THE ANALYSIS OF PAINTS AND PAINTING MATERIALS Published by the McGreiw- Hill Book. Company \oi*lt to theBookDepartments of tKe McGraw Publishing Company Hill Publishing" Company Publishers of Books for Electrical World The Engineering and Mining Journal Engineering Record Power and The Engineer Electric Railway Journal American Machinist Metallurgical and CKemical Engineering THE ANALYSIS OF PAINTS AND PAINTING MATERIALS BY HENRY A. GARDNER DIRECTOR, SCIENTIFIC SECTION, EDUCATIONAL BUREAU, PAINT MANUFACTURERS' ASSOCIATION OF THE UNITED STATES AND JOHN A. SCHAEFFER INSTRUCTOR IN CHEMICAL PRACTICE, CARNEGIE TECHNICAL SCHOOLS, PITTSBURG, PA. McGRAW-HILL BOOK COMPANY 239 WEST 39TH STRFET, NEW YORK 6 BOUVERIE STREET, LONDON, E. C. 1911 COPYRIGHT, 1910 BY THE MCGRAW-HILL BOOK COMPANY Printed by The Maple Press York, Pa. To DR. EDGAR F. SMITH Provost-elect, University of Pennsylvania, whose teachings have been a source of in- spiration in our work, this book is dedicated. 222495 PREFACE. The authors are presenting in this book a series of selected methods for the analysis of materials used in the manufacture of paints. Acknowledgment is made to Walker, Mcllhiney, and others for several methods of importance, which have been included and correlated with new and valuable methods worked out by the authors. It is assumed that the reader is well versed in the ordinary quantitative methods used in analytical chemistry, and no attempt, therefore, has been made to explain such methods in detail. It is the hope of the authors that this book will prove of value to all those engaged in the manufacture or use of painting materials. December, 1910. Vll CONTENTS. PAGES CHAPTER I. The Analysis of Dry Pigments 1-39 CHAPTER II. The Analysis of Mixed Pigments and Paints 4O~47 CHAPTER III. The Analysis of Paint Vehicles and Varnishes 48-77 APPENDIX A. Analysis of Bituminous Paints 78-88 APPENDIX B. Paint Specifications 88-96 IX THE ANALYSIS OF PAINTS AND PAINTING MATERIALS CHAPTER I. THE ANALYSIS OF DRY PIGMENTS. ! ZINC OXIDE. Zinc Oxide. Zinc oxide contains approximately 80 per cent, of metallic zinc, the balance being combined oxygen. This pigment is completely soluble in acetic acid. Some varieties, however, contain a small percentage of impurities, such as lead sulphate, zinc sulphate, sulphur dioxide, silica, iron, and traces of metallic zinc. This pigment may be analyzed either gravimetrically or volumetrically. Weigh i gram into a beaker, dissolve in acetic acid, filter off any insoluble residue and determine the percentage of zinc in the filtrate by one of the following methods: 1. Gravimetric Method. Heat the acetic acid filtrate to boiling. Completely precipitate the zinc with hydrogen sulphide, and boil for ten minutes, having the solution fit the end of the operation smelling strongly of hydrogen sulphide. Filter, wash, and dissolve the precipitate in hydrochloric acid. Cool, add sodium carbonate solution drop by drop until the solution becomes turbid. Heat to boiling, add 2 drops of phenolphthalein solution and continue the addition of sodium carbonate solution until just alkaline, when the zinc will be completely precipitated as carbonate. Filter in a Gooch crucible, while still hot wash, ignite and weigh as zinc oxide. 2. Volumetric Method. Treat the acetic acid filtrate with ammonium hydroxide until alkaline. Then add hydrochloric acid until faintly acid. Three c.c. of concentrated hydrochloric acid in excess are then added, the solution diluted to 250 c.c., and 2 ANALYSIS OF PAINTS AND PAINTING MATERIALS. titrated with standard potassium ferrocyanide as in the standard- ization of the solution. This method is not applicable in the presence of iron or manganese. Standardization of the Ferrocyanide Solution. Ten grams of pure metallic zinc are carefully weighed off and dissolved in hydrochloric acid. The solution is made up to i liter and a volume equivalent to . 2 gram is measured out. The remaining solution may be kept for restandardizing the ferrocyanide solu- tion which, on standing, appears to change from time to time. In place of using the standard zinc solution, . 2 gram of pure metallic zinc may be used for each standardization. The ferrocyanide solution is made by dissolving 22 grams of crystallized potassium ferrocyanide in a liter of water. One c.c. of this solution will be equal to about .005 gram of metallic zinc. The indicator is prepared by dissolving uranium acetate or uranium nitrate in water until a faint yellow color is produced. A 5 per cent, solution will usually give a good end reaction. A number of drops of this solution are placed on a spot plate, and the end point determined by introducing a few drops of the solution which is being titrated. The acid solution containing . 2 gram of zinc is made faintly alkaline with ammonium hydroxide, using litmus paper to deter- mine the end point. Reacidify faintly with hydrochloric acid and add 3 c.c. of concentrated hydrochloric acid in excess. Dilute to about 250 c.c. and heat to about 80 C. The hot zinc solution is divided into two equal portions. One portion is titrated by slowly running in a few c.c. of ferro- cyanide solution at a time, with vigorous stirring, until a few drops of the solution give a brownish tinge to the uranium acetate indicator on the spot plate. The remainder of the zinc solution, with the exception of a few c.c., is now added to the titrated solution and the end point again determined. The titrated solu- tion is now poured back into the original beaker containing the few remaining c.c. of untitrated solution. The titration is finished by adding two drops of the ferrocyanide solution at a time, testing for the end point after each addition. As the end point develops slowly, it is well to examine each spot, after standing for a brief time. The first one developing a brown tinge is taken as the end point. THE ANALYSIS OF DRY PIGMENTS. 3 A blue color will appear in the hot zinc solution upon the addition of the ferrocyanide solution. This color gradually becomes lighter, and when the end point is reached changes to a white. By repeated titrations, this end point can be easily noted and serves to shorten the time required for the outside testing with uranium acetate. It, however, should not be taken as final, as the uranium acetate gives a more definite end point. The blue color will not be present in an excess of ferrocyanide solution. It is necessary to make a correction for the amount of ferrocyanide solution required to develop a brown color in the uranium acetate indicator when zinc is absent. This correction is deducted from the total amount of ferrocyanide solution used and will usually run between . i and . 2 c.c. BASIC CARBONATE WHITE LEAD. Basic carbonate white lead (2PbCO 3 Pb(OH) 2 ) contains ap- proximately 80 per cent, metallic lead and 20 per cent, car- bonic acid and combined water, with traces sometimes of silver, antimony, lead, and other metals. The analysis of white lead can best be carried out by Walker's* method. (a) Total Lead. " Weigh i gram of the sample, moisten with water, dissolve in acetic acid, filter, and wash, ignite, and weigh the insoluble impurities. To the filtrate from the insoluble matter add 25 c.c. of sulphuric acid (i : i), evaporate and heat until the acetic acid is driven off; cool, dilute to 200 c.c. with water, add 20 c.c. of ethyl alcohol, allow to stand for two hours, filter on a Gooch crucible, wash with i per cent, sulphuric acid, ignite, and weigh as lead sulphate. Calculate to total lead (PbSO 4 Xo . 68292 =Pb) , or calculate to basic carbonate of lead (white lead) by multiply- ing the weight of lead sulphate by 0.85258. " The filtrate from the lead sulphate may be used to test for other metals, though white lead is only ra ely adulterated with soluble substances; test, however, for zinc, which may be present as zinc oxide. * P. H. Walker, Bureau of Chemistry Bulletin No. 109, revised, U. S. Dept. of Agriculture, pp. 21 and 22. 4 ANALYSIS OF PAINTS AND PAINTING MATERIALS. " Instead of determining the total lead as sulphate it may be determined as lead chromate by precipitating the hot acetic acid solution with potassium dichromate, filtering on a Gooch crucible, igniting at a low temperature, and weighing as lead chromate. (b) Complete Analysis. " When it is necessary to determine the exact composition of a pure white lead, heat i gram of the pigment in a porcelain boat in a current of dry, carbon-dioxide-free air, catching the water in sulphuric acid and calcium chloride and the carbon dioxide in soda lime or potassium hydroxide (1.27 specific gravity). By weighing the residue of lead monoxide in the boat all the factors for determining the total composition are obtained. Figure the carbon dioxide to lead carbonate (PbCO 3 ) , calculate the lead monoxide corresponding to the lead carbonate (PbCO 3 ) and sub- tract from the total lead monoxide, calculate the remaining lead monoxide to lead hydroxide (Pb(OH) 2 ), calculate the water cor- responding to lead hydroxide and subtract from the total water, the remainder being figured as moisture. "This method assumes the absence of acetic acid. Thomp- son* states that acetic acid varies from 0.05 per cent, in Dutch process white lead to o . 7 per cent, in some precipitated white leads. It is then more accurate to determine the carbon dioxide by evolution; this is especially the case when working with a lead extracted from an oil paste, as the lead soap and unextracted oil will cause a considerable error by the ignition method. In determining carbon dioxide by the evolution method, liberate the carbon dioxide with dilute nitric acid, have a reflux condenser next to the evolution flask and dry the carbon dioxide with cal- cium chloride before absorbing it in the potassium hydroxide bulbs. (c) Acetic Acid. " It is sometimes necessary to determine acetic acid. The Navy Department specifications demand that white lead shall not contain ' acetate in excess of fifteen one-hundred ths of i per cent, of glacial acetic acid.' Thompson's method* is as follows : *J. Soc. Chem. Ind., 1905, 24: 487. THE ANALYSIS OF DRY PIGMENTS. 5 " ' Eighteen grams of the dry white lead are placed in a 500 c.c. flask, this flask being arranged for connection with a steam supply and also with an ordinary Liebig condenser. To this white lead is added 40 c.c. of syrupy phosphoric acid, 18 grams of zinc dust, and about 50 c.c. of water. The flask containing the material is heated directly and distilled down to a small bulk. Then the steam is passed into the flask until it becomes about half-full of condensed water, when the steam is shut off and the original flask heated directly and distilled down to the same small bulk this operation being conducted twice. The distillate is then transferred to a special flask and i c.c. of syrupy phosphoric acid added to ensure a slightly acid condition. The flask is then heated and distilled down to a small bulk say 20 c.c. Steam is then passed through the flask until it contains about 200 c.c. of condensed water, when the steam is shut off and the flask heated directly. These operations of direct distillation and steam distillation are conducted until 10 c.c. of the distillate require but a drop of tenth-normal alkali to produce a change in the presence of phenolphthalein. Then the bulk of the distillate is titrated with tenth-normal Sodium hydroxide, and the acetic acid cal- culated. It will be found very convenient in this titration, which amounts in some cases to 600-700 c.c. to titrate the distillate when it reaches 200 c.c., and so continue titrating every 200 c.c. as it distils over/ " If the white lead contains appreciable amounts of chlorine it is well to add some silver phosphate to the second distillation flask and not carry the distillation from this flask too far at any time. " The method used by the chemists of the Navy Department is as follows: Weigh 25 grams of white lead in an Erlenmeyer flask, add 75 c.c. of 25 per cent, phosphoric acid, distil with steam to a 500 c.c. distillate, add to the distillate some milk of barium carbonate, bring to a boil, filter, keeping the solution at the boiling point (it is not necessary to wash), add an excess of sulphuric acid to the filtrate and determine the barium sulphate in the usual manner; subtract 53 milligrams from the weight of the barium sulphate and calculate the remainder as acetic acid (BaSO 4 X 0.515 =CH 3 COOH). The object of this rather in- direct method is to avoid any error that might arise from fatty acids being carried over by the steam distillation. For white 6 ANALYSIS OF PAINTS AND PAINTING MATERIALS. lead that has not been ground in oil, Thompson's method is to be preferred." Volumetric Method. The following volumetric method for the determination of lead has been found by the authors to give ex- cellent results when the precautions given are carefully observed. A .5 gram sample is dissolved in 10 c.c. of concentrated hydrochloric acid and boiled until solution is effected. Cool, dilute to 40 c.c., neutralize with ammonium hydroxide. Add acetic acid until distinctly acid. Dilute to 200 c.c. with hot water. Boil and titrate with ammonium molybdate as given in the standardization of ammonium molybdate. Standardization of Ammonium Molybdate. Four and one- fourth grams of ammonium molybdate are dissolved to the liter, so that each c.c. is equivalent to i per cent, of lead when . 