated. The employment of a factor for correcting for the volume of precipitate may be avoided by Scheibler's method of" double dilution" (see page 30), in which two solutions of different volume are compared. The following is a summary of the method given by H. W. Wiley and E. E. Ewell 24 : The polari- meter used in this experiment was adapted to a normal weight of 26.048 sucrose, and 32.91 grams of lactose in 100 c.c. gave a reading of 100. The amount of milk taken was double this quantity, 65.82 grams, which were placed in a 100 c.c. flask, 10 c.c. of the acid mercuric nitrate added, the flask filled to the mark the contents well mixed, filtered, and polarized. A similar quan- tity of the milk was placed in a 200 c.c. flask and treated in the same way. The true polarization is obtained by dividing the product of the readings in the two flasks by their difference. The following experiments are given by Wiley and Ewell : READING IN 200 READING IN 100 APPARENT PERCENT- TRUE PERCENT- c.c. FI.ASK. c.c. FLASK. AGE LACTOSE. AGE LACTOSE. 10.15 20.84 5-2i 4.95 The polarimeter used had a tube 4 decimeters long. The figure for apparent percentage is obtained by dividing the reading of the small flask by 4. The true percentage is obtained by multiplying 10.15 by 20.84, dividing by their difference (10.69), and taking one-fourth this quotient. Unless the instrument be highly accurate, and great care be taken in the work, the results are less satisfactory than by the method first described, in which an allowance is made for the volume of the precipitate. Birotation. When freshly dissolved in cold water, milk sugar shows a higher rotation than that given above. By standing, or immediately on boiling, the rotatory power falls to the point mentioned. In preparing solutions from the solid milk-sugar, care must be taken to bring them to the boiling- 2l6 FOOD ANALYSIS point previous to making up a definite volume. This pre- caution is unnecessary when operating upon milk. Adulterations. The addition of water to milk is usually detected by the diminution in the amount of solids. The addition of water decreases the specific gravity, while abstraction of fat increases it. P. Vieth has pointed out that in normal milks the ratio sugar : proteids : ash = 13 : 9 : 2 exists, and a determination of these ratios may aid in the attempt to distinguish genuine but abnormal milks from watered milks. In the case of a watered milk the proportion would remain unchanged, but in abnormal milk it has been found to vary. H. D. Richmond finds that "the most constant figure in normal milks is the proportion of ash to solids not fat, which averages 8.3 per cent, and very rarely passes outside of the limits of 8.0 per cent, and 8.5 per cent. In cases of low solids not fat this proportion has been disturbed, and the ash has had a higher ratio to the solids not fat." Other observers have found the same. Richmond also states that when unadulterated milk is notably deficient in solids not fat, the deficiency is principally in the lactose. According to Richmond, the determination of the amount of water that has been added to milk is best calculated from the figures obtained by adding the difference be- tween the specific gravity of the sample and 1000 to the figure representing the percentage of the fat. Thus, jf a milk have the specific gravity of 1029.2 and contain 3.27 per cent, of fat, the figure from which the water is calculated is 29.2 -f- 3.27 = 32.47. The mean figure from unadulterated milks was found to be 36.0, but 34.5 is considered to be a safer limit. Accepting this figure, the percentage of added water in the sample given above would be found by the proportion : 34.5 : 32.47 : : 100 : 94.1 ; MILK AND MILK PRODUCTS 217 i. e., the sample would contain 5.9 per cent, of water. Ex- periments on milks which had been diluted with known proportions of water showed that this method of calculating the added water gave nearer approximations to the truth than by calculating from the figure for non-fatty solids. For ordinary milk control it will suffice to take the specific gravity by the lactodensimeter (see page 200) and the fat by the Leffmann-Beam method. From the figures thus obtained the total solids can be ascertained by the table or Richmond's slide-rule. Coloring and Thickening Agents. Several instances of the use of brain-matter, dextrin, and gelatin have been recorded. It is also stated that sugar, salt, and starch have been added. Coloring-matters are used to conceal inferiority in quality. At the present time preparations of annatto, turmeric, and some coal-tar colors are mostly used, especially the latter. Caramel is occasionally used, saffron and carotin but rarely. Annatto may be detected by rendering the sample slightly alkaline by acid sodium carbonate, immersing a slip of filter- paper, and allowing it to remain overnight. Annatto will cause a reddish-yellow stain on the paper. A. Leys gives the following method for detecting annatto : 50 c.c. of the sample are shaken with 40 c.c. of 95 per cent, alcohol, 50 c.c. of ether, 3 c.c. of water, and 1.5 c.c. of ammonium hydroxid solution (sp. gr. 0.900), and allowed to stand for 20 minutes. The lower layer, which in presence of annatto will have a greenish-yellow tint, is tapped off and gradually treated with half its measure of 10 per cent, solu- tion of sodium sulfate, the separator being inverted, without shaking, after each addition. By this treatment the casein separates in flakes, which conglomerate and rise to the sur- face, when the adjacent liquid is tapped off, strained through wire gauze, and placed in four test-tubes. To each of these amyl alcohol is added, and the tubes shaken and immersed 19 218 FOOD ANALYSIS in cold water, which is gradually raised to 80. This causes the emulsion to break up, and the alcohol, holding the annatto in solution, to come to the surface. The alcoholic layer is separated from the lower stratum, evaporated to dry- ness, and the residue dissolved in warm water containing a little common alcohol and ammonia. A bundle of white cotton fibers is introduced and the liquid evaporated nearly to dryness on the water-bath. The fiber, which is colored a pale yellow, even with pure milk, is washed and immersed in a solution of citric acid, when it will be immediately colored rose-red if the milk contained annatto. Saffron, turmeric, and the coloring-matter of marigolds do not give a similar reaction. General Method for Colors in Milk. A. E. Leach 2 5 has devised a general method for detecting colors in milk, i 50 c.c. of the sample are coagulated in a porcelain basin, with the addition of acetic acid and heating, and the curd separated from the whey. The curd will often collect in a mass ; but if this does not occur, it must be freed from whey by strain- ing through muslin. The curd is macerated for several hours in a closed flask, with occasional shaking, with ether to extract fat. Annatto will also be removed by it. The ether and curd are separated and treated as follows : The ether is evaporated, the residue mixed with some weak solution of sodium hydro x id, and passed through a wet filter ; and when this has drained, the fat is washed off and the paper dried. An orange tint shows annatto, which may be confirmed by a drop of solution of stannous chlorid, which makes a pink spot. If the curd be colorless, no foreign color- ing-matter is in it ; if orange or brown, it should be shaken with strong hydro- chloric acid in a test-tube. If the mass turns blue giadually, caramel is proba- bly present. The whey should be examined for caramel ( see page 130). If the mass turns pink at once, an azo-color is indi- cated. MILK AND MILK PRODUCTS 2IQ Coal-tar colors may often be detected by the wool-test (p. 77), but H. C. Lythgoe has devised the following method, which he finds very satisfactory : I 5 c.c. of the sample are Vnixed in a porcelain basin with an equal volume of hydro- chloric acid (sp. gr. 1. 20), and the mass shaken gently so -as to break the curd into coarse lumps. If the milk contains an azo-color, the curd will be pink ; with normal milk the curd will be white or yellowish. (See also under " Butter.") Starch may be detected by the blue color developed on the addition of solution of iodin to the milk. Salt and cane-sugar are occasionally added to milk that has been diluted with water. The former is detected by the taste, the increased proportion of ash and of chlorin. Cane- sugar may be detected, if in considerable quantity, by the taste. Cotton devised the following test: 10 c.c. of the sample are mixed with 0.5 gram of powdered ammonium molybdate, and 10 c.c. of dilute hydrochloric acid (i to 10) are added. In a second tube 10 c.c. of milk of known purity or 10 c.c. of a 6 per cent, solution of milk-sugar are similarly treated. The tubes are then placed in the water-bath and the temperature gradually raised to about 80. If sucrose be present, the milk will assume an intense blue color, while genuine milk or milk-sugar remains unaltered unless the temperature be raised to the boiling-point. According to Cotton, the reaction is well marked in the presence of as little as I gram of sucrose to a liter of the milk, and 6 grams and over per liter are usually found in adulterated samples. (See also page 1 14.) The quantitative determination is made by the methods described in connection with condensed milk. GELATIN. A. W. Stokes detects the presence of gelatin in cream or milk as follows : 10 c.c. of the sample, 20 c.c. of cold water, and 10 c.c. of acid mercuric nitrate solution (page 213) are mixed, shaken vigorously, allowed to stand for 22O FOOD ANALYSIS five minutes, and filtered. If much gelatin be present, it will be impossible to get a clear filtrate. A portion of the filtrate is mixed with an equal bulk of saturated aqueous solu- tion of picric acid. If any gelatin be present, a yellow pre- cipitate will be immediately produced. Picric acid will detect the presence of one part of gelatin in 10,000 parts of water. Antiseptic substances are largely used, especially in the warmer season, as a substitute for refrigeration. Many of these are sold under proprietary names which give no indica- tion of their composition. Preparations of boric acid and borax were at one time the most frequent in use, but lately formalin, a 40 per cent, solution of formaldehyde (methyl aldehyde), has come into favor. Sodium benzoate is now in common use as a preservative of cider, fruit-jellies, and simi- lar articles, and may, therefore, be found in milk. Salicylic acid is not so much employed as in former years. Sodium carbonate is occasionally used to prevent coagulation due to slight souring. R. T. Thomson has studied the comparative value of milk preservatives. He finds that a mixture of boric acid and borax is more efficient than the acid alone. The quantity generally used is equivalent to about 0.5 gram of boric acid per liter. Formalin was shown to be by far the most efficient antiseptic. In the proportion of 0.125 gram to the liter, it kept milk sweet for eight days. Formaldehyde. The presence of this body may sometimes be detected by the odor developed on warming the milk. O. Hehner's method, the most characteristic for its detection, depends upon the fact that when milk containing it is mixed with sulfuric acid containing a trace of ferric salt a blue color appears. H. D. Richmond & L. K. Boseley showed that the delicacy of the test is much increased by diluting the milk with an equal bulk of water and adding sulfuric acid of 90 to 94 per cent., so that it forms a layer underneath the milk. MILK AND MILK PRODUCTS 221 Under these conditions, milk, in the absence of formaldehyde, gives a slight greenish tinge at the junction of the two liquids, while a violet ring is formed when formaldehyde is present even in so small a quantity as I part in 200,000 of milk. The color is permanent for two or three days. In the absence of formaldehyde, a brownish color is developed after some hours, not at the junction of the two liquids, but lower down in the acid. Hydrochloric acid containing a small amount of ferric chlorid gives a characteristic violet with quantities of formal- dehyde not over i part per 1000. The test is applied by heating i c.c. of the sample with 4 c.c. of strong hydrochloric acid. If a yellow liquid is formed, the sample should be diluted two or three times and the test repeated. Hydro- chloric acid often contains sufficient ferric chlorid to give the test. The addition of 0.25 gram of ferric chlorid to 1000 c.c. of pure acid will be sufficient. The following test has been found satisfactory by some observers : 5 c.c. of the sample are boiled with 0.05 gram of resorcinol, to which 3 c.c. of a strong solution of sodium hydroxid have been added. If formaldehyde be present, the yellow solution changes to a fine red. O. Hehner also gives the following test: Some of the milk is distilled and to the distillate one drop of a dilute aqueous solution of phenol is added and the mixture poured on strong sulfuric acid contained in a test-tube. A bright crimson zone appears at the line of contact. This color is readily seen with i part of formaldehyde in 200,000 of water. If there is more than i part in 100,000, there is seen above the red ring a white, milky zone, while in stronger solutions a copious white or slightly pink, curdy precipitate is obtained. The reaction succeeds only when carried out as described above ; the phenol must first be mixed with the solution to be tested, and the mixture poured upon the sulfuric acid. Only 222 FOOD ANALYSIS a trace of phenol must be used, and if it be first dissolved in the acid and the formaldehyde solution added, no color is obtained. The precipitate might be utilized for the determination of the strength of dilute formalin solutions. The rate at which formaldehyde disappears from milk has been investigated by Hehner, who found that at the end of a week none could be detected in a sample to which had been added I part in 100,000; after two weeks none could be de- tected in a sample of I part in 50,000 ; and after three weeks only a faint trace could be detected in a sample of I part in 25,000. Determination of Formaldehyde. G. J. Romijn examined several of the quantitative methods and found the following to be satisfactory when no other aldehyde is present in appre- ciable amount : 10 c.c. of the solution are mixed with 25 c.c. iodin solu- * 10 tion and sufficient strong sodium hydroxid solution added to make the liquid bright yellow. After standing 10 minutes, hydrochloric acid is slowly added until a marked brown liquid is produced. The iodin is then titrated with thiosulfate in the usual way. The amount of iodin that has been taken up, multiplied by o. 1 18, will give the amount of formaldehyde. Sodium Carbonate. The following method, due to E. Schmidt, is stated to be capable of detecting o. I per cent, of sodium carbonate or of sodium acid carbonate : 10 c.c. of the milk are mixed with an equal volume of alcohol, and a few drops of a I per cent, solution of rosolic acid added. Pure milk shows merely a brownish-yellow color, but in the presence of sodium carbonate a more or less marked rose-red appears. The delicacy of the test is en- hanced by making a comparison cylinder with the same amount of milk known to be pure. If the salt is present in MILK AND MILK PRODUCTS 223 considerable amount, it may be detected by the increase in the ash, its marked alkalinity and effervescence with acid. Preservation of Milk-samples. Formaldehyde is now gen- erally used ; 0.05 per cent, will keep milk for a month and larger quantities for an indefinite period. E. J. Bevan has, however, noted the fact that the total solids of milk containing formaldehyde are always higher, and that the increase is much greater than can be accounted for, even assuming that the whole of the formaldehyde re- mains in the residue. Experiments on pure solutions of albumin, milk-sugar, and cane-sugar showed in each case an increase in residue when evaporated with formaldehyde. Detection of Boiled Milk. R. Dupouy proposed the fol- lowing method : A few drops of a solution of 1-4 diamido- benzene in water are added to 5 c.c. of the sample, and then a few drops of hydrogen dioxid solution. Raw milk gives a blue color ; milk that has been heated over about 79 gives no color. The solution of diamidobenzene must be freshly prepared. C. H. Rosier has found that 1-3 diamidobenzene will serve, and that if the blue milk be shaken with amyl alcohol, the blue color passes into the latter and is more stable. These tests are applicable for distinguishing between pasteurized and sterilized milks. H. Faber has shown that raw milk may be distinguished from boiled milk or milk that has been heated above 75 by the fact that such treatment coagulates or alters the albumin so that if the liquid be saturated with magnesium sulfate, the albumin is separated along with the albumin casein. H. D. Richmond and L. K. Boseley recommend the fol- lowing methods to distinguish new milk from milk which has been sterilized : (a) 100 c.c. of the sample are allowed to stand in a gradu- ated cylinder for six hours at 15.5 and the percentage of cream noted. If less than 2.5 per cent, of cream has risen 224 FOOD ANALYSIS for each I per cent, of fat in the milk, the milk may be con- sidered suspicious ; if the quantity of cream falls decidedly below 2 per cent, for each I per cent, of fat, it is probable that sterilized milk is present. (fr) The albumin is determined by means of magnesium sulfate. If less than 0.35 per cent, is found, sterilized milk may be considered to be present. (c) The milk-sugar is determined by the polarimeter, and also gravimetrically, in duplicate. If the difference between the two estimations be more than 0.2 per cent., it will be cor- roborative evidence of the presence of sterilized milk. It is doubtful whether a proportion of sterilized milk much below 30 per cent, can be detected. The following figures, by C. H. Stewart, show the per- centage of soluble albumin found in milk raised to various temperatures : SOLUBLE ALBUMIN IN SOLUBLE ALBUMIN IN TIME OF HEATING. FRESH MILK. HEATED MILK. 10 minutes at 60 0.423 0.418 30 60 0-435 0.427 10 65 o-395 0.362 30 65 0-395 0-333 10 70 0.422 0.269 30 70 0.421 0-253 10 75 0.380 0.07 30 75 0.380 0.05 10 80 0-375 none. 30 80 0-375 none. INFECTED MILKS Blue Milk. Milk occasionally becomes blue on the sur- face, the color forming in patches in proportion as the cream rises. The condition is due to the development of a chromo- genic bacillus. The condition sometimes prevails in epidemic form. The butter prepared from such milk possesses a greenish color and a disagreeable butyric odor. Red milk is due to accidental contamination with the Ba- CONDENSED MILK 22 5 cillus prodigiosus and several other forms. The spores of these microbes exist in the atmosphere and rapidly develop when they fall upon any nutritive medium. Ropy Milk. This condition is caused by a special bacillus, and is usually seen during moist warm weather. The milk when drawn may not show any unusual properties, but in a few hours becomes so viscid that a spoonful of it may be lifted several inches without breaking the connection between the two portions. CONDENSED MILK The form of condensed milk called " evaporated cream " con- sists merely of whole milk concentrated to about two-fifths of its bulk, but most condensed milks contain a considerable amount of cane-sugar. These samples represent, usually, wHole milk concentrated to about one-third or two-sevenths of its original volume. A small amount of invert-sugar may be present. Portions of the lactose may crystallize from con- densed milk, and when solutions are prepared for analysis, abnormal polarimetric reading will result unless the liquid stands for some hours or is heated for a short time to 100. The most common defect in condensed milks is deficiency in fat, due to preparation from closely-skimmed milks. Preser- vatives (other than cane-sugar) and coloring- matters are rarely, if ever, used, nor is it likely that foreign fats will be present. ANALYSES OF COMMERCIAL CONDENSED MILKS TOTAL SOLIDS. FAT. PROTEIDS. LACTOSE. SUCROSE. ASH. ANALYST. 36.7 10.5 9-7 14.2 none 2.1 Pearmain and Moor 31.2 9.6 9.2 10.9 none i-S F. J. Aschman 28.1 8.8 8.5 9.8 none 1.8 F. J. Aschman 78.4 93 9.1 13-4 40.4 2.0 F. J. Aschman 74.2 9.0 9-3 10.2 43-7 1-9 F. J. Aschman 70.9 1.4 11.4 I 4 .6 41.9 1.6 Pearmain and Moor The sucrose in the last sample was determined by difference. 226 FOOD ANALYSIS The analysis of unsweetened condensed milks is conducted as with ordinary milk, the sample having been previously diluted with several times its weight of water heated to boil- ing, cooled, and made up to a definite volume. The fat may be readily estimated by the L-B. process. The full analysis of sweetened condensed milk is difficult, and many of the published figures are probably erroneous. The large amount of cane-sugar interferes with the extraction of the fat by solvents. The same difficulty occurs in the analysis of some prepared infant-foods, such as mixtures of milk with malt and glucose. For the general operations, a portion of the well-mixed contents of a freshly-opened can should be accurately weighed, diluted with a known amount of water, and well mixed, from which mass the portions for analysis may be taken and the results calculated to the original sample. 