LIBRARY UNIVERSITY OF CALIFORNIA. Class ! ANALYSIS OF MIXED PAINTS, COLOR PIGMENTS, AND VARNISHES BY CLIFFORD DYER HOLLEY, M.S., PH.D., Professor of Industrial Chemistry, North Dakota Agricultural College, and Chemist on the Staff of the North Dakota Experiment Station. Joint Author of Paint and Paint Products ; and Paints and Their Composition. Formerly Chemist for the D. B. Hand Company, Scranton, Pennsylvania AND E. F. LADD, B.S. Professor of Chemistry, North Dakota Agricultural College, State Chemist and Food Commissioner for North Dakota FIRST EDITION FIRST THOUSAND NEW YORK JOHN WILEY & SONS LONDON : CHAPMAN & HALL, LIMITED 1908 VX^ OF THE \ UNIVERSITY ) OF / T? GENERAL /h*t COPYRIGHT, 1908, BY C. D. HOLLEY AND E. P. LADD Stanhope ipresa F. H. GIUSON COMPANY BOSTON. U.S.A. PREFACE. THIS book was written primarily to meet the needs of the author's own classes in Industrial Quantitative Analy- sis, and it is given to the public in the belief that there is a demand for a concise work on the analysis of paints and paint products. Numerous books have been written during the past few years dealing with the subject of Paints, discussing in a general way the properties of the various pigments and their methods of manufacture. But the author is not acquainted with a single work that will serve as a guide to a chemist of ordinary training in taking a can of mixed paint, of practically any shade or tint, making a complete analysis of it and furnishing him sufficient data, derived from a large number of analyses, so that he may interpret the results of his own analysis in a rational manner. It is the object of the author as far as may be to fill this much felt want, and the methods given in the following pages should be of interest to advanced college students who may wish to inform themselves on methods of paint analysis; to the industrial chemist who has more or less paint work to do ; and especially to the young paint chemist who is just starting out in his career. Each method given in this work has been tested out in the author's laboratory and its working value thoroughly demonstrated. The various analyses given are believed to be representative of the composition of the pigments they illustrate, and it is hoped that they will be of service in enabling the analyst to pass on paint products with fairness to both the manufacturer and the consumer. The iii iv PREFACE. chapters on varnish analysis are admittedly incomplete. Our present literature on varnish, and especially varnish analysis, is meagre, and much of it of a contradictory nature, but the author hopes in the near future to be able to present data that will be of further value to varnish chemists. In conclusion the author wishes to express his sincere thanks to Commissioner E. F. Ladd for the portion con- tributed by him, and for his kindly guidance and interest in the entire work; and also to Mr. Clarence E. Kinney, who has assisted in much of the analytical work. C. D. HOLLEY. FARGO, N.D. Feb. 19, 1907. TABLE OF CONTENTS. PART I. CHAPTEB. PAGE I. READY MIXED PAINTS 1 Why Paints Fail; North Dakota Paint Law; Groups of Pigments; Sublimed Lead; Lithopone; Leaded Zinc; Zinc Lead White; Form of Label; Labels that Mislead ; Need of Paint Law ; Water in Paint ; Imitation White Leads; Paints supposed to be White Lead and Zinc; Whitewash; Short Measure and Weights; Relation of Lead to Zinc. PART II. I. ANALYSIS OF MIXED PAINTS 29 1. Preparation of Sample; 2. Separation of the Vehicle from the Pigment; 3. Ratio of Pigment to Vehicle; 4. Typical Analyses of White and Gray Paints; 5. Composition of Colored Paints; 6. Reds; 7. Blues; 8. Yellows; 9. Greens; 10. Browns; 11. Greys and Grays. II. ANALYSIS OF THE VEHICLE 36 12. Water, Occurrence; 13. Detection; 14. Estima- tion; 15. Linseed Oil, Extraction from Paint; 16. Estimation of the Volatile Oils; 17. Specific Grav- ity; 18. Spot Test; 19. Mineral Oils; 20. Separa- tion of Mineral Oil from Rosin Oil; 21. Cotton- seed Oil; 22. Corn Oil; 23. Fish Oil; 24. Rosin and Rosin Oils ; 26. Linseed Oil from Inferior Seed ; 28. Specifications for Boiled Linseed Oil, Navy Department, 1905. III. ANALYSIS OF THE VOLATILE OILS 48 29. Analysis of the Volatile Oils, Identification; 30. Estimation of Petroleum Products; 33. Analyses of Volatile Oils; 34. Excessive Use of Volatile Oils. vi CONTENTS. CHAPTER. PAGE. IV. SPECIAL METHODS ON OIL ANALYSIS 54 35. Determination of the Iodine Number; 36. Prep- aration of Reagents; 37. Determination; 38. Iodine Numbers of Various Oils; 39. Determina- tion of the Bromine Absorption of Oils; 40. Table of Bromine Values of Various Oils; 41. Estima- tion of Rosin in Mixtures of Linseed Oil and Min- eral Oil; 42. Volumetrically ; 43. Gravimetrically; 44. Determination of Free Fatty Acids in Linseed Oil; 45. Determination of the Saponification Value; 46. Determination of the Flash Point of Linseed Oil; 49. Evaporation Test; 50. Determination of Flash Point and Fire Test of Petroleum Products; 51. Covered Testers; 52. Open Testers; 53. Fire Test; 54. Specifications for Various Oils; 55. Lin- seed Oil; 56. Deodorized Benzine; 57. Engine Oil; 58. High Pressure Cylinder Oil; 59. Lithographic Varnish; 60. Kerosene Oil; 61. Lard Oil; 62. Sperm Oil; 63. Gasoline. V. ANALYSIS OF WHITE LEAD 69 64. Color; 65 Lead Acetate; 66. Opacity; 67. Painting Test; 68. Sandy Lead; 69. Foreign Pig- ments; 70. Estimation of Carbon Dioxide, Knorr's Apparatus; 72. Scheibler's Apparatus; 75. Typi- cal Analyses of White Leads ; 76. Determination of Acetic Acid in White Lead; 78. Analyses of Mis- cellaneous White Leads; 79. Short Weights of White Lead Packages. VI. ANALYSIS OF SUBLIMED LEAD, ZINC OXIDES, AND ZINC- LEAD PIGMENTS 81 Analysis of Sublimed Lead; 80. Lead and Zinc Oxide; 81. Sulphates; 82. Sulphur Dioxide; 83. Compo- sition of Sublimed Lead; 84. Identification and Estimation of Sublimed Lead in Mixtures ; 85. Analysis of Zinc Oxides, Leaded Zincs, and Zinc- Lead Whites; 86. Moisture; 87. Sulphur Dioxide; 88. Zinc Sulphate; 89. Insoluble Matter; 90. Lead; 91. Sulphuric Acid; 92. Zinc Oxide; 93. Calculations; 94. Classification: (1) Green Seal and Florence Red Zinc Oxides; (2) New Jersey Zinc Oxides; (3) Mineral Point Zincs; (4) Leaded Zincs; CONTENTS. Vil CHAPTER. PAGE. VI. ANALYSIS OF SUBLIMED LEAD, ZINC OXIDES, AND ZINC- LEAD PIGMENTS Continued. (5) Zinc-Lead White; 95. Estimation of Arsenic and Antimony in Zinc-Lead Whites; 98. Anti- mony. VII. ANALYSIS OF ZINC SULPHIDE WHITES AND INERT PIG- MENTS 92 Analysis of Lithopone, Ponolith, etc.; 99. Moisture; 100. Barium Sulphate ; 101. Total Zinc; 102. Zinc Sulphide; 103. Zinc Oxide; 104. Calcium; 105. An- alyses of Zinc Sulphide Whites; Analysis of White Mineral Primer, White Ochre, Magnesite, Whiting, Paris White, English Cliffstone, etc. ; 106. Moisture ; 107. Silica; 108. Alumina andiron; 109. Calcium; 110. Magnesium; 111. Calcium and Magnesium Oxides; 113. Analyses of Calcium and Magnesium Carbonate Pigments; 114. Analyses of Agalite, Terra Alba, etc.; 115. Analyses of Calcium Sul- phate Pigments; Analysis of Silicas, Clays and other Insoluble Pigments; 117. Fusion with So- dium Carbonate. 119. Moisture; 120. Combined Water; 121. Determination of the Alkali Metals, Sodium and Potassium; 122. Analyses of Silicas and Silicates; 123. Specifications for Paste Wood Filler. VIII. DETERMINATION OF FINENESS, COVERING POWER AND TINTING STRENGTH OF PIGMENTS 102 124. Determination of the Comparative Fineness of Pigments; 125. Comparison of Paints for Covering Power; 127. Determination of the Tinting Strength of Colors; 128. Chrome Yellows, Ochres, and Greens; 129. Reds; 130. Blues and Blacks; 131. Paste Goods ; 135. Gravity and Volume of Pigments. IX. THE PRACTICAL TESTING OUT OF PAINTS 107 136. Paints should be Tested out by the Chemist; 137. Equipment; 139. Requisites for a Good Paint ; 140. Relation of the Surface to the Paint; 141. Test Structures; 143. Application of the Priming Coat ; 147. Oil Reductions; 150. Turpentine Reductions; 157. Application of the Middle Coat; 160. Applica- tion of Third Coat; 161. Application of Paste Leads and Paste Paints; 162. Driers. viii CONTENTS. CHAPTER PAGE. X. ANALYSIS OF WHITE PAINTS 119 164. Qualitative Analysis of White Paints; 166. Quantitative Analysis of White Paints. Total Lead ; 167. Calcium; 168. Magnesium; 169. Zinc Oxide; 170. Lead Sulphate ; 171 . Basic Carbonate of Lead ; 172. Insoluble Residue; 173. Barium Sulphate; 174. Silica; 175. Alumina; 176. Calcium and Mag- nesium Oxides; 177. Mixed Carbonates and Sul- phates; 178. Calculations; 179. Typical Analyses of Mixed Paints; 181. Calculation of Approxi- mate Cost of Mixed Paints; 182. Analyses of Sub- limed Lead Paints; 183. Analyses of Leaded Zinc Paints; 184. Analyses of Mixed Paints for Inside Use; 185. Analyses of Cheapened Mixed Paints; 186. Analyses of White Paints According to Thompson. XI. ANALYSIS OF INDIAN REDS, VENETIAN REDS, TUSCAN REDS, RED OXIDES, AND OCHRES 135 196. Hygroscopic Moisture; 197. Combined Water; 198. Silica and Barium Sulphate; 199. Ferric Ox- ide; 200. Preparation of Reagents; 201. Alumina; 202. Calcium; 203. Magnesium; 204. Analyses of Indian Reds, Red Oxides and Venetian Reds; 207. Analyses of Ochres and Iron Oxide Pigments; 208. Specifications for Venetian Red. XII. ANALYSIS OF BLACK AND BROWN PIGMENTS AND PAINTS. 143 Analysis of Black Pigments; 209. Composition; 210. Moisture; 211. Oils; 212. Ash; 213. Carbon; 214. Calcium; 215. Phosphoric Acid; 216. Preparation of Reagents; 217. Magnesium; 218. Calculations; 219. Specifications for Drop Black; 220. Speci- fications for Carbon Black; 221. Composi- tion of Ivory and Bone ; 222. Analyses of Various Blacks ; Analysis of Mixed Paints Tinted with Black and Oxide of Iron Pigments; 223. Carbon; 224. Ferric Oxide; 225. Alumina; 226. Zinc Oxide; 227. Calcium and Magnesium; 228. Residue Insol- uble in Hydrochloric Acid; 229. Lead Sulphate; 230. Analysis of Paints Tinted with Blacks, Ochre, and Iron Oxides; Vandyke Brown; 231. Composi- tion; 232. Analyses; Analysis of Umbers and CONTENTS. ix CHAPTEB. PAGE. XII. ANALYSIS OF BLACK AND BROWN PIGMENTS AND PAINT Continued. Siennas; 233. Hygroscopic Moisture; 234. Com- bined Water; 235. Silica and Barium Sulphate; 237. Ferric Oxide; 238. Manganese; 241. Alu- mina; 242. Calcium and Magnesium; 243. Analy- sis of Umbers and Siennas; 244. Analysis of Mixed Paints Containing Umbers, Siennas, Ochres and Chrome Yellows. XIII. ANALYSIS OF BLUE PIGMENTS AND PAINTS 159 Analysis of Prussian Blues, Chinese Blues, etc. ; 245. Hygroscopic Moisture; 246. Water of Combination; 247. Iron; 248. Aluminum; 249. Calcium; 250. Alkali Metal and Alkaline Salts; 251. Cyanogen; 252. Barytes, Silica, Clay, etc.; 253. Calculations; 254. Analyses of Pure Prussian Blues; 255. An- alyses of Chinese Blues; 256. Analysis of Mixed Paints Containing Prussian Blue, Chinese Blue, etc. ; Analysis of Ultramarine ; 258. Properties ; 259. Moisture; 260. Silica; 261. Alumina; 262. Sodium Oxide; 263. Total Sulphur; 264. Com- bined Sulphuric Acid ; 265 and 266. Analyses of Ultra- marines by Author and by Hurst ; 267. Analysis of Cobalt Blues; 268. Moisture; 269. Alumina; 270. Calcium and Magnesium ; 271. Cobalt Oxides. XIV. ANALYSIS OP YELLOW, ORANGE AND RED CHROME LEADS. ANALYSIS OF VERMILIONS 166 272. Composition; 273. Moisture; 279. Barytes, Sil- ica and Clay; 275. Lead; 276. Chromium; 277. Calcium; 278. Magnesium; 279. Combined Sul- phuric Acid; 280. Calculations; 281. Analysis of Chrome Leads; Analyses of Mixed Paints Contain- ing Chrome Yellows and Ochres ; 282. Barytes, Sil- ica and Clay; 283. Lead; 284. Iron; 285. Chro- mium; 286. Aluminum; 287. Zinc; 288. Calcium, Magnesium and Combined Sulphuric Acid; Analy- sis of Vermilions; 289. Properties; 290. Detection of Vermilionettes, Para and Alizarine Reds; 291. Barytes, Silica and Clay; 292. Lead; 294. Estima- tion of Lead and Mercury, Calcium Compounds Present; 295. Ferric Oxide; 296. Zinc Oxide; 297. Calcium and Magnesium; 298. Calculations; 299. Analyses of Vermilions; 300. Antimony Vermilion and Orange. X CONTENTS. CHAPTER. PAGE. XV. ANALYSIS OF CHROME GREENS AND EMERALD GREENS. 