5 gram sample is taken. Standardize with . 2 gram pure lead foil. Dis- solve the lead in nitric acid, evaporate nearly to dryness, add 30 c.c. of water, then 5 c.c. sulphuric acid specific gravity i . 84, cool, and filter. Drop the filter containing the precipitated lead sulphate into a flask, add 10 c.c. hydrochloric acid, sp. gr. i .19, boil to complete disintegration, add 15 c.c. of hydrochloric acid, 25 c.c. of water, and ammonium hydroxide until alkaline. Make acid with acetic acid and dilute to 200 c.c. with hot water and boil. Titrate, using an outside indicator of one part of tannic acid in 300 parts of water. The following precautions must be observed in carrying out this method. Calcium forms a molybdate more or less insoluble, and when calcium is present, results are apt to be high. However, when less than 2 per cent, of calcium is present and a high percentage of lead, there appears to be no interference from the calcium. This method is only good for samples con- taining more than 10 per cent, of lead. Should a lower percent- age of lead be present, it must be precipitated as the sulphate then redissolved and titrated as in the method of standardization. Carbonic Acid. The carbonic-acid content of white lead may be determined by using the Scheibler apparatus, as follows : One gram of the dry pigment is placed in the small tube (B) contained in the flask (F). Dilute hydrochloric acid is placed in the flask (F) on the outside of the small tube. Water is brought above the zero mark in the tube (M), by forcing water from the flask (E) by means of the bulb (A). On opening the THE ANALYSIS OF DRY PIGMENTS. M FIG. i. Scheibler Apparatus. 8 ANALYSIS OF PAINTS AND PAINTING MATERIALS. stopcock (D), water is allowed to reach a level on the zero mark in the two tubes (M) and (N) . The flask (F) is then inverted and the acid is allowed to act on the sample. The gas evolved passes into the rubber balloon (H) which causes the water in the tube (M) to lower and that in (N) to rise. The pinchcock (K) is opened and the water is allowed to flow out of the tube (N) at such a rate so that the liquid in the two tubes will be on the same level, as nearly as possible. When the gas ceases to come off, the pinchcock (K) is closed and the apparatus allowed to stand for several minutes, after which the flask (F) is shaken several times so as to complete the action. After action has ceased, which should take place in from a half to three-quarters of an hour, the water in the two tubes is brought to the same level and the amount of gas which has been evolved is noted. It is essential that temperature and barometric readings be made at the same time, so that corrections may be made for errors arising from these factors. The calculation is made directly by referring to the volume of carbon dioxide evolved at the given temperature and pressure in the tables which are given for this conversion, making correction also for the absorption of carbon dioxide in dilute hydrochroric acid, the tables taking directly into account the errors arising from temperature and pressure. In some cases where calcium carbonate is present in a pigment made from dolomitic limestones, it is necessary that the contents of the flask be boiled, although this need be done only in rare cases. The following Dietrich tables are so arranged that the con- versions can easily be made. THE ANALYSIS OF DRY PIGMENTS. O ON ON co iO OO O CS ?O ^ NO t"* ON O co ^" *O NO *> 00 ONO ON rj- r^. M O \O O & ON OOO rJ-O to ^ to t^. oo 10 vo t^ co ON ON VH % 1 8 s 3 -s I \O a tOT)-iO\O ^O ON H 10 ON co ON Tj- 10 NO CO \f) \n \o r- co ON MVOOO ^-t-.0 ^ NV ON *CN TtCO^-^- 1 ^-lOTf-tOrl-lOTt-lOT)-lO < | CO gn * d 88888 88888 88888 88888 8 S . I HH g 5 V SE E1U | l~^ vO lO TJ- ro Q II 88888 88888 88888 88888; 8 I s.s rf vO ON w ro ^O ^O OO O W co ^O ^O OO O^ O H 04 CO ^~ t^* *O lO ^t" <^O VO p 'a o 3 88888 88888 88888 88888 8 3 o "8 s.s ifcgsi ft^g.g i^ 10 VO t^ 00 CN vo 10 T)- PO w vO vO vO vO vO vO BLE II. entimetei , vO IS 00 8 8 8 8 8 88888 88888 80 o o o OOOO 8 < o H .0 JQ 3 O SO 3 K ^^^82 0^^^?.^ vO vo ^~ ro 04 \O vO vO vO vO VO vO L of One Sao t> O iO TJ- ro IS N O vO vo vO vO H vO CO M cs oo 88888 88888 88888 88888 8 ! r-. 'o n s.s ^S^ g'ggBj Hjrij 1-1 CO C * ON o CM d ON to CO C CO ON 8 R CM a g d CO 00 C ON NO rO CO CM _ d CO C ^ ON rj- CO 5 CM & M O ON CO l^. t^* t^* NO NO NO 8O OOOOO OOOOO OOOOO O O OOOOO OOOOO OOOOO O 88888 88888 8888 OOJ^ 8OO OOOOO OOOOO OOOOO OO OOOOO OOOOO OOOOO 88888 88888 88888 88888 8 88888 88888 88888 88888 8 ON COt^ 12 ANALYSIS OF PAINTS AND PAINTING MATERIALS. ^ d .2 N ^" ^O OO O d co ^O vO OO ON M c^ co Tf* to VO t 1 *^ OO O\ O H t^,VO l OlOTJ" CO^MOOs ONOOt-^O^O ^-COCIHH O s o \O ON 88888 88888 88888 88888 8 O^ S ch Tabl d ^ ONMCOtot^ OOOHro^h vOt^.OOO'O HWco^to vO vO'OtO'i-ro 10 TJ- ro CM H o ON OO OOt^vOvori- co g 00 ONONOOOOOO COOOOOOOOO COCOOCt^t^ r-.t^t>t^t^ t^ S d I 8 I 88888 88888 88888 8 go ON oo oo co co ooocoooo'co co oo oo t- r r^t^.t^.r^i^ t^ 2. o 11^88 88888 88888 88888 8 r- to 2'^ ooooooooco coooooooco oooot^t^-t^ r^r^t^t^r^ t o 2 s 88888 8888888888 88888 8 t^ co _< d Tt-vOOOOH ro^vOt^CO O H-rt ON OO r t^ VO vorj-ro.t^r^t^t^ t^ o 5 88888 88888 88888 88888 8 t-^ fO _;d' ^VOOOOH covovOt^ON OHCO^VO vovOt^OOON O H -! OO r^* vO vO vo TJ" ro cs M O O ON GO t^* vo vo ^~ co CN M H SQQ OOOOOOOOOO OOOOOOOOOO COt^l>-l>.t^ t^t^t^t^t^. t^. ^ o 88888 88888 88888 88888 8 t^ co j-j ONHCOIOI^ OOOHro-* go co"oo"o?oo > oo cxcx?oooooo o 88888 88888 88888 88888 8 t^. co o O O H W co ^}" ^O \O l>* 00 O^ O w CJ CO ^t" ^O \O t"* 00 ON O (J HHHHM HMMHH C^MWC^C^ C^WC O & V rh 02 vo D (M N r^-iotoo lOHOOflPlofiOfHOfO ; ; ; : ! i ' ! j 8 I <37 4 0.9233 1.91 188.4 129.8 5" I ? o O 6 132 6 7 i -?6 o Average 0.9234 i . 90 188.2 130-7 It is evident that the iodine value of soya bean oil is the only chemical characteristic that markedly differentiates it from linseed oil. Therefore, in the detection of soya bean oil and its estimation, the iodine values of several samples of mixed oils are given as being of interest in this connection: Iodine Values Of Linseed Oil And Mixed Oils. Sample No. Straight linseed i 25% soya. 75% linseed 50% soya. 50% linseed 75% soya. 25% linseed i 2 3 190.3 i89.5 188.0 175.2 J75-9 !75-4 160. 7 161 . 7 160.3 140.4 140. 8 J39-9 Average 189.3 J 75-5 160.9 140.4 The authors have found that treatment of a few drops of soya bean oil, or oil containing any considerable percentage of soya bean oil, with one drop of concentrated sulphuric acid will produce a distinct fluorescent yellowish-green color. This color is entirely different from that produced with pure linseed oil, which is of a brownish-red and of a begonia-shaped pattern. This test is best conducted on the lid of a porcelain crucible. Subsequent examination under the microscope is of value in THE ANALYSIS OF PAINT VEHICLES AND VARNISHES. 6 1 confirming the test. The comparatively slow drying of soya bean oil will often indicate its presence. CHINESE WOOD OIL. Investigations, extending over several years, conducted by Kreikenbaum,* determined that Chinese wood oil as it comes to the paint trade is fairly uniform in its constants. Kreiken- baum 's work also determined that the Hanus method for the determination of the iodine number, although applicable in the case of linseed oil, could not be used when working on Chinese wood oil, as it gave abnormally high results. The average constants of a large number of commercial samples determined by Kreikenbaum follow: Specific gravity .941 to .943 Free acid, 4 . 4 Saponification number, I 9-9 Hubl iodine number, 169 to 171 Working with the Hubl method a six-hour absorption is sufficient to get good accurate results when determining the iodine number of this oil. SPIRITS OF TURPENTINE, PETROLEUM AND LIGHT OILS. For a quick test to determine whether a turpentine is pure, the chemist may mix in a test-tube 10 c.c. of the material under examination and 10 c.c. of aniline oil. If the turpentine is pure, the two materials will mix without turbidity. If petroleum products are present, they will be indicated by a cloudiness and quick separation in a distinct layer from the turpentine and aniline oil. The following methods have been given by Walker f for the analysis of the volatile solvents used to a great extent in the manufacture of paints: * Adolph Kreikenbaum. Constants of Chinese Wood Oil, Vol. II, No. 5, Jour. Indus, and Engineer. Chem. f P. H. Walker. Some Technical Methods of Testing Miscellaneous Supplies, Bull. 109, revised, Bureau of Chemistry, U. S. Dept. of Agriculture, 1910, pp. 13, 14, and 15. 62 ANALYSIS OF PAINTS AND PAINTING MATERIALS. SPIRITS OF TURPENTINE.* i. Color. "The best quality of spirits of turpentine should be water- white. 2. Specific Gravity. " Determine the specific gravity with a pyknometer, plum- met, or hydrometer at 15 . 5 C. Pure gum turpentine should have a density between 0.862 and 0.875. Wood turpentine may, however, range from 0.860 to 0.910 or even higher. 3. Distillation. "Connect a distilling flask of 150 c.c. capacity with a con- denser having a thermometer. Introduce 100 c.c. of turpentine and heat with a Bunsen burner. The initial boiling point should be about 156 C., and 95 per cent, should distil over between 153.5 and 165.5 C. 4. Residue on Evaporation. "Evaporate 10 grams on the steam-bath; the residue should be less than 2 per cent. 5. Refractive Index. " Determine with a Zeiss direct reading refractometer at 20 C. The index of refraction for gum turpentine should be from i . 4690 to i . 4740; for wood turpentine, i . 4685 to i .5150. 6. Action of Sulphuric Acid (Polymerization). "Measure 6 c.c. of turpentine in a stoppered, thin-walled tube graduated to o.i c.c. (carbon tubes). Place the tube in cold water and pour in slowly a mixture of four parts of strong sulphuric acid and one part of fuming sulphuric acid. Add the acid slowly, and avoid an excessive rise in temperature. Shake the tube so as to mix the turpentine and the acid, add finally about 20 c.c. of the acid, stopper the tube, mix thoroughly, cool, allow to stand thirty minutes, and note the volume of un- polymerized oil that collects on top of the acid layer. Then * If wood turpentine has been carefully refined, it will comply with all the tests given for spirits of turpentine, but it can almost invariably be distinguished from the latter by its characteristic odor. THE ANALYSIS OF PAINT VEHICLES AND VARNISHES. 63 let stand for eighteen hours and again note the volume. A pure turpentine should show less than 0.3 c.c. unpolymerized at the end of thirty minutes, and less than 0.5 c.c. after eighteen hours. " This method will indicate gross- adulteration, but will not detect admixtures of very small amounts of mineral oil. Donk has perfected a method which determines the presence of as little as i per cent, of mineral oil in turpentine. This method is as follows : "Sulphuric acid of thirty-eight times the normal strength (101.5 P er cent.) is prepared by mixing very strong sulphuric acid with fuming sulphuric acid. It must be determined by titration that this reagent is of the exact strength required, for with 37.5 times normal acid (100 per cent.) the turpentine is not completely destroyed, and with acid stronger than 101 . 