50 grams mixed with 100 c.c. of water will be a convenient quantity. For the polarimetric determination of lactose, a special procedure will be necessary ; but for determination of solids, ash, total proteids, and total reducing sugars, the ex- amination may be made as with ordinary milk upon this diluted sample. Fat. The Adams method is usually employed. J. F. Geisler has investigated its application to condensed milks and devised the following method : A quantity of the dilute solution equal to not more than I gram of the sample is dis- tributed on a fat-free paper coil as described on page 203 .and extracted for five hours w r ith petroleum spirit or a mixture of petroleum spirit and anhydrous ether containing I 5 per cent, of the latter. The Werner-Schmid method may be employed, but the fat is apt to be contaminated with caramel. It should be dissolved in anhydrous ether, by which the caramel will be left adher- ing to the glass ; and after washing this with a little more CONDENSED MILK ether, it should be dried and weighed and the fat determined by difference. The estimation of fat by centrifugal method is seriously impeded by the carbonization of the sucrose, and various methods have been proposed for overcoming this difficulty. A. E. Leach devised the following method, which he finds to be more trustworthy than ordinary extractions with solvents. Leach applied the process to a centrifugal method not identical with the one described on page 206, but this is not important : 15 c.c. of diluted material are measured into the test-bottle, water added sufficient to fill it to the beginning of the stem, and then 4 c.c. of the copper sulfate solution used for sugar determination, the mixture shaken well, and the precipitate settled by whirling the bottle in the machine. The super- natant liquid is drawn off with a slender-stemmed pipet the opening of which is covered with a small piece of absorbent cotton. On withdrawing the pipet this cotton is dislodged by pressing it against the neck so that it remains in the bottle. The precipitate is washed twice with water by the same method, settling the precipitate in each case by the use of the centrifuge, taking care that the mass is well stirred with the water in each operation. After the second washing, about 15 c.c. of water are put in, the precipitate stirred up, the amyl alcohol mixture added, then the sulfuric acid, as directed on page 206, the mixture whirled, and the fat measured. The percentage of fat will be that based on the 15 c.c. used, and the amount in the original sample may be calculated from the dilution. Sugars. If regard is to be given to the presence of invert- sugar, a special method must be followed. The processes first given consider lactose and sucrose only. Lactose. The heating employed in the manufacture of con- densed milk may reduce the rotatory power of the sugar sufficiently to cause error in the polarimetric method. The 228 FOOD ANALYSIS reducing power with alkaline copper solutions is not seriously affected. Sucrose. This determination may be made by difference ; that is, subtracting the sum of the other ingredients from the total solids. This will serve for ordinary inspection pur- poses, since the amount present is almost always large, gen- erally more than the total of milk-solids, and an error even of several per cent, does not affect the judgment as to the wholesomeness of the sample. Exact work requires, how- ever, that the cane-sugar be determined directly, and several processes have been devised for the purpose. Sucrose exerts but little action on Fehling's solution, but invert-sugar acts powerfully, and some processes depend on determining the reducing power before and after inversion. Since the polari- metric reading is also markedly changed by the inversion, the difference in polarization may be employed. Processes of fermentation may be so conducted as to remove the sucrose (also any form of glucose) while the lactose is unaffected. This method is chiefly valuable for recognizing invert-sugar or either of its constituents. When inversion methods are used, they must be such as to secure prompt inversion of the sucrose without affecting the lactose. Experiment shows that citric acid and invertase are the most suitable agents. A. W. Stokes and R. Bodmer have worked out the citric acid method substantially as follows : 25 c.c. of the diluted sample are coagulated by addition of I per cent, of citric acid, without heating, and made up to 200 c.c. plus the volume of the precipitated fat and proteids (see p. 214). The liquid portion, which now measures 200 c.c., is passed through a dry filter. The reducing power with alka- line copper solutions is determined at once upon 50 c.c. of this filtrate. To another 50 c.c., I per cent, of citric acid is added and the solution boiled for 10 minutes and the reducing power also determined. The increase over that of CONDENSED MILK 22Q the first solution is due to the invert-sugar formed by the action of the citric acid on the sucrose. It is necessary to bear in mind that the reducing equivalents of lactose and invert-sugar are not the same. If a volumetric method be employed, it is probable that the Gerrard-Allen method (page 1 1 8) will be satisfactory. The following method is based on the difference in polari- metric reading before and after action of invertase. About 75 grams of the sample are accurately weighed in a 100 c.c. flask, diluted to about 80 c.c., heated to boiling, cooled, and 7.5 c.c. of acid mercuric nitrate solution added. The mixture is made up to 100 c.c., well shaken, filtered through a dry filter, and the polarimetric reading taken at once. It will be the sum of the effect of the two sugars. The volume of the sugar-containing liquid is calculated by allowing for the pre- cipitated proteids and fat, as described on page 214. 50 c.c. of the filtrate are placed in a flask marked at 5 5 c.c., a piece of litmus paper dropped in, and the excess of nitric acid cautiously neutralized by sodium hydroxid solution. The liquid is then faintly acidified by a single drop of acetic acid (it must not be alkaline), a few drops of an alcoholic solution of thymol are added, and then 2 c.c. of a solution of invertase, prepared by grinding half a cake of ordinary com- pressed yeast with 10 c.c. of water and filtering. The flask is corked and allowed to remain at a temperature of 35 to 40 for 24 hours. The cane-sugar will be inverted, while the milk-sugar will be unaffected. The flask is filled to the mark (55 c.c.) with washed aluminum hydroxid and water, mixed, filtered, and the polarimetric reading taken. The amount of cane-sugar can be determined from the difference in the two readings by the formula on page 125. A powerful solution of invertase may be prepared by the method recommended by O'Sullivan and Tompson. Brewer's yeast is allowed to stand at a temperature of 1 5 for a month. 230 FOOD ANALYSIS The liquid is filtered and sufficient alcohol added to give about 12 per cent, of absolute alcohol. After a few days the liquid is filtered and is ready for use. The alcohol acts as a preservative. W. D. Bigelow and K. P. McElroy propose the following routine method for the determination of the sugars, including invert-sugar, in condensed milk. The solutions used are : Acid Mercuric lodid. Mercuric chlorid, 1.35 grams; potas- sium iodid, 3.32 grams; glacial acetic acid, 2 c.c. ; water, 64 c.c. Alumina-cream. See page 123. The entire contents of the can are transferred to a porcelain dish and thoroughly mixed. A number of portions of about 25 grams are weighed carefully in 100 c.c. flasks. Water is added to two of the portions, and the solutions boiled. The flasks are then cooled, clarified by means of a small amount of the acid mercuric iodid and alumina-cream, made up to mark, filtered, and the polarimetric reading noted. Other portions of the milk are heated in the water-bath to 55 ; one- half of a cake of compressed yeast is added to each flask and the temperature maintained at 55 for five hours. Acid mer- curic iodid and alumina-cream are then added, the solution cooled to room temperature, made up to mark, mixed, fil- tered, and polarized. The amount of cane-sugar is deter- mined by formula on page 125. Correction for the volume of precipitated solids may be made by the double-dilution method (p. 30). The total reducing sugar is estimated 'in one of the portions by one of the reducing methods, and if the sum of it and the amount of cane-sugar obtained by in- version is equal to that obtained by the direct reading of both sugars before inversion, no invert-sugar is present. If the amount of reducing sugar seems to be too great, the milk- sugar must be re-determined as follows : 250 grams of the condensed milk are dissolved in water, the solution boiled, BUTTER 231 cooled to 80, a solution of about 4 grams of glacial phos- phoric acid added, the mixture kept at 80 for a few minutes, then cooled to room temperature, made up to mark, shaken, and filtered. It may be assumed that the volume of the pre- cipitate is equal to that obtained by mercuric iodid solution. Enough sodium hydroxid is then added to not quite neutral- ize the free acid, and sufficient water to make up for the vol- ume of the solids precipitated by the phosphoric acid. The mixture is then filtered and the filtrate is measured in portions of 100 c.c. into 200 c.c. flasks. A solution containing 20 milligrams of potassium fluorid and half a cake of compressed yeast is added to each flask, and the mixture allowed to stand for 10 days at a temperature between 25 and 30. The invert-sugar and cane-sugar are fermented and removed by the yeast in the presence of a fluorid, while milk-sugar is unaffected. The flasks are filled to the mark and the milk- sugar determined either by reducing or by the polariscope. The amount of copper solution reduced by the lactose and invert-sugar, less the equivalent of lactose remaining after fermentation, is due to invert-sugar. BUTTER Butter is a mixture of fat, water, and curd. The water contains milk-sugar and the salts of the milk. Common salt is usually present, being added after the churning. Artificial coloring is frequently used. Butter-fat is distinguished from other animal fats in that it contains a notable proportion of acid radicles with a small number of carbon atoms. Thus, about 91 per cent, consists of palmitin and olein and the remainder of butyrin and ca- proin, along with small amounts of caprylin, caprin, myristin, and some others. According to the experiments of Hehner and Mitchell, stearin is present only in very small quantity. The exact arrangement of these constituents is unknown. 232 FOOD ANALYSIS The composition of commercial butter usually varies within the following limits : Fat, . . 78 per cent, to 94 per cent. Curd, I " "3 " Water, 5 " "14 " Salt, o " "7 " Batter containing over 40 per cent, of water is sometimes sold. Such samples are pale and spongy, lose weight, and become rancid rapidly. The official methods of the A. O. A. C. for the analysis of butter are as follows : Preparation of the Sample. If large quantities of butter are to be sampled, a butter trier or sampler may be used. The portions thus drawn, about 500 grams, are to be per- fectly melted in a closed vessel at as low a temperature as possible, and when melted the whole is to be shaken violently for some minutes until the mass is homogeneous and suffici- ently solidified to prevent the separation of the water and fat. A portion is then poured into the vessel from which it is to be weighed for analysis, and should nearly or quite fill it. This sample should be kept in a cold place till analyzed. Water. From 1.5 to 2.5 grams are dried to constant weight at the temperature of boiling water, in a dish with flat bottom, having a surface of at least 20 sq. cm. The use of clean dry sand or asbestos with the butter is admissible, and is necessary if a dish with round bottom be employed. Fat. The dry butter from the water determination is dis- solved in the dish with absolute ether or with petroleum spirit (sp. gr. 0.680). The contents of the dish are then transferred to a weighed Gooch crucible with the aid of a wash-bottle filled with the solvent, and are washed until free from fat. The crucible and contents are heated at the tem- perature of boiling water till the weight is constant. BUTTER ^*55fc 233 The fat may also be determined by drying the butter on asbestos or sand, and extracting by anhydrous alcohol-free ether. After evaporation of the ether the extract is heated to constant weight at the temperature of boiling water and weighed. Casein, Ash, and Chlorin. The crucible containing the residue from the fat determination is covered and heated, gently at first, gradually raising the temperature to just below redness. The cover is removed and the heat continued until the material is white. The loss in weight represents casein, and the residue mineral matter. In this mineral matter dis- solved in water slightly acidulated with nitric acid, chlorin may be determined gravimetrically with silver nitrate, or, after neutralization with calcium carbonate, volumetrically, using potassium chromate as indicator. Salt. About 10 grams are weighed in a beaker in por- tions of about I gram at a time taken from different parts of the sample. Hot water (about 20 c.c.) is now added to the beaker, and after the butter has melted, the mass is poured into the bulb of a separating funnel, which is then closed and shaken for a few moments. After standing until the fat has all collected, the water is allowed to run into an Erlenmeyer flask, with care not to let fat globules pass. Hot water is again added to the beaker, and the extraction is repeated from ten to fifteen times, using each time from 10 to 20 c.c. of water. The resulting washings contain all but a mere trace of the salt originally present in the butter. The chlorin is determined volumetrically in the filtrate by means of standard silver nitrate and potassium chromate indicator and calculated to sodium chlorid. Adulteration with Foreign Fats. The chief adulteration of butter consists in the substitution of foreign fats, especially the product known as oleomargarin. When fats are saponified and the soap treated with acid, the 234 FOOD ANALYSIS individual fatty acids are obtained. It is upon the recognition of the peculiar acid radicles existing in butter that the most satisfactory method of distinguishing it from other fats is based. Since the relative proportion of these radicles differs in different samples, the quantitative estimation cannot be made with accuracy ; but when the foreign fats are substituted to the extent of 20 per cent, or more, the adulteration can be detected with certainty and an approximate quantitative deter- mination made. The detection of adulteration of butter-fat by other fats is generally carried out by the determination of the volatile acid, but some other confirmatory processes are occasionally em- ployed. The data for interpreting results will be found in the table on page 168. Volatile Acids. The glycerol-soda method (page 146) is sufficient for the purpose. No advantage will result from using the tedious method with alcoholic solution ; indeed, under ordinary circumstances the latter is probably less accu- rate. Butter (5 grams) yields a distillate requiring from 24 to 34 c.c. of decinormal alkali. Several instances have been pub- lished in which genuine butter has given a figure as low as 22.5 c.c., but such results are uncommon. The materials employed in the preparation of oleomargarin yield a distillate requiring less than I c.c. of alkali. Commercial oleomargarin is usually churned with milk in order to secure a butter flavor, and, thus acquiring a small amount of butter-fat, yields distillates capable of neutralizing from I to 2 c.c. of alkali. , If coconut oil (see page 168) has been used in the prepara- tion of the oleomargarin, the figure will be higher, but there will still be no difficulty in distinguishing pure butter. Saponification Value. In the absence of coconut oil, the saponification value will give valuable indications as to the BUTTER 235 purity of a butter sample. It is possible to make oleomar- garin, by the addition of coconut oil, which would have the same saponification value as pure butter. Specific Gravity. According to Skalweit, the greatest differences between the specific gravity of butter and its adulterants are found at a temperature of 35, but the deter- mination is more conveniently made at the temperature of boiling water. The Sprengel tube or Westphal balance may be employed for the purpose. The determination of the Reichert number will usually give sufficient information as to the nature of a butter sample. In doubtful cases it may be of advantage to apply other tests as corroborative evidence. The determination of soluble and insoluble acids may be employed, but Valenta's test and the refractometric examination are especially mentioned as fur- nishing results with little trouble in a short time. Soluble and Insoluble Acids. The proportion of insoluble acids in butter is usually about 87.5 per cent, and of soluble acids, calculated as butyric, about 5 per cent. The insoluble acids may be present to the extent of 88.5 per cent., but, according to most authorities, they will only reach 90 per cent, in the presence of adulterants. These figures apply to fresh samples. After keeping until rancidity has developed the proportion of insoluble acids may be increased I per cent, or more. Mixtures of butter, oleomargarin, and coconut oil may have the same proportion of insoluble acids as butter. Valenta's Test. Jones recommends the employment of a standard butter with which to standardize each fresh batch of acid, and dilution of the acid to such a point that the turbidity temperature with this butter-fat is 60 In this way the results are comparable with those of previous tests. With such acid oleomargarin gave temperatures from 95 to 1 06, and generally from 100 to 102. 236 FOOD ANALYSIS Refrac tome trie Examination. This is most satisfactorily made by the oleorefractometer or the butyrorefractometer. F. Jean prepares the sample for examination in the former as follows : 30 grams of butter are melted in a porcelain dish at a temperature not exceeding 50, stirred well with a pinch or two of gypsum, and allowed to settle out at the same temper- ature. The supernatant fat is decanted through a hot-water funnel plugged with cotton and poured while warm into the prism of the apparatus, stirred with the thermometer until the fat has cooled to 45, and the deviation observed. Ether must not be used for the solvent, as minute traces of it seriously influence the result. The following table is a summary of the results obtained by several observers, including F. Jean and T. M. Pearmain : DEGREES IN OLEOREFRACTOMETER. Butter, 25 to 34, usually 30 Oleomargarin, 13 to 18 Butter with lop. c. oleomargarin ( 17), . 28 Butter with 50 p. c. oleomargarin, . . . 23 Lard, 8 to 14 Coconut oil, .... 59 Arachis oil, , 3.5 to 7 Cottonseed oil, 12 to 23 Cottonseed " stearin," 25 De Bruyn found as low as 2 1 in butter from animals fed on linseed cakes. A mixture of coconut oil and oleomargarin may be made having the same refractive power as pure butter Evidently, therefore, it is not possible from this datum alone to state that a given sample is pure butter, but a sample ex- hibiting a refraction of 20 or under may be pronounced adulterated. The results obtained by examination in Zeiss's butyrore- fractometer are in the main the same as those just given. The instrument is said to be superior to the oleorefractometer, and is less costly. Commercial forms of oleomargarin and butter exhibit char- BUTTER 237 acteristic differences on heating, which may be utilized for rapidly sorting a collection of samples. When butter is heated in a small tin dish directly over a gas flame, it melts quietly, foams, and may run over the dish. Oleomargarin, under the same conditions, sputters noisily as soon as heated and foams but little. Even mixtures of butter and other fats show this sputtering action to a considerable extent. The effect depends upon the condition in which the admixed Avater exists, and the test is not applicable to butter which has been melted and reworked (renovated or process butter). An alcoholic solution of sodium hydroxid, heated for a moment with butter, and then emptied into cold water, gives a distinct odor of pineapples, while oleomargarin gives only the alcoholic odor. Butter Colors. Most of the butter and practically all but- ter substitutes are colored either with preparations of turmeric and annatto or azo-colors allied to methyl-orange. The lat- ter forms are now most largely used. They may be detected by the test devised by J. F. Geisler. 26 A small amount of the sample, or, better, the fat filtered from it, is mixed on a porcelain plate with a little fuller's earth. Azo-colors give promptly a red mass, while if they are not present, the mix- ture becomes only yellow or light brown. All samples of fuller's earth are not equally active, and tests should be made with different samples by using fat known to contain the azo- compound until a good specimen of the earth is secured. The precipitate obtained by Geisler by mixing fuller's earth with a sample of highly colored butter was washed with light petroleum to remove the fat and gave a violet-red powder on drying. Alcohol immediately decolorized it, but the color reappeared on evaporation of the alcohol. Boiling alcohol extracted the color from the earth, producing a yellow solu- tion. The color so extracted dissolved in sulfuric acid to a 238 FOOD ANALYSIS yellow solution, which, on dilution, developed a bright pink or red color. For the detection of very minute quantities of the color, the sample may be dissolved in light petroleum, and the fuller's earth added to the solution, when the pink color will appear as a .distinct ring or zone at the edge of the deposited layer of the reagent. According to Geisler, the yellow azo-dye is generally used in conjunction with an orange variety which does not respond to the above test. A. H. Low has proposed the following test for the yellow azo-color : A few cubic centimeters of the filtered fat are mixed in a large test-tube with an equal volume of a mixture of one part strong sulfuric acid and four parts glacial acetic acid. The contents of the tube are then heated almost to boiling and thoroughly mixed by violently agitating the bot- tom of the tube. When now allowed to stand and separate, the lower layer of mixed acids will be strongly colored wine-red if the azo-color be present. Pure butter-fat imparts no color to the acids, or, at most, only a faint brownish tinge. For turmeric and annatto mixtures, E. W. Martin's test will usually be satisfactory : 2 c.c. carbon disulfid are mixed with I 5 c.c. of alcohol, by adding small portions of the disul- fid to the alcohol and shaking gently ; 5 grams of the butter- fat are added to this mixture in a test-tube and shaken. The disulfid falls to the bottom of the tube, carrying with- it the fatty matter, while any artificial coloring-matter remains in the alcohol. The separation takes place in from one to three minutes. If the amount of the coloring-matter is small, more of the fat may be used. If the alcoholic solution be evaporated to dryness and the residue treated with concen- trated sulfuric acid, annatto will be indicated by the produc- tion of a greenish-blue color. With many samples of oleo- f CHEESE 239 margarin a pink tint will be obtained, which indicates an azo-color. Presen>atives. The preservatives used in milk may be found in limited amount in butter, but boric acid is now sometimes added as a substitute for salt. It will be detected by the method given on page 89 in the water obtained by melting the butter and allowing the mass to settle. Glucose 2 7 is now used as a preservative, especially in butter intended for export to tropical countries. C. A. Crampton found as much as 10 per cent, in a sample of Beurre rouge (a highly colored butter) intended for exportation to Guadeloupe. For the detection of glucose the phenylhydrazin test might be used. For determination of glucose, Crampton used the fol- lowing method : 10 grams of the sample were washed with successive portions of convenient bulk, the solution made up to 250 c.c., and an aliquot portion determined, as given on page 1 1 6. The solution may also be clarified by alumina-cream or acid mercuric nitrate and examined in the polarimeter. CHEESE Cheese is the curd of milk which has been separated from it, pressed, and undergone some fermentation. The precipita- tion is produced either by allowing the milk to become sour when the lactic acid is the agent or by rennet. The first- named method is mainly applied to the manufacture of so- called Dutch or sour-milk cheese, green Swiss cheese, and cottage cheese. More commonly cheese is obtained by means of rennet derived from the fourth stomach of the calf. The action is due to an enzym which acts directly on the proteids and does not produce its effect through the intervention of acids. The curd (cheese) undergoes, by keeping, various decompositions, some essentially putrefactive, and due to the 24O FOOD ANALYSIS action- of microbes. The decomposition of the cheese is termed ''ripening." In the sour-milk cheeses, ripening is restricted intention- ally, since there is liability to an irregular and miscellaneous bacterial growth by which the fermentations may be carried too far, undesirable and even harmful products being formed. Such cheeses are intended for prompt use. Cheese contains no casein, if by this term is meant the proteid as it exists in milk, or when precipitated from milk by acids. When milk is coagulated by rennet, only a part of the proteids enter into the curd; true casein contains about 15.7 per cent, of nitrogen, but the proteid matter of cheese con- tains about 14.3 per cent. Under the process of ripening this is further decomposed, amido- and ammonium com- pounds, peptones and albumoses, being formed. The following figures, obtained by L. L. Van Slyke, will serve to give some idea of the extent to which the curd is changed in ripening. The figures represent average percent- age on the total nitrogen. The cheese was an American cheddar : GREEN CHEESE. AFTER FIVE MONTHS. Soluble nitrogen compounds, . . .4.23 35- 5 2 " amido " ... none u.66 " ammonium " ... none 2.92 Van Slyke's experiments seem also to indicate that the cheese ripened more rapidly when the curd was precipitated by a larger quantity of rennet and, especially, that cheese rich in fat ripened more rapidly than skim-milk cheese. In addition to the fat and nitrogenous compounds just mentioned, cheese may contain a small amount of milk-sugar and of lactic and other organic acids. There is present also a certain proportion of mineral matter, alkaline and earthy phosphates, along with any salt that has been added. Traces of nitrates have been found. CHEESE 241 Skimmed milk is not infrequently used for the production of cheese. Partially- skimmed milk is used in the preparation of certain Dutch cheeses. Foreign fats, such as are used in