176 Analysis of Chrome Greens; 301. Moisture; 302. Organic Color; 303. Barytes, Silica, Clay, etc.; 304. Lead; 305. Iron; 306. Chromium; 307. Alu- minum; 308. Calcium and Magnesium; 309. Cyanogen; 310. Combined Sulphuric Acid; 311. Calculations; 312. Analyses of Chrome Greens; Analysis of Emerald Green, Paris Green and Arsenic Insecticides; 313. Properties; 314. Water Soluble Arsenious Oxide ; 315. Total Arsenious Oxide ; 316. Analyses of Paris Green; 317. Moisture; 318. Ani- line Color; 319. Insoluble Residue; 320. Lead Chromate; 321. Copper; 322. Arsenic; 323. Chro- mium and Zinc; 324. Calcium; 325. Magnesium; 326. Acetic Acid; 327. Analyses of a Paris Green. XVI. EXERCISES IN COLOR MAKING 184 329. Para-Nitoraniline Lake; 330. Crimson Red Lake ; 331. Emerald Green; 332. Pale Lemon Chrome; 333. Medium Chrome Yellow; 334. American Ver- milion; 335. Chinese Blue No. 1 ; 336. Chinese Blue No. 2; 337. Chinese Blue No. 3; 338. Brunswick Greens. XVII. ANALYSIS OF JAPANS AND DRIERS 188 340. Determination of the Drying Salts; 341. Lead; 342. Manganese; 343. Zinc; 344. Calculations; 345. Determination of the Volatile Oils; 346. Separation of Benzine and Turpentine; 347. De- tection of Rosin ; 348. Practical Tests. XVIII. ANALYSIS OF SHELLAC AND SPIRIT VARNISHES .... 194 Analysis of Shellac: 351. Detection of Rosin; 352. Estimation of Rosin; 354. Iodine Numbers of Shellacs; Analysis of Shellac Varnish; 355. Com- position; 356. Determination of the Body of Shel- lac Varnishes; 357. Determination of Strength of Alcohol Used; 358. Examination of Solvent; 359. Detection of Benzine; 360. Columbian Spirit and Wood Alcohol; 361. Detection and Estimation of Wood Alcohol in Mixtures with Grain Alcohol; 366. Detection and Estimation of Rosin; 367. Estimation of Rosin, Mannhardt's Method; 368. Practical Test for Brewers' Varnish ; 369. Analysis of Shellac Varnishes; 370. Damar Varnish; 371. Tests. CONTENTS. Xl CHAPTER. PAGE. XIX. ANALYSIS OF OIL VARNISHES 206 374. Specific Gravity; 375. Viscosity; 376. Separa- tion, Identification and Estimation of Volatile Oils; 377. Separation of the Resin Gums from the Oil, Twitchell's Method; 379. Separation of the Gums from the Oil; 380. Short Oil Varnishes; 382. Long Oil Varnishes; 383. Determination of the so-called Insoluble and Soluble Gums; 384. Detection and Estimation of Rosin in Varnishes; 391. Navy Specifications for Interior Varnish; 392. Navy Specifications for Black Asphaltum. XX. THE PRACTICAL TESTING OF VARNISHES 218 394. Smell; 395. Consistency; 396. Working and Flowing; 398. Time of Drying; 399. Sponge Test; 401. Toughness and Elasticity; 404. Hardness; 405. Classification of Varnishes; 406. Floor Varnishes; 407. Interior Varnishes; 409. Exterior Varnishes; 410. Short Volume; 411. Significance of Lime in Varnishes; 412. Table of Analyses; 415. Trade Names of the Principal Paint Pigments with Chem- ical Names; 416. Atomic Weights of the More Common Elements; 417. Factors for Gravimetric Analysis; 418. Measure, Weights and Temperatures. PART I. READY MIXED PAINTS. BY E. F. LADD. xiii ANALYSIS OF MIXED PAINTS. READY MIXED PAINTS. THE rapid increase in the manufacture and consumption of ready mixed paints during the past third of a century has been quite phenomenal. To-day it is claimed that fully 70,000,000 gallons of paints mixed and ready for use are annually consumed in the United States. It is not strange, therefore, where without being placed under legis- lative restraint of any kind, in such a great industry and one so little understood by the general public, that abuses have arisen which will require courage, persistency, and legislative action to correct. It is unfortunate that some of the mixed paints have so little of merit, and how are the public to separate the good from the bad? With competition so fierce as has been the case within the past few years, it is safe to say that paint manufacturers have not, as a rule, produced a paint as good as they knew how to produce, but rather that the best of them were making as good a paint as they could sell in the face of the kind of competition practised. There are many other manufacturers producing paint as cheaply as they can, and with little regard for wearing quality as a first consideration. The writer maintains that a house well painted, primed and two good coats applied, should not require re-painting for protective purposes oftener than once in five to seven years. If every condition is favorable the paint may still be well preserved at the end of ten years. Not a few l 2 ANALYSIS OF MIXED PAINTS. houses as now treated need re-painting at the end of two or three years, and not infrequently the old paint must be burned away before the new can be applied. Something is wrong where this is required, not always the fault of the paints, sometimes the methods of application are faulty; conditions existing at the time of painting may be responsible for the trouble, or the paint previously used may be the source of the difficulty, and even the difference in the expansive properties in the two paints may be a cause for trouble. In average conditions there is no valid reason why paints should ever crack, peel, blister, or pull away from the wood. It not infrequently does one of these, as well as show many other faults, all of which need to be understood and explained. A knowledge of the chemical and physical properties of the paint are the first essentials for under- standing the reasons for these faults where the work has been well done. Why at times do paints crack, peel, scale, blister, or pull away from the wood, and do many other unreasonable things? Why in some instances will the paint wear well when the house is painted for the first time, and when re-painted with a different paint show many of these faults? These and scores of other questions are asked by the general public, and they are demanding an answer. They are demanding an answer from those in whom they have confidence, and who, from their position, have no reason to become biassed. Our Experiment Stations must furnish this new sought for information. The chemist must acquaint himself with the subject, investigate, experiment, keep in touch with the processes of manufacture, and aid the consumer in arriving at a rational explanation. He must go farther, and know paints. The paint manufac- turer's chemist can do much, but he is usually an interested READY MIXED PAINTS. 3 party, and a more searching investigation is required than he can command time or means to give to the problem. There is needed such investigation as only well-equipped experiment stations can command for such a study. The North Dakota Experiment Station has undertaken this line of work, and has erected several experimental paint fences of the type shown in the frontispiece of this book, as well as undertaking to conduct paint tests on a broad scale upon a number of buildings, employing various combinations of pigments. These tests will be continued for a series of years ; and frequently repeated and the whole question studied, in order to determine what is best with conditions such as exist in North Dakota and like adjoining territory. Let us not be too severe in our criticism of the paint manufacturer until the full truth is known, and this as the results of honest investigation. No man can prevent the dishonest use of data given to the public in the best of faith and when rightly used of great value, but in the hands of dishonest salesmen distorted and abused. The methods of salesmanship usually, however, reflect the true character of the house behind the men, and therefore are beacon lights not to be wholly ignored. At the present time nearly all families are users of paints, nevertheless but few persons are familiar with the compo- sition or working qualities of paints. There are few sub- jects of greater importance to the builder, since the appear- ance of a building is to be judged largely by the character of the finishing coat, which is paint. And yet how little the average person knows of the subject of paints. Nearly all would be able to tell you something concerning building materials, cements, methods of construction, and would recognize good work in any of these lines, but few know the composition or properties of paints used to give the 4 ANALYSIS OF MIXED PAINTS. finishing coat and proper protection to the walls of our homes. Only a limited number would be able to intelli- gently criticise the work. That some paints wear well, some crack or aligator, others peel and some blister, while others chalk, is generally recalled, but the reason for this is not considered. The average property owner from the East will tell you that the paint on buildings does not wear like it formerly did, and they wonder why. Is it, they say, because of the inferior quality of the white lead used at the present time, or because of poor workmanship? They do not consider that there are many other factors which may have entered in as a cause for present existing conditions, among which may be mentioned, the inferior character of some of the wood now employed for sidings; the condition of the wood at the time the paint is applied which may be unfit to receive the coat of paint. Or it may be due to the character of the priming coat which was of inferior quality, perhaps a low grade of ochre, wholly unfit to be used as a primer. Even the character of the oil not properly ripened, etc., may be a determining agent. It may be due in part to the physical condition of the paint, for it is a well-known fact that there are now on the market numerous paints, the physical condition of which cannot be commended, certainly not if, as has been claimed, that fineness is an essential for good wearing quality. More often it is due to the character and condition of the adul- terants which are added to the paint, for it cannot be denied but what some of the products in the proportion in which they are added, whatever their individual merits may be, can only be looked upon as adulterants. Or it may be due to the presence of an excessive amount of water used in the paint, for many of the paints which have been sent out of late years have contained unnatural proportions of water, not intended to add value to the paint, or to READY MIXED PAINTS. 5 serve for preventing its settling and hardening. Not more than from one to two per cent of water is needed, if at all necessary, for this purpose. It is not uncommon for paints to contain from ten to twenty-four per cent of water in the liquid portion. This, with the small amount of added alkalies and jelly-like constituents, has produced serious results for the paint consumer. Excessive quan- tities of benzine, kerosene, gasoline, and various other thinning vehicles have likewise, been a source of trouble. What is needed first of all, is a better acquaintance with the whole question of paint manufacture and use. The first essential is that the public should become acquainted with the chemical composition of paints: having made themselves acquainted with their composition, they will then know whether the products purchased are what they are represented to be. They will then need to become familiar with the physical properties of paints, and their working qualities under the brush. This will then natu- rally lead to a study of paints upon buildings, and the public will become familiar with their wearing qualities; thus they will be able to understand some of the causes which lead to the deterioration of paints, and they will then demand products of far better quality than much of that which has been sent into the state in the past, even by some well-known firms. It is true that competition has forced honest manufac- turers to lower their standards so that they are producing paint not as good as they know how to produce, but as good as the general public are willing to pay for in the face of existing competition with unscrupulous manufac- turers and catalog house goods, which have fast forced down the standard of products in all lines handled by department stores and run as money-making ventures. 