5 per cent, the amount of mineral oil dissolved becomes excessive. "Place about 25 c.c. of the special sulphuric acid in a flask having a narrow graduated neck (a Babcock bottle does very well), cool in ice- water, add 5 c.c. of the turpentine to be tested and cool the flask again, shaking it carefully and avoiding any excessive rise in temperature by frequent cooling. The flask should never be too hot to hold in the palm of the hand. Then place it in a bath of cold water and heat the bath at such a rate that in about five minutes the temperature will be 65 C. Dur- ing the heating shake the bottle about every fifty seconds, finally shaking very thoroughly so as to insure the contact of every particle of the sample with the acid. Cool to room temperature and add ordinary strong sulphuric acid in sufficient amount to bring the unpolymerized liquid up in the graduated neck. Let stand overnight or whirl in a centrifuge and read the volume on the neck. " Pure turpentine should leave a residue of not over 0.04 c.c., which is not limpid and which has a refractive index of not less than i . 500. "If the unpolymerized residue is" 0.04 c.c. or less, mineral oil may be assumed to be absent. If the residue is greater, calculate from it the percentage of mineral oil present. This will be, of course, only approximate, for there is some residue from pure turpentine and some mineral oil is dissolved by the acid; but for all practical purposes it may be assumed that 64 ANALYSIS OF PAINTS AND PAINTING MATERIALS. the errors balance one another, and hence it is not advisable to apply any correction. 7. Spot Test. "Place a drop on filter-paper and allow it to dry at room temperature; it should leave no stain. 8. Flash Point. " Support a crucible, such as is used in determining the flash point of linseed oil, in a vessel of water at 15 to 20 C.; the water should cover about two-thirds of the crucible. Fill the crucible to within about 2 cm. of the top with turpentine, insert a thermometer, and heat the water bath slowly, i per minute. Begin at 37 and test for the flash at each rise of 0.5. The turpentine should not flash under 40.5 C. Wood Turpentine. The steam method* for the distillation of wood turpentine, as worked up by Geer, Bristol, Hawley, and others of the Forest Products Laboratory of the United States, separates the various high and low boiling-point fractions, all of which have different characteristics. BENZINE AND LIGHT PETROLEUM OILS. "The term benzine is used for a number of light petroleum oils. In the painting trade it generally refers to a product of about 62 Baume (0.7292 sp. gr.). The petroleum benzine of the U. S. Pharmacopoeia is a lighter oil, being a light gasoline. i. Specific Gravity. " Determine with a spindle, pyknometer, or plummet at 15.5 C. The determination can be made at room temperature and corrected to 15.5 C. 2. Sulphur (Sodium Nitroprusside Test). "To 100 c.c. of the sample in a flask add about i gram of bright metallic sodium, connect with a reflux condenser, and boil for one hour. Cool, add water drop by drop until the metal * The Analysis of Turpentine by Fractional Distillation with Steam , by Wm. C. Geer, U. S. Dept. of Agriculture, Forest Service Circular THE ANALYSIS OF PAINT VEHICLES AND VARNISHES. 65 is dissolved, separate the aqueous liquid, and test with a drop of sodium nitroprusside solution. A fine violet-blue coloration indicates sulphur. 3. Sulphur Compounds and Pyrogenous Products (U. S. P. Test). "To 100 c.c. of the sample add 25 c.c. of a solution of 10 per cent, anhydrous ammonia in 95 per cent, alcohol (spirit of am- monia U. S. P.), add i c.c. of silver nitrate solution. Boil gently for five minutes. A brown coloration indicates sulphur compounds or pyrogenous products. 4. Residue on Evaporation. "Place 25 c.c. in a 100 c.c. platinum dish, heat on steam-bath for thirty minutes, and weigh residue. No residue should be left by this test. 5. Fractional Distillation. "Light petroleum oils are usually tested only for specific gravity; but as light and heavy distillates may be mixed, the specifications would be improved by requiring that a certain fraction should distil between specified temperatures. To make this determination distil 100 c.c. in a round-bottom flask 6.5 cm. in diameter; the neck should be 1.6 cm. in diameter and 15 cm. long, with a side tube set in the middle of the neck at an angle of 75. The surface of the liquid should be 9 cm. below the side tube, and the bulb of the thermometer just below the side tube. 6. Benzol. " Mix the sample with 8 volumes of strong sulphuric acid and 2 volumes of nitric acid; heat gently for ten minutes, allow to cool, and note odor. The odor of nitrobenzol indicates benzol. 7. Color and Odor. "Note color of sample and odor both in bulk and after rubbing on hands." ANALYSIS OF VARNISH AND JAPAN. An examination of a varnish should be largely of a physical nature, the chemist determining its appearance, odor, body, clarity, and properties of the dried film. The specific gravity, 5 66 ANALYSIS OF PAINTS AND PAINTING MATERIALS. flash point, viscosity, acid number, ash, and rosin test, as well as the percentage of volatile oils, are determined in the usual manner, as outlined for linseed oil on previous pages. The percentage of fixed oils and gums is determined by weighing that portion left in the flask after distillation of the volatile constituents. Owing to the chemical combinations and changes which are effected when various gums are heated together in the presence of oils, it is almost impossible for the most expert analyst to determine the exact make-up of a varnish. The analyst, however, may determine the total percentage of gums and the percentage total of oils with a fair degree of accuracy, on an original sample by precipitation of the insoluble gums with gasoline, determining the soluble gums in the benzine by extraction with chloroform after evaporation of the gasoline and oxidation of the oil. To make an exact determination of a varnish formula, however, as it was submitted to the varnish maker, is almost impossible. Oils, Gums and Volatile. In ordinary varnish which gen- erally contains oil, gums and volatile solvents like benzine and terpentine, weigh off 10 grams into a tall thin beaker of 400 c.c. capacity. Next add a large amount of ice cold petroleum ether. Cover the beaker and allow to stand for several hours when the gums will be found separated at the bottom of the beaker. Repeat the extraction with cold petroleum ether at least three times, pouring the several decanted portions into a large bottle. After finishing the extraction, add 100 c.c. of ice cold water to the petroleum ether in the bottle and shake thoroughly, causing a small amount of gum which usually dissolves in the ether to reprecipitate. Filter on a tared filter, previously moistened with ice water, and also transfer to this filter the gum contained in the beaker, using a stirring rod and some petroleum ether to loosen it from the glass, washing finally with a small quantity of ice water. Dry at 100 C. and weigh as gums. If the oil is also to be determined, the petroleum ether and water can be separated in a separatory funnel and the ether then evaporated or distilled off, leaving the oil. The sum of the oil and gums subtracted from 100 gives the percentage of volatile thinners benzine, turpentine, etc. Distillation of the volatile solvents from a separate portion of the varnish may be used to determine the percentage of THE ANALYSIS OF PAINT VEHICLES AND VARNISHES. 67 turpentine by the polymerization method previously outlined in this chapter. In spirit varnishes, like shellac, to determine the gums it is only necessary to weigh off 10 grams into a tared porcelain dish and evaporate off the solvent on the water bath- Mcllhiney's method for the analysis of oil varnishes has been used by the authors with success. This method may also be used in the analysis of japan driers. Mcllhiney's Method. Of the materials used in construction few if any present more difficult problems in their testing and analysis than oil varnishes. Any rational system of testing varnishes to determine their suitability for a given use and their resistance to the destructive effects of exposure to the elements, will take account among other tests of a chemical analysis to determine the ingredients of the varnish and the proportions in which they are combined. It is unfortunate that there is not at the present time any method of analysis which will determine with any reasonable degree of accuracy, the proportions in which the oil, hard gum, and common rosin have been combined to form the nonvolatile base from which the varnish is produced by dilution with turpentine or other volatile oil. The proportion of volatile oil in the varnish may be deter- mined by distilling the solvent off with steam at a temperature a little above the boiling point of water and then separating the volatile oil from the aqueous part of the distillate and weighing or measuring it. Its further examination need not be entered upon here since methods of analysis of such volatile oils as are likely to be used as thinnefs for varnish are now generally known and are described at length in such standard works as Allen's Commercial Organic Analysis, and the books on paints and varnishes by Toch, Sabin, and Holley and Ladd. The separation of the hard gum from the oil and the common rosin is the problem which is difficult; the hard gum and the oil do not unite at all, practically, until the hard gum has been melted and from 15 to 25 per cent, of its weight driven off as vapor, the amount so lost depending upon the character of the gum. After this melting the linseed oil may be added if it has been previously heated enough to prevent it from chilling the melted gum. This mixture of oil and gum is usually at this 68 ANALYSIS OF PAINTS AND PAINTING MATERIALS. stage heated for a shorter or longer time to complete the com- bination of the ingredients. The union of oil and hard gum which has been effected by this means cannot be broken up by any solvent, or perhaps it would be more accurate to say that after the combination between hard gum and oil has been successfully made and the mixture thinned with turpentine and stored for a few months, no solvent can be depended upon regularly to effect a separation of the two by its selective solvent action. The process which is here described depends upon the fact that although the union between oil and hard gum is too intimate to be broken up by the selective solvent action of any solvent acting directly upon the original mixture, the combination may be broken up and the oil and gum brought back to more nearly their original condition before they were melted together, by submitting the mixture to the action of caustic potash in alcoholic solution and subsequently acidifying the solution of potash salts so formed. By this means there is obtained from hard gum varnishes a quantity of gum insoluble in petrolic ether very closely approximating the amount of hard gum actually existing in the varnishes, while the linseed oil is represented by its fatty acids which are readily soluble in this solvent unless they have been oxidized, in which case some of the fatty acids of the linseed oil will accompany the insoluble hard gum. In carrying out the method an opportunity is given to determine not only the weight of the oil and of gum but also the Koettstorfer figure and the percentage of glycerine in the mixture. All these data taken together give a basis for cor- roborating the main figures. The process is carried out by weighing into an Erlenmeyer flask 2 to 10 grams of the varnish, adding a considerable excess of approximately half -normal solution of caustic soda or caustic potash in very strong or absolute alcohol, distilling off the major portion of the solvent and redissolving in neutral absolute alcohol. The solution is then titrated with a solution of pure acetic acid in absolute alcohol, approximately half-normal strength, to determine the amount of the excess of alkali present. From this the Koettstorfer figure is determined as the exact strengths of the acid and alkali solutions have been ascertained independently by comparison with known standards. A THE ANALYSIS OF PAINT VEHICLES AND VARNISHES. 