the manufacture of oleomargarin, are sometimes incorporated, the article being known as " filled cheese." The ash of cheese consists largely of calcium phosphate and salt. G. Mariani and E. Tasselli have estimated the total ash, chlorin, calcium, and phosphoric acid in 15 samples of cheese. The amounts of salt (calculated from the chlorin) de- pend on the mode of salting. The proportion of phosphoric oxid was always greater than that necessary to form trical- cium phosphate, ranging from 1.07 and 1.08 equivalents of phosphoric anhydrid to calcium oxid in cheese made from sour milk to 1.56 to I in Gorgonzola, 1.67 to I in skim-milk cheese, and 1.75 to I in Edam cheese. The largest quanti- ties of calcium and phosphoric oxid were found in sheep's- milk cheese and in cheese made from sour milk, whence it follows that acidity does not prevent the precipitation of cal- cium phosphate in the curds. The excess of phosphoric oxid obtained was attributed to acid phosphates. The salt in cheese usually ranges between I and 4 per cent. Analytic Methods. The analytic points usually deter- mined in regard to cheese are water, fat, casein, ash, the pres- ence of fats other than butter-fat, and coloring-matters. In addition to this, especially in comparing the qualities of genuine cheeses, the proportion of proteic, amidic, and ammo- niacal nitrogen is of value. Care should be taken to select for analysis a sample which represents the average composition of the entire cheese. The following methods for the determination of water, fat, ash, total nitrogen, and acidity have been adopted by the A. O. A. C. : Sampling. When the cheese can be cut, a narrow wedge- 21 242 FOOD ANALYSIS shaped segment, reaching from the outer edge to the center of the cheese, is taken. This is to be cut into strips and passed through a sausage-grinding machine three times. When the cheese cannot be cut, samples are taken by a cheese trier. If only one plug can be obtained, this should be perpendicular to the surface, at a point one-third of the distance from the edge to the center of the cheese. The plug should reach entirely through, or only half-way through, the cheese. When possible, draw three plugs one from the center, one from a point near the outer edge, and one from a point half-way between the other two. For inspection pur- poses, the rind may be rejected ; but for investigations requir- ing the absolute amount of fat in the cheese, the rind is included in the sample. It is preferable to grind the plugs in a sausage machine, but when this is not done, they should be cut very fine and carefully mixed. Water. Between 2 and 5 grams of the sample should be placed in a weighed platinum or porcelain dish which con- tains a small amount of material, such as freshly ignited as- bestos or sand, to absorb the fat which may run out. This is then heated in a water-oven for 10 hours and weighed ; the loss in weight is considered as water. If preferred, the dish may be placed in a desiccator over concentrated sulfuric acid and dried to constant weight, but this may require many days. The acid should be renewed when the cheese has become nearly dry. Fat. The extraction-tube described on page 202 is prepared as follows : Cover the perforations in the bottom of the tube with asbestos, and on this place a mixture containing equal parts of anhydrous copper sulfate and pure dry sand to the depth of about 5 cm., packing loosely, and cover the upper surface with a film of asbestos. On this are placed from 2 to 5 grams of the sample, the mass extracted for 5 hours with anhy- drous ether, then removed and ground to fine powder with pure CHEESE 243 sand in a mortar. The mixture is placed in the extraction tube, the mortar washed free from all matters with ether, the washings being added to the tube, and the extraction is con- tinued for 10 hours. The fat so obtained is dried at 100 to constant weight. Total Nitrogen. This is determined by the Kjeldahl-Gun- ning method, using 2 grams of the sample. The percentage, multiplied by 6.25, gives the nitrogen compounds. Ash. The dry residue from the water determination may be taken for the ash. If the cheese be rich, the asbestos will be saturated therewith. This mass may be ignited carefully, and the fat allowed to burn off, the asbestos acting as a wick. No extra heating should be applied during the operation, as there is danger of spurting. When the flame has died out, the burning may be completed in a muffle at low redness. When desired, the salt may be determined in the ash by titra- tion with silver nitrate and potassium chromate. Provisional Method for the Determination of the Acidity in Cheese. Water at a temperature of 40 is added to 10 grams of finely divided cheese until the volume equals 105 c.c., agitated vigorously, and filtered. Portions of 25 c.c. of the filtrate corresponding to 2.5 grams of the cheese are titrated with decinormal solution of sodium hydroxid, using phenol- phthalein as indicator. The amount of acid is expressed as lactic acid. The above processes may be advantageously modified in some respects. The determination of water may be made by the extraction of the cheese with alcohol and ether and drying of the alcohol-ether extract and fat-free solids sep- arately. A. W. Blyth recommends this method as more accurate and less tedious than the direct drying. In the determination of ash, it will be better to extract the charred mass with water and proceed as described in the de- termination of the ash of milk. 244 FOOD ANALYSIS The fat extracted by ether may be examined for other than butter-fat by the distillation method in the usual way. When the composition of the fat is alone desired, it may often be extracted by simpler methods. T. M. Pearmain and C. G. Moor recommend that 50 grams be chopped fine and tied up in a muslin bag, which is placed in a water-bath. When the water is heated, the fat will generally run out clear. If not clear, it can be filtered through paper. O. Henzold suggests the following : 300 grams of the powdered cheese are agitated in a wide-neck flask with 700 c.c. of 5 per cent, solution of potassium hydroxid previously warmed to 20. In about 10 minutes the cheese dissolves, the fat floats, and by cautious shaking may be collected in lumps. The liquid is diluted, the fat removed, washed in very cold water, kneaded as dry as possible, melted, and filtered. It is claimed that the fat is not altered in composition by the process. The fat of cheese may be estimated by the centrifugal method, as follows : About 3 grams of the mixed cheese in small fragments are weighed and transferred to the bottle, the last portions being washed in with the aid of water. A few drops of ammonium hydroxid are added, and sufficient water to make the liquid about 15 c.c. The liquid is warmed with occasional shaking until the cheese is well disintegrated, and then treated as a sample of milk. The percentage of fat is found by multiply- ing the percentage reading by 15.45 and dividing by the num- ber of grams of cheese taken for analysis. W. A. Chattaway, T. M. Pearmain, and C. G. Moor use the following modification : 2 grams of the cheese are placed in a small dish and heated on the water-bath with 30 c.c. of con- centrated hydrochloric acid until a dark, purplish-colored solution is produced. The mixture is now poured into the test bottle, portions of solution remaining in the dish rinsed CHEESE 245 with the hydrochloric acid fusel-oil mixture into the bottle, and, finally, enough strong hot acid added to fill the bottle up to the mark. It is then whirled for about a minute. The difficulty in this method is to get all the fat into the bottle. It is best to weigh the cheese in the bottle. Bondzynski applies the Werner-Schmid method to the de- termination of fat in cheese, as follows : A weighed quantity of the finely-shredded cheese is placed in the tube and decom- posed with 20 c.c. hydrochloric acid of specific gravity i.i, containing about 19 per cent. HC1. On cautiously warming over wire gauze, the melted fat rises to the surface. After cooling, 30 c.c. of ether are added and the tube warmed very gently until the acid and ethereal solution of fat separate sharply. Centrifugal force helps this, but is not essential. After the volume of ether has been read off, 20 c.c. are pipetted off into a weighed Erlenmeyer flask. From this, the quantity of fat in the entire solution may be calculated. Lactose. This may be estimated by boiling the finely di- vided cheese with water, filtering, and determining the reduc- ing power of the filtrate on Fehling's solution. Determination of Proteid Nitrogen (Stutzer's Method). 0.7 to 0.8 gram of the cheese are placed in a beaker, heated to boiling, 2 or 3 c.c. of saturated alum solution added to decom- pose alkaline phosphate, then copper hydroxid mixture (see page 46) containing about 0.5 gram of the hydroxid, and stirred in thoroughly ; when cold, the mass is filtered, washed with cold water, and, without removing the precipitate from the filter, the nitrogen determined by the Kjeldahl-Gunning method. Before distillation, sufficient potassium sulfid solu- tion must be added to precipitate the copper. Ammonium Compounds. About 5 grams of cheese are rubbed up in a mortar with water, transferred to a filter, and washed with a liter of cold water. The filtrate is concentrated by boiling (if alkaline, it must be neutralized before heating), 246 FOOD ANALYSIS barium carbonate added, the liquid distilled, and the ammonium hydroxid in the distillate estimated by titration with standard acid. According to Stutzer, magnesia or magnesium carbonate (the latter usually contains some magnesia) should not be used to free the ammonia, as some of the amido-compounds may be decomposed. Amido-compounds. The nitrogen as amido-compounds is estimated by subtracting from the figure for total nitrogen the sum of the proteid and ammoniacal nitrogen. If nitrates are present, the nitrogen as such should also be determined and subtracted. Van Ketel and Antusch propose the following methods for estimating the nitrogen compounds : Ammonium Compounds. The sample, powdered with the addition of sand, is distilled with water and barium carbonate, and the distillate received in a measured quantity of standard sulfuric acid, and, after boiling, the excess of acid is neutral- ized with standard sodium hydroxid, using rosolic acid as indicator. Amido-compounds. These are estimated by macerating the powdered cheese in water for 15 hours at the ordinary tem- perature. After adding a little dilute sulfuric acid (i 14), the proteids and peptones are precipitated by phosphotungstic acid. The precipitate is filtered off and washed with water containing a little sulfuric acid. The filtrate is made up to a definite bulk, and the nitrogen is determined in an aliquot por- tion of the liquid by the Kjeldahl-Gunning process, allow- ance being made for the nitrogen existing as ammonium. Peptones and Albumoses. These are determined jointly by boiling the powdered cheese (mixed with sand as before) with water and filtering from the un dissolved casein and albumin. In an aliquot portion of the filtrate the peptones and albu- moses are precipitated by adding dilute sulfuric acid and CHEESE 247 phosphotungstic acid. After washing with acidulated water the nitrogen in the precipitate is determined by the Kjeldahl- Gunning process. The total nitrogen of the cheese is also determined, and after allowing for the nitrogen existing as other forms, the balance is calculated to casein. Poisonous Metals, Lead chromate has been found in the rind of cheese, and finely divided lead in a number of Cana- dian cheeses. In England zinc sulfate has been employed under the name of cheese spice to prevent the heading and cracking. Arsenic has also been found ; it may be detected by Reinsch's test. Lead, zinc, and chromium may be detected by ashing a portion of the sample in a porcelain cru- cible and proceeding as on page 68. ANALYSES OF VARIOUS CHEESES (Reports by W. A. Chattaway, T. M. Pearmain, and C. G. Moor) REICHKRT-MEISSL NAME. WATER. ASH. FAT. NUMBER. N. Cheddar, 33.0 4.3 29.5 24.2 4.31 C-orgonzola, . . . .40.3 5.3 26.1 22.1 4.36 Dutch, 41.8 6.3 10.6 27.0 5.11 Gruyere, 28.2 4.7 28.6 30.0 4.93 Stilton, 19.4 2.6 42.2 29.0 4.73 Cheshire, 37.8 4.2 31.3 31.6 4.03 Gloucester, 33.1 5.0 23.5 31.4 4.99 Camembert, ... 47.9 4.7 41.9 31.0 3.83 Parmesan, 32.5 6.2 17.1 28.0 6.86 Roquefort, .... 29.6 6.7 30.3 36.8 4.45 Double Cream, . . . 57.6 3.4 39.3 31.2 3.14 Filled (United States), 30.6 3.6 27.7 3.0 4.84 The common American cheese is known as Cheddar. According to L. L. Van Slyke, this has, when ripe, about the following average composition : Water, 31-5 P er cent. Fat, 37-OO " Proteids, 26.25 " Ash, sugar, etc., 5.25 " 248 FOOD ANALYSIS FERMENTED MILK PRODUCTS The usual fermentation of milk is the conversion of the lactose into lactic acid, but by special methods other changes may be substituted. These modified fermentations are of rather ancient origin, and being produced by mixture of organisms, the products are complex and irregular. The proteids are more or less changed into proteoses and pep- tones. Kumiss is milk which has undergone alcoholic fermentation. The inhabitants of the steppes of Russia prepare it from mare's milk. When cow's milk is used, cane-sugar must be added. It is often made by adding cane-sugar and yeast to skim-milk. P. Vieth gives the following analyses of kumiss at succes- sive stages of fermentation : KUMISS FROM COW'S MILK ONE ONE THREE ONE DAY. WEEK. MONTH. MONTHS. Alcohol, I.I 0.9 i.o I.I Solids, II.3 8.9 86 - 8.5 Fat, 1.6 1.4 i-5 I -5 Casein, ........ 2.0 2.0 1.9 1.7 Albumin, 0.3 0.2 0.2 o. I Sugar, 6.1 3.1 2.2 1.7 Lactic acid, 0.2 0.9 1.3 1.9 Lactoproteid and peptone, 0.3 0.5 0.7 0.9 Soluble ash, o.i 0.2 0.2 0.2 Insoluble ash, 0.4 0.3 0.3 0.3 The item " lactoproteid and peptone" refers to the sub- stances precipitated by tannin after removal of the casein and albumin. KUMISS FROM MARE'S MILK AT THE NITROGENOUS LACTIC END OF: ALCOHOL. FAT. MATTERS. ACID. SUGAR. ASH. I day, . . 2.47 1. 08 2.25 0.64 2.21 0.36 8 days, . . 2.70 I-I3 2.OO 1.16 0.69 0-37 22 " . . 2.84 1.27 I. 9 7 1.26 0.51 0.36 FERMENTED MILK PRODUCTS 249 Kefyr. This is usually made from cow's milk. It has been used in the Caucasus for centuries. For its preparation a peculiar ferment is used, which is contained in the kefyr grains. These are first soaked in water, by which they are caused to swell, and are rendered more active and then added to the milk. If taken out of the milk and dried, the grains may be used repeatedly. The following are analyses of kefyr : KONIG. HAMMARSTEN. Alcohol, 0.75 0.72 Fat, 1.44 3-8 Casein 2.88 2.94 Albumin, 0.36 0.18 Hemialbumose, 0.26 0.07 Peptone, 0.04 Sugar, 2.41 2.68 Lactic Acid, 1.02 0.73 Ash, 0.68 0.71 According to Konig, good kefyr will not contain more than i per cent, of lactic acid. Analytic Methods. Fixed solids and ash are determined by evaporations of a weighed amount in a platinum basin as described on page 36. Acidity is determined by filtration with ^ alkali, using phenolphthalein or methyl-orange as an indicator. The amount of acidity is expressed in terms of lactic acid. The Kjeldahl-Gunning method will give the total nitrogen. For further examination of the nitrogenous bodies, the methods given on pages 245 and 246 may be applied. Total reducing sugars may be estimated as given on page 1 16. If sucrose and common yeast have been added, the fermented material will be likely to contain invert-sugar, with unchanged lactose and sucrose, and the method of examination of sweet- ened condensed milk may be applicable. Fat can, probably in all cases, be determined with sufficient accuracy by the L- B. process. If it be desired to make polarimetric readings, the liquid should be clarified with acid mercuric nitrate solu- 25O FOOD ANALYSIS tion (page 213), as some partly hydolyzed proteids which have rotatory power may not be precipitated by other reagents. The determination of alcohol accurately is difficult, as the quan- tity is usually small. The cautious distillation of a consider- able volume of the material previously neutralized with a little sodium hydroxid will yield a distillate in which alcohol may be determined by specific gravity. Preservatives are not likely to be used, since they would interfere with the fermentation, but attempts may be made to secure better keeping by adding some preservative after the fermentation has occurred. In some cases, therefore, tests for boric acid, formaldehyde, and salicylic acid should be made, as these will be most likely to be used. TEA 251 NON-ALCOHOLIC BEVERAGES TEA Tea is the prepared leaf of several species of T/iea. Black and green tea are derived from the same plant, the difference being due to the preparation. The quality of tea depends FIG. 46. a, Flowery pekoe ; b, orange pekoe ; c, pekoe ; of, souchong 1st ; f, souchong >d ; f t congou; a and b (mixed), pekoe; a, b, c, d, e (mixed), pekoe souchong. much upon the age of the leaf and the time of picking. Many pickings are made in a season, the first being of the finer quality. The above figure, due to Money, 28 indicates the leaves that constitute the different kinds of tea, classified according to age. 252 FOOD ANALYSIS Black tea is prepared by exposing the leaves to the sun until they have withered. They are then rolled and again set aside, usually in the sun, covered with a white cloth until fer- mentation takes place. They are then exposed in a thin layer until they have become quite dark, and are finally dried by heat. Green tea undergoes no fermentation. In Japan, the leaves are steamed until soft, rolled, and dried ; in China, they are heated in pans. In addition to tannin and the usual plant constituents, tea contains a notable proportion of caffein. In a given variety of tea, the proportion of caffein usually, but not always, bears some relation to the quality, and so does the soluble ash and water-extract. Caffein (thein), trimethylxanthin, has been found in tea, coffee, mate (Paraguay tea), guarana, and kola. When slowly crystallized from its solution in chloroform or water, it forms light, silky, flexible needles. These are said to con- tain one molecule of water, but the proportion actually found by experiment corresponds to rather less, owing probably to loss by^ efflorescence. On heating to 100 the alkaloid becomes anhydrous. If the heating be long continued, a little caffein is volatilized, but it does not volatilize with steam. It melts at 231-233, and at 384 boils with partial decomposition. It is slightly soluble in cold water, but dis- solves readily in hot, giving a bitter solution. It is somewhat soluble in rectified spirit, less so in absolute alcohol, only . sparingly in cold ether, nearly insoluble in petroleum spirit, and freely soluble in chloroform and benzene. It is decom- posed by heating with dilute solution of sodium hydroxid, barium hydroxid, or calcium hydroxid. The following analyses by Kozai indicate the difference in composition between green and black Japan teas. The figures represent percentage on the dry material : TEA 253 ORIGINAL LEAVES. GREEN TEA. BLACK TEA. Crude fiber, " protein, . . Ether extract, Other nitrogen-free extract, . . . Ash, . 10.44 37-33 6 -49 . 27.86 4-97 10.06 37-43 5-52 31-43 4.Q2 10.07 38.90 5.82 35-39 4. q-j Caffein, r^o 3. 20 Tannin 12 QI J . 10 64. o Water-extract, Nitrogen, total, " of albuminoid, . . . " of caffein, ... . . " of amido-compounds, . 50-97 5-97 . 4.11 . 0.96 . 0.91 53-74 5-90 3-94 0-93 .I3 47-23 6.22 4.11 0.96 1.16 The proportion of tannin found in black tea is only about one-half that of the green tea. Comparing the same varieties of tea, it will be seen that the commercial value is proportional to the percentage ol soluble ash, extract, tannin, and caffein. Indian teas. Results from a great number of examinations ; Moisture, 5.83 to 6.32 per cent. Insoluble leaf, 47-12 55.87 Extract, 37.80 40.35 Tannin, 13.04 18.87 Caffein, 1.88 3.24 Ash, total, 5.05 6.02 " soluble in water, 3.12 4.28 " insoluble in acid, 0.12 0.30 It is probable that the proportion of cafifein in the above analyses is slightly underestimated. The determination was made by treating the watery extract with magnesia, evapo- rating to dryness, and extracting with ether. AS is evident from the proportion of tannin noted above, Indian teas are much more astringent than Japan or China teas. The tea-leaf is ovate-lanceolate with short stem not sharply distinguished from the blade. The distal two-thirds of the leaf is marked by serrations with slightly curved spines. At the insertion of these spines the leaf tissue is thickened. This structure is wanting in young leaf buds (flowery pekoe). The 254 FOOD ANALYSIS 1 rj* J Q Q w j 9 ^ T}- 00 >x T^- **I 8 J vO pu r^; & ^ N SzoSfeS a o q oo ^ ^. HH M vq 2 2i Q ^ 3 " vo c^ O vO (X, OO i_i 8^ fa M CS a, ro l-O 1-1 W* fcs? tn d ^ ^~ ^ 04 00 ON 1O g^ii|S "o O ^ ^ ro 6 o\ ro vd i-O (N ^ l ~ u 8 - 3 j/j u ^ ^ to VO ^ ^ o D 5 "o to ro 6 ON vd M CJ O fc SJ3 ro LO N Q O *zf - inn tfl s j CM ro VO' ro l-O ro ON VO ON vd q H2 o ^ ** (N| l-O u-> VO t^ 00 M u O . 1 >_ o 'o Cj 3 , ~ s, 4-1 'f. '" 3 g '53 OJ t-* 4-1 o r* ^t^ o '-T. Z j X C/) nJ rt - husks, long-pepper, wheat, buckwheat, cayenne pepper, mus- tard husks, ground olive stones (poivrette or pepperette), almond and coconut shells (often roasted or charred), Egyp- tian corn, spent ginger, and coriander seed. Of mineral PEPPER 293 additions, sand, clay, brick dust, chalk, barium sulfate, and lead chromate are known to have been used. In the examination of pepper, considerable reliance must be placed upon the microscopic characters. Numerous chemi- cal examinations have been made, but the results in many cases have been conflicting, and the uncertainty has been increased by the fact that, until quite recently, hardly any two workers have employed the same methods. The chemical examination should be directed especially to the determination of moisture, ash, ether-extract, and crude fiber. The alcohol and water-extract have been shown to be valueless in this connection. Moisture. This is determined as on page 38. The drying in hydrogen may require to be continued 8 hours before constant weight is attained. The loss in weight will represent a small amount of volatile oil as well as water. Ether-extract. This will contain piperin, resin, and some volatile oil, and for the purpose of detecting adulteration is more convenient and satisfactory than the determination ot piperin alone. If desired, the piperin may be determined as follows : The mixture of piperin and resin obtained by extrac- tion is treated with sodium hydroxid, by which the resin is dissolved ; the residue is dissolved in alcohol, the solution filtered, evaporated, and the residue (piperin) weighed. An- other method is to mix a weighed portion of the powdered pepper with slaked lime and water, dry at 100, and thoroughly extract with ether. The residue left on the evaporation of the ether is purified by solution in alcohol, filtration, and crystallization. The proportion of ether-extract is usually not less than 7 per cent., but may fall below this figure even in pure peppers. (See results page 296.) Crude Fiber. This should be determined on the ether- extracted material as described on page 46. C. Richardson's 294 FOOD ANALYSIS figures and those of Winton in the following table were obtained in this way. Those of Stokes were made without previous exhaustion with ether. Heisch reported " cellulose," but the method of determination is not stated. Using the method as recommended by the A. O. A. C., it is probable that pepper will not yield more than 16 per cent, of fiber. ANALYST, C. RICHARDSON. WINTON. STOKES. HEISCH. Black pepper, White pepper, . 80 to II. o . . 4.1 to 8.0 8.57 to 15.41 3.32 to 4.16 7.38 21. to 26.3 12.7 to 13.8 20 o to 22.3 11.5 to 27.8 3.410 6.7 1. 14 to 12. 9 Pepper shells dust, . . . Olive stones, or / O 22.8 62.2 to 64.2 61.9 to 68.8 Ash. In unadulterated black pepper the proportion of ash rarely exceeds 5 per cent.; over 65 per cent, may be taken as positive evidence of adulteration. The ash of white pepper should not exceed 3 per cent. If long pepper be present, the ash is apt to be high, for the reason given below. Stock has published the following determinations in genuine peppers : TELLICHERRY. SIAM. LAMPONG. PENANG. Ash, 1.05 1.45 2.20 2.75 Fiber, 4.86 4.43 4.90 5.06 Calc. carb. in pepper, .0.58 0.62 0.81 1.67 " " "ash, . .55.20 42.70 36.80 60.70 TELLICHERRY PEPPER. UNHULLED. HULLED. Total ash, 4.02 1.64 Fiber, 10.40 6.80 Ratio of calcium (as carbonate) to ash, . 