6 ANALYSIS OF MIXED PAINTS. North Dakota was the first state to enact any compre- hensive measure affording protection to the public against abuses not uncommon during the past few years. The essential features of the North Dakota paint law are found in Section 1, which reads as follows: " SECTION 1. Ever} 7 person, firm or corporation who manufactures for sale or exposes for sale, or sells within this state, any white lead, paint or compound intended for use as such, shall label the same in clear and distinct gothic letters upon a white background and show the true per cent of each mineral constituent contained in said paint, or if other than linseed oil is used in its preparation, the names of such oils or substitutes shall be shown together with the percentage thereof, and every person, firm, or corporation who manufactures for sale or exposes for sale, or sells within this state any mixed paint or compound intended for use as such, which contains any ingredients other than pure linseed oil, pure carbonate of lead, oxide of zinc, turpentine, Japan drier and pure colors, shall be deemed guilty of a misdemeanor, and upon conviction thereof shall, for each offence, be punished by a fine of not less than twenty-five and not more than one hundred dol- lars and costs, or by imprisonment in the county jail not exceeding sixty days; provided, that any such person, firm or corporation who shall manufacture for sale or expose for sale, or sell within this state any white lead, paint or mixed paint containing ingredients other than those as above enumerated, shall not be deemed guilty of a viola- tion of this act in case the same be properly labelled, show- ing the quantity or amount of each and every ingredient used therein and not specified above, and the name and residence of the manufacturer or person for whom it is manufactured." Like many first laws there is considerable ambiguity READY MIXED PAINTS. 7 and an opportunity for misinterpretation of the spirit of the law. It is true also that the measure has been attacked on the ground of unconstitutionally, and a decision has not as yet been reached by the highest court in the land, and cannot be for some months yet, although the consti- tutionality of the act has been affirmed by the United States District Court for North Dakota. The North Dakota law does not require paints made wholly from commercially pure white lead, zinc oxide, linseed oil, turpentine, Japan drier, and pure colors, to be labelled. All other paints must be labelled so as to show their true composition. There has been a difference of opinion as to whether a law regulating the sale of paints should require all paints to be labelled, or only those which have departed from the constituents which have been long recognized as the basis for paint manufacture. Many arguments have been put forth to show that a law exempting any paints is unfair, but the evidence thus far presented has not been sufficient to show that it would be desirable at this time to recom- mend any change in this direction. It is true that all of the so-called inert materials have been used and are still used to some extent in the various mixed paints, but the paints containing these constituents have generally been represented as being produced wholly from the con- stituents recognized as statutory, and thus the manufac- turers have themselves made this natural and distinctive classification which has been adopted in the North Dakota law. The pigments which have been used as substitutes are divided into two groups. The first group includes chalk, mineral white, barytes (natural or artificial), gypsum, silicates, calcium carbonates under various names, as Spanish white, English white, marble dust, Paris white, 8 ANALYSIS OF MIXED PAINTS. whiting, etc.; magnesia compounds, and various alumina products, as, for example, China clay. The second group includes sublimed lead, lithopone, leaded zinc, and zinc lead white. It may be conceded that products of the first group are possessed of merit for certain purposes, yet they have been most generally employed as adulterants, and are found, possessed of inferior quality, to the greatest extent in low grade paints, or as adulterants for white lead. They are cheap, therefore lend themselves to misuse. It is not generally claimed that they are substitutes for white lead in oil, but rather that they can be used in com- bination with white lead within certain limits and, at times, with advantage. There is, however, no general and fixed consensus of opinion among paint manufacturers or their chemists as to which of these are best, some manufac- turers condemning one and extolling the merits of another, while a competitor will as vigorously contend that the reverse is true. The physical condition of the pigment is often a con- trolling factor, for it is now well recognized that fineness of subdivision of pigment is of vast importance. Again, not all of the products sold under a given name are of like value, or even of like chemical composition. This is well shown in the case of gypsum, much of the Western gypsum being of inferior quality and not the equal of certain East- ern products. If the gypsum is not properly dehydrated then, in the presence of moisture as found in paints, a serious difficulty arises. Or if lime carbonate be present then by the dehydration of the gypsum quicklime is pro- duced and causes complications. It has been asserted also that lime carbonate is desirable to counteract any acid properties in the oil, but it may be asked why will not the white lead or even zinc oxide serve the same purpose? READY MIXED PAINTS. 9 Such arguments seem futile, and certainly if any advantage is to accrue from the use of chalk or marble dust over that of lead or zinc, not to exceed two per cent would be required and the necessity for the presence of any great amount of a neutralizing agent at once raises a doubt as to the value of the linseed oil, that is, as to its freedom from oil pro- duced from foreign seed, and to its proper aging, or, if boiled oil, its method of preparation. With the present confusion and lack of unanimity among paint chemists and manufacturers as to the relative merits of the constituents and the very general belief that the pigments of group one are largely employed as cheapening agents, and not always to the advantage of the purchaser, we may dismiss for the present any consideration of their being the equal of the statutory pigments in ready mixed house paints; at least until such time as their true worth has been demonstrated through a rigid and comprehensive series of practical paint tests checked up by appropriate chemical and physical examinations. It will also be nec- essary to determine to what extent, if any, they can replace white lead, or should t the proportion of white lead remain the same and they be used as a substitute for the zinc oxide. It should not be understood, however, that these pro- ducts when properly used are to be classed as adulterants, for this term is being abused and misused. For example, in lithopone, barium sulphate is a recognized component, and when lithopone is used as such it is a perfectly legitimate product. The same is true of many other pig- ments. With regard to the members of group two, some discus- sion of the several pigments will not, at this time, be inappropriate. Sublimed lead. Sublimed lead sulphate, sometimes 10 ANALYSIS OF MIXED PAINTS. called the oxy-sulphate, or the basic sulphate, seems to have had many ups and downs in its short history. It was first put upon the market commercially about twenty-five years ago and, according to Hurst, its compo- sition was very variable, much depending upon the char- acter of the low grade ores from which it was produced, the temperature in the furnace, and the proportion of air which came in contact with the ore. Writing as late as 1901, Hurst reaffirms his former statement with regard to its variable composition. Many of the manufacturing obstacles have, however, been largely overcome in the last few years, especially in America, and the product is now tolerably uniform, and in the purest form seems to average in composition about: Per cent. Lead sulphate 75 Lead oxide 20 Zinc oxide 5 - 100 The pigment is very fine, possessing good covering power, but in use is not always satisfactory. Sublimed lead seems to differ in many ways from the simple physical mixture of lead sulphate, lead oxide, and zinc oxide. The claim that it is the basic sulphate, or the oxy-sulphate, seems, however, not to have been properly verified at the present writing. It seems to be rather a complex mixture of several of these constituents. That it should differ from a mechanical mixture of the above-named pigments, may be due in part to the greater degree of fineness and more complete intermixture in the process of sublimation. The use of sublimed lead has greatly increased during the past few years, and an increased number of manu- facturers are now using sublimed lead to some extent. In the preparation of mixed paints the firms adopting its READY MIXED PAINTS. 11 use to the largest extent during the past two years, judg- ing from the paints sold in North Dakota, are the ones least equipped for conducting experimental work under the guidance of a trained chemist. Several firms report having in years past tried the product with unsatisfactory results, and have discon- tinued its use in their regular lines of mixed paints. Firms who have been using sublimed lead in their darker shades have not generally adopted its use in the whites. How- ever, in one instance when used with a white this yellow tint was corrected by the addition of a slight amount of blue. For example, a gray and an outside white as examined gave for the essential constituents approximately as follows : White. Gray. White lead 59.00 9.00 Lead sulphate 2.00 45.00 Zinc oxide 34 . 00 44 . 00 There has been considerable complaint regarding the working qualities of sublimed lead paints. In a test made by using sublimed lead ground in oil and with great care to prevent heating, it was found that during the cool part of the day, in the morning and evening, the paint was spread and brushed out with considerable difficulty. Others have reported like experiences. In a more recent test, where a mixed paint composed of 60 per cent of sublimed lead and 40 per cent of zinc oxide was under test, considerable difficulty was experienced toward even- ing as the day became cooler, although all the other condi- tions were most favorable for painting. In the past there has been produced a large number of paints of rather inferior quality, so far as composition is concerned, made up largely of so-called inert material: chalk, barytes, clays, silicates, water, etc., and it is notice- 12 ANALYSIS OF MIXED PAINTS. able that during the past two years, or since the enforce- ment of the North Dakota law, several of these firms have been endeavoring to improve somewhat the quality of their paint, and are substituting sublimed lead or lead sulphate, but even in the best grades of these paints, as examined in this laboratory, it has been found that the lead sulphate is generally used in combination with other products and particularly with white lead proper, and not alone or with zinc oxide only. An example of the change made in one case is clearly shown by comparison of an outside white as produced one year ago, with that produced by the same firm at the present time : Old. New. Lead sulphate . 00 20 . 00 Zinc oxide 53.00 43.00 Calcium carbonate 46 . 00 26 . 00 Silica 11.00 For the new product, it is claimed on the label that the formula is: Per cent. Zinc white 55 Lead white 45 100 This is not at all what the analysis shows it to be. In the case of another sample of paint recently exam- ined we find the proportion to be : Per cent White lead 23 Lead sulphate 19 Lead oxide 6 Zinc oxide 26 Barium sulphate 22 Other constituents 4 100 READY MIXED PAINTS. 13 A mixed paint to be satisfactory must not be too slow in drying, otherwise showers, dust storms, and myriads of insects deface it and give an unsatisfactory surface. The tendency for a paint to become gelatinous is also an unfortunate condition at times met with. These last named properties have been objections strongly urged against the use of sublimed lead. When used in connec- tion with considerable proportions of white lead, zinc oxide, and diluting materials, or inert pigments, it is pos- sible that sublimed lead may give satisfactory results, and this would seem to be true since we have found its use more general under these conditions, also in cases where permanent whiteness is not such an important matter. From personal knowledge the writer would say that sub- limed lead is better adapted for use in paints for farm machinery, where dipping is resorted to rather than brushing. Lithopone. Lithopone is now a fairly uniform product, quite generally used in the preparation of the cheaper enamels, in oil cloth, and floor cloth industries and, to some extent, in floor paints, but it has not, as yet, been used to any great extent in mixed paints. From its nature it cannot be used in paints under certain conditions with any degree of satisfaction, and, therefore, the pur- chaser should know of its presence in order that he may avoid such difficulties. Aside from any objectionable features it is probable that the demand for lithopone for other purposes will be such as to prevent its being gener- ally employed, for some time at least, in the preparation of mixed paints except in certain specialties. Leaded zincs. Leaded zincs show considerable varia- tion as now found upon the market. The New Jersey zinc produced from Franklinite is practically 99 per cent or more zinc oxide, and seldom contains more than a trace 14 ANALYSIS OF MIXED PAINTS. of lead. On the other hand, the Mineral Point zinc con- tains varying amounts of lead sulphate, and above all zinc sulphate which is recognized as an objectionable feature when present in any considerable quantity. There would seem to be three grades of Mineral Point zinc products, the purest of which contains from three to four per cent of lead sulphate. The leaded zincs from the Missouri and Kansas fields show an extremely wide range in composition, containing from four to twenty-five per cent of lead sulphate, and, at times, as high as one and a half per cent of zinc sul- phate. It also at times contains as high as one-half per cent of SO 2 which in some instances in paint manufacture has been a source of great trouble, resulting in heavy loss and in the production of a paint not usable. With regard to zinc sulphate, Hughes says: " Zinc sulphate, an almost invariable ingredient of leaded zinc, and zinc oxide made from sulphides sometimes causes startling changes for which the painter usually is blamed.' 