69 further quantity of the standard solution of acid in alcohol is added so as to exactly neutralize the total amount of alkali originally added. By this means the acid bodies liberated from their combinations with alkali are obtained in solution in strong alcohol. To this solution there is now added a sufficient quantity of petrolic ether to dissolve the oil acids__an petrolic ether being miscible with the strong alcohol forms with it a homogeneous liquid. Water is now added to the mixture in such amount as to so dilute the alcohol contained that it is no longer a solvent for fatty or resin acids; this addition of water causes the petrolic ether which was mixed with the alcoholic liquid to separate carrying with it the fatty acids. The rosin goes with the fatty acids while the hard gum being insoluble in either the petrolic ether or in the very dilute alcohol separates in the solid state. The aqueous and ethereal layers are now separated in a separating funnel and each is washed, the watery layer with petrolic ether and the petrolic ether layer with water. The petrolic ether layer is now transferred to a weighed flask, the solvent distilled off, and the residue of fatty acids and common rosin weighed. This latter is then examined further by Twitchell's method to determine the amount of rosin which it contains or it may be examined qualitatively in a number of ways to establish its identity. The aqueous layer is freed from the suspended hard gum which it contains by filtering, and from any further quantity of gum which the weak alcohol may have retained in solution by evaporating off the alcohol and again filtering. The remaining aqueous liquid contains the glycerin and this is determined by the Hehner method with potassium bichromate the method ordi- narily used for examining spent soap lyes. The hard gum is, according to this plan, precipitated in such a way that it adheres to the sides of the glass vessel in which the alcohol and petrolic ether mixture is diluted with water; the easiest method to weigh it is, therefore, to carry on the operation of dilution in a weighed glass vessel and then to dry and weigh the hard gum in this vessel. It frequently happens that some of the hard gum cannot be conveniently retained in this vessel but that it must be filtered out on a weighed filter and the weight so found added to that of the main portion. If the varnish contains nonvolatile petroleum or other 70 ANALYSIS OF PAINTS AND PAINTING MATERIALS. unsaponifiable matter it will naturally be included in the fatty and resin acids, and it would be necessary to saponify the latter and extract the unsaponifiable matter from them while in the alkaline state; this operation is so familiar to chemists that it is mentioned here only to call attention to the necessity for it in some cases. It would naturally be expected that on account of the well known insolubility of the oxidized fatty acids in petrolic ether, some of the acids of the linseed oil which had been polymerized by heat during the cooking of the varnish, or which had been oxidized during the blowing process to which some linseed oil is subjected before making it up into varnish, would fail to dissolve and would be counted in with the hard gum instead of with the linseed oil. It appears as a matter of fact that this source of error is of slight importance in the case of oil thickened by heat but that the blowing process gives an oil which is not com- pletely accounted for by the soluble fatty acids recovered. This difficulty may be largely overcome by taking advantage of the greater solubility of the oxidized fatty acids in alcohol as compared with the hard gum; the freshly precipitated gum contaminated with oxidized fatty acids is treated with a moder- ate quantity of cold alcohol of about 85 per cent, and allowed to digest for some time. The soluble matter so extracted is then recovered separately by evaporating off the alcohol. The great variety of hard gums in use and in the methods of making them up into varnish make the problem one of great complexity. It is not to be expected that any one method of analysis or any single set of directions for carrying on the operation of making the analysis would be generally applicable, and it is not the intention in this paper to give such detailed instructions. The method described has, however, been found to give, upon samples of known composition made up under conditions which imitate closely the conditions of practice in an ordinary varnish factory, results that were accurate to within reasonable limits. Rosin when present is usually combined with lime in the proportion of about one part of lime to twenty parts of rosin. An examination of the mineral constituents of the varnish is therefore of some value; the extraction of the mineral bases may be effected by treating a quantity of the varnish somewhat THE ANALYSIS OF PAINT VEHICLES AND VARNISHES. 71 thinned with benzine, with strong hydrochloric acid, and examining the aqueous liquid. The amount of fatty acids obtained represents about 92 . 5 per cent, of the linseed oil. The identification of these fatty acids as belonging to linseed oil or to china wood oil may be satisfactorily accomplished in some cases, but there are undoubt^ edly many varnishes in which the analyst will be unable* to identify and determine the oils. The identification of the hard gums after separation from the other constituents of the varnish is a matter for which no rule can be given. The odor and physical characteristics of the recovered gum are quite as important as the known chemical tests of which the acidity and the Koettstorfer figure are among the most important. The chemistry of these gums is as yet almost unknown, but in the near future it is likely that our knowledge both of the nature of these hard gums and of methods for separating them from the other ingredients of the varnishes of which they form a part, will be very greatly increased. For the analysis of gums, the analyst is referred to Vols. I and II of Lewkowitsch, and to Allen's Commercial Organic Chemistry. The following method of Mcllhiney's for the analysis of shellac, being of such great value, is presented at this place : THE ANALYSIS OF SHELLAC. Mcllhiney's Method.* In the last few years the analytical examination of shellac has become much more common because the users of shellac and the dealers in it have become better informed as to the extent to which adulteration has been prac- tised, in the past, and particularly because more accurate and reliable methods of analysis have been devised for examining shellac. The most important adulterant of shellac, in fact almost the only adulterant, is common rosin or colophony, and it is to the detection and estimation of this adulterant that most of the analytical methods have been directed. The price of commercial shellac is determined by its color, freedom from dirt, etc., as well as by its content of colophony, but the chemist is not usually called upon to determine the commercial grade * Presented before the International Congress of Applied Chemistry. 72 ANALYSIS OF PAINTS AND PAINTING MATERIALS. of shellac in other respects than its purity or freedom from adulteration. The methods which have been used with greater or less suc- cess to determine the amount of rosin in shellac depend first upon the different behavior of shellac and of colophony toward alkali; shellac when dissolved in alcohol is capable of neutralizing a much smaller amount of caustic soda or potash than rosin when under similar conditions, and tests based upon this property are used and are of some value particularly as corroborating the results of other tests. The difference, however, between shellac and rosin in this respect is not sufficiently marked nor are the various grades of pure shellac or of rosin sufficiently constant in their behavior when tested by such methods to furnish a fairly satisfactory method of analysis. (See Allen, Commercial Organic Analysis, Vol. II, Part 3, pp. 190-195.) Another property of rosin which has been used to distinguish and determine it in admixture with shellac is the solubility in ether of its compound or salt of rosin with silver while the similar compound of silver with shellac acids remain undissolved. The neutral constituents of shellac, that is, those which generally unite with either soda or silver are, however, also soluble in ether and are likely to be obtained in admixture with the rosin so that this method of analysis is objectionable. Shellac and rosin when treated with proper solutions of iodine behave very differently; the shellac absorbs a relatively small amount, varying from 7 to 18 per cent, of its weight of iodine, the amount depending upon the details of the process used, while rosin under similar conditions absorbs from 120 to 230 per cent, of its weight of iodine. For many years it was the practice to use for the examination of shellac in this way the Hubl process in which the iodine and the rosin to be tested are used in solution in alcohol to which a little chloroform has been added. This Hubl process was originally designed for the examination of fats and oils and although it was in its day a very useful process it has in recent years been replaced by others which are more rapid and accurate. The process which has been for the past few years in most common use in the United States for the determination of rosin in shellac is the iodine process which was originally suggested for use upon fats and oils by Wijs and which was later studied THE ANALYSIS OF PAINT VEHICLES AND VARNISHES. 73 and adapted for use upon shellac by Langmuir and was finally recommended by the Sub-committee on Shellac Analysis of the American Chemical Society in Journal of American Chemical Society, XXIX, 1221 to 1227, as the most reliable of those in use up to that time. The process consists in brief of the following steps: in a treatment of a fixed amount, 200 milligrams of the shellac to be tested dissolved in 20 c.c. of acetic acid of 99 per cent, strength to which 10 c.c. of chloroform is added, with 20 c.c. of a solution of iodine monochloride in acetic acid of 99 per cent, strength for exactly one hour at a temperature of 21 to 24 C. The amount of iodine which is absorbed under these conditions by rosin is assumed to be 228 per cent, of the weight of the rosin while shellac absorbs less than 18 per cent, of its weight and in making the calculation the iodine figure of the shellac is assumed to be 18. This process has given excellent results in practice particularly as it is capable of giving in the hands of different operators closely agreeing results upon the same sample. The objections to the use of this process are first that it is likely to give results below the truth and second that the method of ascertaining the amounts of rosin is an indirect one and any other substance having a high iodine figure would be counted as rosin; the rosin itself is at no stage of the process sepa- rated from the shellac and submitted to a separate examination. The need of a process of analysis which would actually separate the rosin from the shellac so that it can be examined by itself has led the writer to devise a process which has recently begun to be used in which the rosin is so separated from the shellac. This process which was described at length in the " Journal American Chemical Society, " XXX, 867 to 872, depends upon the fact that rosin is soluble in petrolic ether while shellac is not. Although it is not practicable to extract the rosin from solid shellac with petrolic ether, the latter may be used to separate the two resins when they are dissolved in a suitable solvent. The shellac to be examined is in this process dissolved in absolute alcohol or in glacial acetic acid; with both of these solvents petrolic ether is miscible. It is, therefore, added to the solution of the rosin, and to the resulting mixture water is added. This results in a separation of the alcoholic and petrolic ether layers as the diluted alcohol is no longer miscible with the petrolic ether. The petrolic ether carries with it the rosin, the wax 74 ANALYSIS OF PAINTS AND PAINTING MATERIALS. contained in the shellac, providing sufficient petrolic ether was used to dissolve it, and traces of shellac or of some constituent of shellac. Several methods of separating the shellac wax from the rosin may be used, but the most convenient is to extract the petrolic ether solution of the two with an alkaline solution which removes the rosin and leaves the wax dissolved in the petrolic ether. From the alkaline solution of the rosin the latter may be recovered by acidifying, extracting the acidified solution with a solvent such as ether and distilling of! the ether to obtain the rosin which may then be weighed. After considerable experience with this method the following , details as to mode of procedure hav^e been found convenient as well as tending to give accurate results. Place 2 grams of the shellac to be examined in a i6-oz. flask and add to it 20 c.c. of absolute alcohol; dissolve the shellac in the alcohol by gentle heating. Now add slowly and with constant agitation 100 c.c. petrolic ether boiling below 80 C. The first addition of petrolic ether to the alcoholic solution does not occasion the precipitation of any shellac, but as further quantities are added the mixed solvent of alcohol and petrolic ether becomes incapable of retaining the whole of the shellac in solution and it gradually precipitates out. It is necessary that the addition of the petrolic ether should therefore be made slowly and with stirring in order that the precipitating shellac may not carry out with it mechanically any of the rosin contained in the solution. When the whole of the 100 c.c. of petrolic ether has been added 100 c.c. of water is added also with agitation. The first additions of water cause the separation of the liquid into two layers one of which is rather strong alcohol, which may dissolve some part of the rosin which is afterward precipitated by the rest of the water. The necessity for agitation during this stage is to insure the collection into the petrolic ether of all the rosin. When all the water has been added the liquid is poured into a tapped separator and the flask rinsed out with a little more petrolic ether. The two liquids in the separator readily separate and the watery layer is drawn off. The petrolic ether is then washed with a little water which is also drawn off. The petrolic ether is then filtered into a clean separator and to it is added 25 c.c. of a solution of N/5 caustic soda in 50 per cent, alcohol. This caustic soda solution is measured into the separator accurately THE ANALYSIS OF PAINT VEHICLES AND VARNISHES. 