27.30 62.00 It is thus seen that calcium compounds are more abundant in pepper. Excess of hulls results in a lowering of this ratio, but the proportion may be altered in samples that have been bleached or faced with mineral matter. Stock considers that in pure pepper the proportion of calcium carbonate to total ash is never greater than 60 per cent. It is advisable to shake up a portion of the pepper-sample PEPPER 295 with chloroform in a tapped separator. The heavier mineral additions will sink, along with more or less husk, and may be removed by means of the tap and examined with the micro- scope and chemically. In this way it may be possible to distinguish between added mineral matter and that naturally present. From the results of examination of samples, either known to be pure, or in which the microscope failed to show any structure except that natural to pepper, A. L. Winton has proposed the following limits of composition for black pepper : Ether-extract dried at 100, . . not less than 6.5 per cent. Fiber, not more than 16.0 " Ash, " " 6.5 " Sand, " " 2.0 " The methods of the A. O. A. C. were used in the examina- tions. The same observer has called attention to the fact that in the ether-extract of pure pepper the piperin invariably crystallizes out from the resin on cooling, but that when pepper is adulterated with material containing fat or oil, the latter may conceal the crystals or prevent their formation. Absence of piperin crystals is regarded as positive evidence of adulteration. If the fat or oil introduced by the adulterant increases the weight of the extract to the amount which is found in pure pepper, a determination of the nitrogen in the extract from 10 grams will often disclose its real nature. A sample of pure white pepper gave an extract containing 3.25 per cent, of nitrogen, and that from pure black pepper 2.64 per cent. In adulterated samples the proportion will often fall considerably below 2 per cent. A sample of pepper shells (pepper dust) examined by Winton gave the following results : Water, 8.36 ; ether-extract, 6.98 ; fiber, 22. 88 ; total ash, 9. 19 ; sand, 2.28. According to the figures given by the A. O. A. C., the 296 FOOD ANALYSIS following limits of composition will probably include all good pepper. All samples having over 5 per cent, of ash or over 1 1 per cent, of fiber are regarded with suspicion : BLACK PEPPER. WHITE PEPPER. Moisture, 8 to 12 12 to 15 Ash, 2.75106.5 0.8 to 2.9 Starch (direct inversion by hydro- chloric acid), 32 to 38 40 to 53 Fiber, 9 to 16 4 to 8 Albuminoids, 7 to 12 8 to 12 Non-volatile ether extract, not less than, 6.5 7 to 8 Starch. Many determinations have been made, but the methods used have been faulty and the indications often un- satisfactory. C. Heisch boiled the pepper for three hours with 10 per cent, hydrochloric acid and measured the optic activity of the resulting liquid. The gum and other soluble matters were found to cause a rotation equivalent to about I per cent, of starch. Lenz extracted the pepper with water, boiled the residue with hydrochloric acid, and determined the reducing sugar. All the samples of pepper examined gave a reducing sugar equivalent of over 50 per cent., while the adulterants, except those containing starch, gave under 30 per cent. Rottger, however, found Lampong pepper to give a " reducing-sugar equivalent " of only 41.7 per cent. Richard- son found the starch in 5 samples of black pepper to vary between 34 and 38 per cent, of the dry ash-free material. In two samples of white pepper the figures were about 40 and 43 per cent, respectively. Substances other than starch are converted into sugar by the above processes, and more satisfactory conclusions might be drawn from an accurate determination of the starch by the diastase method, as described on page 97. Total Nitrogen. This is determined by the Kjeldahl-Gun- ning method. Richardson found 1.83 and 1.90 per cent, of PEPPER 297 nitrogen in two samples of white pepper and from 1.57 to 2.10 per cent, in five samples of black pepper. Busse considers that the true value of a pepper is best shown by a quantitative estimation of the brown coloring- matter, which is only found in the husk. He proposes the following method : 5 grams of the sifted and dried pepper are treated with boiling absolute alcohol. The extract, after being freed from alcohol in the drying oven, is ground up with a little water in a basin, and then washed into a flask with 50 to 60 c.c. of boiling water. 25 c.c. of a 10 per cent, solu- tion of sodium hydroxid are added and the flask warmed on the water-bath for five hours, with frequent shaking. Con- centrated acetic acid is added until the liquid is only feebly alkaline, then 250 c.c. of water, and the flask well shaken. After 12 hours the liquid is filtered with the aid of a filter pump. To 50 c.c. of the filtrate concentrated acetic acid is added to acid reaction and 20 c.c. of a 10 per cent, solution of lead acetate in dilute acetic acid. After mixing, the liquid is diluted to 100 c.c. with water, well shaken, and filtered. 10 c.c. of the filtrate are decomposed with 5 c.c. of sulfuric acid (1:3) and 30 c.c. of alcohol, the precipitate filtered after some time, washed with alcohol, the lead sulfate ignited in the usual manner, and the amount of lead calculated. The amount of lead in grams which has been obtained by the pro- cess from I gram of the dried pepper is designated as the " lead number." The following figures are given : LEAD NUMBER. White pepper, 0.006 to 0.027 Black pepper, . 0.054 to 0.075 Husks 0.129100.157 Pepper dust, 0.109100.122 Ground olive -stones, termed " poivrette " and " pepperette," have been much used to adulterate pepper. J. Campbell Brown, who first called attention to this use, has given the results of analysis of samples : 26 298 FOOD ANALYSIS ASH. White pepperette, 1.33 Black pepperette, 2.47 Ground olive-stones, i.6l Ground almond-shells, 2.05 FIBER. 48.48 47.69 45-3 51.68 None of the samples contained starch. Poivrette is a pale buff or cream-colored powder, which cannot be distinguished from the materials of genuine pepper a FIG. 50. a, Cells associated with the vascular bundles, also some stone-cells ; z, inner layer of hard cells, with endothelium en ; p, cells from the fleshy portion of the fruit; ep, epidermis of the seed wall, with brown parenchyma showing through it ; ea, exterior layer of the endosperm. Some spiral vessels are also shown. X I ^. by simple inspection. The particles are, however, tough and hard, and may be sometimes detected by crushing the sample between the teeth. Under the microscope the powder shows dense ligneous cells, some entire, with linear air-spaces, others torn and indistinct. Figure 50 shows some structures of olive seed and figure 5 I some structures of nut-shells. Both are from J. Moeller's work. 36 PEPPER 299 By treatment with dilute sodium hydroxid solution and washing by decantation poivrette will appear yellow and pepper husk dark. Although poivrette contains no starch, it yields a reducing substance on boiling with hydrochloric acid. Bleached pepper husks are distinguished from poivrette by the microscopic appearance. An incomplete separation of poivrette may be effected by shaking the sample in a mixture of equal parts of glycerol and water, in which poivrette sinks more rapidly. Several color tests have been proposed. Gillet advises the use of a 7 per cent, alcoholic solution of iodin, which stains pepper brown and poiv- rette bright yellow. Chevreau uses a solution of anilin in three parts of acetic acid. Pure pep- per is almost unaffected, but poivrette becomes bright yel- low, and under the microscope the stone cells exhibit a pure gamboge yellow. Pabst uses a solution of dimethyl- 1 -4-di- amidobenzene, prepared as fol- lows : i gram of commercial di- methylanilin is mixed in a por- celain dish with 2 grams of strong pure hydrochloric acid, 10 grams of broken ice are added, and, little by little, with con- stant stirring, a solution of 0.7 gram of sodium nitrate in 10 c.c. of water. After half an hour 3 to 4 grams of hydrochloric acid and 2 grams of tin-foil are added. The reduction is allowed to go on for an hour, when the tin in solution is precipitated by means of zinc. The decanted and filtered liquid is treated with a slight excess of sodium carbonate and the precipitate thus produced redissolved by the addition of acetic acid. I gram of sodium acid sulfite is added and the liquid diluted FIG. 51. Exterior layer; m, intermediate layer ; i, inner layer. 3OO FOOD ANALYSIS to 200 c.c. In testing pepper, 2 c.c. of the solution are placed in a shallow dish and a pinch of the pepper sprinkled into it. In a few minutes the particles of olive stones become a brilliant carmine, while the grains of pepper remain unal- tered or become only faintly pink. If some water be now added, the heavy particles of olive stones fall to the bottom and are detected with ease. Ground nut-shells are colored in the same way. The phloroglucol-hydrochloric acid solution (page 35) pro- duces with olive stones and nut-shells a deep crimson stain which is very characteristic. The action is obtained promptly on moistening the sample with a few drops of the reagent. Under a magnifying power of about 200 diameters the stained stone-cells are clearly seen. Dhoura Corn. This is a variety of sorghum, known in England as Turkish millet and in America as Egyptian corn. J. Campbell Brown has called attention to its use as an adulterant for pepper, and gives the following analyses and description. The samples examined contained 1 1 per cent, of moisture, and the figures given are percentages of the dry material : Ash, 1.31 1.69 Starch, 73.20 73.20 Cellulose 2.56 4.19 Ether-extract, li.io 7.30 Nitrogen, 1.82 1.78 The material designated "cellulose" is probably crude fiber, obtained by using stronger solutions than directed in the A. O. A. C. method. The grain is roundish, oval, or some- what flattened, 2 to 5 mm. in diameter. The body is white and consists mainly of roundish starch granules, ranging from 1.5 to 2.5 microns in diameter, showing a cross under polar- ized light, and larger granules, ranging from 12.5 to 32.5 PEPPER 3OI microns in diameter, showing almost no cross. Some of the smaller granules have a star-like central hilum. Coriander Seed. Hanausek has called attention to the adulteration of pepper with ground coriander seed. The following peculiarities were observed under the microscope : (a) bundles of corrugated bent fibrous cells ; (b) coarse parenchyma overlaid with narrow cells of a yellow color, with parallel walls ; (c] colorless cellular parenchyma firm in the walls and inclosing numerous crystalline rosettes and granules. The last two peculiarities were recognized as characteristic of a fruit of the order Umbelliferce, the bundles of fibers, as well as the absence of vittae (oil cavities), pointing to coriander. Cayenne pepper is often added to adulterated pepper to restore pungency. It may be detected by the characteristic irritating vapor produced on heating some of the separated red particles. An alcoholic or ethereal solution also gives off such vapors. LONG PEPPER Long pepper is the fruit of at least two species, formerly included under the genus Piper L. (Piperacece), now included under the genus Cliavica Miq. It consists of long, nearly cylindrical spikes, covered with closely packed coalesced fruit, which are picked unripe. The Chavica officinarum, from Java, consists of spikes about 4 to 6 cm. in length. The spikes of the Chavica Roxburghii are about half as long. The latter is the more common form. Long pepper usually contains a considerable proportion of extraneous matter (clay and soil) embedded in the crevices and irregularities of the fruit. The outer husk and central woody stem are not readily removed, as in the case of black pepper, so that the proportion of woody fiber is larger than in ground black pepper of the same shade, but not so high as in most husky black pepper. Long pepper contains less piperin than most black pepper, and has a disagreeable odor STARCH AND MATTER CON- INSOL VERTIBLE ETHER- HC1. INTO SUGAR. FIBER. EXTRACT. NITROGEN. ANALYST. 1.2 44.04 15-7 5-5 2.1 J. C. Brown I.I 49-34 10.5 4-9 2.0 i-S 4461 10.7 8.6 2.3 < < . . 7.28 7.24 A. L. Winton 3O2 FOOD ANALYSIS and flavor ; in the ground state, it is not a recognized article of commerce. It is used whole in pickles and has been employed to adulterate ground black and white pepper. The following are some results of analysis of long pepper : TOTAL ASH. 8.91 8.98 9.61 8.10 Winton's figures were obtained by the A. O. A. C. methods. According to J. Campbell Brown, long pepper may be detected in ground pepper by the following characters : The presence of any considerable quantity of long pepper will impart to the ground material its peculiar slaty color ; but this is made much lighter by the practice of sifting out much of the darker or husky portions of the long pepper before mixing. Bleaching is also resorted to. The odor of the mixture when warmed is unmistakable, even if the quantity is comparatively moderate. The ether- or alcohol-extract also, if the solvent has been evaporated at a low temperature, yields the characteristic odor when warmed. Long pepper often introduces a considerable amount of mineral matter, especially sand and other material insoluble in acid. This fact is important in examining white peppers, in which the proportion of ash is low. Long pepper, even if the husk particles have been sifted out, will still introduce some sand, as well as spent bleach, if an attempt has been made to bleach it. The woody matter in ground long-pepper is always con- siderable. If the sample be spread out in a smooth thin layer on paper by means of an ivory paper-knife, pieces of fluffy woody fiber will be detected, especially if the smooth thin layer be tapped from below. These pieces come from the CAYENNE PEPPER 303 central part of the indurated catkin, which cannot be com- pletely ground fine, and are very characteristic. Some of the starch granules of long pepper are of larger size (0.005 mm.) than those of ordinary pepper, which are but slightly smaller than those of rice. According to Stokes, long pepper may be detected by placing, a small portion on a microscope slide, adding a drop of glycerol, and examining under a power of about 50 diam- eters and crossed Nicols. If ordinary pepper only be pres- ent, the field will remain dark, but long pepper presents a luminous white appearance. The same is true of particles of rice. By treating the finely powdered material for 24 hours with chloral solution, it is rendered more transparent, and more satisfactory examination may be made. Rimmington recommends shaking the material several times, first with alcohol and then with water in a test-tube, and allowing to subside. Several strata are usually formed, the uppermost of which should be removed by means of a pipet and examined with a power of 250 diameters. Every particle will be seen clear and well defined and foreign bodies easily recognized. CAYENNE PEPPER Cayenne pepper is the ground pods of several species of Capsicum, usually C. annuum L. or C. fastigiatum Blum. The latter is official in the United States and British pharma- copeias. It is known in commerce as African or bird pepper, and in Great Britain as Guinea pepper and as chillies. The- pods are bright scarlet and from 12 to 18 mm. in length. Those of C. annuum are much larger, 5 to 10 cm., yellowish or red, and, when dry, brownish ; in other respects they resemble those of C . fastigiatum. Cayenne pepper is a brick-red powder of intensely pungent taste and characteristic odor. When heated, an acrid, irritat- 304 FOOD ANALYSIS ing vapor is given off, the production of which maybe utilized as a test for the pepper, even on a minute quantity of the material. This is due to a crystalline body, " capsaicin." It melts at 59 and volatilizes at 115. It may be obtained by extracting the pepper with petroleum spirit, evaporating, and treating the dry extract with a dilute solution of potassium hydroxid. On saturating the liquid with carbon dioxid the capsaicin is precipitated in small crystals, readily soluble in alcohol, ether, amyl alcohol, and fixed oils, but less so in petroleum spirit and carbon disulfid. Capsaicin is more abundant in the pods than in the seeds, in which it exists dissolved in the fixed oil. It was discovered by Thresh, who found also a small quantity of an alkaloid resembling conin. The coloring-matter of cayenne pepper is but slightly soluble in alcohol, but dissolves readily in oils, carbon disulfid, petroleum spirit, ether, and chloroform. The odor is due, at least in part, to the presence of a minute quantity of volatile oil. Cayenne pepper contains no starch. The following are some published analyses : Fruit of Capsicum annuum, grown in Hungary (C. Richard- son) : WHOLE SEED. POD. FRUIT. Water at 1 00, 8.12 14-75 I][ -94 Albuminoids, 18.31 10.69 13.88 Ether-extract, 28.54 5.48 15.26 Nitrogen-free matter by difference, . 24.33 3^-73 32.63 Crude fi er, 17.50 23.73 21.09 Ash, . . 3.20 6.62 5.20 Nitrogen, 2.93 1.71 2.22 Average of several analyses by Blyth : Water-extract, 32.10 Alcohol-extract, 25.79 Benzene-extract, . . . .- 20.00 Ether-extract, 10.73 Nitrogen, 2.04 Ash, 5.69 GINGER 305 Two analyses by C. Richardson : ETHER- ALBUM- NITRO- WATER. ASH. EXTRACT. FIBER. INOIDS. GEN. Zanzibar, 2.35 9.06 26.99 16.88 13. 13 2.10 Crosse and Blackwell, . .5.74 5.24 17-9 18. 10 11.20 1.79 Adulteration. The adulterant most commonly added to cayenne pepper is rice flour or similar material. Brick dust is also used. - A. H. Allen found iron oxid, salt, and red lead. Starch-containing materials are readily detected by the microscope or by the iodin test. Results obtained at the Connecticut Agricultural Experi- ment Station indicate that pure cayenne pepper will contain not less than 16 per cent, of non-volatile ether-extract and between 4.5 and 8 per cent, of ash. The determinations of extract, ash, nitrogen, and moisture are made by the methods elsewhere given. Barium com- pounds have been found in some samples, and it has been al- leged that they are normal, but this seems to be a mistake. An artificial red, containing barium, is sometimes used to color inferior samples, and possibly barium sulfate has been added as a make-weight. The following data have been furnished as the range of composition in cayenne pepper. An ether-extract of less than 1 8 per cent, is suspicious : Moisture, 2 to 10 per cent. Ash, 5 to 10 Fiber, 16 to 18 Nitrogen, 1.7 to 2.2 Ether-extract, 16 to 30 Alcohol-extract, 25 to 45 GINGER Ginger is the rhizome of the Zingiber officinale Roscoe, of the order Zingiberacece. It exists in commerce in two forms, either with the outer integument present, called 306 FOOD ANALYSIS "coated ginger," or removed by scraping, as in " uncoated " or " scraped ginger." Scraped ginger is sometimes known as white ginger, and the same name is applied to samples that have been bleached either with sulfurous acid or hyposulfites. It is also sometimes coated with lime or gypsum. Jamaica ginger is preferred in the United States. It forms a lighter colored powder than the other varieties. Ginger contains a volatile oil, a pungent resin, starch, gum, and the usual plant constituents. The volatile oil has the odor but not the pun- gency of ginger. Adulteration. The most common adulteration of ginger is admixture with ginger that has been exhausted with dilute alcohol or water. For the detection of this, indications are furnished by the determination of the cold-water extract taken in conjunction with the soluble ash, as suggested by A. H. Allen and C. G. Moor. The following are some results ob- tained : JAMAICA. a. b. COCHIN. AFRICAN. Moisture 13.9 12.7 13.5 15.9 Total ash, 3.9 3.2 3.8 3.6 Soluble ash, .... 3.0 1.7 2.0 2.2 Cold-water extract, .14.4 12.2 8.6 10.8 Neither the soluble ash nor the cold-water extract alone will afford a means of deciding as to the presence of exhausted ginger, but by a combination of the two data it is possible to arrive at a positive conclusion. Thus, there is no diffi- culty in ascertaining the presence of the adulterant when it has been added in such quantities as to bring the soluble ash down to about I per cent, and the cold-water extract to less than 8 per cent. Stock recommends also a determination of the amount of potassium. The following are some results obtained by him : SOLUBLE ASH. POTASSIUM. Pure ground ginger (94 samples), . 1.7 to 3.6 0.7 to 1.5 Exhausted ginger, 0.2 to 1.6 0.016100.7 NUTMEG 3O7 Turmeric, flour, ground husks and shells, seeds, or seed- cake are possible adulterants of ginger, and are best detected by means of the microscope. The form of the starch granules present will often furnish valuable indications. Comparison with the following figures, obtained by the examination of pure samples, may also aid in some cases : RICHARDSON. KONIG. Water, 9.0 to il.o 10.171012.08 Ash, 3.39 Volatile oil, 0.96 Fixed ether-extract, . . 2.29 Starch, 46.16 Crude fiber 1.70 Proteids, ...... 5.25 7.02 3.79 2.54 1.68 4-58 3-44 53-33 45-70 7-65 4.3 6 10.85 7-12 6.74 2.70 3-53 54.60 8.88 8.34 NUTMEG Nutmeg is the kernel of the seed of the Myristica fragrans Houttyn, of the order Myristicaccce. The fruit is gathered and dried by slow heating, after which the shell is removed and the inclosed nutmeg usually is coated by dipping in thick milk of lime. The nutmeg is oval or elliptical and about an inch in length. It has a strong, pleasant odor and warm, aromatic, somewhat bitter taste. Nutmegs contain between 3 and 5 per cent, of volatile oil, considerable fat, starch, and proteids. The volatile oil is colorless or pale yellow and of specific gravity 0.92 to 0.95. It is freely soluble in alcohol and commences to boil at 1 60. It is dextrorotatory. According to Cloez, the most volatile portion is a terpene and is levorotatory. There is present also myristicol, dextro- rotatory and boiling at 224. On standing, myristic acid sometimes separates from the volatile oil. Adulteration. Nutmeg is little subject to adulteration, being almost exclusively sold unground. Artificial nutmegs, containing some nutmeg oil, are said to have been prepared from starchy or mineral matter, but such imitation would 3O8 FOOD ANALYSIS readily be detected by the appearance of the cross -section compared with that of a genuine sample. The following are the results of some analyses by Richard- FIXED ETHERT DESCRIPTION. WATER. ASH. VOL. OIL. EXTRACT. FIBER. NITROGEN. Whole 6.08 3.27 2.84 34-37 11-30 0.83 Ground 4.19 2.22 3.97 37.30 6.78 0.87 6.40 3.15 2.90 30.98 9.55 0.84 For methods of analysis, see under " Cloves." MACE Mace is the dried mantle or arillus of the nutmeg. It consists of smooth branching bands about 40 mm. long, 2 mm. at the base, and thinner above. It is brownish, has an odor like nutmeg, and a warm aromatic taste. Mace contains a volatile oil and a resin. It is stated that it contains no fat, but this does not accord with Spath's statement, given below. According to Fliickiger, there is also present an uncrystal- lizable sugar and a body that turns blue with iodin, and, after drying, reddish-violet. It appears to be intermediate between starch and mucilage. Adulteration. In addition to the usual spice adulterants, mace is liable to contain Bombay mace, a variety which contains neither the fragrance nor the taste of true mace. Starch-containing adulterants maybe detected by the fact that pure mace, boiled with water, yields an easily filtered solution, which is not blued by iodin. Determination of the amount of starch will furnish a rough indication of the proportion of adulterant present. False or Bombay mace may be distin- guished by the altered proportion of volatile oil and of ether- extract. The following are some results obtained from true or Java mace compared with a sample of false mace : MACE 309 FIXED ETHER- WATER. ASH. VOL. OIL. EXTRACT. FIBER". NITROGEN. . 5.67 4.10 4.04 27.50 8-93 0-73 . 