7 In the light of present experience, therefore, zinc sul- phate in such quantities cannot be looked upon other than with some degree of suspicion in mixed paints, although Toch does not consider it harmful to the extent that has been generally claimed. It would seem, therefore, that before one is justified in assuming the presence of zinc sulphate as without preju- dicial influence, it will be necessary to conduct investiga- tions in practical tests to determine under what condi- tions, if any, it can be safely allowed in paints, and to what extent. Zinc lead whites. Zinc lead white is largely a product from Colorado low grade ores, a mixture of zinc oxide and lead sulphate very intimately combined at the high temperatures at which these products are volatilized, and READY MIXED PAINTS. 15 t then arc oxidized in appropriate chambers. Only during the past five years has there been attained anything like uniformity in composition and, even at the present time, as shown under the analyses of zinc lead whites by Pro- fessor Holley, they have been found to contain the follow- ing range for arsenic, antimony compounds, and zinc sulphate : I II III IV Per cent. Per cent. Per cent. Per cent. Arsenious oxide 68 .47 .32 1.60 Antimony oxide 20 .33 .20 .88 Zinc sulphate 78 .55 1.61 .84 In other words there may be present as much as three and one-half per cent of these objectionable constituents. The writer seriously questions whether the presence in these proportions of such constituents does not very materially detract from the good quality of paint. Cer- tainly arsenic and antimony compounds are not more desirable for interior paints than are the arsenic com- pounds desirable in our wall papers, the presence of which in wall paper in the past has proven such a menace to health. The writer cannot do other than maintain that when any of the foregoing pigments are used in place of the long recognized statutory pigments, the public have a right to know of their presence, and they are not to be classed as possessed of the same degree of merit for paint production as are the statutory pigments. At least it cannot be claimed that experience has, as yet, demon- strated their like worth. Further, the fact that the manufacturer of those pigments is constantly striving to eliminate certain constituents; adopting new devices in manufacture, and bringing out new products and pre- sumably better than that previously produced, is indicative 16 ANALYSIS OF MIXED PAINTS. of needs for further improvements and clearly indicates an unsettled condition. If there are standards recognized for food products, for drugs, for beverages, such as whiskey, for commercial fertilizers, etc., why should not like standards, generally recognized from their long and favorable use, be accepted as a basis for paints of high quality ? Any attempt, there- fore, to secure legislation requiring all paints to be labelled under like conditions is an attempt to place all constituents entering into the composition of paints on a like footing. Every honest paint manufacturer knows that such claim is not true. In dealing with this question the writer would have it understood, of course, that his reference has been to that class of mixed paints used as house paints, and not those special paints prepared for use upon structural steel, for lighthouse purposes, or even upon railway cars, where conditions are quite different, and where, as a rule, expert chemists are employed to see that the products furnished are in compliance with previously prepared specifications, none of which conditions pertain to paints as ordinarily met with in commerce. Otherwise, who is to safeguard the consumer against such abuses, or how is the producer of honest paints to have proper protection? Under the North Dakota law it is required, where con- stituents other than statutory ones are employed, that the paint shall be labelled to show the composition of the same, and the form which presents this information most satis- factorily for the public, it seems to the writer, is the one adopted in reporting the analyses made at the North Dakota Experiment Station, and is as follows: . i, \^>v> ^' OF THE " UNIVERSITY ^~ YDY MIXED PAINTS. 17 FORM FOR LABEL. Contents of can gal. Ibs. Per cent of pigment, by weight 62 Per cent of thinner or vehicle by weight 38 100 The thinner or vehicle is composed of: Per cent. Linseed oil 70 Turpentine 5 Japan drier Benzine 10 Water 10 100 Composition of pigment: Per cent. White lead 25 Sublimed lead 20 Zinc oxide 30 Calcium carbonate 6 Barytes 15 Color 1 4 100 This should be followed or preceded by the name of the manufacturer and his address. This does not preclude however, the use also of the name of the jobber on the same label if it is desired. Where water is present not to exceed 1.5 per cent of the fluid portion it is considered as incidental. Or where Western zincs are employed and carry not to exceed 5 per cent of lead sulphate, and are free from other in- jurious impurities, the products are considered as com- mercially pure and labelling is not necessary, provided all other conditions are in compliance with the requirements of the law. 1 The color is composed of: (name of ingredients and composition when necessary to be given.) 18 ANALYSIS OF MIXED PAINTS. Where coloring matter is used to secure the desired tint, it is assumed that this coloring matter is commercially pure, but where the coloring matter is of such a character as to require an unusual amount of color, then the product should not be deemed as properly labelled unless the analysis of this color be given. It is a well-known fact that some of the ochres are of such inferior quality that not less than 20 per cent of the color may be used as pig- ment, and not more than 8 or 10 per cent of this should properly be classed as real color, and the other constituents enumerated as dilutants. The question may be raised as to the reasons for label- ling as indicated in the foregoing. It will be observed in the study of paints that the manufacturer who uses the largest amount of cheap, inferior pigments will employ the least amount of oil, for when calculated according to vol- ume, oil is more expensive than some of the pigments. He, therefore, adds water and recommends that the con- sumer add the necessary oil and turpentine to thin the same for use. On the other hand, the manufacturer pro- ducing the highest grade of paints tries to combine pig- ment and vehicle in such proportion that they are ready for use ; but linseed oil is cheaper than white lead, and, therefore, some paint manufacturers employ as large a per cent of oil as can well be used, and advertise the great spreading power of their paints. It is thus important that we have full measure or weight, and proper information with regard to the proportion by weight of pigment and thinner. By separating the thinner or vehicle from the pigment, the facts are most clearly indicated to the untrained mind, for example, the proportion of water; for instance, ten pounds in every hundred of the liquid portion. Or in the pigment thirty pounds of chalk or marble dust or READY MIXED PAINTS. 19 barytes to each hundred pounds. Where the pigment and vehicle are combined the relative proportion of barytes, benzine, water, etc., is made to appear considerably less than where they are calculated on the actual amount of thinner employed, and this to the advantage of the manu- facturer. To make a statement for the express purpose of mis- leading, is as much a falsehood as to deliberately tell a lie, and indicates that there is back of it, one not wholly to be relied upon in matters upon which he should be an authority. To say that the lead and zinc in the paint are "guaranteed to be strictly pure/' when they constitute but part of the pigment, is to perpetrate a fraud, and to deliberately falsif}^ Yet this is not an uncommon practice in regard to paint literature furnished by manufacturers. Or, if not found in the literature, it is spoken by the salesman who represents the product. Take this statement: "This mixed paint contains the proper proportion of zinc. It is a lead, zinc, and oil paint the real thing." Is this a truthful statement when the composition is : Per cent. White lead 25 Lead sulphate 25 Zinc oxide 25 Barytes . . . 25 100 No honest manufacturer of paints should make a state- ment like the foregoing, or allow his salesmen to mis- represent facts. And yet if you are to eliminate all as friends who follow such a course, there would remain but few manufacturers for one to associate with. Such ingen- ious statements do not give one a good opinion of busi- ness men engaged in the manufacture of paints, and if 20 ANALYSIS OF MIXED PAINTS. their word is questioned on paint matters they have no just reason for resenting it, until such time as paint litera- ture is properly revised. Commercial practise rather than inherent dishonesty is at fault, for much of this unfortu- nate condition, also lack, on the part of some manufac- turers, of moral courage to lead in a crusade for honest labelling. Time and forced changes must soon remedy this condition. Here is another example of fraud, where the manu- facturer labels his product as " white lead " and says: " We guarantee our white lead to be superior to any white lead on the market as regards opacity or body-covering capacity. It is also extremely durable, possessing in this particular great merit. For whiteness and fineness of texture it will be found unsurpassed." Now he has told but a small part of the real truth. Now the public are justified in believing that this pro- duct is the equal of any white lead upon the market. In fact, that it is chemically pure white lead. The analysis shows the pigment to contain : Per cent. White lead 37.51 Lead sulphate 7 . 84 Zinc oxide 25 . 87 Calcium carbonate 20 . 36 Barytes, silica, and undetermined 8 . 42 100.00 Another product labelled as white lead was found to contain 90 per cent of barytes, and no white lead at all. Now such claims as the foregoing are intentionally mis- leading and false, are given out solely for the purpose of deceiving the public, and inducing them to purchase these products at exorbitant prices. These products usually retail at about the same price as does genuine Old Process Dutch White Lead, and it is to secure this unwarranted advantage that many of these products are so advertised. READY MIXED PAINTS. 21 As showing the need of: a law to prevent fraud in paints we may cite a few examples. We give three analyses of products sold as white lead and usually at approximately the same prices per pound as received for Old Process Dutch White Lead. White lead Lead sulphate .... Zinc oxide No. 1. 00 . 20 20 No. 2. 00 5 25 No. 3. 39 5 34 Calcium carbonate . . Barvtes . 8 52 70 19 3 Many manufacturers dwell much upon the importance of having pure linseed oil and turpentine, and maintain that the life of the pain1< is largely dependent upon the linseed oil. Some of the paints found upon the market in North Dakota at the time the law went into force, clearly shows a kind of "doping " not at all commendable or in keeping with what the public had a right to presume they were purchasing. We cite the following examples as showing the com- position of the liquid portion of some of these paints. Linseed oil Turpentine Benzine . . Water . . 