75 with a pipette and a similar pipette full of the same solution is titrated with standard hydrochloric acid, using methyl orange as an indicator. The separator containing the alcoholic soda solution and the petrolic ether is then thoroughly agitated, allowed to settle, and the watery layer drawn off into a tared flat, bottomed dish. The petrolic ether is then washed by agitating with a little 50 per cent, alcohol and the washings are added to the tared dish. There is further added to the contents of the tared dish the same volume of the same standard hydrochloric acid as were required by the check portion of 25 c.c. of the N/5 soda. J.TL this way the entire quantity of soda is neutralized with hydrochloric acid and the resinous matters contained in the solution are left uncombined. The contents of the dish are then allowed to evaporate at a low temperature until the residue is dry, when the dish with its contents is weighed. The check portion of 25 c.c. of N/5 soda is, after being neutralized with standard acid as described, evaporated in a similar dish and in this way the amount of sodium chloride produced from the 25 c.c. portion is ascertained. By deducting the weight of sodium chloride so found from the combined weight of the resinous matter and sodium chloride the weight of the former is ascertained. The dried contents of the dish may now be further examined. The odor of the resin and its consistency may be observed, its acidity may be determined by solution in neutral alcohol and titration with N/io alkali or if it is desired the resinous matter may be separated from the sodium chloride by dissolving it in ether or some other solvent. By this process it is practicable to actually separate, examine, and exhibit the rosin which had been added to the shellac as an adulterant. It is also practicable to determine the amount of wax present providing, however, that a much larger amount of petrolic ether had been used than is necessary for the complete extraction of rosin alone. It has been found necessary to use at least 200 c.c. of petrolic ether per gram of shellac in order to insure the complete extraction of the wax, while 50 c.c. of petrolic ether per gram of shellac appears quite sufficient to extract any reasonable amount of rosin. As previously stated the petrolic ether dissolves traces of pure shellac. It becomes important, therefore, to know how much will be dissolved from pure shellac when examined by the 7 6 ANALYSIS OF PAINTS AND PAINTING MATERIALS. process above described. A great many pure shellacs have therefore been examined by this process and at the same time their iodine figures have been ascertained by the Wijs-Langmuir process. The following figures are representative of the results obtained : Grade Acidity of e Iodine % Extract- matter per figure ed matter in c . c . N /io extracted 2 grams KOH. Angelo-B-Pure Button. Pure T-N 14 . 7 2.12 1.6 18 o i 70 is , Pure T-N 177 I O ? 08 Pure T-N 16 o 2 19 i 6 Pure T-N ICQ 2O3 I Z Pure T-N Pure orange 17.6 1.82 1.5 174. 1^8 12 Sticklac 14 7 ^07 2 3 It will be noted that there seems to be a tendency for the higher grades to give a larger amount of rosin soluble in petrolic ether than the lower grades. The amount given by such grades of shellac as are likely to be found adulterated may safely be assumed to be less than 2 per cent. If the shellac is of the highest grades, those which seldom contain rosin and which consequently seldom need to be examined by the analyst, the amount of soluble matter may with safety be assumed to be less than 3 per cent. The rosin which is to be determined consists principally of acid bodies which readily unite with caustic soda, but it also con- tains a certain amount of unsaponifiable matter which is not extracted from the petrolic ether by the soda solution. The amount of rosin which is finally weighed cannot, therefore, be greater than the amount of free acids originally contained in it. The amount of unsaponifiable matter contained in the rosin used is, therefore a matter of interest, but unfortunately it is impossi- ble to ascertain the exact amount. It is reasonable to assume, however, that not more than 85 per cent, of the rosin will be recovered and weighed in the process above described. This assumption agrees perfectly with the experience in this labora- tory in working upon a considerable variety of rosins. THE ANALYSIS OF PAINT VEHICLES AND VARNISHES. 77 In calculating the amount of rosin content from the weight of extracted resinous matter in this process, allowance must be made for the small amount of pure shellac extracted and also for the shortage in the weight of rosin as finally weighed on account of the unsaponifiable matters contained in it. In making this calculation the following formula is used: If Y=per cent, rosin, M =per cent, of extract of pure shellac, N =per cent, of extract of pure rosin. A=per cent, of extract of mixture, Th V rhenY= ~x~-M~ Here M=2.o or in the case of high grade shellac, 3.0, and N=85.o. IPO (A 2). ThenY= -^- Shellac varnishes may contain beside true shellac not only rosin, but other gums and resins soluble in alcohol. It becomes, therefore, a matter of interest to ascertain how some of these other resins behave when treated by this process. Two samples of manilla, when treated, using absolute alcohol as the first solvent, gave, respectively, 41.2 and 43.3 per cent, of matter soluble in petroleum ether. The acidity of these two lots of matter soluble in petroleum ether was in the case of the first sample such that i c.c. of normal alkali neutralized 411.7 mg. and in the case of the second 470.7 mg. Two samples of Kauri gave, respectively, 37.9 and 27.0 per cent. Upon titrating with standard alkali these portions soluble in petro- leum ether, it appeared that i c.c. of normal alkali was capable of neutralizing 903.6 mg. and 742.5 mg., respectively. Of Sandarac, two samples, when similarly analyzed, gave 34.96 and 36.19 per cent., having such an acidity that of the first 541.2 mg. would neutralize i c.c. normal alkali, and of the second 552.5 mg. would neutralize i c.c. Of Dammar, 89.9 percent. proved to be soluble, while the resin of Shorea roburta, a sample of which was kindly sent by Mr. W. Risdon Griper, of Calcutta, gave 69.5 per cent, of soluble matter. APPENDIX A. THE ANALYSIS OF BITUMINOUS PAINTS. At the present time many bitumens and artificial bitumens are frequently used, either alone or in combination, in the manufacture of paints, black varnishes, and japans. The as- phaltic compounds are naturally occurring products in many cases containing comparatively large percentages of sulphur. Mineral matter, which is present in widely varying roportions, consists usually of limestone, clay, or sandstone, containing the usual impurities found in these materials. Petroleum residuum and coal-tar pitch are sometimes used alone as paints, but more frequently petroleum residuum is added to asphaltic compounds as a flux. Free carbon also finds application as a color agent for deepening such mixtures, but experience has shown that the percentage of free carbon should not exceed 20 per cent. While a chemical analysis of such mixtures will disclose little concerning their true value as paints, nevertheless it is in many cases advisable and necessary that an examination be made so as to determine their general composition. The following methods will be found to give good approximate results in the examination of paints made from asphaltic and bituminous compounds. Separation and Determination of Volatile Constituents. 100 grams of the paint, after being thoroughly mixed, are placed in a distilling flask and the volatile constituents separated in the usual way, as described on page 66, all the volatile con- stituents distilling over up to 180 C. being carefully collected. The amount of distillate thus found will give the percentage of volatile constituents present. The distillate is then fractionated so as to determine the percentage of benzol, benzene, turpentine, and volatile oils. This operation is carried out by the usual fractionation methods, fractions being weighed and the percent- age of each constituent determined. Separation and estimation 78 ANALYSIS OF BITUMINOUS PAINTS. 79 of the turpentine in the distillate is best done by the polymer- ization method described on page 62. Any water present in the vehicle or in the asphalt itself, as so frequently occurs in asphaltic mixtures, will distil over at the above temperature and will be found in the distillate. It must also be understood that some low-boiling oils which are so often present in bituminous mixtures may distil over at or below 180 C. When such oils are present, it is impossible to differentiate between them and the oils present in the vehicle. In such cases, however, they may be assumed to act in the role of vehicle and may be reported as such. Nonvolatile Residue. The residue left in the flask after distillation is then examined for bituminous matter (petrolene and asphaltene), nonbituminous matter, carbon, sulphur, and the constituents entering into the ash. Petrolene and asphaltene are the names applied to the sub- stances obtained by the use of certain solvents on the natural and artificial bitumens. The portion soluble in petroleum spirit, ether, or acetone is known as petrolene, while the portion in- soluble in petroleum spirit but dissolved by boiling turpentine and cold chloroform is known as asphaltene. The total bituminous matter is considered to be that portion of the asphaltic mixture which is soluble in the above solvents or in carbon bisulphide, the portion insoluble being considered as nonbituminous matter. Pure asphalt, as used in the manu- facture of painting materials, should be completely soluble (with the exception of 4 or 5 per cent, which may be mineral matter) in carbon disulphide, oil of turpentine, or chloroform. Nonbituminous Matter, Carbon, and Ash. The residue remain- ing after the extraction by the carbon bisulphide method is dried and weighed. The loss between the original weight of the non- volatile residue and the weight of the unextracted matter, gives the percentage of bituminous matter (asphaltene and petrolene) present. The insoluble residue after weighing is ignited until all the carbon has been burned off. The weight is again taken and the loss reported as nonbituminous matter and carbon. It is advisable before weighing to treat the ash with a little am- monium carbonate to reconvert any carbonates which may have been decomposed by the heating to their original form. Ash. The constituents of the ash are determined in the 80 ANALYSIS OF PAINTS AND PAINTING MATERIALS. manner outlined under the analysis of mixed pigments, or by any of the methods used in the analysis of limestones, clays, or sandstones. The mineral matter present quite frequently exists in com- bination with the bituminous matter forming resinous-like compounds which partially dissolve in the solvents used for fractionation of the nonvolatile residue, thus giving high results for the bituminous matter and low results for ash. These errors, however, serve to counterbalance each other and are frequently so inappreciable that they may be neglected. The correct percentage of ash should be determined by ignit- ing a new sample of the nonvolatile residue until all the carbon has been destroyed. Sulphur. It is often necessary that the sulphur content of asphaltic mixtures be determined. This may be approximately determined by following Eschka's method : Mix intimately i gram of the finely ground, nonvolatile residue with i gram of calcined magnesium oxide and .5 gram of mixed sodium-potassium carbonates, in a platinum or porce- lain crucible. After thorough mixing, the crucible (uncovered) is heated to a dull red heat with an alcohol or Bunsen flame, in the latter case the crucible being placed in a hole cut into an asbestos board, thus preventing any sulphur from the flame from contaminating the mixture. The action is hastened by frequent stirring of the mixture. The heating is continued until the contents of the crucible become a dull yellow. Cool the crucible and mix the contents intimately with about i gram finely powdered ammonium nitrate. Heat until the ammonium nitrate is completely decomposed. Any sulphites formed by the first treatment are thus completely converted into sulphates. The contents of the crucible, after cooling, are carefully transferred to a beaker and extracted with hot water. Evapo- rate, wash, acidify with hydrochloric acid and precipitate the sulphate present in the usual way with barium chloride. Weigh as barium sulphate and calculate to free sulphur. It has been found that the sodium peroxide method is apt to give results which are low. The Hempel- Graef e * method for determining the percent- * J. of Ind. and Eng. Chem., May, 1910, p. 187. ANALYSIS OF BITUMINOUS PAINTS. 