4-86 2.6 5 8.66 29.08 4.48 0.98 . 10.47 2. 2O 8.68 23-33 6.88 o.8l . 18.21 1.62 3 37 21.90 3-70 . . . 7.04 1.36 0.27 56.75 8.17 . . True mace, Bombay mace, E. Spath extracted a number of samples of mace with petroleum spirit and determined the constants of the material obtained. The figures obtained from mace from Banda, Menado, Penang, Macassar, and Zanzibar closely agreed with each other : MELTING- ZEISS MEISSL POINT SAPONI- REFRACTO- COEFFICIENT NUMBER IN OPEN FICATION lODIN METER OF (BANDA TUBE. NUMBER.-' NUMBER. AT 40. REFRACTION. MACE). True mace, . . 25-26 169.9-173 75.6-80.8 76-85 1.480-1.487 4.1-4.2 Bombaymace, . 31-31.5 189.4-191.4 50.4-53.5 48-49 1.463-1.464 i.o-i.i From m a c e - scales, i.f. t "the covering inside the seed-mantle," 28.5-29 148.2-148.8 71.3-73.4 . . According to Konig, a sample containing less than 3 per cent, of volatile oil or more than 35 per cent, of extract on the dry substance cannot be regarded as true mace. False mace is also distinguished by the presence of a peculiar coloring- matter, analogous to that of turmeric, rather freely soluble in alcohol and but slightly soluble in ether. The large oil cells of the false mace contain, according to Hanausek, a resinous body with which alcohol produces a yellow or greenish-yellow solution, turned orange-red by alkalies. If 10 to 20 c.c. of alcohol are shaken with 2 or 3 grams of powdered mace for a few minutes and the liquid filtered, the filtrate, but not the filter-paper, becomes colored. In the case of false mace the strongly colored filtrate dyes the paper a fixed yellow. If the filter is dried, freed from the attached powder, and touched with a weak alkaline solution, the presence of turmeric is indi- 3IO FOOD ANALYSIS cated by a brown, and of false mace by a blood-red, color. If the alkali be removed by washing the filter with water, a trace of acid will be sufficient to bring back the yellow. Hefelman suggests decomposing an alcoholic extract with lead acetate. Genuine mace gives a milk-white turbidity ; false mace, even when mixed with a large proportion of true mace, gives a red flocculent precipitate. Turmeric produces a somewhat similar color. If a strip of filter-paper be dipped into the alcoholic extract, gently dried, and then drawn through a cold saturated solution of boric acid in water, the presence of a very small quantity of turmeric will be indicated by an orange or red-brown tint. With false mace, on the other hand, the yellow color of the paper will remain un- changed. P. Soltsien has called attention to the difference between Bombay and Banda mace as regards the quantity of matter extracted by ether after removal of the fat-like bodies by petroleum spirit, and suggests that advantage be taken of the fact in order to distinguish between the two. The difference is very considerable, the quantity being about ten times as great with Bombay mace as with true mace. Soltsien has never found more than 4,8 per cent, of matter extracted by ether in a pure Banda mace and suggested 5.5 per cent, as a maximum. The manipulation is carried out as follows: 10 grams of powdered mace are exhausted by boiling petroleum spirit in an extraction apparatus. On cooling, an oily portion tends to separate at the bottom of the vessel, and this belongs prop- erly to the extractive matter soluble in ether. The petroleum extract is poured off, the separated oily portion in the flask washed with petroleum spirit and dissolved in absolute ether, and then a second extraction is made with boiling ether. In the ether-extract there is also a tendency for a portion to sep- arate out. The extract is poured off, the separated matter , ALLSPICE 3 1 I washed with ether, and the washing added to the extract, which is then filtered, evaporated, and dried in the water- bath, the residue being weighed. ALLSPICE Allspice or pimento is the dried, nearly ripe fruit of the Eugenia pimehta DeC. It is nearly globular, 6 mm. or less in diameter. Allspice contains volatile oil, fixed oil, resin, tannin, starch, sugar, and mucilage. The volatile oil is simi- lar in composition and general properties to oil of cloves. The yield is usually between 3 and 4 per cent. Adulteration. On account of its cheapness, allspice is less subject to adulteration than other spices. In addition to the usual spice admixtures, clove stems and the lowest grades of cloVes are sometimes added. These latter may be detected by the microscope, and also, in some cases, by the greatly increased proportion of volatile oil. The following results from a sample of whole allspice are given by Richardson : FIXED ETHER WATER. ASH. VOL. OIL. RESIDUE. CRUDE FIBER. NITROGEN. 6.19 4.01 5.15 6.15 14-83 0.70 According to figures published by the A. O. A. C., the variations in composition of pure samples will usually range within the following limits : PER CENT. Moisture, 5.5 to 12 Ash 3 to 5 Volatile oil, 2 to 5 Ether extract, 7 to 13 Fiber, 13 to 22 A sample of pure, whole Jamaica allspice examined by A. L. Winton gave the following results : Volatile oil, 3.52 ; non-volatile ether extract, 6.48; ash, 4.57. 312 FOOD ANALYSIS 12 samples of commercial ground allspice, in which no adulterant could be detected, gave results as follows : Volatile oil, 2.05 to 2.84 Non-volatile ether-extract, 3.98 to 5.62 Ash, 4.62 to 5.50 Analytic Methods. Moisture, volatile oil, and fixed ether- extract are determined as described under cloves (p. 316). CINNAMON Cinnamon is the inner bark of several species of Cinnamo- mum t of the order Lauracece. Commercial cinnamon may be divided into three classes, as follows : 1. True or Ceylon cinnamon, from C. Zeylanicum Nees. This is the finest quality, and is the one which is official in most pharmacopeias. It is rarely found in the grocery trade, and is used as a drug. In its preparation for the market it is deprived entirely of the outer coating and inner cortical lay- ers, and forms long strips, usually not above the thickness of stout writing-paper. 2. Common or Chinese cinnamon, C. cassia Blum., and known as cinnamon cassia or cassia bark. It is thicker than true cinnamon and generally covered with patches of cork. It has a less delicate and more astringent taste than true cin- namon. The variety of cassia known as Saigon cassia is said to have greater strength than true cinnamon. 3. Cinnamon barks from various unidentified species or varieties, including inferior qualities obtained in the East Indies and adjacent mainlands. It is from these that the common ground cinnamon of the retail trade is usually prepared. Microscopically, true cinnamon may be distinguished from cassia by the presence in the former of long cells of woody fiber, which are especially well shown under polarized light. CINNAMON The following are some analyses of pure samples : 313 ANALYST. WATER ETHE- REAL OIL. FIXED ETHER EX- TRACT. CRUDE FIBER. NITRO- GEN. ASH. Konig and Krauch Ceylon cinna- mon, . . . 12.44 1-45 35-46 0.64 3-28 C. Richardson Ceylon cinna- mon, . . . 10.00 3-14 3-30 16.18 o.6l 3-70 tt Ceylon cinna- mon, . . . 5-40 1.05 1.66 33-08 0.48 4-55 <( Ceylon cinna- mon, . . . 7-93 0.82 1.58 25-63 0.62 3-40 Konig and Krauch Cassia bark, . 13-95 3-26 17.72 0.62 2.22 << < 14.44 1.24 17.76 0.46 1.96 C. Richardson 9.42 58 1.40 17-73 0-45 2-35 ' " 11.04 1. 21 1.86 15.45 0.72 2. 4 8 < 17-45 o-55 0.74 14-33 0.64 5-25 The ash of pure cinnamon is usually white, while that of cassia is often brown, due to the larger proportion of man- ganese oxid. The following results were obtained by Dyer and Gilbard, on 5 samples of pure cinnamon : . ALCO- FIXED HOL Ex- TOTAL ASH ASH MOISTURE VOLATILE ETHER TRACT v ASH, SOLUBLE INSOL. (LOSS AT OIL EX- AFTER LESS IN IN NlTRO- IOO). (APPROX.). TRACT. ETHER. SAND. WATER. WATER. FIBER. GEN. 11.33 -77 1-87 ii. o 2.97 o.io 2.07 32.90 0.42 to to to to to to to to to 13.00 1.93 2.30 13.27 5.00 0.90 4.70 35.67 0.54 Ground walnut shells gave following results : 9.97 0.27 i. 60 3.67 0.87 0.37 0.50 47.67 0.20 The items volatile oil, alcohol-extract, insoluble ash, and 27 314 FOOD ANALYSIS nitrogen appear to furnish the most assistance in determining the proportion of admixture. The chemical composition of cinnamon and cassia is in the main the same. Each contains a volatile oil, tannin, sugar, mannite, starch, and mucilage. The essential oil of C. Zeylan- icum is pale yellow or reddish, becoming darker and thicker on exposure, and finally depositing crystals of cinnamic acid. It has a strong odor of cinnamon and a sweet, warm, aromatic taste. The specific gravity of the fresh oil is 1.035. I* 1 some cases it is slightly levorotatory. The essential oil of cassia has similar properties, but its color is more brownish, taste less sweet, odor less delicate, specific gravity greater (1.055 to 1.065), and is sometimes slightly dextrorotatory. Both oils contain variable quantities of hydrocarbons, but consist chiefly of cinnamic aldehyde, and, when old, contain resin and cinna- mic acid. Adulteration. The chief adulteration consists in the substi- tution of the inferior cassia for the true cinnamon. As noted above, the true cinnamon is now only obtained as a drug. They may be distinguished by the difference in their micro- scopic characters. Aside from this, the most important adulteration consists in the partial abstraction of the ethereal oil, on which the value of the spice depends, either by alcohol or by distillation with water. Sophistication of this kind is difficult to detect, by reason of the variations of the original bark in composition. The lower grades of ground cinnamon are also adulterated with barks of allied species, refuse found in the bundles of cinnamon as imported, mahogany and other woods, flours of various kinds, oil-cake, and similar materials. These are often readily detected by the microscope. In Austria, Bavaria, and Switzerland, cinnamon or cassia containing more than 5 per cent, of ash or I per cent, of sand is held to be adulterated. CLOVES 3 i 5 CLOVES Cloves are the unexpanded flower of the Eugenia aromatica O. Kuntze, of the order Myrtacece. They consist of a dark brown, cylindrical calyx, 3 to 4 mm. thick, bearing a several- celled ovary and a globular head of four petals. Many oil glands are under the epidermis. Cloves contain a volatile oil, resin, tannin, and gum, but no starch. The volatile oil is thicker than most essential oils and becomes still thicker and darker with age. It has the odor of cloves and a burning aromatic taste. Its specific gravity is from 1.034 to 1.056 ; it boils at 240. The oil obtained from clove stalks has a specific gravity of 1.009. Oil of cloves dissolves freely in alcohol. Strong solution of potassium hydroxid converts it into a crystalline mass of potassium eugenate. It is sometimes slightly dextrorotatory. It con- sists principally of a hydrocarbon and eugenol (eugenic acid). On distilling a mixture of cloves and potassium hy- droxid solution, the hydrocarbon is obtained as an oil of specific gravity 0.918, boiling at 251. By decomposing potassium eugenate with sulfuric acid and distilling, eugenic acid is obtained as a colorless oil of specific gravity from 1.076 to 1.078, boiling at 247.5. Caryophyllin and a salicylic ester have also been found. Adulterations. In addition to the adulterants usually em- ployed for ground spices, clove stems and the fruit of the clove, the so-called " mother cloves," may be added. The analysis of a sample of clove stems is given below. They may be detected by the microscope by the presence of numerous stone cells, bast fibers, and scaliform ducts. The form of the stone cells varies greatly ; the walls are thick and the interior cavity may be simple or ramifying. The bast fibers are usually long, spindle-shaped, and thick. The scaliform ducts, together with the stone cells, are the best evidence of the presence of 310 FOOD ANALYSIS clove stems. In mother-cloves, the stone cells are very thick- walled and have a nodulated exterior, which enables them to be distinguished easily. The seeds contain starch and raphides. The starch granules resemble those of some kinds of arrow-root ; they are principally pear-shaped, or, rather, slender and slightly curved, generally single, and show a well- marked cross under polarized light. There is a small hilum at the broad end. The resemblance to arrowroot starch is not likely to cause confusion, as the latter is too costly for use as an adulterant. Cloves are also adulterated by the addition of samples from which a portion of the essential oil has been removed. This is usually difficult of detection on account of the great varia- tion in the amount of oil found in pure samples. ANALYSES OF CLOVES AND STEMS WHOLE CLOVES. STEMS. Water 16.39 4.84 16.98 6. 20 10.56 o-95 Laube and Allendorf 2.90 to 10.67 5.25 ' 13-05 10.23 ' 18.89 7.12 ' 10.24 6.18* 9.75 0.76 ' 1. 12 Richardson, 7 samples 9 to 21 Dietsch 10.18 6.96 4.40 4-03 I3-58 0.92 Richardson Ash, Volatile Oil Fixed ether-residue, .... Crude fiber, Nitrogen Analyst, In 20 samples, either known to be pure, or in which no adulteration could be detected by the microscope, A. L. Win- ton found the following range in composition : PER CENT. Volatile oil, .10.01101832 Fixed ether-extract, 4.90 " 6.20 Ash, 6.50 " 7.95 ANALYTIC METHODS. The presence of a large amount of volatile oil necessitates a departure from the methods usually MUSTARD 3J7 employed for spices. The following method for non-volatile ether-extract and volatile oil is practically the same as that adopted by C. Richardson and A. L. Winton : 2 grams of the material are weighed into a fat-free paper thimble, which, with its contents, is dried by standing in a desiccator over sul- furic acid for 16 hours, after which the ether-soluble matters are extracted as described on page 49. The ethereal solu- tion is transferred to a tared receptacle and allowed to evapo- rate at the ordinary temperature. After standing 18 hours over sulfuric acid, the total ether-extract is weighed. It is then heated first at 100 for 6 hours, and then at 1 10, until the weight becomes constant, the loss being volatile oil, and the residue the fat and resin. The fiber may be determined as usual on the residue insoluble in ether (p. 46). MUSTARD Mustard is prepared from the seeds of the Brassica nigra Koch (black mustard) and B. alba Hkr. f. (white mustard). Commercial mustard may be a mixture of the two forms. The seeds are finely powdered and passed through a sieve in order to remove husks. Both forms contain a fixed oil in fairly con- stant proportion, albuminous matter, gum, sinapin thiocyanate, and an enzym, myrosin, but no starch. White mustard con- tains also the glucosid, sinalbin ; and black mustard the glu- cosid, potassium myronate. These glucosids are decomposed by the enzym, on addition of water, but the action is not hydrolytic. Allyl isothiocyanate, volatile oil of mustard, is a colorless liquid, specific gravity j* 1.018, boiling at 148-150, and volatile in a current of steam. It has a strong mustard-like odor and the vapor excites a flow of tears. It is slightly sol- uble in water and much more so in alcohol, ether, petroleum FOOD ANALYSIS spirit, and carbon disulfid. It is a powerful rubefacient and vesicant. Acrinyl isothiocyanate is a yellow liquid of pungent burning taste. It is a less powerful vesicant than the oil from black mustard and is but slightly volatile in steam. It is insoluble in water, but soluble in alcohol and ether. Black mustard seeds do not contain sufficient myrosin to convert all of the potassium myronate present. White mus- tard seeds, on the contrary, contain more myrosin than is required to convert the sinalbin, so that by a judicious mixture of the two a greater yield of allyl isothiocyanate is secured. White mustard yields only traces. Myrosin is coagulated by heat, so that if mustard be intro- duced into boiling water, no volatile oil is produced. It is said to recover its converting power by immersion in water for some days. The fixed oil of mustard has the following physical and chemical constants : Sp. gr., -^-, 0.914 to 0.920 ; saponifica- tion value, 170 to 175 ; iodin value, 92 to 106. About 35 per cent, is usually present. Commercial samples of good quality may contain much less, a portion having been ex- pressed in the manufacture of the mustard flour. The following are some results of examination of pure samples : Mean of three closely concordant analyses of white mustard by Leeds and Everhart : Water, 6. 83 per cent. Potassium myronate, 0.64 Sinapin thiocyanate, 11.12 Myrosin and albumin, 28.48 Fixed oil, , .... 29.21 Ash, 3.75 Variations in composition of ground mustard seeds, accord- ing to figures published by A. O. A. C. : FLAVORING EXTRACTS 319 PER CENT. Moisture, 3 to 8 Ash, 4 to 7 Ether-extract, 31 to 37 Fiber, 4 to 6.5 Aqueous extract, 30 to 38 Sulfur, I to 1.6 When prepared from partially expressed seeds, the mustard will contain less oil (ether-extract) and a correspondingly larger proportion of the other ingredients. Adulteration. The most common adulterant for mustard is rice flour or wheat flour. These are readily detected by the microscope and by the presence of starch. This may also be present as a constituent of turmeric, added to color pale samples. Starch may be detected by boiling a portion of the sample with water, filtering, and adding iodin to the filtrate. It is estimated as on page 97. The proportion of starch in wheat flour is about 72 per cent. A. H. Allen suggests the determination of the amount of fixed oil, which is usually about 35 per cent., and calculating from its deficiency the proportion of diluent present. In view of the practice of some manu- facturers of pressing the seed, such a method is no longer reliable, but may often be of value as corroborative evidence. Of mineral additions, calcium sulfate, chalk, and lead chromate have been employed. These are detected in the ash. Yellow coloring-matters are frequently employed, the most common being turmeric, Martius' yellow, and naphthol yel- low S. Coal-tar colors may be detected by methods given on pages 7782 ; turmeric, by the test given under " Mace" or by the principle of the test for boric acid, page 89. FLAVORING EXTRACTS Vanilla Extract. The highest grade of this preparation is obtained by macerating vanilla beans with alcohol of 50 per 32O FOOD ANALYSIS cent. The cheaper grades contain cumarin, artificial vanillin, some glycerol, and caramel or coal-tar colors. The cumarin may be either added as such or obtained by macerating tonka beans in the solvent. In cheap extracts a very dilute alcohol is used and the solvent action aided by some alkaline substance, generally acid potassium carbonate. The following is a pub- lished formula for a very cheap imitation extract : Vanillin, I gram Cumarin, I gram Alcohol, 125 c.c. Glycerol, 65 c.c. Water, I liter Caramel to color. Commercial vanilla extracts have been examined by W. H. Hess. He gives the following test as a critical one in dis- tinguishing true from imitation extracts : A portion of the sample should be mixed with a few drops of lead acetate solution; if a bulky flocculent precipitate does not form, the extract is not of high quality. The process given by Hess may then be applied to establish its general character : 5 c.c. of the extract are diluted slowly with 10 c.c. of water and the mixture shaken. A flocculent reddish-brown precipitate shows that no alkali has been added. A milky solution indicates a foreign resin. Hydrochloric acid is added drop by drop to a portion of the diluted liquid ; only a slight turbidity should result. If the turbidity is considerable and the color fades, alkali has been employed in making the extract. 25 c.c. of the sample are concentrated on a water-bath until the alcohol is removed and made up to the original volume with water. The vanilla resin will appear as an amorphous, flocculent, reddish-brown mass if alkali be absent. The cold solution is acidified with hydrochloric acid, when the whole of the resin will separate, leaving the liquid nearly colorless. After standing several hours the residue may be FLAVORING EXTRACTS 321 collected on a filter, washed with water, and the filtrate and precipitate further tested. A piece of the filter with resin attached is placed in sodium hydroxid solution. A deep red solution should be formed. A solution of a portion of the precipitate in alcohol should not give any marked reaction with ferric chlorid or hydro- chloric acid. A portion of the filtrate is concentrated at a low tempera- ture until its color approximates that of the original sample, a few drops of strong hydrochloric acid are added, and gently heated. Caramel will produce a yellowish-red flocculent pre- cipitate. The liquid is allowed to cool, filtered, and the precipitate washed with water ; if from caramel, the precipitate will be insoluble in water, alcohol, and ether, soluble in sodium hydroxid, glacial acetic acid, and dilute alcohol. & small portion of the filtrate is made alkaline with am- monium hydroxid ; natural color is much deepened. Zinc dust is added, and the liquid warmed gently. The color should return to about the tint it possessed before the am- monium hydroxid was added, but azo-colors will be com- pletely bleached. If the latter effect occurs, some of the liquid should be mixed with hydrogen dioxid, when the color will return. The caramel test described on page 1 30 will probably be of service in these examinations. Detection of Cumarin and Vanillin. 50 c.c. of the sample are evaporated at low temperature, with addition of water from time to time, until the alcohol is removed. Lead acetate solution is added slowly, with constant stirring, until precipi- tation ceases. The liquid is filtered, the precipitate washed with a few c.c. of hot water, the filtrate cooled, and agitated with successive portions, 20 c.c. each, of chloroform until a few drops of the latter leave no residue when evaporated on a watch-glass. Four extractions will usually be sufficient. 28 322 FOOD ANALYSIS The chloroform extracts are mixed and shaken with successive portions, 2 c.c. each, of ammonium hydroxid solution, sp. gr. 0.960, until the latter no longer becomes yellow. Vanillin dissolves in the ammoniacal solution, while the cumarin remains in the chloroform. The chloroform is evaporated, best under reduced pressure, and the residue dried, either at low pressure over sulfuric acid, or in an air-bath not over 45, is repeatedly extracted with very light petroleum (so-called ligroin), boiling about 35, until a drop of the solvent leaves no residue. The col- lected ligroin solutions are evaporated and (best at low pressure) dried at not above 45. The residue is cumarin. The melting-point (67) and odor will serve to confirm the analysis. The ammonium hydroxid solution is rendered slightly acid with hydrochloric acid and the vanillin removed by repeated agitation with chloroform. The chloroform is evaporated, the residue dried at not above 55, and washed repeatedly with small portions -of ligroin, the portions collected evaporated as before, and the residue, vanillin, is weighed. It may be identified by melting-point (8o-8i) and the other tests. The process may be simplified if merely the qualitative recognition of cumarin in commercial vanilla extracts be re- quired. Lemon Juice and Lemon Sirup. A. Borntrager fur- nishes the following analyses of lemon juice : RIPE FRUIT. UNRIPE FRUIT: Citric acid, 7.25 7.70 Reducing sugar, 0.75 0.21 Sucrose, 0.19 0.78 Ash, 0.39 0.49 Total solids, 8.87 9.30 Borntrager also examined several samples of lemon sirup giving the following results. No. 2 has been sophis- ticated : CATSUP AND TABLE ACCESSORIES 323 No. i. No. 2. Citric acid, 14-4 5-42 Tartaric acid, o.oo 10.70 Reducing sugar expressed as dextrose, .30.10 38.42 Sucrose, o.oo o.oo Ash, 0.32 0.72 Total solids, 81.92 80.56 The reducing sugar may result from the inversion of the cane-sugar. The following formula for a cheap lemon-extract is quoted from a trade circular : Lemon oil, I gram Lemon grass oil, O.I c.c. Citric acid, 0.5 c.c. Alcohol, 16.0 c.c. Water, . . no.oc.c. Turmeric tincture to color. Magnesium carbonate is used as a clarifying agent, but is removed by filtration. Artificial colors, especially naphthol yellow S, are often used as coloring agents. Analytic examinations will be usually directed to determine the presence of artificial colors, glucose, and preservatives, for which see pages 77, 115, and 86. Tartaric acid may be determined as follows : 20 grams of the sirup are mixed with 5 grams of potassium chlorid, the solution neutralized with potassium hydroxid and made up to 50 c.c. with water. 