1 . . 55 24 . . 21 2 69 ie 15 3 52 26 22 4 70 11 i9 5 57 21 22 6 72 4 24 7 64 6 14 16 This certainly shows a remarkable condition, and one which all paint chemists have condemned, and yet this represents not alone the low grade paints, but some of the products produced by manufacturers of the highest standing. As to the use of water in paints, without further com- ment we may quote Toch: "Three per cent is entirely excessive in an exterior linseed oil paint, and a manufac- turer has no right, either morally or legally, to hide behind 22 ANALYSIS OF MIXED PAINTS. a misrepresentation of his paint when the paint is largely adulterated for the purpose of overcoming his ignorance in the manufacture." That the water further exerts an injurious effect is also noted by the same author, who says: " Ethics would clearly indicate that no manufacturer has a moral right to label his paint as being entirely pure and composed of four materials, when as a matter of fact an excessive quantity of water was added which destroyed in a large degree the value of the other materials." On the other hand, as showing about the proportion of the constituents entering into the fluid portion of some of the best made paints, we quote the following example : ANALYSIS OF THINNER. 1 2 3 4 5 6 Linseed oil ... . . 93 91 86 95 90 94 Turpentine drier . . . 7 9 14 5 10 6 Water . . Benzine . . In the best prepared paints we have usually found from 4 to 7 per cent of turpentine drier in the liquid portion. For a heavy-bodied oil this seems to be ample. Without entering into any further discussion as to the relative merits of the various pigments we may consider a few cases where the public were justified in assuming they were purchasing a paint made wholly from white lead and zinc oxide. ANALYSIS OF PAINT PIGMENTS. 123456 White lead 00 9 00 00 00 00 Zinc oxide 52 44 40 24 47 43 Calcium carbonate 46 . . 34 5 . . 26 Magnesium carbonate 1 Barytes 22 66 Lead sulphate 45 4 5 .3 19 Clay and silica 2 . . . . 49 12 READY MIXED PAINTS. 23 Without commenting on the physical condition of these several paints which in some instances were not at all desirable we may ask: Is the public not entitled to some protection against the sale of paints so labelled as to give the impression that they are getting white lead and zinc oxide? Not all of the above paints are by any means to be classed as catalog house paints. It is not for one moment to be supposed either, that the paints are ideal in composition or that the honest paint manufacturer so considers them. Here is a type of a different class of paints put up in dry form and largely advertised. Per cent. Moisture and combined water 5 . 74 Casein 14.59 Ferric oxide 19.26 Soluble alumina 1 . 24 Gypsum 21.53 Lime 7.60 Magnesium silicate 30.04 100.00 The constituents other than casein in this costs about one cent per pound, and it is a good example of what might properly be classed as a " fake " paint. If a cheap paint is desired it is better to use a good white- wash, for it would probably serve as a protective coat better than the above. What is known as the Govern- ment formula for whitewash is as follows: " Slack one-half bushel of lime with boiling water, keep- ing it covered during the process. Strain it, add a peck of salt dissolved in warm water; three pounds ground rice put in boiling water and boiled to a thin paste; one-half pound powdered Spanish whiting, and a pound of clear glue dis- solved in warm water; mix these well together and let the mixture stand for several days. Keep the wash thus pre- 24 ANALYSIS OF MIXED PAINTS. pared in a kettle or portable furnace, and, when used, put it on as hot as possible with painter's or whitewash brush." Short measure and weights. Another feature quite com- mon is short measure in mixed paints and short weight in paste paints. In case of white lead and combination leads they average 10 to 12 per cent short weight, or kegs sold for 12J pounds will run 10 to 10J pounds, and 25 and 50 pound kegs, respectively, about 22 and 46 pounds. All weights should be net as represented. In the mixed paints they run not infrequently 10 to 13 per cent short in measure. In two- quart containers we have found them to run as follows: Number. Quarts. 1 1.92 2 1.82 3 1.76 4 1.75 5 1.70 One of the gallon containers purchased direct from the producer actually contained 3.41 quarts. Relation of lead to zinc. Much has been said concerning the fact that the North Dakota law is silent regarding the proportion of lead to zinc permissible in statutory paints. Who shall at the present time say what proportion is best? The relation of lead to zinc for exterior work would undoubt- edly be different than in paints intended for interior house painting. The difference in cost between the best grades of those two pigments is not so great that manufacturers of high grade paints will be likely to cheapen the product at the expense of what to him seems safe for the locality where his paint is most largely used. At the present time we find that some are using 30 per cent of white lead to 70 of zinc oxide. This is the limit for zinc. Others employ these in proportion of 50 per cent for each, and there are READY MIXED PAINTS. 25 now a few using 60 per cent of white lead and 40 per cent of New Jersey zinc oxide. There are many practical painters who express the opinion that the proportion should be from 66 to 75 per cent lead, or not more than one-fourth to one-third of the pigment should be zinc oxide, while the advocate of white lead would have none of zinc. A few of the white lead advocates would use 10 to 25 per cent of zinc oxide in the finish coat. Experiments are necessary to determine in what proportion these pigments shall be added in order to secure the best results. Experience may teach us that some of the other pig- ments are preferable to either of the above named. If so, we should welcome the proof and prepare to adopt stan- dards of comparison based on such proof. The author is a believer in mixed paints, but maintains that when other constituents, either as thinner or pigment, are introduced in place of those generally recognized as being present, this fact should be clearly set forth and that false or exaggerated statements regarding all claims of paints should be dis- countenanced alike by the general public and the honest manufacturer, who in the past has suffered through abuses of commercial methods based upon an erroneous idea of the science of right and of right character and conduct in business affairs. In the end, in paint matters as well as elsewhere, that which is true and just will prevail. PART II. ANALYSIS OF PAINTS, COLORS, AND VARNISHES. BY C. D. HOLLEY. 27 CHAPTER I. ANALYSIS OF MIXED PAINTS, 1. Preparation of sample. If a dry color, and in bulk, great care must be exercised in securing a uniform sample which should be thoroughly mixed on the mixing cloth. If the sample be a liquid paint in the unbroken package, the brand, manufacturer, and guarantee should be carefully noted. The package is then weighed, opened, and the con- dition and volume of the contents noted. If the pigment has settled hard in the bottom of the can, pour off the oil into the mixing can and work up the paste until free from lumps, gradually adding the oil portion and stirring to a uniform consistency; pour into the mixing can, scraping out the contents of the package thoroughly. Stir until thoroughly convinced that the sample is uniform in com- position. The entire success of the analysis depends upon securing a uniform sample, and more analyses are incorrect because of carelessness in the preparation of the sample to be analyzed than from any other source. The volume and weight of the empty can are also noted. 2. Separation of the vehicle from the pigment. Much difficulty is often experienced in extracting the vehicle from the pigment, due to the fineness of the pigment particles and the ease with which they pass through the walls of the extraction tubes. This difficulty, however, may be entirely avoided by the use of the apparatus illustrated below. The extraction thimble, containing a filter folded cylin- drically, is dried in the hot water oven for one hour, weighed, and 10 to 15 grams of the sample weighed into it, 29 30 ANALYSIS OF MIXED PAINTS. extracted with ether for 24 to 36 hours, dried and weighed again. The loss in weight represents the vehicle, and the FIG. 2. EXTRACTION APPARATUS. residue remaining, the pigment, which is reduced to a fine powder and kept tightly stoppered until examined. Any ANALYSIS OF MIXED PAINTS. 31 casein or similar product in the paint will remain unex- tracted by the ether, and unless detected will interfere with the proper analysis of the pigment. 3. Ratio of pigment to vehicle. It is customary with a large number of manufacturers to have one ratio of pigment to vehicle for white paints, and another ratio for the tints. In some cases this is necessary., owing to the low specific gravity of the tinting colors; but in many instances where only one or two per cent of color is added to the white base, it is not necessary to reduce the propor- tion of pigment, even though such paints may hide better than the whites. 4. Typical analyses of white and gray paints, from the same manufacturers, showing the change in the ratio of pigment to vehicle. ] [. I I. II [. White. Lead Color. White. Gray. White. Gray. Pigment Vehicle 65.6 34.4 57.2 42.8 62.6 37.4 54.9 45.1 63.2 36.8 54.9 45.1 Vehicle: Linseed oil .... Drier Water 100.0 88.9 9.3 1.8 100.0 89.5 8.6 1.9 100.0 86.0 12.6 1.4 100.0 84.7 13.8 1.5 100.0 97.0 2.0 1.0 100.0 83.9 14.9 1.2 Pigment : White lead .... Lead sulphate . . . Zinc oxide Calcium carbonate . Silica Magnesium silicate . Undetermined, color, etc. 100.0 14.65 0.34 63.42 20.91 0.68 100.0 14.18 0.27 63.27 20.14 2.14 100.0 44.08 4.62 41.41 4.59 5.10 0.20 100.0 27.29 4.39 50.94 7.10 6.94 3.34 100.0 50.52 0.00 46.06 3.18 0.24 100.0 33.98 2.84 41.80 6.94 12.14 2.30 100.0 100.0 100.0 100.0 100.0 100.0 Analyses by the author. 32 ANALYSIS OF MIXED PAINTS. 5. Composition of colored paints. After the extraction of the vehicle it is necessary to examine the pigment qualitatively in order to ascertain the ingredients to be determined. The usual qualitative scheme may be fol- lowed with advantage. The colors as given on the color cards of paint manufacturers are usually confined to a limited number of combinations, the possible components of which may be easily ascertained, and which, in fact, are usually well known to paint chemists; but to the chemist who has had but little experience along paint lines, the following tables of color ingredients will be of interest. Unfortunately, manufacturers are not agreed among themselves as to standards for naming colors; for example, a tea green put up by one manufacturer may not correspond with a tea green put up by another; but by a careful study of the color cards issued by reputable paint manufacturers, it is usually possible to identify the color to be analyzed. Also the same or closely the same color may be produced by different combinations of color pig- ments, hence it is necessary to state all of the possible constituents that may be used, as far as the author has been able to ascertain them, even though it is quite probable that they may not all be present in the same paint. 6. Reds: Brick. Base white, ochre and Venetian red. Flesh Color. Base white, ochre, Venetian red, and sometimes orange chrome yellow. Indian Red. Indian red. Lilac. Ultramarine, carmine, Indian red, ochre, lamp- black. Maroon. Carmine, ultramarine, lampblack, Tuscan red. Pink. Base white, orange chrome yellow. ANALYSIS OF MIXED PAINTS. 33 Terra Cotla. Base white, burnt sienna, umber, chrome yellow, Venetian red, ochre. Salmon. Base white, vermilion, lemon chrome yellow, sienna, ochre, Venetian red, orange mineral. Tuscan Red. Tuscan red, Indian red, Para vermilions. Venetian Pink. Base white, Venetian red. Venetian Red. Venetian red. 7. Blues: Azure Blue. Base white, ultramarine blue, chrome green, Prussian blue. Bronze Blue. Black, Prussian blue. Dark Blue. Base white, chrome green, Prussian blue, ultramarine, black. Light Blue. Base white, ultramarine, Prussian blue. Neutral Blue. Base white, Prussian blue, umber, black. Robin's Egg Blue. Base white, ultramarine, lemon chrome green. Sky Blue. Base white, cobalt blue, Prussian blue, ultramarine blue, chrome yellow. 