8 1 age of sulphur in bitumens or pyro-bitumens, consists in burn- ing a small quantity of the material under examination, in an atmosphere of oxygen, with absorption of the gas in sodium peroxide. Subsequent neutralization and precipitation is made. In determining the presence and identification of vegetable or fossil gums, such as rosin or kauri gums, the methods of Mc- Ilhiney for the analysis of shellac together with the methods given for the analysis of varnish will prove useful. Examination of the Nonvolatile Residue. A portion of about 50 grams of the nonvolatile residue is placed in an Erlenmeyer flask and shaken with a considerable quantity of carbon bisulphide. After sufficient time has elapsed for the carbon bisulphide to exert its solvent power on the petro- lene and asphaltene, the contents of the flask are poured upon a suitable filter. If pigments are present, they will be found upon the filter and may be examined by the methods outlined for the analysis of pigments in mixed paints. If drying oils, such as linseed oil, are present in the non- volatile residue, they may be removed by treating another por- tion of the residue with 88 gasolene for eight or ten hours. Evaporation of the filtrate from this product will leave the oils which may be present in a condition suitable for analysis. Rosin and resinates are also extracted by this treatment and should be looked for. Fossil gums, however, are apt to be pre- cipitated by the gasolene. FORREST METHODS. The Examination of Black Varnishes and Enamels. The following method for the examination of paints contain- ing bitumens or pyro bitumens has been prepared for this book by Mr. C. N. Forrest, Chief Chemist of the New York Testing Laboratory, where extensive tests on the nature of bituminous materials have been conducted. These methods are of great im- portance and serve to give much new information regarding Bituminous Paints. 6 82 ANALYSIS OF PAINTS AND PAINTING MATERIALS. For the purpose of an analysis, bituminous paints should be divided into three classes, as follows: Asphaltum varnish. Asphaltum enamel. Coal-tar enamel. Asphaltum varnish, as its name implies, does not contain a pigment but consists of a base of asphatum and other substances, reduced to a fluid consistency with a suitable volatile solvent. Asphaltum enamel consists of an asphaltum varnish in com- bination with a pigment, and may be either black or colored. Coal-tar enamel, although generally considered as a varnish or paint, always contains carbon in suspension and therefore should be classified as an enamel. A distinctive feature of bituminous varnishes and enamels is that they dry by evaporation rather than by oxidation. If a drying oil is present a certain degree of hardening of the film subsequently occurs, but the intinal drying of such varnishes and enamels depends upon the spontaneous evaparation of the volatile thinners present, and the rapidity of drying upon the degree of volatility of the volatile solvent. Any linseed or other oil present should be considered as a constituent of the base. An asphaltum varnish will therefore consist of a basic ma- terial dissolved in from 25 to 60 per cent, of some volatile solvent, such as turpentine, benzine, heavy petroleum spirit, or coal-tar spirit. Occasionally carbon disulphide or some special solvent may be employed, but that would be unusual. An asphaltum enamel will contain black or colored pigments combined with a varnish of essentially the same nature as has just been described. A coal-tar enamel will consist essentially of a base of coal- tar pitch dissolved in benzole or other coal-tar spirit. The free carbon present is very finely divided and will remain suspended for an indefinite period. There are several kinds of hard asphaltum available for var- nish-making, but the principal and most generally used types are mentioned in the following table, which also gives the im- portant characteristics of the same. ANALYSIS OF BITUMINOUS PAINTS. Refined Gilsonite. Nanjak. Grahamite. Bermudez asphalt. Gil pitch. Specific gravity at 77 F 1.049 i .0844 1.171 1-0575 1.0703 Color of powder .... Brown. Dark Black. Black. Black. brown. Melting-point 325F. 35F. Intumesces. i 7 oF. i6 4 F. Bitumen soluble in CS 2 QO . 0% QO 2 % 04 i % 06 o% 08 2% Mineral matter .... W V f" . I y y . ^ /(j 3 V T * /V 5-7 y-' ** /v 2 .O v /^ Trace. Difference .0 5 . 2 2 .0 1.8 IOO . O IOO .0 IOO . IOO. O IOO.O Bitumen soluble in 88 naphtha 15.9 26 . 9 4 69 . I 69.6 This is per cent, of total bitumen. . . . 15-9 27.0 4 71.9 70.9 Residual coke 1 3 4. 2 S O C-I . -2 14 . o 10 "? Paraffine A o t None. * j v None. JO None. None. - 1 V .8 Characteristics o f asphaltenes i n - soluble in 88 naphtha. Color Black. Black. Black. Brown. Brow^n. Condition Hard. Hard. Hard. Soft. Soft. Residual coke 15-2% 55-6o% 50-55% 30-35% 50-60% 8 4 ANALYSIS OF PAINTS AND PAINTING MATERIALS. The characteristics of the most select grades of coal-tar pitch suitable for the manufacture of enamel are as follows : Coal-tar Pitch. Hard. 1 Soft. Specific gravity at 77F I 24. I 2 ^ Color of powder Black Black. Melting-point i6iF i4oF Bitumen soluble in CS 2 04 . I % 92 2% Mineral matter I i Free carbon etc ^ 8 77 Bitumen soluble in 88 naphtha. . This is per cent, of total bitumen Residual coke. . 85 o 9 -3 87.0 94.4 25.1 The characteristics of the most select grade of stearine pitch, Calabrea pitch, and of the resins sometimes included in black varnishes are as follows: CALABRIA PITCH. Specific gravity at 77 F. Color of powder Melting-point Bitumen soluble in CS 2 . . Mineral matter . . Bitumen soluble in 88 naphtha This is per cent, of total bitumen Residual coke Characteristics of asphaltenes insoluble in 88 naphtha. Color Condition .... Residual coke 1.030 Black. i6iF. 99-5% 5 IOO . O 41.3 41-5 Black. Spongy melts. 21.8% ANALYSIS OF BITUMINOUS PAINTS. 85 Resins. Colophony. Kauri. Copal. Soluble in 88 naphtha 1 00% 4. 0% 25 0% Residual coke Trace Trace Trace There is no established custom followed in the selection of the other materials which are combined witn hard asphaltum in the preparation of the base of a varnish. Such materials include rosin, fossil gums, linseed oil, China wood-oil, mineral oil, driers, and other substances. The purpose of the use of such materials is to modify the degree of hardness and flexibility, facilitate the thinning operation and increase durability according to the service the finished varnish is to perform. A coal-tar enamel is usually nothing more than a coal-tar pitch dissolved in coal-tar spirit. It may sometimes contain rosin or a small amount of linseed oil, but that is unusual. It is not customary to mix coal-tar pitch and asphaltum for a varnish base as the two materials do not combine readily and, if com- bined, are furthermore generally but partially soluble in petro- leum spirit, the least costly solvent employed in this industry. A practical test should always be made by applying a coat of the varnish or enamel on a surface similar to that upon which it is to be used and the covering or hiding capacity, spreading qualities, time of drying, etc., noted. An outdoor exposure test on a small steel plate of the materials intended for such use should also be made. The first step in the analysis of bituminous varnishes and enamels should be to separate the volatile thinners from the base, and this is most conveniently done by distilling about 50 grams in a flask by gentle heat. A nonoxidizing atmosphere should be maintained in the flask during the distillation by the intro- duction of CO, or other inert gas. The difference in the boiling- point of the solvent and the base is so great that a clean separa- tion may be readily made by this method. The temperature at which the volatile thinners pass over should be noted and a subsequent examination of the distillate for volume, specific gravity, flash-point, and indifference to strong 86 ANALYSIS OF PAINTS AND PAINTING MATERIALS. sulphuric acid will give sufficient data for the identification of the same and the amount present. While the base in the distilling flask is still fluid it should be poured into a shallow tin box. The portion adhering to the flask may be removed with carbon disulphide, the solvent expelled, and the residue combined with the chief portion. This precaution, however, need not be observed unless a pigment is present. The amount of pigment may be determined by treating 10 to 50 grams of the base with 100 c.c. carbon disulphide in a small Erlenmeyer flask and filtering through a Gooch crucible, washing with the same sovlent, or by extracting with carbon disulphide in a Soxhlet. Having separated the pigment as above and recovered the soluble portion by evaporating off the solvent, the analysis should proceed exactly as in the case of a clear asphaltum var- nish base. From i to 5 grams of the base, in a finely divided condition, should be treated in an Erlenmeyer flask with 100 to 200 c.c. 88 naphtha and allowed to stand over night at laboratory temperature. The naphtha is then decanted through a Gooch or filter-paper, the residue transferred to the filter and washed with the solvent until the filtrate runs through clear. The filtrate will contain the rosin drying and petroleum oils and a portion of the asphaltum or pitch if any is present. The insoluble residue will consist essentially of the so-called asphaltenes of the asphaltum, and will generally represent from 30 to 85 per cent, of the amount of asphaltum in the base, depending upon what variety of the same has been employed. In the case of Grahamite, it would represent practically all of the asphaltum present, but that material is not in general use in varnishes. The color and hardness of the insoluble residue should be noted and a determination of residual coke or fixed carbon made as follows: One gram of residue is ignited in a platinum crucible, as in the proximate analysis of coal, Jour. Amer. Chem. Soc., Vol. 21, p. 1116, 1899. If the residue is dark brown and soft and has a fixed carbon of about 50 per cent, the asphaltum is probably an oil pitch. ANALYSIS OF BITUMINOUS PAINTS. 