5 grams of citric acid are added, the solution well stirred, and allowed to stand overnight. The precipitated acid potassium tartrate is washed first with a satur- ated solution of the same substance, then twice with a 10 per cent, solution of potassium chlorid, and titrated hot with standard alkali. CATSUP AND TABLE ACCESSORIES Catsup is prepared from the pulp of tomatoes with addition of vinegar and various spices. The bottled catsups almost always contain artificial colors and preservatives. The pre- 324 FOOD ANALYSIS servative is usually salicylic acid or sodium benzoate, but boric acid may be used. It must be borne in mind that small amounts of boric acid may exist in some of the materials used in making the catsup, and also that some manufacturers buy the tomato pulp from canning establishments, and this may be treated with a little salicylic acid to prevent it spoiling in warm weather. The detection of artificial colors and pre- servatives will be attained by the general processes given in the sections on those subjects. Many other articles, such as pickles, pickled onions, chow- chow, horseradish, and sauces, are now sold in bottles or cans. These are rarely colored, but may contain preservatives, especially salicylic acid or sodium benzoate, detected as noted above. Desserts. Under this head will be included ice-cream, water-ices, jams, jellies, marmalades, fruit sirups, fancy cakes, pies, and custards. The component parts of the higher grades of these articles will be found in cook-books. The analytic investigations will be limited to the detection of preservatives, artificial colors, starch, gelatin, and substitutes for cane-sugar. The detection of these substances is given elsewhere, except as to gelatin, for which the following process has been proposed : The material is boiled with water, filtered, the filtrate boiled with excess of potassium dichromate, cooled, and a few drops of sulfuric acid added. If gelatin is present, a flocculent pre- cipitate will be formed. It is probable that the reaction of gelatin with formaldehyde could be utilized in these examinations. Ice-cream is not subject to serious adulteration. The cheaper grades contain much starch, and often artificial fla- vors and colors. In hot weather, milk and milk products are liable to become very poisonous by the development of bacteria, and such cases are often wrongly charged to adul- teration. Ice-cream and similar refreshments hawked about CATSUP AND TABLE ACCESSORIES 325 the streets of large cities are very apt to be dirty, containing bodies of insects and other filth. The method employed by L. K. Boseley for the analysis of marmalade will be applicable in many cases to jams, jellies, and similar articles. Water. Several grams of the well-mixed sample are weighed in a flat basin with a glass rod. The mass is warmed and 5 c.c. of 40 per cent, alcohol added. 15 grams of dry quartz sand are stirred in. The dish is heated on a water- bath for one hour, 5 c.c. of absolute alcohol added, and again heated for one hour, and then in an air-bath until the weight is practically constant, which may require more than 24 hours. Polarimetric Examination^. A weight of the well-mixed sample equal to 2.5 times the normal weight of the instru- ment to be used (i. e., 65.12 for instruments adapted to a con- centration of 26.048) is dissolved in about 50 c.c. of cold water, added in small portions with stirring, transferred to a 250 c.c. flask, the residue washed, and the washings added to the contents of the flask. Lead subacetate is added in amount not quite sufficient to remove the acidity, the flask filled to the mark and the liquid passed through a dry filter, the first 20 c.c. rejected, and the polarimetric reading of a por- tion of the remainder of the filtrate taken in the usual man- ner. It will be almost always decidedly positive. 50 c.c. of the filtrate are inverted as described on page 124 and the reading again taken at a temperature as near as possible to that of the first reading. For the calculation of sucrose see rules on page 125. 326 FOOD ANALYSIS ALCOHOLIC BEVERAGES CIDER Cider is the juice of apples either before or after ferment- ing ; when the alcohol is in considerable amount, the liquid is often called "hard cider." Cider differs from wine in con- taining no tartrates, and larger amounts of malates and calcium compounds. Pear cider, often called " perry," contains more sugar than apple cider, and therefore, yields more alcohol when fully fermented. The following analyses of apple cider by R. Kayser, quoted by A. H. Allen, represent the same sample before and after fermentation. The figures are grams per 100 c.c.: UNFER- MENTED. FERMENTED. Total solids, 16.25 2.36 Alcohol, 4.6 (5. 8 c.c.) Ash, 0.35 0.31 Malic acid, 0.33 0.30 Acetic acid, . . 0.08 Sugar, 12.50 0.75 Glycerol, 0.68 G. S. Cox obtained the following results from unfermented cider : Total solids, 14.83 13.36 Ash, .... 0.525 0.286 Percentage of ash to solids, . . 3.54 2.14 The following are some analyses, by J. Embrey, of English and American ciders : VOL. ACID FIXED ACID ALCOHOL. EXTRACT. ASH. SUGAR. AS ACETIC. AS MALIC. American : I, 2.91 9.2 0.3 7.91 0.096 0.33 2, 3.49 9.6 0.32 8.2 0.048 0.671 3, 2.45 8.96 0.24 6.93 0.128 0.712 English : Unfermented juice from choice apples, 0.2 1 1 2. 06 0.3 10.84 0.024 0.549 New English cider, . 3.32 6.7 0.34 3.86 0.144 0.244 Old English perry, . . 3,64 4.5 0.3 0.36 0.222 0.244 SPIRITS 327 From the above and other examinations Embrey is of the opinion that unwatered cider will not contain less than 0.25 per cent, of ash. ADULTERATIONS. The usual adulterations of cider are dilution with water, addition of soda or lime in order to correct acidity, and addition of preservatives. The ash of cider con- tains no sodium. When heated, it volatilizes at a compara- tively low temperature, and imparts to flame a pure potassium color. The dilution of cider with ordinary water containing even a small proportion of sodium may be detected by this test. The proportion of ash to the original solids may furnish some indication of the nature of a sample under examination. In unfermented cider the proportion of ash to total solids will range from 2 to 6 per cent. If the sample be fermented, an allpwance must be made for the loss in solids. (See under " Cider Vinegar.") According to the recommendations made to the A. O. A. C. in 1897 by the referee on food adulterations, pure cider will have the following composition : GRAMS PER 100 c.c. Alcohol, below 7 Extract, 2.0 to 8.0 Sugar, 0.4 to 4.0 Total acidity, calc. as sulfuric acid, 0.2 to 0.5 Fixed acids, calc. as sulfuric acid, o. I to 0.27 Ash, 0.17 to 0.35 Potassium carbonate, 0.14100.23 The preservatives used are commonly salicylic acid and sulfites, but formaldehyde is now sometimes used. The analysis of cider is to be conducted according to the methods given for alcoholic beverages proper. SPIRITS Spirits are the liquors obtained by the distillation of alcoholic liquids. The latter are the results of fermentation of saccha- 328 FOOD ANALYSIS rine infusions derived from barley, oats, wheat, maize, rice, potatoes, or from the juice of fruits, sugar-cane, beet-root, etc. The distilled liquor contains water and ethyl alcohol along with a small proportion of its homologues (fusel oil), aldehyde, acetic acid, and various esters. The amount and nature of these associated bodies will depend upon the nature of the fermented material and the method of manufacture. The character of the distilled spirit is further modified by the addi- tion of various flavoring materials. WHISKEY Whiskey is the spirit distilled from fermented grain. In some cases malted grain is used, but more usually a mixture of malted and unmalted grain is employed. Spirit from raw grain usually contains a larger proportion of fusel oil. The grain commonly employed in the United States is rye, but wheat and maize are also used to a considerable extent and glucose is a frequent addition. The weak spirit (so-called " low wine ") which is obtained by distillation is usually re- distilled, by which it is obtained stronger and less charged with fusel oil. When only malted grain is used, the liquid is sometimes distilled in small stills, called "pot heads," and at once set aside to age without redistillation. Freshly distilled whiskey is colorless and of disagreeable flavor. It is usually stored in sherry casks, where it is allowed to remain for a considerable time until it has aged or ripened, the process consisting in the conversion of the fusel oil into various esters of agreeable smell and taste. At the same time a small amount of tannin and other matters are extracted from the cask, and the whiskey acquires an amber or yellow color, which is frequently heightened by the addition of caramel, logwood, catechu, tea infusions, etc. Old whiskey has an acid reaction, due to the presence of a small amount of acetic WHISKEY 329 and possibly other acids. The acidity increases with age, but is rarely over o. I per cent, expressed as acetic acid. The U. S. Pharmacopeia defines whiskey to be "a distillate from the mash of fermented grain, as maize, wheat, or rye. It is an amber-colored, slightly acid liquid. The specific gravity should be not more than 0.930 nor less than 0.917, corresponding to an alcoholic strength of from 44 to 50 per cent, by weight or 50 to 58 per cent, by volume. If 100 c.c. be slowly evaporated in a tared capsule in a steam-bath, the last portion should not have a harsh or disagreeable odor (ab- sence of more than mere traces of fusel oil.) The residue, dried at 100, should not weigh more than 0.21 gram, have no sweet or distinctly spicy taste, should dissolve almost com- pletely in 10 c.c. of cold water to form a solution not more deeply colored than light green by a few drops of ferric chlorid solution (absence of more than traces of oak tannin). 100 c.c. of whiskey should not require more than 12 c.c. ^ sodium hy- droxid to render it distinctly alkaline." In Scotland and Ireland the drying of the malt takes place in kilns in which peat is used as fuel, and the spirit whiskey made from it has a strong smoky flavor. This is often im- itated by the addition of two drops of creasote to the gallon of spirits. A variety of whiskey is sometimes made by distilling cider, and is known as apple-whiskey or apple-brandy. English whiskies are occasionally adulterated with methyl alcohol. Cayenne pepper is also said to be added in order to give greater warmth of taste, and thus enable a weak spirit to be sold for a strong one. In some cases it appears to have been added simply as a flavor. Lead, copper, and zinc have been found in whiskey, and are probably derived from the apparatus employed in the dis- tillery. They are also said to have been added directly. The following are some results of analyses of commercial whiskey by A. H. Allen : 330 FOOD ANALYSIS COMMERCIAL COMMERCIAL SCOTCH WHISKEY. IRISH WHISKEY. Specific gravity, 0.9416 o. Alcohol (percentage by weight), 39. 05 39-3 Secondary constituents, expressed in grains per imp. proof-gallon : Free acid, as acetic, 10.2 6.8 Ethers in terms of acetic ether, . . . . 46.5 23.1 Higher alcohols in terms of amyl alcohol, 89.6 78.8 Aldehyde, Trace. Trace. Furfural, " " BRANDY Brandy, also called French brandy or " cognac," is the spirit obtained by distilling wine. An inferior quality is manufactured from skins and stalks (" marc ") of the grapes. Such brandy usually contains more fusel oil than that made from wine. So-called British brandy is made from grain spirit to which is added flavoring esters, such as ethyl acetate, pelargonate and nitrate, bitter almonds, spices, and caramel. Freshly distilled brandy is colorless, but on standing in casks it dissolves a minute quantity of tannin and other bodies and acquires an amber tint. It is also frequently colored with caramel. Ordonneau obtained the following results from a French brandy, 25 years old, by fractional distillation : GRAMS PER 100 LITERS. Normal propyl alcohol, 40.0 Normal butyl alcohol, 218.6 Amyl alcohol, ... 83.8 Hexyl alcohol, 0.6 Heptyl alcohol, 1.5 Fthyl acetate, 35.0 Ethyl propionate, butyrate, and caproate, 3.0 CEnanthic ether, 4.0 Aldehyde, 3.0 The ferment of grape skins, Sac char omyces ellips aides, pro- duces normal butyl (tetryl) alcohol, but in fermentation by brewer's yeast (S. cerevisicz) isobutyl alcohol is formed. By MALT LIQUORS 33! the use of the former ferment, with saccharine solutions other than grape-juice, a spirit may be produced having characters similar to French brandy. GIN Gin, and the varieties known as Hollands or Schnapps, are usually prepared by redistilling grain spirit which has been fla- vored with various bodies, among which may be mentioned juniper berries or oil of juniper, turpentine, coriander and car- damon seeds, capsicum, orris, angelica, and calamus roots. Gin is without color and is comparatively free from fusel oil and the associated bodies found in brandy and whiskey. RUM Rum is the spirit obtained by distilling the fermented juice of the sugar-cane, or, more commonly, by distilling fermented molasses. The flavor of rum is due largely to the presence of ethyl butyrate and ethyl formate. It is colored either by long keeping in casks, or by the addition of burnt sugar. Much of the commercial article is made from grain spirit to which has been added butyric acid or butyric or acetic esters. Pineapple and tannin-containing materials are also added. According to A. H. Allen, the presence of formates might serve to distinguish genuine rum from the factitious product. The rum should be evaporated .almost to dryness with a slight excess of sodium hydroxid and the residue treated with phosphoric acid and distilled. The distillate from genuine rum will strongly reduce silver nitrate, and give the other reactions for formic acid. MALT LIQUORS These are, strictly speaking, infusions of malt, fermented by yeast, and rendered bitter by the addition of hops. Hop- 332 FOOD ANALYSIS substitutes are little used unless the price of hops advances, when quassia, chiretta, and aloes may be employed. The common substitutes for malt are unmalted cereals, glucose, and starch. Two methods of fermentation are in use for the prepara- tion of beers. The " high " or " surface " fermentation, em- ployed for English beers, takes place at a temperature of 15 to 20, and is completed in from 4 to 8 days. The "low" or "bottom" fermentation, employed in Germany, takes place at a temperature of from 4 to 8, and requires from 20 to 24 days for completion. In this process the yeast remains at the bottom of the vat. In each of these there is a predominance of particular species of yeasts, and unless carefully selected and cultivated, the yeast mass will contain species producing irregular and often objectionable fermenta- tion-products. In this way malt liquors may acquire unpleas- ant bitterness or odor, or troublesome turbidity. The following are the principal varieties of malt liquors : ALE, made from a light-colored malt, usually with addition of glucose, and a large proportion of hops. So-called "mild ales " are usually sweeter, contain a larger proportion of alcohol, and are less bitter. PORTER and STOUT are principally distinguished from the above by their flavor, derived from the use of a certain pro- portion of roasted malt. They also contain less hops. Ale, porter, and stout are made by the high fermentation process. LAGER or GERMAN BEER is prepared by the low fermentation process and contains less alcohol, more sugar, dextrin, and nitrogeneous matter, and is more highly charged with gas. Lager beers are liable to undergo a second fer- mentation unless kept at a low temperature. So-called WEISSBIER is light-colored and about half the strength of lager beer. Rice is often used in its manufac- ture. u la 2 IS / MALT LIQUORS ^ t^ r-~ voX) co 00 ON O O O O O O O d d d d d d d VCAU^ -M X rt < N N C4 M M CO CO o* d d d d d d "o 22 M M VO VO N 00 - vO vo vovO ON t*>00 So u r < S Tj- CO O w S & s 3 00000 00 u*^ d d d s 3 11- 'u D W c OQ t^ co M r-^ N oo pi co co co e4 M co OH 1 ! O X) vo CO N t^ N C4 00 ONOO VO O MD H O O IH M H< pi S O H 5 Q Tj- i-l Tj- COOO tH VO t-^ f^ t^ t^ vo vO vO d d d d d d d ' a, H S S o OOONTj-MTj- VOON^- t*) !> CO C^ CO VO *-^ t s ^> ?5- ^S vo vo vo t^ vo vovo vO vovo VO vol^ c^ j 1 O c^vO ON co co O OO CO rf CS O vO 05 o Tf CO CO ^ P< ^- ^VO vovo vo vovo 1 C/5 to > s 'ft rt C ONX) vo rJ-vO 00 O O vo O 00 N CO 1 ^- u> m | 5 *% 'il JD S a " y " * ^ S << ^^ o ^ "^ ~ o a i^ [jj .j Q rn < ^n O 00 ON 00 TT m ro vO 00 ^ ^ ^5- in cs M in O co OH O O o o o o 0000 d d i U - Q q m cs "8 Q\ O O J>* o o" o o 5 cs ff) M in O O O O moo o o" g d o o o o O O O O O O S O co vQ CS vO CS 2 a 1$ %$>V3^ S S S & cTi- to < O O O o- oo oo oo O O O O S 3" vO M -d- m rooo cooo JO-Jg; vo^ 8JJ 2 M O M MM 00 00 0000 M M i c^S Soo" 5 T J.^. L0 OlQ tfl Q^ CS N N O Tt M moo 00 OO ^-m s cs in ^O g d d d g d 2 d rroo O -^ CS CO vO 00 Q Q U on i J O 00 M M M ON oo oo ^00 ojo^^^in ON^in- 0. ^0 X&j ^ O -" O o o 00 00 00 00 0000 H U H 00 tt ooo comONCOvOvn ro ro CS "i rooo >-i <* 0,000^ - *O l>* co^ S 00 M M fO csin. OO OO t^oo o\oo 2 S-w* vo' d\ (-^inoo'-J oo' M od^ m t^ *H ON TfvO oo S oS > S3 D G bjo 'a a a * a * d * g ^ 'a a 'a a 's a 'a a C ^ ^ rrt 'a s 'a s 'a a c x 1 s SOURCE. Must : Rhine wine mus Various musts, av i 43 CJ G v OJ i 1 i I 1 I | | a. - bitter, c ar a- FILTRATE. The excess of lead is removed by hydrogen sulfid, and the filtered liquid concentrated to about 150 c.c. and tasted. If bitter, the liquid is slightly acidulated with dilute sulfuric acid, and shaken re- mel- bitter, peatedly with chloroform. op he lie acid (from chir- etta), phos- phates, albu- CHLOROFORM LAYER, on evaporation, leaves a bit- AQUEOUS LIQUID is shaken with ether. minous mat- ter extract in the case of ters, etc. gentian, calumba, quas- ETHEREAL LAYER leaves AQUEOUS LI- 1 sta. and old hops (only a bitter residue in the QUID, if slightly or doubtfully bit- ter in the case of chiretta). The residue is case of chiretta, gen- tian, or calumba. It is still bitter, is rendered dissolved in a little alcohol, hot .water dissolved iir a little al- alkaline added, and the hot solution treated with cohol, hot water added, and ammoniacal basic lead acetate and filtered. and the hot solution shaken treated with ammoni- with ether- acal basic lead acetate c hlor o- PRECIPITATE contains old FILTRATE is and filtered. form. A hops, gentian, and traces boiled to re- bitter ex- of caramel products. It is move ammo- tract may suspended in water, de- composed by hydrogen sulfid, and the solution nia, a n d treated with a slight ex- P R E C I P I- TATE is treated FILTRATE is treated wilh a be due to berberin (calumba) agitated with chloroform. cess of sul- with slight ex- or strych- furic acid, fil- water cessof di- nin. tered and and de- lute sul- CHLOROFORM AQUEOUS tasted. I f composed fnric LAYER is ex- amined by special tests for gentian and old hop- bitter. LIQUID contains traces of caramel- bitter. bitter, it is agitated with chloro- form, and the residue examined for calumba by hydro- gen sul- fid. The filtered liquid is bitter in presence acid, fil- tered and tasted. Bitter- ness indi- cates cal- umba or The aqueous liquid, separated from the ether-chlo- roform , and quassia. of gen- tian. chiretta, which may c on- tain cara- mel-bitter may be re-ex- or cholin. tracted with ether and fur- ther ex- amined. ^=* or 356 FOOD ANALYSIS Methyl Alcohol, Crude methyl alcohol is sometimes added to ethyl alcohol to unfit it for use as a beverage. This prac- tice is not followed in the United States, but the invention of methods for refining methyl alcohol by which a nearly pure article is produced, has led to its use in adulterating ethyl alcohol and alcoholic beverages. S. P. Mulliken and H. Scudder have devised the following test. If the sample be a concentrated spirit, it should be diluted three or four times before taking a portion for test. When various organic bodies are present, as in malt liquors and tinctures, the sample should be distilled and the portion pass- ing over between 50 and 100 collected. This distillate should give a clear colorless solution when shaken with water. In some cases, as when acids or phenolic bodies are present, it will be advisable to add sodium hydroxid before distilling. A close spiral of about 2 cm. long is made by winding light copper wire around a lead-pencil. The metal is super- ficially oxidized by heating in the upper part of a burner flame, and while red hot plunged in 3 c.c. of the sample, diluted, if necessary, as above. The treatment is repeated at least once ; if the percentage of methyl alcohol is supposed to be small, the treatment should be repeated several times, cooling the liquid between each immersion. One drop of 0.5 per cent, aqueous solution of resorcinol is added and the mixture poured cautiously upon strong sulfuric acid. A rose-red zone will be promptly developed if methyl alcohol was originally present. The hot wire converts the methyl alcohol into formaldehyde, which gives the color. Care must be taken not to use much resorcinol. If much ethyl alde- hyde be present in the sample, it will be of advantage to boil the liquid, after the hot wire treatment, in a flask attached to an inverted condenser, as ethyl aldehyde evaporates more readily under these conditions than formaldehyde. It is also ANALYTIC METHODS 357 well to make a blank test with the resorcinol solution, sulfuric acid, and the untreated sample to determine if any bodies are present that simulate or mask the color reaction. Polarimetric Examination. In the routine examination of wine polarimetric readings are taken directly (after clarifica- tion, if necessary). Sweet wines are examined directly, also after inversion and fermentation. The following are the direc- tions for these processes given by the A. O. A. C. : Clarification. For white wines, 60 c.c. of the sample are mixed with 3 c.c. of lead subacetate solution and 3 c.c. of water and filtered. 33 c.c. of the filtrate are mixed with 1.5 c.c. of a saturated solution of sodium carbonate and 1.5 c.c. of water, again filtered, and examined in the polarimeter. The reading must be multiplied by 1.2 to compensate for the dilution. For red wines the same amount of sample is taken, and 6 c.c. of lead subacetate solution are used without addi- tion of water. 33 c.c. of the filtrate are treated with 3 c.c. saturated sodium carbonate solution, filtered, and the reading multiplied by 1.2. With sweet wines 100 c.c. are mixed with 2 c.c. of lead subacetate solution and 8 c.c. of water and fil- tered. 55 c.c. of the filtrate are mixed with 0.5 c.c. of satu- rated sodium carbonate solution and 4.5 c.c. of water, filtered, and the reading multiplied by 1.2 ; 33 c.c. of the filtrate, prior to the addition of the sodium carbonate, are mixed with 3 c.c. of hydrochloric acid and the liquid inverted according to the method on page 1 24. The liquid is cooled quickly, filtered, the reading taken at known temperature, and multiplied by 1.2. 