8. Yellows: Buff. Base white, ochre, black, red chrome lead. Canary. Base white, lemon chrome yellow, chrome green. Citron. Base white, Venetian red, Prussian blue, chrome yellow. Cream. Base white, ochre, Venetian red. Deep Cream. White, ochre, Venetian red. Ecru. Base white, ochre, chrome yellow, black, chrome " green. Ivory. Base white, chrome yellow, ochre. Lemon. Base white, chrome yellow. Manilla. Base white, ochre, chrome yellow. 34 ANALYSIS OF MIXED PAINTS. Stone. Base white, ochre, umber, chrome yellow. Straw. Base white, chrome yellow, ochre, Venetian red. 9. Greens: Ivy Green. Ochre, lampblack, Prussian blue. Light Green. White, Prussian blue, chrome green. Manse Green. Chrome green, chrome yellow, ochre. Moss Green. Base white, ochre, chrome green, lamp- black. Olive Green. Lemon chrome yellow, ochre, ultramarine blue, Prussian blue, Indian red, chrome green, lamp- black. Pea Green. Base white, chrome green, very rarely emerald green. Sap Green. ' Base white, chrome yellow, lampblack, chrome green. Sea Green. Base white, chrome green, sienna, ochre. Tea Green. Base white, chrome green, chrome yellow, lampblack. hi/^" Willow Green. Base white-chrome green, umber, ivory, black. 10. Browns: Acorn Brown. Sienna, carmine, Indian red, lampblack, ochre. Brown. Indian red, lampblack, ochre. Chocolate. Similar to acorn brown. Cork Color. Base white, ochre, Indian red, lamp- black, umber. Dark Drab. Base white, Indian red, lampblack, Prus- sian blue, yellow ochre. Doe Color. Base white, sienna, umber, ochre, lamp- black. Dove Color. Base white, Prussian blue, lampblack, ochre, Indian red, umber, sienna. ANALYSIS OF MIXED PAINTS. 35 Drab. Base white, umber, Venetian red, yellow ochre, black. Fawn. Base white, ochre, Indian red, lampblack, sienna, umber, chrome yellow, Venetian red. Lava. Base white, black, chrome orange, chrome yellow. Sandstone. Umber. Snuff Brown. Base white, ochre, Indian red, Venetian red. 1 1 . Greys and grays : l Ash Gray. Base white, ochre, lampblack, sienna, ultramarine blue. Dark Slate. Base white, Prussian blue, lampblack. French Gray. Base white, black, ultramarine, Prus- sian blue, Venetian red. Granite. Base white, ochre, lampblack. Gray stone. Base white, black, Prussian blue, ultra- marine, Venetian red. Lead. Base white, lampblack, Prussian blue. Light Grey. Base white, lampblack, Prussian blue. Pearl. Similar to French gray. Silver Gray. Base white, ochre, lampblack, chrome yellow. Smoke Gray. Base white, ochre, lampblack. Steel Gray. Base white, chrome yellow, lampblack. Stone Gray. Base white, chrome yellow, black. Warm Gray. Base white, ochre, lampblack, sienna, Prussian blue. 1 Grey is understood to mean an admixture of black and white, while gray is an admixture of black and white to which another color has been added, provided, of course, that the black and white pre- dominate. CHAPTER II. ANALYSIS OF THE VEHICLE. 12. Water, Occurrence. A fraction of 1 per cent of water may occur normally in the vehicle. A small per- centage, 1 to 3 per cent, may be incorporated into the paint by the manufacturer under the belief that it secures better penetration when applied to surfaces that are slightly damp, and also that it will prevent the pigment from settling hard in the can. Oftentimes, however, large quantities are introduced for the purpose of cheapening the product. The water may be added to the paint and prevented from separating out, by forming an emulsion with the oil with the aid of an alkali, or by grinding it into the pigment, using an adhesive such as glue or casein. In the first case the nature of the ash left on burning some of the vehicle, separated as described under Linseed Oil, will indicate whether an alkali has been used or not. In the second case the vehicle will yield less than one per cent of water when distilled with a dry, inert substance such as sublimed lead, as the water remains with the pigment. 13. Detection. Water may be tested for qualitatively in light colored paints, by rubbing with a little eosin on a glass plate. If water is present the paint will take on a strong pink color, otherwise the color will remain prac- tically unchanged. If the paint contains considerable coloring material, rendering the eosin test inapplicable, a weighed strip of gelatine may be immersed in the paint for several hours. If water is present the gelatine will ANALYSIS OF THE VEHICLE. 37 soften and increase in weight, the adhering paint being removed by the use of petroleum ether and drying for a minute or two between sheets of filter paper. An immer- sion of the gelatine for 18 to 24 hours will show the pres- ence of water in a paint containing as little as 2 per cent. 14. Estimation. Quantitatively, the water is best esti- mated by distillation, using a retort, the neck of which forms the inner tube of a condenser, the outside tube being a Welsbach chimney. One hundred grams of the paint is weighed into an aluminum beaker and mixed with a thoroughly dried, inert pigment like silica or sublimed lead until it ceases to be pasty, and then transferred to the retort, which is heated in an oil bath, the water being collected in a graduate calibrated to fifths of cubic centi- metres. Toward the end of the distillation, the tempera- ture of the contents of the retort being raised to 200 C., a very slow current of air or illuminating gas is admitted to the retort through a tube passing nearly to the surface of the pigment. This will carry over the last traces of moisture. It is advisable to pass the illuminating gas through a wash-bottle containing sulphuric acid, which not only serves to remove moisture, but acts as an indi- cator for the rate of flowing gas. The heating should be continued for at least two hours at the above temperature to insure the complete removal of the combined water from the basic carbonate of lead which may be present. This should be deducted from the total amount of water obtained, by multiplying the basic carbonate present by 2.3 per cent, which represents the average per cent of combined water in white lead. It is impossible to re- move the water by this method, without decomposing part of the lead hydroxide of the white lead, as it begins to lose the combined water at 105-120 C., the total 38 ANALYSIS OF MIXED PAINTS. combined water being driven off at 150 C. for 6 hours with little or no loss of carbon dioxide. An exposure of 4 hours at a temperature 175 results in the loss of all FIG. 3. ESTIMATION or WATER. the water and a slight amount of carbon dioxide; at 200 an exposure of 2 hours is sufficient to remove all of the combined water and about one-quarter to one-third of the carbon dioxide. ANALYSIS OF THE VEHICLE. 39 In each case a blank should be run in order to ascertain that the inert pigment and illuminating gas are free from condensible moisture. The author believes that a current of air obtained by the use of an aspirator is preferable to the use of illumi- nating gas, as with the latter there is the possibility of the formation of water from the hydrogen of the illumi- nating gas and the lead oxide present, if the temperature is raised too high. Of eighty mixed paints analyzed by the author, white and gray shades, the water content calculated on the basis of total vehicle, was as follows: Amount of Water. Number of Paints. to 1 per cent 26 1 to 3 per cent 25 3 to 6 per cent 5 6 to 10 per cent 3 10 to 24 per cent 21 15. Linseed oil. Extraction from paint. One to two hundred grams of the paint are heated to about 65 C. on the water bath and centrifuged rapidly until the oil is freed from pigment. This operation may be con- ducted with advantage in a steam-heated Babcock milk tester. 1 6. Estimation of the volatile oils. The clear oil is weighed and introduced into a suitable sized Erlenmeyer flask connected with a rather large condenser. The con- tents of the flask are brought to 130 C. by means of an oil bath and a current of steam conducted through the oil. The volatile oils rapidly distil over and are collected in a weighed short-stemmed separatory funnel, the water being drawn off from time to time as may be necessary. 40 ANALYSIS OF MIXED PAINTS. The distillate is allowed to stand for several hours to insure the complete separation of the water, which is then drawn off and the volatile oils weighed and bottled for subsequent examination. The aqueous portion of the distillate will inevitably carry with it a small quantity of volatile oil, but the amount will be slight, amounting to about 0.4 gram per 100 c.c. of water distillate. After calculating the percentage of volatile oil, the linseed oil is calculated by difference, by subtracting the percentages of volatile oil and water from 100. The results obtained above may be checked up by weigh- ing 6 or 7 grams of the thoroughly stirred paint into a weighed petri-dish and heating to 120 C. for 3 hours, cooling in a desiccator and weighing. A pure raw or boiled oil will undergo no appreciable change in weight, while the volatile matters will be practically all driven off. Know- ing the amount of vehicle present, the percentage of the volatile oils may be readily calculated, and likewise the percentage of linseed oil. The linseed oil, after being freed from the volatile oils, is allowed to stand for several hours in a warm place until thoroughly settled, and may then be tested for the presence of other oils as follows. 17. Specific gravity. Determine the specific gravity by means of a pycnometer or a Westphal balance. The specific gravity may fee taken at room temperature and calculated to 15.5 C. Correction for 1 C. = .000650 Correction for 1 F. = .000361 The usual limits for pure raw oil at 15.5 C. are 0.931 to 0.937; boiled oils usually do not exceed 0.940. A low specific gravity may indicate: I ANALYSIS OF THE VEHICLE. 41 a. Mineral oils. b. Cotton-seed oil. c. Corn oil. A high specific gravity may indicate a. Rosin or resinous products. b. Rosin oils. c. Excessive heating or unusual addition of metallic driers. 18. Spot test. One or 2 c.c. of the oil are poured on a porcelain plate and a drop of concentrated sulphuric acid added carefully. If pure, the spot formed will bear a marked resemblance to a begonia leaf. If rosin or rosin oil be present a black, gummy mass immediately results; cotton-seed oil gives a spot without the characteristic mark- ings of the linseed-oil spot. Mineral oils give a scum-band rapidly spreading out over the surface from the drop, the margin of the band being uniformly circular. Fish oils give a similar reaction, but the margin of the band is not at all uniform, and may be readily distinguished from mineral oils. With a little practice and working with oils of known composition, this test can be relied upon to detect any appreciable adulteration with the above oils. 19. Mineral oils. The spot test for petroleum products may be confirmed by allowing a sample of the oil to flow down a sheet of glass, the other side of which has been painted jet black. If petroleum products are present even in a minute quantity, the sample will exhibit the " bloom " characteristic of mineral oils. A standard sample should always be run for comparison. It is possible to remove the " bloom " of mineral oils by the 42 ANALYSIS OF MIXED PAINTS. use of nitrobenzine or similar compounds, but the author is of the belief that this is very seldom resorted to in the paint industry. Quantitatively the mineral oil may be estimated by saponifying 10 grams of the oil with alcoholic potash for 2 hours, using a return condenser. The alcohol is distilled off and the soap dissolved in 75 to 100 c.c. of water, transferred to a separatory funnel and 50 c.c. of ether added. The liquids are then shaken, avoid- ing the formation of an emulsion as far as possible. The aqueous solution is then drawn off, the ethereal layer washed wtih a few cubic centimetres of water to which a little caustic potash has been added, and poured into a weighed flask. The soap solution is then returned to the separator, and twice extracted with ether in the same way as before. The combined ethereal solutions are distilled off on the water bath, the flask dried and weighed. The increase in weight represents the amount of unsaponifiable matter, and unless rosin oil is present, represents the mineral oil with the exception of about 2 per cent, the average amount of unsaponifiable matter in linseed oil. 20. The mineral oil may be separated from the rosin oil in the unsaponifiable material by heating 50 c.c. of nitric acid of 1.2 specific gravity to boiling in a flask of 700 c.c. capacity, the source of heat removed, and the unsaponifiable material added. The flask is then heated on the water bath with frequent shaking for about one-half hour, and 400 c.c. cold water added. After cooling, 50 c.c. of petroleum ether is added and the flask agitated, the mineral oil is dissolved, while the resinous matters remain in suspension. The liquid is then poured into a separatory funnel, leaving behind as much of the resinous material as possible. After settling, the aqueous liquid is drawn off ANALYSIS OF THE VEHICLE. 