87 If it is black and hard and has a fixed carbon of about 50 per cent, it is probably grahamite. If black and hard and about 15 per cent, fixed carbon it is gilsonite. If dark brown and soft and about 30 per cent, fixed carbon it is probably Bermudez asphalt. The filtrate after expelling the solvent used in the extraction may be tested for saponification and iodine values and for rosin by the Lieberman or Storch test. If a quantitative separation of rosin is desired the laborious Twitchell method must be re- sorted to. The difference between the saponifiable and the total soluble in 88 naphtha will give the mineral oils and so-called petrolenes of the asphaltum. A positive test for and approximate determination of coal-tar may be made by distilling a small amount of the base in a glass retort to coke, and mixing 4 c.c. of the distillate thus obtained with 6 c.c. dimethyl sulphate in a graduated tube. Coal-tar distillates are entirely soluble in dimethyl sulphate, while those from asphaltum, petroleum, and vegetable paint oils and resins are insoluble. See Jour. Ind. and Eng. Chem., Vol. II, p. 186, May, 1910. The pigment separated from asphaltum enamels may be examined in detail if desired by the same methods employed in the analysis of linseed oil and house paint. The combinations in use by various manufacturers in the making of black varnishes are frequently very complicated. Baking enamels for certain specific uses require speicia formulae, but for the general line of black varnishes the princpall object is to produce a base of high gloss and deep color, having some flexibility, which will reduce with turpentine or benzine at a temperature sufficiently low to avoid excessive loss of solvent in the manufacturing process. To this end it is usually sufficient to fuse an asphaltum of the gilsonite type with rosin, linseed, or mineral oil in sufficient amount to reduce the melting-point of the asphaltum without rendering it unduly soft. The durability of the film of varnish is affected by the fluxing material used as well as its degree of hardness and flexibility, and the desire to produce a cheap varnish frequently overbalances the desire to produce a durable one. 88 ANALYSIS OF PAINTS AND PAINTING MATERIALS. The base of a varnish for outdoor exposure to sunlight and atmospheric conditions should be of a different character both in degree of hardness and composition from varnishes intended for damp-proofing, insulating, and acid, and alkali resisting purposes. There is nothing to be gained by the use of turpentine and other expensive solvents instead of benzine or heavy petroleum spirit, provided the base is entirely soluble in the latter and a proper selection has been made to assure the drying properties desired. Varnish makers' benzine (62B.) evaporates too fast to be satisfactory as the thinning material of a heavy brush varnish. On the other hand, it is indispensable in thin quick- drying brush varnishes and dips. On account of the extremely complex nature of black varnish bases it is quite impossible to prescribe a general method which may be followed without modification and cover all features of this subject. The foregoing is, therefore, given more as an outline for the guidance of those analysts who are capable of adapting the general schemes of classification and separation to the particular purpose at hand, and supplementing the same with such further tests as will develop the special features of the material if the simple separations, etc., specifically mentioned are not sufficient . APPENDIX B. The following specifications of the Army and Navy Depart- ments are given so that the chemist engaged in the examination of such materials may become better acquainted with the requirements. These specifications, however, refer only to the chemical requirements, and for full specifications the reader is referred to the Bureau of Supplies and Accounts of the United States Navy, Washington, D. C. SPECIFICATIONS ISSUED BY THE ARMY DEPARTMENT. Pure White Lead. White lead must be of the best quality, finely ground in pure well-settled raw linseed oil; must be of maximum whiteness; must work freely under the brush, and not be crystalline in structure nor deficient in density and opacity. Dry pigment must contain at least 98 per cent, of hydrate carbonate of lead. Its workings under the brush, maximum whiteness, body, and covering qualities to be determined by practical test. White Zinc. American Process. The dry pigment must contain at least 98 per cent, of oxide of zinc, not more than 0.5 per cent, of sulphur in any form, and be of the quality known as "XX." French Process. The dry pigment must contain at least 99 per cent, of oxide of zinc and not more than 0.25 per cent, of sulphur in any form, and to be of maximum whiteness as compared with standard sample. Venetian Red. The dry pigment must contain at least 40 per cent, of sesquioxide of iron, not more than 15 per cent, of silica, the balance to consist of sulphate of lime that has been fully dehydrated by dead burning and rendered incapable of taking up water of crystallization. Indian Red. Must be of good rich color. The dry pigment must contain at least 95 per cent, of oxide of iron (Fe 2 O 3 ), and QO ANALYSIS OF PAINTS AND PAINTING MATERIALS. be free from sulphur and alkali. Pale shade is desired in the absence of other specifications. Vermilion. American (dry). Must be of good, bright color, and contain at least 98 per cent, of basic chromate of lead, and be free from any foreign coloring matters. English (dry). Must contain at least 99 per cent, of red sulphide of mercury; must be free from any foreign coloring matters or alkali in any form. Artificial. The dry pigment must be the lead-barium lake of the azo dye known commercially as " Lithol." Raw and Burnt Sienna. The dry pigment must be equal in quality to the best selected Italian sienna, and must not contain more than 5 per cent, of lime in any form. Yellow Chromes. Must be of good bright color and full strength. The dry pigment must contain at least 98 per cent, of normal chromate or basic chromate of lead. Yellow Ochre. It must be equal in color and quality to the best French ochre and be free from any chromate of lead or foreign coloring matter. The dry pigment must contain at least 20 per cent, of oxide of iron and not more than 5 per cent, of lime in any form. Chrome Green. Chrome green must be of good bright color. The dry pigment must contain 25 per cent, chrome green made by mixture of pure chrome yellow and Russian blue and 75 per cent, barium sulphate. Medium shade is desired in absence of other specifications. Drop Black. Drop black must be of good deep luster and consist of calcined bone-black only. The addition of blue or gas carbon-black will be ground for rejection. The paste must contain not less than 45 per cent, of pure pigment. Oil Lamp-black for Tinting Purposes. The pigment must be the perfectly calcined product of oils only and show less than 2 per cent, of ash. It must be absolutely neutral, free from oil or greasy matter, grit, and all impurities. The pigment reduced in white must give a clear blue-gray tone or tint. Japan Drier. Japan drier must not flash below 103 F. (open tester) ; must be of the best quality and made from pure kauri gum, pure linseed oil, pure turpentine and the proper driers only; must set to touch in from one-fourth to one hour, dry elastic in from eighteen to twenty-four hours at a temperature PAINT SPECIFICATIONS. 9 1 of 70 F., and must not rub up or powder under friction by the ringer. When mixed with pure raw linseed oil in the proportion of eight parts of oil to one part of drier must remain clear for two hours and set to touch in from six to seven hours at a temperature of 70 F. Varnish. All varnishes other than those which have definite specifications must be pure turpentine hard-gum varnishes and absolutely free from rosin or any turpentine substitutes. Damar Varnish. It must be made from solution of the very best quality of damar gum; such solution to contain at least 50 per cent, of gum with 45 per cent, turpentine. It must be digested cold and well settled. It must be as clear as and not darker than the standard sample. It must be free from benzine, rosin, and lime or other mineral matter. Its specific gravity at 60 F. must be between .935 and .937 and its flash point between 105 and 115 F. It must set to touch in not more than twenty minutes, and when mixed with pure zinc oxide must show a smooth glossy surface equal to that shown by the standard sample. Tests. Besides chemical tests to determine the above quali- ties and practical tests to determine its qualities of finish, a board properly coated with a mixture of zinc and the liquid will be exposed to the weather for a period of one month, and at the end of this time must have stood such exposure equally as well as the standard sample. A similarly prepared sample will also be baked at 250 F., and must not at this temperature show any greater signs of cracking, blistering, or any other defects than standard samples under the same conditions. Asphaltum Varnish. Asphaltum varnish must be made of pure high-grade asphaltum of the very best quality, of pure linseed oil and pure turpentine dryers only, and must not con- tain less than 20 gallons of prepared linseed oil to 100 gallons of varnish. It must not flash below 103 F. (open tester). It must mix freely with raw linseed oil in all proportions; must be clear and free from sediment, resin, and naphtha. When flowed on glass and allowed to drain in a vertical position the film must be perfectly smooth and of full body, and must equal in this last respect the standard sample. It must set to touch in from one and one-half to two and one-half hours and must dry hard in less than twenty hours at 70 F. When dry and 92 ANALYSIS OF PAINTS AND PAINTING MATERIALS. hard it must not rub up or powder under friction by the finger. The application of heat must quicken the time of drying and give a harder film. SPECIFICATIONS ISSUED BY THE NAVY DEPARTMENT. White Lead in Oil. The dry pigment must be of the best quality, must not be crystalline in structure or deficient in density or opacity. Unless otherwise specified, white lead will be delivered in paste form, the pigment finely ground in pure raw linseed oil, and in paste form must not contain more than 0.5 per cent, of moisture. The dry pigment must be a pure hydrated carbonate of lead, free from all adulterants, and equal in quality to the best commercial grades. The total acetate must not be in excess of the equivalent of 0.15 per cent, of absolute acetic acid. Specifications for Whiting. The material must be free from grit; must contain not more than i .5 per cent, of matter insoluble in dilute hydrochloric acid, and not more than 4/10 per cent, oxides of iron and aluminum (determined together). Specifications for Chrome Green. The dry pigment must be of a good bright color and must contain at least 98 per cent, by weight of pure lemon chrome and Chinese blue, which mix- ture must not contain more than 10 per cent, by weight of lead sulphate and rnust be equal in all respects to the standard sample. A medium shade is desired in the absence of other specifications. Metallic Brown. i. The dry pigment must contain not less than 45 per cent., by weight, of oxide of iron and must not contain more sulphur in combination than the equivalent of 2 per cent., by weight, of sulphur trioxide (SO 3 ). 2. It must be ground perfectly pure, not made from or adulterated with the by-products of sulphuric acid works, and must be free from makeweights or adulterants. When in paste form, it must contain at least 20 per cent., by weight, of pure raw linseed oil. Chinese Blue. i. The dry pigment must contain not less than 98 per cent., by weight, pure coloring matter of the best quality, free from adulterants, and equal in every respect to the standard sample. PAINT SPECIFICATIONS. 93 2. When in paste form, the paste must contain not less than 50 per cent, by weight of pure pigment ground in absolutely pure, well-settled, and perfectly clear raw linseed oil of the best quality only to a medium stiff consistency, which will break up readily in thinning, and must be free from grit, adulterants, and all impurities. Red Lead, Dry. The dry pigment must be of the best quality, free from all adulterants, and contain at least 94 per cent, of true red lead( p ^) equivalent to 32.8 per cent, of lead peroxide ( Pb ) , the balance to be practically pure lead monoxide (PbO). It must contain less than o.i per cent, of metallic lead, and to be of such fineness that not more than 0.5 per cent, remains after washing with water through a No. 21 silk bolting cloth sieve. It must be of good bright color and be equal to the standard sample in freedom from vitrified particles and in other respects. Chrome Yellow (Medium Orange). i. The dry pigment must be of good bright color and full strength, and must contain at least 98 per cent, by weight of normal chromate or basic chro- mate of lead. 2. The pigment must be of the best quality, finely ground in absolutely pure, well-settled, and perfectly clear raw linseed oil of the best quality only to a medium stiff paste, which will break up readily in thinning, and must be free from grit, adulterants, and all impurities. Specifications for Spar Varnish. i. To be of the best quality and manufacture and equal in all respects, including body, covering properties, gloss, finish, and durability, to the standard sample in the general storekeepers' offices at the various navy yards. To be made exclusively from the best grade of hard- varnish resins, pure linseed oil, pure turpentine, and lead- manganese driers, and to be free from all adulterants or other foreign materials. 