50 c.c. of the sample are freed from alcohol by concentration, made up to the original volume with water, mixed with some well-washed beer yeast, and the mass kept at 30 until fer- mentation is complete, which will usually require from 48 to 72 hours. The liquid is then transferred to 100 c.c. flask, a few drops of acid mercuric nitrate added (p. 213), then some lead subacetate solution, followed by the saturated sodium 358 FOOD ANALYSIS carbonate solution. The flask is filled to the mark, the liquid mixed, filtered, and the reading multiplied by 2. The polarimetric data obtained in the above examinations are interpreted according to the following schedule : If the direct examination shows no rotation, the sample may nevertheless contain invert-sugar associated with the dextro- rotatory unfermentable impurities of glucose or with sucrose. If inversion results in a levorotation, sucrose was present. If fermentation results in dextrorotation, it shows that invert- sugar (or some other levorotatory fermentable carbohydrate) and the unfermentable constituents of glucose were present. If the inversion or fermentation produces no change, sucrose, unfermentable constituents of glucose, and levorotatory sugars are absent. If the direct examination shows dextrorotation, sucrose and the unfermentable constituents of glucose may be present. If after inversion it is levorotatory, sucrose was present ; if dextrorotatory to more than 2.3 divisions of the sugar scale, the unfermentable impurities of glucose were present ; if the dextrorotation is less than 2.3 divisions and more than 0.9, a portion of the original specimen must be submitted to the following treatment: 210 c.c. are mixed with o.i gram of potassium acetate and evaporated to a thin sirup, which is mixed with 200 c.c. of 90 per cent, alcohol, with constant stirring, the solution is filtered, the alcohol removed by distil- lation until about 5 c.c. remain, the residue is mixed with washed bone-black, filtered into a graduated cylinder,' and washed until the filtrate amounts to 30 c.c. If this filtrate shows a dextrorotation of more than 1.5 divisions on the sugar scale, the impurities of glucose were present. If the direct examination, shows levorotation, and this is increased by inversion, sucrose and levorotatory sugar were present. If the sample after fermentation shows levorotation of 3 divisions, it contains only levorotatory sugars. If after MALT-EXTRACTS 359 fermentation it rotates to the right, levorotatory sugars and the unfermentable impurities of glucose were present. MALT-EXTRACTS Some commercial malt-extracts are semi-solid mixtures of diastase with hydrolyzed starch, /. e., maltose, dextrose, and dextrin. No alcohol is present ; preservatives and coloring- matters are not likely to be used. Other extracts are dark- colored liquids, containing from 3 to 7 per cent, of alcohol, 5 to 15 per cent, of solids, mostly organic, but little, if any, active diastase. Preservatives are liable to be used in this class, salicylic acid being the most common. The usual examination of malt-extracts will involve detec- tion of preservatives (page 86), determination of alcohol, solid matter, and diastatic power. Qualitative tests for diastase may be made as follows : 50 c.c. of a solution of 5 grams arrowroot starch in looo c.c. of water are mixed with I gram of the extract to be tested, and the mixture heated in a water-bath within the limits of 35 and 45. Every few minutes a drop of the liquid is tested on a porcelain plate with a drop of iodin solution (page 35), until the blue color ceases to appear. It is not worth while to continue the ex- periment beyond a half hour, as a malt-extract that will not transform the starch in that time is of little value. The solu- tion should not be acid. This method is of no value for quantitative measurement. For such purpose, it is necessary to estimate the reducing sugar formed in presence of a large amount of starch. 10 grams of arrowroot starch are stirred into about 100 c.c. of cold water, the mixture added, with constant stirring, to 250 c.c. of boiling water, and the boiling continued until the starch is well diffused through the mass. The solution is diluted to 500 c.c. when cold. 50 c.c. of this solution are mixed with 0.5 gram of the sample and the mix- ture kept at a temperature between 35 and 45 for half an 360 FOOD ANALYSIS hour. The reducing sugar is measured by the volumetric method described on page 1 16, care being taken that the liquid is sufficiently diluted. An experiment without addition of starch must be made to determine the amount of reducing substance in the extract. In some cases rough comparative approximations may be made by comparing the color produced by iodin at the end of the heating, but the liquid must be largely diluted, and the indications are merely suggestive. FLESH-FOODS Descriptions of anatomic and histologic characters of flesh- foods need not be given here. The following table, from data compiled by A. H. Allen, will show the principal constituents of meats from different classes of animals. The figures are percentages ; they must be regarded as approximations, as the analytic processes are still imperfect : MEAT FROM : WATER. PROTEID. FAT. ASH. Ox (lean), 76.7 20.7 1.5 .2 Ox (fat), 55.4 17.1 26.3 .1 Mutton, 76.0 17.1 5.7 .3 Mutton (fat), . . .... 48.0 14.8 36.4 0.8 Pig, 72.6 19.9 6.2 .1 Horse, 74.3 21 6 2.5 .o Hare, 74.1 23.3 .1 .1 Deer, . , 75.7 19.7 .9 .1 Chicken, 76.2 19.7 .4 .3 Pigeon, 75.1 22.1 .o .o Lobster, 76.6 19.1 .1 .1 Oyster, 80.3 14.1 .5 .7 Herring, 74.6 14.5 9.0 .7 Mackerel, 71.2 19.4 8.0 .3 Salmon, 64.3 21.6 12.7 .3 Cod, 82.2 1 6. 2 0.3 .3 ANALYTIC METHODS. Water. 5 grams of the finely divided material are dried according to the methods described on pages 3741, Parsons' method being especially worth trial in this connection. FLESH-FOODS 361 As/i. The dry residue obtained in the water determina- tion is incinerated according to the methods given on pages 47-49- Total Nitrogen. The Kjeldahl-Gunning process is em- ployed. The nitrogen, multiplied by 6.25, will give an approximation to the proteids present. If nitrates are present, as will be the case with some preserved meats, the modified process, page 45, must be used. Fat. Much of the fat in meat-samples can be removed by mechanical methods, but some adheres obstinately to the muscle-tissue, and it is probable that errors have been made in this respect, as with condensed milk. It has been suggested that the muscle-tissue be digested with pepsin and hydro- chloric acid and the fat extracted from the mass. Good results have been claimed for the following process : 2 grams of the material are shaken frequently for six hours with 200 c.c. of ether and 2 c.c. of mercury and the fat determined in an aliquot part of the mixture. Most investigators use too much material. It is probable that results near enough for practical purposes could be obtained by continuous extraction for some hours of a few grams of the material, but care should be taken that the sample represents a fair average of the specimen and that it is very finely divided without loss of fat. If the fat is to be examined, a large amount of it should be extracted by mechanical means, and not with solvents, unless there are special reasons to the contrary. Adulteration. Meats are not adulterated in the sense in which that word is commonly used, but cheap meats are sub- stituted for dear (e. g., horse meat in sausages and mince- meat), the meat of diseased and immature animals is often sold, preservatives are employed, and applications made to improve color or texture. The detection of entozoa is a matter of importance. Tests for incipient and actual decom- 362 FOOD ANALYSIS position may be required. A large amount of canned meat is now sold. Much of it is free from adulteration. Horseflesh. The detection of horseflesh is difficult. Many processes have been proposed, but they are all open to objec- tion. The principal reliance is upon the detection of glycogen, which is present in horseflesh in much greater proportion than in most other flesh. The following process, by Courlay and Coremons, seems to be the most trustworthy : 50 grams of the material, as fresh as possible, are finely divided and boiled for thirty minutes with 200 c.c. of water. The liquid is filtered when cold and tested with a few drops of potassium iodid- iodin solution (page 35). A brown tint, disappearing at 80 and returning on cooling, indicates horseflesh. If starch be present, the original broth should be treated with several times its measure of strong acetic acid, and the test applied to the filtrate. The above test has been modified by T. Bas- tien, by increasing the time of boiling to one hour and allow- ing the liquid to concentrate to one-third of its original bulk. The quantity of iodin solution should be quite small, in which case it is said that horseflesh will give only a transient reddish- violet. The strength of the acetic acid is not given in the report of the method. H. Bremer states that the most definite test for horseflesh is the character of the intramuscular fat. For this test, all visible fat is removed from a sample, the mass finely minced, and heated in water for an hour at 100. The fat that floats is poured off with the water, the flesh washed several 'times with boiling water, dried for twelve hours at 100, and the material then extracted for several hours with petroleum spirit of low boiling-point. Part of the fat thus obtained may be set aside for the determination of iodin number, but most of it should be saponified, the excess of alkali carefully neu- tralized with acetic acid, and any alcohol that may have been used in the saponification removed by evaporation on the FLESH-FOODS 363 water-bath. The glycerol-soda method would seem to be applicable here. The soap is dissolved in water, a hot solu- tion of zinc acetate added in the proportion of I part of the salt to 2 of fat, the precipitate washed with hot water and alcohol, pressed between folds of filter-paper, and heated with ten times its volume of anhydrous ether for thirty minutes under a reflux condenser. The solution is cooled, filtered into a separating funnel, mixed with dilute hydrochloric acid, the ethereal layer, which contains the acids, washed with water, and parts of it filtered into weighed flasks, the ether evaporated, and the iodin number determined. It is stated that horseflesh always gives a reddish- brown tint to the petroleum spirit solution, but bull's flesh also gives such a tint. If, however, glycogen has been detected by the tests already mentioned, the petroleum spirit solution is reddish-brown, the iodin number of the fat exceeds 65 and that of the liquid acids, obtained as above, is considerably over 95, the presence of horseflesh may be inferred. Coloring-matter. Meats are not infrequently colored to give them a fresh look or to improve naturally pale samples. Sausage meats are often colored. Carmine and coal-tar colors, especially the latter, are often employed. Fuchsin and eosin are among these, but Allen states that benzo- purpurin is the most common. The detection of artificial colors will generally be accomplished satisfactorily by the test on page 77. E. Spath has found that heating the material for a short time on the water-bath with a 5 per cent, solu- tion of sodium salicylate will often dissolve out colors not otherwise soluble. Ordinarily, water or alcohol will take out sufficient for the wool-test. For the detection of carmine, the method of Klinger and Bujard, modified by Bremer, should be used : 20 grams of the minced material are heated for several hours with a mixture of equal parts of glycerol and water slightly acidulated with tartaric acid. The yellow 364 FOOD ANALYSIS liquid is freed from fat, filtered, and the coloring-matter pre- cipitated as a lake by the addition of alum and ammonium hydroxid. This is washed, dissolved in a little tartaric acid, and examined in the spectroscope. Absorption bands lying between the position of b and D of the solar spectrum are characteristic of carmine. Improvers and Preservatives. Mixtures of potassium ni- trate, sodium chlorid, and other mineral preservatives with a little coloring-matter the latter almost always a coal-tar color are sold for improving the appearance of meat. Sali- cylic acid, boric acid, and sulfites are also apt to be used, and should be sought for according to the methods given on pages 86 to 91. As they are all soluble in cold water, they may be extracted by simple maceration, the watery solution being concentrated at a low temperature and treated as directed at the above reference. Formaldehyde is not likely to be used in meat on account of its hardening action on proteids. Putrefaction. To detect incipient putrefaction, Ebers pro- posed the following test : A rod moistened with a mixture of hydrochloric acid I c.c., alcohol 3 c.c., and ether I c.c. is held over the suspected material. The formation of fumes of ammonium chlorid shows that putrefaction has begun. Care must be taken not to mistake the fumes of the hydrochloric acid for those of ammonium chlorid. It has been proposed to detect putrefaction by macerating the finely divided material in water, cautiously distilling the liquid, best probably in a current of steam, and testing the distillate for phenol. The reactions noted on page 91 would probably be useful. In the early stages of decay phosphor- escent microbes are sometimes developed which render the meat luminous in the dark, but this is not common. Diseased and Immature Meats. The detection of these conditions are questions of pathology and veterinary medi- cine. Ebers attempted to devise a scheme for the detection FLESH-FOODS 365 and estimation of the hydrogen sulfid evolved by diseased meat, but the work did not pass beyond the experimental stage. Infected Meats. The lower animals are subject to para- sitic diseases communicable to human beings. The most important are two species of so-called tapeworm and the Trichina spiralis. One species of tapeworm, Tcenia saginata, is found in one stage of development in beef; another species, 7. solium, is found in pork. This condition is often termed " measles." Trichina spiralis is principally found in pork. Many other animal parasites are known, but recognition of them belongs to pathology and biology. Tcenia saginata Goeze, also called T. mediocannellata, occurs in beef as little white cysts among the muscular fibers, like knots in wood. The mature animal is developed from the cysts when the meat is eaten. It is the common tapeworm of the United States. Tcenia solium L. occurs in the flesh of the hog. It differs from 7. saginata in the important fact that the latter can not pass through all its stages of development in the same ani- mal, while T. solium can extend its infection to various organs of the host. Trichina spiralis Owen is a worm that occurs in -hog-flesh as light-colored cysts, smaller than a pin's head, and usually lying with the long diameter in the direction of the muscular fiber. The cysts contain immature worms, which are released when the cyst is digested ; the worm quickly reaches matur- ity, muliplies rapidly, and distributes itself through various tissues of the host. The detection of the various parasites of meat can often be attained by examining with a good hand-glass. With higher powers, the organism can be seen in more detail. Canned Meats. These are now usually prepared on a 366 FOOD ANALYSIS very large scale at establishments under inspection and hence are but little liable to adulteration. Preservatives, except common salt and niter, are not likely to be employed. If any other preservative should be used it will probably be boric acid or possibly salicylic acid, either of which can be easily detected in the extract with cold water by methods given elsewhere. Tin and sometimes lead are absorbed in small amounts from the can or solder. These may be tested for by the methods given on page 69. Careful examination under moderate magnifying power will detect parasitic infection. Meat-extracts. These are now offered in great variety. Some contain partly digested proteids (proteoses and peptones), but in many cases the most abundant nitrogenous ingredients are the so-called meat-bases, a class of amido-derivatives of which kreatin, kreatinin, and xanthin are examples. Many investigations of these preparations have been made, but the processes of analysis are still in dispute and the results obtained by different observers are often discordant. The following methods are compiled from the works of A. H. Allen 38 and C. A. Mitchell. 39 Water, Ash, and Total Nitrogen are determined as indicated under those titles in the introductory part. Fat is usually present in but small amount, and is extracted more accurately by petroleum spirit than by ether, applying the methods described on pages 49 to 53. Insoluble matter, which may include some meat-fiber, is determined by treating from 5 to 25 grams (depending on whether the preparation is solid or liquid) with cold water, filtering, and drying the residue at 100. A microscopic examination of this should be made. Proteids, Peptones, and Meat-bases. The following method has been suggested by A. H. Allen, partly from his own experiments and partly from those of A. Bomer : FLESH-FOODS 367 50 c.c. of a solution of a known weight of the sample, of such strength as to contain about 1.5 grams of nitrogenous bodies, are freed from insoluble material, mixed with I c.c. of diluted sulfuric acid (i to 4), and saturated with zinc sulfate by stirring in the powdered salt until no more dissolves. Zinc sulfate containing the full amount of water of crystallization dissolves in about half its weight of water at room tempera-, ture, but the commercial salt is usually partly effloresced, and will often cake when added to the solution. When the liquid is saturated with zinc sulfate, the precipitate is assumed to contain all the albumin and gelatin and immediate derivatives (proteoses), but no peptone. It is separated by filtration, washed with a saturated solution of zinc sulfate, and the filter and precipitate treated by the Kjeldahl-Gunning method. The nitrogen obtained, multiplied by 6.25, will give approximately the 'amount of nitrogenous bodies precipitated. The filtrate and washings are made up to 200 c.c., mixed, and 100 c.c. transferred to a flask of the larger form described on page 42, enough hydrochloric acid added to make the liquid strongly acid to litmus, and then bromin water by moderate portions, with active shaking or stirring, until there is an excess of bromin present. The precipitate may be flocculent at first, but most of it soon becomes viscous and adherent. It is allowed to stand until the free portions have settled, when it is decanted through an asbestos filter either in a Gooch cru- cible or in an apparatus similar to that described on page 120. The precipitate is washed several times with cold water con- taining some hydrochloric acid and bromin, but it is advisable to keep the washings at first separate from the main filtrate. The contents of the filter-tube are returned to the vessel in which the precipitation was made, 10 c.c. of sulfuric acid added, and the mass cautiously treated until it chars and vapors of bromin are evolved, after which 10 grams of potas- sium sulfate are added and the operation conducted as 368 FOOD ANALYSIS described on pages 44 and 45. The nitrogen, multiplied by 6.33, will give approximately the peptone. By deducting from the total nitrogen the sum of the nitro- gen figures obtained from the zinc sulfate and bromin precipi- tates, and multiplying the remainder by 3.12, an approxima- tion to the meat-bases will be obtained. These meat-bases are in the filtrate from the bromin precipitate, but the bromin, hydrochloric acid, and zinc sulfate will be likely to interfere with the determination of the nitrogen. The zinc sulfate can be removed by cautious addition of either potassium carbon- ate or barium hydroxid, but the bromin will be apt to form hypobromites, which will promptly decompose some of the amido-compounds, with evolution of nitrogen. A more satisfactory plan seems to be that outlined by K. Baumann and A. Bomer : The remaining portion, 100 c.c., from the zinc sulfate precipitate is mixed with excess of so- dium phosphomolybdate (see page 275), by which the meat- bases, peptones, and ammonium compounds are precipitated. This precipitate is removed by filtration under pressure, so as to draw out as much as possible of the mother-liquor, and the nitrogen determined as usual. The nitrogen due to pep- tone being known, that due to meat-bases and ammonium compounds can be calculated. To determine the ammonium compounds, a known weight of the original sample should be distilled with barium carbonate, the distillate being collected in a known quantity of standard acid, which is afterward titrated. Meat-extracts sometimes contain coagulable proteids. These may be estimated by rendering the filtered solution distinctly acid with acetic acid and boiling for five minutes. The coagulum may be weighed directly or the nitrogen in it estimated by the Kjeldahl-Gunning method and multiplied by 6.25 for albumin. FLESH -FOODS 369 As solutions of proteids, proteoses, and peptones are strongly levorotatory, while most of the meat-bases that occur in these extracts are inactive, some information might be gained by examining the liquid from the zinc sulfate precipitate in the polarimeter. A solution that had no appreciable optic activity would not be likely to contain much peptone. Another special test that may be applied to this liquid is the so-called biuret reaction. A. Bomer applies this as follows : The filtrate from the zinc sulfate precipitation is decolorized by shaking with animal charcoal and the zinc sulfate decomposed by excess, of sodium carbonate or cautious addition of barium hydroxid. The filtered solution is rendered alkaline with sodium hydroxid and a drop or two of very dilute solution of copper sulfate added. Peptones give a rose-red tint. Preservatives may be added to meat-extracts, although this is not usual. Boric acid will be most likely to be used, and the methods on page 89 will suffice for its detection. Pois- onous metals are not likely to be present, but may be sought for, if deemed necessary, by the methods given on pages 68 to 72. APPENDIX ADDENDA To page 237 : So-called " process" or "renovated" butter, made by rendering old or inferior samples, purifying the fat, coloring, salting, and molding it, is now a familiar commercial article. Process butter when heated in a dish sputters with but little foaming, as does oleomargarin ; but yields with alcoholic soda the pineapple odor, as does butter. The fat of process butter gives refractometric data and Reichert-Meissl number similar to those of ordinary dairy butter, but is said to give a different figure with Valenta's test. Precise information on the last point is not at hand. If, therefore, a sample sputters in the pan, but gives the other reactions for butter, as just noted, it may be assumed to be process butter. W. H. Hess and R. E. Doolittle have ascertained that the curd of process but- ter has characteristic qualities, and have devised the following method for detecting it : 50 grams of the sample are melted in a beaker at about 50. Ordinary butter yields a clear fat almost as soon as melted, while with process butter the fat may remain turbid for a long while. When the curd has largely settled, as- much of the fat is poured off as possible, and the remaining mix- ture is thrown on a wet filter, by which the water will drain away, carrying the soluble proteids and salt. A few drops of acetic acid are added to the filtrate and the mixture is boiled. The filtrate from ordinary butter gives but a slight milkiness, but that from process gives a flocculent precipitate. Quantitative examination is made by dissolving 50 grams ADDENDA of the sample in ether ; if it is ordinary butter, the curd is so finely divided that it remains suspended for some time. As much as possible of the solution is decanted and the mass transferred to a separator, the casein, water, and salt removed, and the remainder washed three times, at least, with ether to remove the fat. The curd is collected on a filter, washed with water, and the nitrogen determined by treating the pre- cipitate with the filter by the Kjeldahl-Gunning method. The filtrate from the curd is made slightly acid with acetic acid, boiled, the precipitated proteids collected on a filter, and the total nitrogen determined. The factor 6.25 may be used in each case for converting the nitrogen into proteids. A distinction between ordinary and process butter may often be made by microscopic examination under polarized light with crossed nicols (i. e. t dark field), when the process butter appears mottled, owing to the presence of crystals. To page 239 : J. F. Geisler found paraffin in oleomargarin ; his observa- tion has been confirmed by several other chemists. Geisler uses the specific gravity of the rendered fat as a sorting test, making special examination only of samples that show below 0.9018 at ~r^o-. Microscopic examination under polarized light, with and without selenite, will often sh'ow amorphous masses of paraffin mixed with the crystals of fat. To isolate the paraffin, Geisler saponifies 2.5 grams of the fat with 20 c.c. of alcohol and I gram of potassium hydroxid, and dilutes the liquid with an equal bulk of water. By alternately heat- ing and cooling the liquid much of the unsaponifiable matter may be collected. It is also possible to isolate it by the pro- cess given on page 165, or by destroying the fat by strong sulfuric acid. It must be borne in mind that most fats contain notable amounts of unsaponifiable matter, and hence the material must be identified as paraffin. 