43 and the ethereal layer poured into a weighed flask. Another portion of petroleum ether is added to the rosin remaining in the flask, and allowed to act upon it for about ten minutes, when it is added to that in the weighed flask. After distilling off the ether, the oil is weighed. Mineral oils lose about 10 per cent when treated with nitric acid in this way, and hence the weight of the oil found must be divided by 0.9 in order to find the amount present in the sample analyzed. 21. Cotton-seed oil. This oil is seldom found in house paints, but is often used in certain classes of barn paints. The spot test may be confirmed by the Halphen test, the apparatus required being a large test tube provided with a condensing tube and a brine bath; the reagent employed being a 1.5 per cent solution of sulphur dissolved in carbon bisulphide with an equal volume of amyl alcohol added. Equal volumes of the oil and reagent are heated in a steam bath at first, and after the violent boiling has ceased, in the brine bath at 105-110 C. for about 30 minutes. As little as 1 per cent of cotton-seed oil will give a crimson wine coloration. Cotton-seed oil heated to 250 C. does not respond to this test. Quantitatively, the amount of cotton-seed oil can only be approximated in a very general manner by means of the iodine values. Let x percentage of one oil, and y = percentage of the other oil. m = average iodine value of pure oil x. n = average iodine value of pure oil y, and / = iodine value of sample under examination. Then . x m n 44 ANALYSIS OF MIXED PAINTS. 22. Corn oil. This oil gives a spot test much resem- bling that given by linseed oil, but may be detected in lin- seed oil, if in quantity, by the following test. Dilute with four volumes of benzine, add one volume of strong nitric acid, shake. Linseed oil turns a white color, while corn oil turns to a reddish orange. Quantitatively, corn oil can be estimated only approxi- mately when in linseed oil by the same method used for cotton-seed oil. 23. Fish oils. In addition to the spot test these oils may be detected by rubbing a little of the sample vigorously between the palms of the hands. Fish-oil mixtures give the characteristic odor of oils of this class. In mixtures with linseed oil, the amount present can only be determined crudely by means of the " rise of tem- perature " with sulphuric acid with the Maumene appara- tus described under the analysis of the Volatile Oils. Allen found the rise of temperature with sulphuric acid to be 104 to 111 in the case of linseed oil, and 126 in the case of menhaden oil. 24. Rosin and rosin oils. These products are best detected qualitatively by means of the Lieberman-Storch reaction, which is of sufficient delicacy to detect the pres- ence of even very small quantities of rosin oil or rosin drier in boiled oil. One to 2 c.c. of the oil under exami- nation are shaken in a test tube with acetic anhydride at a gentle heat, 'cool, pipette off the anhydride and place a few drops on a porcelain crucible-cover and add one drop of sulphuric acid (34.7 c.c. sulphuric acid and 35.7 c.c. water) so that it will mix slowly. If rosin or rosin oil is present, a characteristic, violet, fugitive color results. Certain fish oils will give a very similar color, but if present are easily detected by the fish-like odor of the oil on warming. ANALYSIS OF THE VEHICLE. 45 Old samples of pure boiled oil give a color that might be easily mistaken for rosin or rosin oils; in such cases it is best to warm the oil with alcohol so as to extract the bulk of rosin present and test the alcoholic extract. Rosin may be more completely separated and estimated by Twitchell's process (J. Soc. Chem. Ind., 1891, 10, 804) or by Cladding's method (Amer. Chem. J., 3, 416). This process depends upon the solubility of silver resinate in ether, while the silver salts of fatty acids are insoluble. A much used test for determining the presence of a cheap rosin drier in boiled linseed oil, is to make a paste with the suspected oil and moisture-free litharge. If of good quality, the paste should not thicken or harden inside of 24 to 48 hours. If such hardening occurs, the oil should be condemned. A standard sample of oil should be run for comparison each time. 25. In the preparation of gloss paints a little varnish is added, the gums of which might be mistaken in the above tests for rosin. In the cheaper paints a large excess of rosin is used in the resinate drier added. An easy method of detecting rosin and other rosins and estimating the rela- tive amount present, is to stir up about 100 grams of the paint with 500 c.c. petroleum ether, allow to stand 24 hours, siphon off the ether, and examine the skin formed on top of the pigment. This will harden in the course of another day so that it may be removed, placed on a watch glass, washed free of adhering pigment with more petro- leum ether and dried. The color and other physical prop- erties will enable one to judge whether it is rosin or some of the other varnish gums. 26. Linseed oil from inferior seed. This includes oil prepared from impure or adulterated seed, giving an oil of inferior quality; or, what is essentially the same thing, the screened foreign seeds are separately crushed and pressed 46 ANALYSIS OF MIXED PAINTS. and the resulting oil used to blend with a pure linseed oil. Such oils dry slowly and imperfectly, and the resulting film lacks the " hardness " given by the pure oils, and often give the consumer as just cause for complaint as the more grossly adulterated varieties. When sold as raw oil, such oils usually have a greenish tinge which disappears or is masked in the boiling. Chemi- cally this form of adulteration is more difficult to detect than when other oils of distinctively different chemical properties are used. With this class of oils, the specific gravity, iodine number, saponification value, and unsaponi- fiable matter remain nearly normal, and the leading tests that may be applied to such suspected oils are their oxygen absorption power and the time required for drying. Both the per cent of oxygen and the rate of absorption will be found markedly lower, depending on the amount of foreign seed oil present. In order to obtain comparable results, a standard oil of known purity should be carried through the tests along with the suspected oil, as the weather conditions may seriously affect the rate of drying. 27. Spread about one gram of precipitated lead, weighed off accurately, on a somewhat large watch glass in a thin layer, and then allow to fall on to it from a pipette 0.6 to 0.7 gram (not more) of the oil to be tested, placing each drop on a different portion of the lead, and taking care that the drops do not run into one another. Then allow the watch glass to stand at the ordinary temperature in a place exposed to light and protected from falling dust. Weigh at frequent intervals in order to note the rapidity with which the oil is absorbing oxygen and to determine accurately when the oil ceases to gain in weight. The lead powder is prepared by precipitating a lead salt with zinc, washing the precipitate rapidly in succession with water, alcohol and ether, and finally drying in a vacuum. ANALYSIS OF THE VEHICLE. 47 A weighed quantity of the oil will gain 16 to 11 \ per cent in weight in drying; boiled oil somewhat less, varying from 15 to 17 per cent. Instead of precipitated lead, thin aluminum plates 3 inches by 6 inches may be used. The plates are weighed, and 0.1 gram to 0.2 gram of oil rubbed over the plate, giving a thin uniform film, weighed, set aside in a dust-free place, and the increase in weight noted from time to time. 28. Specifications for boiled linseed oil, Navy Depart- ment, 1905. Must be absolutely pure kettle-boiled oil of the best quality, and the film left after flowing the oil over glass and allowing it to drain in a vertical position must dry free from tackiness in 12 hours at a temperature of 70 F. It must contain no rosin. The specific gravity must be between 0.934 and 0.940 at 60 F. To be purchased by the commercial gallon; to be in- spected by weight, and the number of gallons to be deter- mined at the rate of 7J pounds of oil to the gallon. CHAPTER III. ANALYSIS OF THE VOLATILE OILS. 29. Identification. The volatile oil distilled from lin- seed oil is tested qualitatively for spirits of turpentine, stump turpentines, rosin spirit, petroleum naphtha and benzole by the following test. 1 Shake in a test tube equal volumes of the turpentine to be tested and concentrated sulphurous acid until quite thoroughly mixed. Set aside, noting the time of separation and the color of the two strata. Samples of known purity should be run alongside of the sample to be tested, and the time of shaking the samples should be as uniform as pos- sible. Deadwood turpentine if highly rectified gives a reaction approaching that of livewood turpentines. 1. American Turpentine. Separation takes place very slowly. Upper Stratum Opaque ; milky white. Lower Stratum Translucent; milky white. Odor Slight terpene smell. 2. Russian Turpentine. Quick separation. Upper Stratum Translucent; faint turbidity. Lower Stratum Clear and colorless. Odor Slight pungent smell. 1 Scott's Test for Turoentines, Drugs, Oils and Paints, 1906. 48 ANALYSIS OF THE VOLATILE OILS. 49 3. Deadwood Turpentine. Medium slow separation. Upper Stratum Opaque ; light buff color. Lower Stratum Translucent; yellow-amber color. Odor Distinct tar smell. 4. Livewood Turpentine. Medium quick separation. Upper Stratum Translucent ; lemon yellow color. Lower Stratum Clear and colorless. Odor Mild tar smell. 5. Rosin Spirit. Medium slow separation. Upper Stratum Translucent; golden-yellow color. Lower Stratum Translucent; creamy-white color. Odor Pungent rosin smell. 6. Benzine (Petroleum Naphtha). Quick separation. Upper Stratum Clear and colorless. Lower Stratum Clear and colorless. Odor Sulphurous smell. 7. Benzole. Quick separation. Upper Stratum Slight turbidity; faint yellow color. Lower Stratum Clear and colorless. Odor Benzole and sulphurous smell. 30. Estimation of petroleum products. If the qualita- tive test indicates the presence of live or dead wood tur- pentine in appreciable quantities, the amount of petroleum product that may be present is best estimated as follows: A measured quantity of the volatile oil is allowed to drop slowly into 300 c.c. of fuming nitric acid, contained 50 ANALYSIS OF MIXED PAINTS. in a flask provided with a return condenser and immersed in cold water. A violent reaction takes place, and the flask should be shaken occasionally. When all action has ceased the contents of the flask is poured into a separatory funnel and thoroughly washed with successive portions of hot water to remove the products of the action of the acid on the turpentine. The remaining petroleum oil is sepa- rated and measured or weighed. 31. Wood turpentine being absent, the amount of petro- leum products may be very closely approximated by the " Sulphuric Acid Number." The apparatus and materials required being a large test tube of considerable diameter, bedded in closely packed cotton, in a fibre mailing case of suitable size, a thermome- ter provided with a platinum flange attached to the lower end, the lower part of the flange being bent at right angles to the stem of the thermometer. A mailing case packed with cotton offers considerable advantages over the regulation asbestos fibre mixed with plaster of Paris, in that if the test tube is broken during the estimation, the bottom of the mailing case may be readily removed and the acid soaked cotton replaced at once with fresh, while the plaster of Paris composition has to be washed and dried out, an operation requiring several hours. 