2. The varnish must not flash below 105 F. (open tester), and when flowed on glass must set to touch in from six to twelve hours and dry hard in from thirty to forty-eight hours at a temperature of 70 F. To be as clear as and not darker than the standard sample, and to be equal to it in all respects as above specified. Interior Varnish. i. To be of the best quality and manu- 94 ANALYSIS OF PAINTS AND PAINTING MATERIALS. facture and equal in all respects, including body, covering properties, gloss, finish, and durability, to the standard sample in the general storekeepers' offices at the various navy yards; to be made exclusively from the best grade of hard-varnish resins, pure linseed oil, pure spirits of turpentine, and lead-manganese driers, and to be free from all adulterants or other foreign materials. 2. The varnish must not flash below 105 F. (open tester), set to touch in from six to eight hours and dry hard within twenty-four hours in a temperature of 70 F. It must stand rubbing with pumice-stone and water in thirty-six hours without sweating, and must polish in seventy-two hours with rottenstone and water; to be as clear as and not darker than the standard sample and to be equal to it in all respects, as above specified. Japan Drier. i. Japan drier must not flash below 105 F. (open tester) ; must be of the best quality, light in color, and be made from pure kauri resin, pure linseed oil, pure spirits of turpentine, and lead-manganese driers, and be free from adulter- ants, foreign material, sediment, and suspended matter. When flowed on a glass plate and allowed to drain in a vertical position the material must not come off when touched lightly with the finger after from fifteen to sixty minutes, and must dry elastic in not less than eight hours nor more than twenty-four hours at a temperature of 70 F., and must not rub up or powder under friction by the finger at the end of this time. When mixed with pure raw linseed oil (that will not break under 600 F.) in the proportion of eight parts of oil to one part of drier the mixture must remain clear for at least two hours, and when flowed on a glass plate must not come off when touched lightly with the finger at the end of eight hours at a temperature of about 70 F. Raw Linseed Oil. Must be absolutely pure well-settled linseed oil of the best quality; must be perfectly clear and not show a loss of over 2 per cent, when heated to 212 F., or show any deposit of foots after being heated to that temperature. The specific gravity must be between 0.932 and 0.937 at 60 F. To be purchased by the commercial gallon; to be inspected by weight, and the number of gallons to be determined at the rate of 7 1/2 pounds of oil to the gallon. Boiled Linseed Oil. Must be absolutely pure kettle-boiled oil of the best quality, and the film left after flowing the oil over PAINT SPECIFICATIONS. 95 glass and allowing it to drain in a vertical position must dry free from tackiness in twelve hours at a temperature of 70 F. It must contain no resin. The specific gravity must be between o . 934 and o . 940 at 60 F. To be purchased by the commercial gallon; to be inspected by weight, and the number of gallons to be determined at the rate of 7 1/2 pounds of oil to the gallon. Spirits of Turpentine. i. The turpentine must be the prop- erly prepared distillate of the resinous exudation of the proper kinds of live pine or live pitch pine, unmixed with any other substance; it must be pure, sweet, clear, and white, and must have characteristic odor. 2. A single drop allowed to fall on white paper must com- pletely evaporate at a temperature of 70 F. without leaving a stain. 3. The specific gravity must not be less than 0.862 or greater than 0.872 at a temperature of 60 F. 4. When subjected to distillation, not less than 95 per cent, of the liquid should pass over between the temperature of 308 F. and 330 F., and the residue should show nothing but the heavier ingredients of pure spirits of turpentine. If at the begin- ning of the operation it shows a distillation point lower than 305 F., this will constitute a cause for rejection. 5. A definite quantity of the turpentine is to be put in an open dish to evaporate, and the temperature of the dish will be maintained at 212 F. ; if a residue greater than 2 per cent, of the quantity remains on the dish it will constitute a cause for rejection. 6. Flash Tests. An open tester is to be filled within 1/4 inch of its rim with the turpentine, which may be drawn at will from any one can of the lot offered under 'the proposal. The tester thus filled will be floated on water contained in a metal receptacle. The temperature of the water will be gradually and steadily raised from its normal temperature of about 60 F. by applying a gas or spirit flame under the receptacle. The tem- perature of the water is to be increased at the uniform rate of 2 F. per minute. The taper should consist of a fine linen or cotton twine (which burns with a steady flame), unsaturated with any substance. When lighted it is to be used at every increase of i temperature, beginning at 100 F. It is to be drawn horizon- 96 ANALYSIS OF PAINTS AND PAINTING MATERIALS. tally over the surface of the turpentine and on a level with the rim of the tester. The temperature will be determined by plac- ing a thermometer in the turpentine contained in the tester so that the bulb will be wholly immersed in the liquid. The turpentine must not flash below 105 F. 7. Sulphuric Acid Test. Into a 30 cubic centimeter tube, graduated to tenths, put 6 cubic centimeters of the spirits of turpentine to be examined. Hold the tube under the spigot and then slowly fill it nearly to the top of the graduation with con- centrated oil of vitriol. Allow the whole mass to become cool and then cork the tube and mix by shaking the tube well, cooling with water during the operation if necessary. Set the tube ver- tical and allow it to stand at the ordinary temperature of the room and not less than half an hour. The amount of clear layer above the mass shows whether the material passes test or not. If more than 6 per cent, of the material remains undissolved in the acid this will constitute a cause for rejection. INDEX. Acetic acid, in white lead, 4 Thompson's method, 4 navy method, 5 Acid number, linseed oil, 52 Aluminium, determination i n mixed pigments, 41 separation from iron, 41-34 separation from chromium, 3 7 American vermilion, analysis of, 35 Antwerp blue, analysis of, 33 commercial method, 34 Asbestine, analysis of, 23 Asphaltene, determination of, 79-86 Asphaltic compounds, distinction from coal-tar compounds, 87 paints, analysis of, 78 Asphaltum varnish, specincations, army, 91 B Barium sulphate, determination of, 2 I in barytes, 2 1 in blanc fixe, 2 1 in lithopone, 20 in mixed paints, 41, 44, 46 Barytes, analysis of, 21 Basic carbonate white lead, anal- ysis of, 3 sulphate white lead, analysis of, 17 Benzine, analysis of, 64 Bituminous paints, analysis of, 78 Black pigments, analysis of, 38 Blanc fixe, analysis of, 2 1 Blue pigments, analysis of, 32 Calcium, determination of, 22 as oxalate, 22 volumetric method, 23 carbonate, analysis of, 22 sulphate, analysis of, 22 Thompson's method, 45 Carbon dioxide, determination of, 4 De Horvath method, 1 5 Scheibler's method, 6 China clay, analysis of, 23 Chinese blue, analysis of, 33 commercial method, 34 specifications, navy, 92 wood oil, examination of, 61 Chromium, determination of,3 5, 3 7 as oxide, 35 separation from aluminum, 3 7 separation from iron, 37 Chromes, specifications, army, 90 Chrome green, analysis of, 36 specifications, army, 36 yellow, analysis of, 3 5 specifications, navy, 92, 93 Coal-tar compounds, distinction from asphaltic compounds, 87 Damar varnish, specifications, army, 91 Dietrich Tables, 9 Driers, japan, analysis of, 65 Drop black, analysis of, 3 8 specifications, army, 90 Eschka's method, sulphur, 80 97 IDNEX. Ferrocyanide solution, standard for volumetric zinc, 2 Flash-point, linseed oil, 50 Foots, linseed oil, 50 Graphite, analysis of, 38 Green pigments, analysis of, 36 Gypsum, analysis of, 22 H Hexabromide test, linseed oil, 53 Hughes' method, sublimed white lead, 17 Indian red, analysis of, 26 specifications, army, 89 Interior varnish, specifications, navy, 93 Iodine values, linseed oil, 52 mixed oils, 60 Iron, determination of, 27, 41 as oxide, 41 in mixed paints, 4 1 in oxides, 27 separation from aluminum, 4i, 34 from chromium, 37 volumetric, bichromate method, 25 permanganate method, 27 J Japan, analysis of, 65 Mcllhiney's method, 67 driers, analysis of, 65 specifications, army, 90 L Lamp-black, analysis of, 38 specifications, army, 90 Lead, as chromate, 4 as sulphate, 3 volumetric method, 6 in mixed paints, 41, 43, 44, 47 impurities in metallic lead, 16 Lead chromate, analysis of, 35 dioxide, determination, volu- metric method, 28 sulphite, determination, Thompson's method, 47 Leaded zinc, analysis of, 18 Lemon chrome, analysis of, 35 Light petroleum oils, analysis of, 64 Linseed oil, analysis of, 49 boiled, specifications, navy, 94 flash-point, 50 foots, 50 iodine values, 52 raw, specifications, navy, 94 M Magnesium, determination as pyro- phosphate, 24 Mannhardt's method, ochers, siennas, umbers, 25 Maumene test, 55 Mcllhiney's method, for Japan, 67 for shellac, 7 1 for varnish, 67 Mercury, gravimetric methods, 30 Metallic brown, analysis of, 2 6 specifications, navy, 92 Mineral black, analysis of, 38 Mixed paints and pigments, analy- sis of, 40 Thompson's methods, 43 Mixed colored paints and pig- ments, analysis of, 47 Navy specifications, 92 O Ocher, analysis of, 2 5 specifications, army, 90 Oil lamp-black, specifications, army, 90 Orange chrome, analysis of, 35 mineral, analysis of, 28 pigments, analysis of, 35 INDEX. 99 Organic colors in pigments, exam- ination of , 3 1 Paint vehicle, analysis of, 48 separation from pigment, 40, 48 Paris white, analysis of, 22 Petrolene, determination of, 78 Petroleum oils, analysis of, 64 Prussian blue, analysis of, 33 commercial method, 33 Red lead, analysis of, 28 specifications, navy, 93 pigments, analysis of, 28 Rosin, 53 in linseed oil, 53, 58 oil, determination of, 53 Lewkowitsch's method, 58 gravimetric method, 59 volumetric method, 58 as an adulterant, 7 1 Saponification number, linseed oil, 52 Separation vehicle from pigment, 40, 48 Shellac, analysis of, 7 1 Mcllhiney's method, 71 Sienna, analysis of, 25 specifications, army, 90 Silex, analysis of, 23 Silica, analysis of, 23 in mixed paints, 46 Sodium, determination of, 24 as chloride, 2 5 as sulphate, 25 separation from potassium, 2 5 Soluble sulphates, in barytes and blanc fixe, 22 Solvent, for extraction of vehicle from pigment, 40 Soya bean oil, examination of, 59 Spar varnish, specifications, navy, 93 Specifications, army, 89 navy, 92 Spirits of turpentine, analysis of, 62 specifications, navy, 95 Sublimed white lead, complete analysis, 17 Sulphates, in barytes and blanc fixe, 22 in sublimed white lead, 1 7 Sulphur, Eschka's method, in as- phaltic and bituminous compounds, 80 in ultramarine blue, 33 Sulphur dioxide, in sublimed white lead, 1 8 Turpentine, spirits of, analysis of, 6-1 specifications, navy, 95 Ultramarine blue, average com position, 33 Varnish, analysis of, 65 damar, specifications, army, 9i interior, specifications, navy, 93 Mcllhiney's method, 67 spar, specifications, navy, 93 specifications, army, 91 Vehicle, analysis of, 48 separation from pigment, 40, 48 Venetian red, analysis of, 26 specifications, army, 89 Vermilion, analysis of, 29 specifications, army, 90 Viscosity, linseed oil, 49 W Water, in vehicle, Nemzek method, 48 100 INDEX. White lead, analysis of, 3 Zinc, as oxide, i specifications, army, 89 volumetric method, i navy, 92 in mixed paints, 42 White pigments, analysis of, i Zinc chromate, analysis of, 3 5 Whiting, analysis of, 2 2 lead, analysis of, 1 8 specifications, navy, 92 oxide, analysis of, i specifications, army, 89 sulphide, in lithopone, 20 Zinc, determination of, r 14 DAY USE RETURN TO DESK FROM WHICH BORROWED LOAN DEPT. This book is due on the last date stamped below, or on the date to which renewed. Renewed books are subject to immediate recall. General Library University of California Berkeley LD 21A-50m-4,'59 (A1724slO)476B U,C. BERKELEY LIBRARIES UNIVERSITY OF CALIFORNIA LIBRARY