372 FOOD ANALYSIS SPECIFIC GRAVITY OF WATER FROM o TO 100 Water at o = 0.99987 Water at 4 = i.ooooo I 0.99992 26 0.99686 51 0.98772 76 0.97438 2 9 6 27 60 52 25 77 0.97377 3 99 28 33 53 0.98677 78 16 4 i .00000 29 05 54 29 79 -97255 5 0-99999 30 0.99576 55 0.98581 80 0.97194 6 97 3i 77 56 34 81 32 7 93 3 2 47 57 0.98486 82 0.97070 8 88 33 0-99485 58 37 83 07 9 82 34 52 59 0.98388 84 0.96943 10 74 35 18 60 38 85 0.96879 ii 65 36 0.99383 6 1 0.98286 86 15 12 54 37 47 62 34 87 0.96751 J 3 43 38 10 63 0.98182 88 0.96687 14 29 39 0.99273 64 28 89 22 15 16 40 35 65 0.98074 90 0.96556 16 oo 41 0.99197 66 19 91 0.96490 17 0.99884 42 58 67 0.97964 92 23 18 65 43 18 68 08 93 0.96356 19 46 44 0.99078 69 0.97851 94 0.96288 20 25 45 37 70 0.97794 95 19 21 04 46 0.98996 7i 36 96 0.96149 22 0.99782 47 54 72 0.97677 97 0.96079 23 60 48 10 73 '8 98 08 24 36 49 0.98865 74 0.97558 99 0.95937 25 12 50 19 75 0.97498 100 0.95866 THERMOMETRIC TABLE 373 CORRESPONDENCE OF CENTIGRADE AND FAHRENHEIT DEGREES i 2 3 4 5 6 7 8 9 20 392.0 393-8 395-6 397-4 399-2 401.0 402.8 404.6 406.4 408.2 19 374-0 375-8 377-6 379-4 381.2 383-0 384.8 386.6 388.4 390.2 18 356.0 357-8 359-6 361.4 363-2 365-0 366.8 368.6 370.4 372.2 17 338.0 339-8 341.6 3434 345-2 347-o 348.8 350.6 352-4 354-2 16 320.0 321.8 323-6 325-4 327.2 329-0 330-8 332.6 334-4 336-2 15 302.0 303-8 305.6 37-4 309.2 311.0 312.8 3H.6 3 l6 -4 318.2 14 284.0 285.8 287.6 289.4 291.2 293-0 294.8 296.6 298.4 303.2 13 266.0 267.8 269.6 271.4 273.2 275.0 276.8 278.6 280.4 282.2 12 248.0 249-8 257.6 2 53-4 255-2 257.0 258.8 260.6 262.4 264.2 II 230.0 231.8 233-6 235-4 237-2 239.0 240.8 242.6 244.4 246.2 10 212.0 213.8 215.6 217.4 219.2 221.0 222.8 224.6 226.4 228.2 9 194.0 195.8 197.6 199.4 201.2 203.0 204.8 206.6 208.4 2IO.2 8 176.0 177.8 179.6 181.4 183.2 185.0 186.8 188.6 190.4 192.2 7 158.0 159.8 161.6 163.4 165.2 167.0 168.8 170.6 172.4 174.2 6 140.0 141.8 143 6 145-4 147-2 149.0 150.8 152.6 '54-4 156.2 5 122.0 123.8 125.6 127.4 129.2 I3I.O 132.8 134.6 136.4 138.2 4 104.0 105.8 107.6 109.4 III. 2 II3.0 II4.8 116.6 118.4 120.2 3 86.0 87.8 89.6 91.4 93-2 95-o 9 6.8 98.6 100.4 IO2.2 2 68.0 69.8 716 73-4 75-2 77-o 78.8 80.6 82.4 8 4 .2 I 50.0 51.8 53-6 55-4 57-2 59-o 60.8 62.6 64-4 66.2 32.0 33-8 35-6 37-4 39-2 41.0 4 2.8 44-6 46.4 48.2 15.55 c - = 60 F. o -I -2 -3 -4 -5 -6 -7 -8 -9 o 32.0 30.2 28.4 26.6 24.8 23.0 21.2 19.4 17.6 15.8 -I 14.0 12.2 10.4 8.6 6.8 5-o 3-2 1.4 -0.4 -2.2 -2 -4.0 -5-8 -7.6 -9-4 -II. 2 -13.0 -I 4 .8 -16.6 -18.4 -20.2 -3 -22.0 -23-8 -25.6 -27.4 -2 9 .2 -31.0 - 3 2.8 -34-6 -36.4 -38.2 -40 C. == -40 F. 374 FOOD ANALYSIS ELEMENTS, SYMBOLS, AND ATOMIC WEIGHTS Corrected according to list published in the Journal of the American Chemical Society, February, 1901. Aluminum, .... Antimony, Argon Al Sb A 27.1 120.4 7Q Q Necdymium, . . . Neon, Nickel Nd Ne Ni 143.6 20 eS 7 Arsenicum, . . Barium, As Ba 75-0 1-27 A Nitrogen, .... Osmium, .... N Os 14.04 IQI Bismuth, . ... Boron, Bi B 208.1 ii Oxygen, .... Palladium, .... O Pd 16 IO7 Bromin, Cadmium, .... Calcium, .... Br Cd Ca 79-9 112.4 40.1 Phosphorus, . Platinum, .... Potassium, .... P Pt K 3 1 194.9 39- T * Carbon, .... c 12 Praseodymium, . . Pr 140 c; Cerium, .... Cesium, .... Ce Cs 139 I 12 Q Rhodium, .... Rubidium, . . Rh Rb 103 85 4 Chlorin Cl Ruthenium, Ru 101 7 Chromium, .... Cobalt, Columbium, . . . Copper, Cr Co Cb Cu 59 93-7 6s. 6 Samarium, .... Scandium, .... Selenium, .... Silicon, .... Sm Sc Se Si 150-3 44.1 79-2 28.4 Erbium, .... Fluorin, Gadolinium, . . . Gallium, Germanium, . . . Glucinum, .... Gold, Helium, .... E F Gd Ga Ge Be Au He 1 66 19.05 157 70 72.5 197.2 4 O Silver, Sodium, Strontium, .... Sulfur, Tantalum, .... Tellurium, .... Terbium, .... Thallium Ag Na Sr S Ta Te Tb Tl 107.92 23-05 87.6 32.07 182.8 127-5 1 60 204 15 Hydrogen, .... Indium, . . . . . H In 1.008 114 Thorium, .... Thulium Th Tm 232.6 1 70.7 lodin I 126 85 Tin Sn I IQ Iridium, ....'. Iron, Jr Fe I93-I ce Q Titanium, .... Tungsten Ti W .48.15 l84 Krypton, . . Kr 8l.8 Uranium u 2^0 6 Lanthanum, . . . Lead La Pb 138.6 206 92 Vanadium, .... V x 51-4 128 Lithium, Li 7.0^ Ytterbium, .... Yb 173.2 Magnesium, .... Mg 24.3 Yttrium, .... Y 89 Manganese Mn cc Zinc Zn 65 4 Mercury 2OO Zirconium Zr QO A Molybdenum, . , . Mo 9 6 ^^x^-^r REFERENCES 1 Laurent. Das optische Drehungsvermogen. 2 Bull. 46, Rev. Ed., U. S. Dept. of Agriculture. 3 Bull. 176, U. S. Geological Survey. 4 Dingler's Polyt. Jour., 232 (1879), 461. 258. 551- 12. Com'l Org. Anal., I, 66. 9 111,1,497-8-9- 10 Bull. 59, U. S. Dept. of Agriculture. umgier s roiyi. jo 5 J. A. C. S., 1899, 6 J. C. S., 1883, 551 7 J. A. C. S., 1901, " 13,5," 13 << < 14 (( <* (( 15 J. A. C. S., 1901, 60-1. 16 jCom'l Org. Anal., I, 371-2. 17 Bull. 123 (1896), Connecticut Agric. Exp. Station. 18 Analyst, 1897, 287. (The reference is misplaced ; see list of corrections.) 19 Com'l Org. Anal., II, 1, 85. 20 Chem. Anal. Oils, Fats, and Waxes, 165. 21 J. A. C. S., 1900,453; 1901, I. 22 J. A. C. S., 1897, 796. 23 Analyst, 1890, 170. 24 T. A. C. S., 1896,428. 25 J. A. C. S., 1900, 207. 26 J. A. C. S., 1898, no. 27 J. A. C. S., 1898, 207. Bull. 13, 7, U. S. Dept. of Agriculture. 29 Food Adulteration and its Detection. 30 Bull. 13, 7, U. S. Dept. of Agriculture. 31 Com'l Org. Anal., Ill, 2, 547. 32 Analyst, 1899, 281. 33 See Zeit. Anal. Chem., Jan., 1901, fora new process for separating theo bromin and caffein from cacao. 34 Bull. 13, 7, U. S. Dept. of Agriculture. 35 Mikroskopie der Nahrungs und Genussmittel. 36 <( i< " 37 Com'l Org. Anal., I, 545. 38 < IV 39 Flesh -Foods. 375 1. Tea ( Thea chinensis Link.). 2. Mate- (Ilex paraguayensis Lam- bert). 3. Thea japonica Baillon. 4. Hawthorn (Cratcegtts sp.). 5. Box elder (Negundo aceroides Moench.). 6. Horse chestnut (sEsculus hippocas- tanum L.). 7. Sycamore (Plafanus occidentalis L.). 8. Rose (Rosa sp.). 9. Plum (Prunus sp.). 10. Elm (U/mus fulva Michx.). 11. Ash (Fraxinus sp. ). 12. Willow (Sa/ixsp.). 13. Willow (Satixsp.). 14. Beech (Fagus ferruginea Ait.). 15. Oak ( Quercus sp. ) . 1 6. Missouri currant (Ribes aureum Pursh.). 17. Ash ( Fraxinus sp. ) . 18. Red currant (Ribes rubrum L.). 19. Birch (Betula lenta L.). 20. Poplar (Populus alba L.). 21. Raspberry (Rubus sp.). 22. New Jersey Tea ( Ceanothus Ameri- canus L. ). Potato. Arrowroot. Wheat. %*m Bean. Pea. Barley. i I Rye. Rice. Maize. Ginger. Sago. Buckwheat. o VI Oat. NDEX AHRASTOL, 84 Acetyl number, 162 value, 162 Acidity, total, 349 Acid mercuric iodid, 230 nitrate, 213 value, 150 Acorn starch, 95 Acrinyl isothiocyanate, 318 Adams' method, 203 African pepper, 303 Albumin, 193, 210, 212 Albuminoid nitrogen, 46 Alcohol, detection, 342 determination, 343 ethyl, 64 methyl, 65 detection, 356 tables, 344-5-6 Alcoholic beverages, 326 Ale, 332, 333 Allen, A. H.,9,i;, 28,31, 68,69,78, 109, 118, 140, 141, 182, 260, 261, 286, 287, 289, 305, 306, 319, 326, 333. 355. 360, 363, 366 Allihn's method, 119, 121 Allspice. 311 Allyl isothiocyanate, 317 Almen's reagent, 21 1 Alum in bread, 107 in flour, IOI Alumina-cream, 123 Ammonium in baking powders, 113 Amphoteric milk, 194 Angell, A., 145 Annatto, detection, 217, 220 Apple brandy, 329 whiskey, 329 Arata's test, 77 Arachidic acid, 178 ArachiHin, 177 Arachis oil, 177 Archbutt, L., 151, 178, 180 Archil in wine, 352 Arrow- root starch, 94 Arsenic, detection, 71 Asaprol, 84 Aschmann F. J. , 225 Ash, 47 Ashby, A., 288 Astruc, H., 340 Axtell, F. C., 58 BABCOCK'S method, 202, 204 Baking powders, no soda, 109 Ballantyne, H., 152 Banana starch, 94 Barium in pepper, 305 Barley, 101, 103 starch, 95 Bases, meat-, 366 Battershall, J. B., 254, 256 Baudouin's test, 170 Baumann, A., 368 Beam, W., 146, 205 Bean flour, 103 starch, 95 Bechi's test, 169 Beckmann, E. O., 135-137 Beef fat, 191 stearin, 189 Beer, 332 - root, 334 Bell,}., 277 Benzene, 65 Benzoates, 88 Benzoic acid, 84, 88 Berthelot,M., 21, 148 Beurre rouge, 239 Bevan, E. J., 223 Bigelow, W. D., 89, 103, 230 Bird pepper, 303 Birotation, 215 Bitters in beer, 355 377 373 INDEX Bitteryst, A., 280 Biuret reaction, 369 Bjorkland's test, 183 Blue miik, 224 Blyth, A. W., 107, 243, 261, 304 Bodmer, R., 70 Boiled milk, detection, 223 Boiling-point, 21 Bonier, A., 366, 368 Borax, 85, 89 Boric acid, 85, 89 Borntrager, A , 312 Borofluorids, 86, 90 Boseley, L. K., 21 1, 223, 325 Bouquet, 335 Brandy, 330 apple, 330 Bread, 105 commercial, 106 Bremer, H., 362 Bromas, 282 Bromin, thermal value, 152 Brown, J. C, 297, 300, 302 Buckwheat, 101, 104 starch, 96 Bumping, prevention, 54, 59 Burners, 62, 63 Batter, 231 cacao-, 182 colors, 237 composition, 232 fat, 191 milk, 196 peanut, 177 vegetable, 182 Butyrorefractometer, 157 CACAO, 274 butter, 182 essence, 278 husks, 278 masse, 278 red, 276 starch, 95 Caffearin, 262 Caffein, 252, 263, 27 f, 275 determination, 257, 268 Caffetannic acid, 262 Caldwell, G. C, 37 Candies, 138 Cane-sugar, 113, 126, 219 Canna starch, 94 Caper tea, 256 Caramel, 127, 129, 272, 352 Carr,0.,39 Caryophyllin, 315 Casein, 192, 210, 212 Cassal, C. A., 270 Cassia, 312 . ore, 314 Catsup, 323 Centrifuge, 6 1 Cereals, 99 Champagne, 3^6 Chandler, C. F., 27 Chattaway, W. A., 151, 244, 247 Cheese, 339 Chicory, 266 Chillies, 303 Ching suey, 256 Chittendcn, R. H., loo Chocolate, 274 nuts, 277 Cholesterol, 160 Chr.imium, detection, 69 Cider, 326 vinegar, 284 Cinnamon, 312 - oil, 314 starch, 95 Clove oil, 315 Cloves, 315 Cobalt nitrate test, 113 Cochineal, 67 Cochran, C. B , 190, 196, 197, 198 Cocoa, 274 Cocoas, soluble, 278 Coconut oil, 182 olein, 182 stearin, 182 Coffee, 262 essence, 273 extracts, 273 Colors, 72-82 in butter, 237 in candies, 139 in meat, 363 in milk, 217, 218 in wine, 351 test for oil-, 141 Colostrum, 198 Colza oil, 181 Condensed milk, 225 Condenser, 42, 57 Condiments, 283 Confections, 138 Congou paste, 256 tea, 254 Constants for oils, 168 INDEX 379 Copper, detection, 69 hydroxid mixture, 46 in bread, 108 in flour, 102 Coriander seed, 301 Corn, Dhoura, 300 oil, 170 Cottonseed oil, 175 stearin, 175 Counley, A. T., 70, 257 Cox, G. S., 204, 326 Crampton, C. A., Ill, 130, 239,352 Cream, 196 evaporated, 225 of tartar, 109 Crude fiber, 46 Cumarin, 321 DAVY, E. W., 342 De Koningh, L. , 144 Delican's titer-test, 20 Desserts, 324 Dextrin in honey, 135 in wine, 349 Dextrosazone, 114 Dextrose, determination, 116 Dhoura corn, 300 starch , 300 Distillation, 54 Doolittle, R. E. , 370 Drying of oils, 158 ovens, 37 property, 158 Dry wine, 336 Dupouy, R., 223 Dyer, B., 270, 313 ELEADIN test, 156 Electrolytic apparatus, 122 methods, 65 Elements, 374 Ergot, 102 Erucin, 181 Essence of cacao, 278 of coffee, 273 Ether purification, 50 Eugenic acid, 315 Eugenol, 315 Evaporated cream, 225 Ewell, E. E., 215, 217, 281, 282 Extract, 36 Extraction apparatus, 49, 5 2 Extracts, coftee, 273 malt, 359 meat, 366 FACING coffee, 265 tea, 255, 258 Farnsteiner, K., 283 Fat of milk, 192. Fats, 140 Fehling's solution, 116 Fermented milk, 248 Fiber, crude, 46 Filter-tubes, 117, 120 Flesh-foods, 360 Flour, 98, 101 Fluorescence, 31 Fluorids, 86, 90 Foreign leaves in tea, 260 Formaldehyde, 84, 90, 220 Formalin, 84, 220 Fractional distillation, 60 Fuchsin in wine, 352 Furfural test, 170 Fusel oil, determination, 353 GALACTOSAZONE, 115 Gallisin, 130, 354 Geisler, J. F., 226, 237, 371 Gelatin, detection, 219, 324 German beer, 332 Gerrard, A. W., 118 Gin, 331 Ginger, 305 starch, 94 Gingli oil, 180 Gliadin, 98 Globulin, 193 Glucose, 130 vinegar, 284 Glutenin. 98, Glycerol in wine, 350 soda, 146 Glycogen, 362 Gomberg, H., 257 Graham flour, 101 Grape-juice vinegar, 284 Grape-sugar, 130 Gum in wine, 349 Gutzert's test, 72 Gypsum in bread, 108 HAGER, H., 9, 183, 260, 342 Halphen's test, 169 INDEX Hardy, J., 342 Hehner, O., 145, 152, 185, 207, 221, 231, 270, 286, 289 value, 158 Heisch, C., 294, 296 Henzold, O., 294 Hess, W. H., 54, 320, 370 Hollands, 331 Honey, 132 Hopkins, C. G., 176, 177 Horseflesh, detection, 362 Hubl's reagent, 142 Hydrometers, 15 ICE-CREAM,'324 Immiscible solvents, 53 Improvers, meat, 364 Index of refraction, 157 Infected milks, 224 Insoluble acids, 158 Inversion methods, 124, 228 Invert-sugar, 113, 119, 230 lodin number, 142 value, 142 Irish whiskey, 330 JAMS, 324 Jean, F. , 236 Jellies, 324 Jones, B. W., 189, 235 KAYSER, R., 326 Kefyr, 249 Kjeldahl-Gunning method, 41 Knorr, A. E., 52, ill, 117 Konig, J., 138, 249, 263, 272, 307, 313 Kottstorfer number, 148 Kraemer, H , 103, 105 Kreatin, 366 Kreatinin, 366 Krug, W. H., 96 Kumiss, 248 Kunze, W. E., 274, 275 LACTOSAZONE, 115 Lactose, 131, 193, 213 Ladd, E. F., 257 Lager beer, 332 Lard, 184 Laurent polarimeter, 29 Laureol, 182 Laurin, 182 Leach, A. E., 218, 227 Lead, detection, 69 number, 297 subacetate, 123 Leavening materials, 109 Leffmann-Beam method, 205 Leguminous flours, 103 Lemon juice, 322 sirup, 322 Lentil starch, 95 Leonard, N., 91 Levulosazone, 214 Lewkowitsch, J., 141, 189 Lieben's test, 342 Lie tea, 255 Lignoceric acid, 178 Litmus, 66 Livache's test, 158 Long pepper, 301 Low, A. H., 238 Low-pressure distillation, 58 Low wine, 284, 328 Lubricants, 59 Lythgoe, H. .,219 MACE, 308 false, 310 Maize, loi, 103, 105 oil, 176 starch, 96 Malt extract, 97, 359 liquors, 331 Maltosazone, 115 Malt vinegar, 284 Maple sugar, 132 syrup, 132 Maranta starch, 94 Marmalade, 325 Matthews, J. M., 78 Maumene's test, 151 McElvoy, K. P., 112,230 McGill, A., 13, 269 Mead, 334 Meade, R. K. , 65 Meal, 98 Meat bases, 366 extracts, 366 Meats, canned, 365 infected, 365 Meissl, E., 146 Melting-point, 16 Mercuric iodid, acid, 230 nitrate acid, 213 Metals, poisonous, 68 INDEX Methyl alcohol, 65 detection, 356 orange, (,6 Microscope, 32 Milk, 192 ' - boiled, 195 Miscible solvents, 49 Mitchell, C. A., 152, 185, 231, 366 Mixed flours, 103 Moeller, J., 255, 298 Mohr's cubic centimeters, 29 Molasses, 128 Moor, C. G., 70, 151, 225, 244, 247, 273, 286, 287, 306 Mother cloves, 315 starch, 94 Mulliken, S. P., 356 Must, 335 Mustaid, 317 -oil, 317 Muter, T., 93, 144 Myristic acid, 307 Myronic acid, 317 Myrosin, 317 NAPHTHOL, 84, 91 Nickel detection, 69 Nitric acid test, 141 Nitrogen, albuminoid, 46 total, 41 Normal weight, 29 Nucoline, 182 Nutmeg, 307 oil, 307 Nutshells, 299 OATS, 101, 103 Oat starch, 96 Ogden, A. W., 132 Oil, arachis, 177 cassia, 314 cinnamon, 314 cloves, 315 coconut, 182 colza, 181 corn, 176 cottonseed, 175 gingli, 180 maize, 176 mustard, 317 nutmeg, 307 olive, 171 pepper, 292 Oil, rape, 181 sesame, 180 teel, Oleomargarin, 234 Oleorefractometer, 157 Olive oil, 172 stones, 297 Original solids, 286 Osborne, T. B., 39, 98, 100 Ovens, 37, 39 PARAFFIN in oleomargarin, 370 Parsons, C. C., 41 Paul, B. H., 70, 257, 268, 269 Pea flour, 103 Peanut butter, 177 Pearmain, T. M., 151, 225, 236, 244, 247 Pea starch, 95 Pekoe tea, 254 Pepper, 290 African, 303 bird, 303 cayenne, 303 Pepperette, 297 Pepper, long, 301 starch, 96 Peptones, determination, 366 Perry, 326 Petroleum spirit, 65 Phenol, 91 Phenol phthalein, 66 Phenylhydrazin test, 114 Phillips, F. C, 59 Phytosterol, 1 60 Piperidin, 291 Piperin, 291 Plastering of wine, 339 Platinum, care of, 63 Poisonous metals, 68 Poivrette, 297 Polarimetry, 22, 123, 357 Porter, 332 Potato flour, 104 starch, 94 Prescott, A. B., 55 Preservaline, 85 Preservatives, 83, 86, 223 Priest, M., 273 Process butter, 370 Proteids, determination, 209, 366 Proteoses, determination, 366 Prune juice, detection, 352 Prussian blue, detection, 258 INDEX Putrefaction, detection, 364 Pyknometer, 10 RAPE oil, 181 Recknagel's phenomenon, 194 Red milk, 224 Reduction, 1 21 Refraction index, 157 Refractometer, 157 Reichert, E., 145 Reichert-Meissl number, 146 Reichert number, 146 Reinsch's test, 71 Renovated butter, 370 Rex magnus, 85 Rice, 101-4 starch, 96 Richardson, C. , 294, 296, 304, 307, 308, 311,313, 316, 317 Richmond, H. D., 91, 194, 196, 201, 204, 207, 211, 216, 223 Ricketts, P. de P., 27 Ritthausen method, 209 Rock and rye drops, 139 Romijn, G. J., 222 Root beer, 334 Ropy milk, 225 Rosier, C. H., 223 Rum, 331 Rye flour, 99, 101, 104 starch, 95 -SACCHARIN, 84, 88 Sago starch, 95 Salicylic acid, 83, 87 Salol, 91 Sand, 65 Saponification equivalent, 150 value, 148 Sawdust in flour, 105 Scales for polarimeter, 29 Scheibler's method, 30 Schmidt and Hansch scale, 29 Schnapps, 331 Schumann, O., 21 Scotch whiskey, 330 Scudder, H., 356 Separated milk, 196 Sesame oil, 180 Silicofluorids, 86, 90 Simons, F. D. , 130, 352 Sinalbin, 317 Sinapin thiocyanate, 317 Sirup, 128 Smith, A. W., 284, 288, 341 Smith, H. M., 91 Sodium benzoate, 83, 88 phosphomolybdate, 275 Solidifying-points, 16 Solids, original, 286 Soluble acids, 158 cocoas, 278 Solvents, immiscible, 53 misciUe, 49 Souchong tea, 254 Soxhlet, F , 49, 116, 119 Spain, E., 309, 363 Specific gravity, 9, 140 bottle, 10 rotatory power, 28 temperature reacton, 152 Spectroscope, 30 Spirit, essig, 287 Spirits, 327 Sprengel tube, II Standard solutions, 65 Stannous chlorid in bread, 108 Starch, 92 Starches, characters of, 94-6 Stearin, beef, 189 coconut, 182 cottonseed, 176 Stock, W. F. K., 190, 294, 306 Stokes, A. W., 219, 228, 294, 303 Stout, 332 Stutzer's method, 46, 245 Sucrose, 113, 219 Sublimation, 54, 60 Sugar, cane-, 113,219 Sugars, 116 Sulfates in baking powders, 113 Sulfites, 85, 350 Sulfur chlorid test, 189 Sulfuric acid in vinegar, 289 Sulfurous acid determination, 350 Sweetser, W. S., 103 Symbols, 374 TABLE accessories, 323 Taenia, forms of, 365 Tallow, .189 Tapeworm, 365 Tapioca starch, 95 Tartaric acid, 277, 313 Tea, 25 1 Teeloil,'i8o Terra alba in bread, 1 08 INDEX 383 Thein,252 Theobromin, 274, 275, 280 Thermal reactions, 151, 152 Thompson, R. T., 85, 152, 220 Thome, L. T., 58 Tin detection, 69, 70 in bread, 108 Titer-test, 20 Trichina, 365 Turmeric, 310 starch, 94 ULTRAMARINE blue, 126 Unsaponifiable matter, 165 VALENTA'S test, 150 Vanilla extract, 320 Vanillin, 321 Van Slyke, L. L. , 198, 240, 247 Vegetable butter, 182 Vegetal ine, 182 Vieth, P., 196, 214, 216, 248 Vinegar, 283 cider, 284 malt, 285 spirit, 284 wine, 283 Viscosity, 164 Volatile acid, 145, 234 Voorhees, E. B., 98, 100 Vulte, H. T., 177 WATER determination, 36 specific gravity of, 372 Weigmann, H., 275 Weissbier, 332 Werner-Schmid method, 204 Weston distillation apparatus, 56 Weslphal balance, 13 Wheat, 98, 99, 101, 103 starch, 95 Whey, 196 Whiskey, 328 apple, 329 - Irish, 330 Scotch, 330 Wild's scale, 29 Wiley, H. W., 27, 34, 52, 70, 96, 113, 117, 184, 213, 215 Wine, 335 low, 284, 328 vinegar, 283 Winton, A. L., 284, 295, 302, 311, 3 l6 >3i7 Wool test, 77, 127 XA\THIN, 366 ZINC, detection, 69, 70 A Classified Catalogue of Books on Medicine and the Collateral Sciences, Phar- macy, Dentistry, Chemistry, Hygiene, Microscopy, Etc. P. Blakiston's Son & Company, Pub- lishers of Medical and Scientific Books, 1012 Walnut Street, Philadelphia No. 8. 10-4-01. SUBJECT INDEX. Special Catalogues of Books on Pharmacy, Dentistry, Chemistry, Hygiene, and Nursing will be sent free upon application. All inquiries regarding prices, dates of edition, terms, etc., will receive prompt attention. SUBJECT. 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Interleaved, for taking Notes, $1.00. 4^- These Compends are based on the most popular text-books and the lectures of prominent professors, and are kept constantly re- vised, so that they may thoroughly represent the present state of the subjects upon which they treat. JJES"- The authors have had large experience as Quiz-Masters and attaches of colleges, and are well acquainted with the wants of students. J^- They are arranged in the most approved .form, thorough and concise, containing over 600 fine illustrations, inserted wherever they could be used to advantage. 4- Can be used by students of any college. 4S~ They contain information nowhere else collected in such a condensed, practical shape. Illustrated Circular free. No. i. POTTER. HUMAN ANATOMY. Sixth Revised and Enlarged Edition. Including Visceral Anatomy. Can be used with either Morris's or Gray's Anatomy. 117 Illustrations and 16 Lithographic Plates of Nerves and Arteries, with Explanatory Tables, etc. By SAMUEL O. L. 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By ORVILLB HORWITZ, B. s-, M.D., Clinical Professor of Genito-Urinary Surgery and Venereal Diseases in Jefferson Medical College ; Surgeon to Philadelphia Hospital, etc. With 98 Formulae and 71 Illustrations. No. 10. LEFFMANN. MEDICAL CHEMISTRY. Fourth Edition. Including Urinalysis, Animal Chemistry, Chemistry of Milk, Blood, Tissues, the Secretions, etc. By HENRY LEFFMANN, M.D., Professor of Chemistry in the Woman s Medical College of Penna ; Pathological Chemist, Jefferson Medical College Hospital. No. II. STEWART. PHARMACY. Fifth Edition. Based upon Prof. Remington's Text-Book of Pharmacy. By F. E. STEWART, M.D., PH. G.. late Quiz-Master in Pharmacy and Chemistry, Phila- delphia College of Pharmacy ; Lecturer at Jefferson Medical College. Carefully revised in accordance with the new U. S. P. No. 12. BALLOU. VETERINARY ANATOMY AND PHY- SIOLOGY. Illustrated. By WM. R. BALLOU, M.D., Professor of Equine Anatomy at New York College of Veterinary Surgeons ; Physician to Bellevue Dispensary, etc. 29 graphic Illustrations No. 13. WARREN. DENTAL PATHOLOGY AND DEN- TAL MEDICINE. Third Edition Illustrated. Containing a Section on Emergencies. By GEO. W. WARREN, D.D.S., Chiet of Clinical Staff, Pennsylvania College of Dental Surgery. No. 14. HATFIELD. DISEASES OF CHILDREN. Second Edition. Colored Plate. By MARCUS P. HATFIBLD, Profes- sor of Diseases of Children, Chicago Medical College. No. 15. THAYER. GENERAL PATHOLOGY. By A. E. THAYER, M.D. .Cornell University Medical College. Illustrated. No. 16. SCHAMBERG. DISEASES OF THE SKIN. Second Edition. By JAY F. SCHAMBERG, M.D., Professor of Diseases of the Skin, Philadelphia Polyclinic. Second Edition, Revised and Edition. By JAY F. SCHAMBERG, M.D., Professor of Diseases of the Skin, Philadelphia Polyclinic. Se Enlarged. 105 handsome Illustrations. No. 17. GUSHING. HISTOLOGY. By H. H. GUSHING, M.D., Demonstrator of Histology, Jefferson Medical College, Philadel- phia. Illustrated. No. 18. THAYER. SPECIAL PATHOLOGY. Illustrated. By same Author as No. 15. Price, each. Cloth, .80. Interleaved, for taking Notes, $1.00. Careful attention has been given to the construction of each sentence, and while the books will be found to contain an immense amount of knowledge in small space, they will likewise be found easy reading ; there is no stilted repetition of words ; the style is clear, lucid, and dis- tinct. The arrangement of subjects is systematic and thorough ; there is a reason for every word. They contain over 600 illustrations. THE STANDARD TEXT-BOOK MORRIS' ANATOMY SECOND EDITION Rewritten, Revised. Improved WITH MANY NEW ILLUSTRATIONS Has been recommended as a text-book at more than seventy of the most prominent medical schools in the United States and Canada, and is considered by all anatomists as a standard authority. It contains many features of special advantage to students. A complete Text-book. Edited by HENRY MORRIS, F.R.C.S., Surgeon to, and Lecturer on Anatomy at, Middlesex Hospital, assisted by J. BLAND SUTTON, F.R.C.S., J. H. DAVIES-COLLEY, F.R.C.S., WM. J. WALSHAM, F.R.C.S., H. ST. JOHN BROOKS, M.D., R. MAR- CUS GUNN, F.R.C.S., ARTHUR HENSMAN, F.R.C.S., FRED- ERICK TREVES, F.R.C.S., WILLIAM ANDERSON, F.R.C.S., PROF. W. H. A. JACOBSON, and ARTHUR ROBINSON, M.R.C.S. Octavo. With 790 Illustrations, of which a large number are printed in colors CLOTH. $6.00; LEATHER, $7.00 "The ever-growing popularity of the book with teach- ers and students is an index of its value, and it may safely be recommended to all interested." From The Medical Record, New York. " Of all the text-books of moderate size on human anatomy in the English language, Morris is undoubtedly the most up-to-date and accurate." From The Philadel- phia Medical Journal. THUMB INDEX IN EACH COPY f30m-6/ii] Pood analysis Sept 4 1912 Piatrafes Y V3638