32. A neutral mineral oil is required giving a rise when treated with sulphuric acid of not more than 3C. Also a standard bottle of concentrated sulphuric acid kept for this purpose and a sample of turpentine known to be pure. Fifty c.c. of the neutral oil are pipetted into the large test tube, the temperature noted, and 20 c.c. of the acid, of the same temperature, added from the burette in a steady stream, stirring rapidly meanwhile with a uniform motion to maximum temperature, which is noted. After cleaning and cooling the apparatus, the experiment is repeated ANALYSIS OF THE VOLATILE OILS. 51 exactly as before, but with the addition of 10 c.c. of pure turpentine to the neutral oil. The rise in temperature is again noted. Similar determinations are made with mix- tures of 50 per cent of turpentine and 50 per cent benzine, and also of 75 per cent of turpentine and 25 per cent of benzine. Having thus ascertained standards for compari- son, 10 c.c. of the sample under examination is carried through in exactly the same manner, the maximum tem- perature noted and the per cent of turpentine and of petro- leum product calculated. Commercially pure turpentines will give closely uniform results; wood turpentines give lower figures which approach that of turpentine the more carefully the product is prepared and purified. Rosin spirits give a rise of 7 to 10 C., benzine and benzole 3 to 8 C. Samples of turpentine which have been exposed to strong light are liable to have undergone oxidation changes which will markedly affect the " temperature rise." In which case, Mcllhiney's bromine addition and substitution method will serve to distinguish such oxidized turpentines. A scheme much in use by some paint chemists for sep- arating mixtures of turpentine and benzine is to introduce 15 c.c. of the suspected sample into a glass-stoppered cylinder graduated to tenths of cubic centimetres, and then add 35 c.c. of cold concentrated sulphuric acid. Shake carefully 12 to 20 times, keeping the top of the cylinder turned away from operator. Allow to stand over night, and read off the volume of the benzine layer direct, the turpentine portion having combined with the sulphuric acid. There is considerable danger of an explosion in using this method; the danger, however, may be much reduced by cooling both the sample and acid to below 10 C. 52 ANALYSIS OF MIXED PAINTS. 33. ANALYSES OF VOLATILE OILS BY THE AUTHOR. No. Name of Oil. Sp. Gr. at 22C. Odor. Rise C. Separation Lower Layer. Upper Layer. 1 Terraben- tine .808 Petroleum 6 Immediate Clear Slightly Milky 2 Turpentine .855 Camphor 52.5 Rapid Almost Lemon Oil Clear 3 Turpentine .862 Character- 57.0 Medium Milky istic Tur- JVlilkv 4 Off Color pentine Turpentine .857 30.5 Slow Clear Clear 5 Turpentine .853 " 48.3 Slow Milky Milky 6 Turpentine .860 it 56.7 Medium Milky Slight tinge of Yellow 7 Wood Spir- Stump its Turpen- Turpentine 52.8 Slow Deep Milky tine .859 Lemon 8 Turpalin Petroleum 1.0 Quick Clear Clear Base .862 No. 1. Petroleum product, probably of Russian origin. No. 2. Wood turpentine. No. 3. Commercially pure turpentine. No. 4. Spirits of turpentine containing about 50 per cent petro- leum naphtha. No. 5. Spirits of turpentine containing about 15 per cent petro- leum naphtha. No. 6. Poorly rectified turpentine. No. 7. Stump turpentine. No. 8. Petroleum product. 34. Excessive use of volatile oils. An excess of thinners or volatile oils is detrimental to the life of the paint. Sabin, in his work on " The Technology of Paint arid Varnish," writes as follows: " Most of the failures of lead and zinc paints are due to the use of these volatile thinners (turpentine and benzine). If raw linseed oil is used, it may be desirable to add 5 per cent of a good drier. This should be pale in color, indi- cating that it has been made at a low temperature, and should be free from rosin. The latter is not an easy thing to detect, but if a fair price is paid, say $1.50 to $2.00 a gallon at retail, and freedom from rosin is guaranteed by a maker of good reputation, the buyer ought to feel safe." ANALYSIS OF THE VOLATILE OILS. 53 The presence of a large amount of thinners renders the paint easier to brush out, and hence the tendency has been to increase the amount of thinners, especially benzine because of its low cost, in mixed paints, resulting in the reducing of the linseed oil to a percentage below that required to give the proper life to the paint. The better class of paint manufacturers seem to consider 4 to 9 per cent of thinners sufficient for outside house paints. Of 71 analyses of white and gray mixed paints made by the author, the amount of thinners came between the following limits: Per Thii Ot 4 5 6 7 8 9 10 11 12 cent iners. o 4 Number of Paints. 6 5 5 6 1 7 6 8 10 9 5 10 . . 11 11 . . 4 12 2 29 21 Excluding the 21 paints containing 12 per cent of thin- ners and over, the average amount of thinners in the remaining 50 paints was 7.3 per cent. The paints high in thinners were, in almost every case, inferior paints, high in inert, pigments. CHAPTER IV. SPECIAL METHODS ON OIL ANALYSIS. 35. Determination of the Iodine Number. The newer Hanus method for the estimation of the iodine number is to be preferred to the older standard Hubl method, as the Hubl solution rapidly loses strength on standing, is very slow in its reaction, and nearly every chemist using it employs a modification of his own, especially as regards the time for the solution to remain in contact with the fat or oil, and hence very different results may be obtained on the same oil or fat by different investigators. Com- parative tests by the two methods made in this laboratory gave results which varied only a few tenths of one unit with oils of medium iodine values. 36. Preparation of Reagents. Iodine Solution. Dis- solve 13.2 grams of iodine in 1000 c.c. glacial acetic acid (99.5 per cent acid, showing no reduction with bichromate and sulphuric acid); add enough bromine to double the halogen content determined by titration 3 c.c. of brom- ine is about the proper amount. The iodine may be dis- solved by the aid of heat, but the solution should be cold when bromine is added. Dednormal sodium thiosulphate solution. Dissolve 24.8 grams of chemically pure sodium thiosulphate, freshly pulverized as finely as possible and dried between filter or blotting paper, and dilute with water to one litre at the temperature at which the titrations are to be made. Starch paste. One gram of starch is boiled in 200 c.c. of distilled water for ten minutes and cooled to room tem- perature. 64 SPECIAL METHODS ON OIL ANALYSIS. 55 Solution of potassium iodide. One hundred and fifty grams of potassium iodide are dissolved in water and made up to one litre. Dednormal potassium bichromate. Dissolve 4.9066 grams of chemically pure potassium bichromate in distilled water, and make the volume up to one litre at the tempera- ture at which the titrations are to be made. The bichro- mate solution should be checked against pure iron. 37. Determination. Standardizing the sodium thiosul- phate solution. Place 20 c.c. of the potassium bichromate solution, to which has been added 10 c.c. of the solution of potassium iodide, in a glass-stoppered flask. Add to this 5 c.c. of strong hydrochloric acid. Allow the solution of sodium thiosulphate to flow slowly into the flask until the yellow color has almost disappeared. Add a few drops to the starch paste, and with constant shaking continue to add the sodium thiosulphate until the blue color just disappears. Weighing the sample. Weigh about 0.5 gram of fat or 0.250 gram of oil on a small watch glass or by other suitable means. With drying oils which have a very high absorbent power 0.100 to 0.200 gram should be taken. The fat is first melted, mixed thoroughly, poured on to the crystal and allowed to cool. Introduce the watch crystal into a wide mouth 16-oz. bottle with a ground-glass stopper. Absorption of iodine. The fat or oil in the bottle is dis- solved in 10 c.c. chloroform. After complete solution has taken place, 25 c.c. of the iodine solution are added. Allow to stand with occasional shaking for 45 minutes. The excess of iodine should be at least 60 per cent of the amount added. Titration of the unabsorbed iodine. Add 10 c.c. of the potassium iodide solution and shake thoroughly, then add 100 c.c. of distilled water to the contents of the bottle. 56 ANALYSIS OF MIXED PAINTS. Titrate the excess of iodine with the sodium thiosulphate solution, which is added gradually, with constant shaking, until the yellow color of the solution has almost disap- peared. Add a few drops of starch paste and continue the titration until the blue color has entirely disappeared. Toward the end of the reaction stopper the bottle and shake violently, so that any iodine remaining in solution in the chloroform may be taken up by the potassium iodide solution. Setting the value of the iodine solution. At the time of adding the iodine solution to the fat, two bottles of the same size as those used for the determination should be employed for conducting the operation described above, but without the presence of any fat. In every other respect the performance of the blank experiments should .be just as described. These blank experiments should be made each time the iodine solution is used. Great care must be taken that the temperature of the solution does not change during the time of the operation, as acetic acid has a very high coefficient of expansion, and a slight change of temperature makes an appreciable difference in the strength of the solution. 38. IODINE NUMBERS OF VARIOUS OILS. Raw linseed oil 170-188 Boiled linseed oil 164-188 Bleached linseed oil 160 Chinese wood oil 163 Com oil 111-123 Cotton-seed oil 101-117 Fish oil 148-160 Turpentine 331-368 39. Determination of the bromine absorption of oils, Mcllheney's method. 1 The advantage of this method is, J. Am. Chem. Soc. XXI, 1084. SPECIAL METHODS ON OIL ANALYSIS. 57 that the absorption of halogen by addition is determined separately from the absorption by substitution, resulting in additional information as to the nature of the substance. The process as at present used is as follows: A quantity of the oil to be analyzed is weighed into a glass-stoppered bottle, 10 c.c. of carbon tetrachloride added to dissolve the oil, and 20 c.c. of third-normal bromine in carbon tetrachloride added from a pipette. It is not found neces- sary in filling the pipette with bromine solution to use any special arrangement to prevent the introduction of bromine vapor into the mouth. Only a rubber tube is necessary. Another pipette full of solution should be added to 10 c.c. of carbon tetrachloride, and this blank titrated with thiosulphate to determine the strength of the bromine solution. The test itself need be allowed to stand only one or two minutes before adding 20 to 30 c.c. of 10 per cent solution of potassium iodide, the amount neces- sary depending upon the excess of bromine present. An excess, of course, does no harm. In order to prevent any loss of bromine or hydrobromic acid which would probably occur on removing the stopper of the bottle, a short piece of wide rubber tubing, of the sort used for Gooch crucibles, is slipped over the lip of the bottle so as to form a well around the stopper. It is advisable, also, to cool the bottle by setting it into cracked ice in order to produce a partial vacuum in the interior. Into the well formed by the rubber tubing is poured the solution of potassium iodide and the stopper opened slightly. If the bottle has been cooled with ice the iodide solution will be sucked into the bottle, and if it was not cooled some of the air from the interior of the bottle will bubble through the iodide solution, being thereby washed, and allow the iodide solution to enter the bottle. When sufficient iodide solu- tion has been introduced the bottle is agitated to insure 58 ANALYSIS OF MIXED PAINTS. the absorption of the bromine and hydrobromic acid by the aqueous solution. The iodine now present is titrated with tenth-normal sodium thiosulphate, and when the titration is finished 5 c.c. of a neutral 2 per cent solution of potassium iodate are added. This liberates a quantity of iodine equivalent to the hydrobromic acid formed, and on titrating this iodine the bromine substitution figure may be calculated. The solution of potassium iodate should be tested for acidity by adding a measured quantity to a solution of potassium iodide, and if any iodine is lib- erated it should be determined with thiosulphate and a suitable correction introduced into the calculation. The potassium iodide, the thiosulphate solution, and the water used should all be tested to see that they are neutral. The reaction between bromine and oil appears to be practically instantaneous as far as the bromine taken up by addition is concerned, but it seems likely that substi- tution is distinctly affected by the length of time that the oil and bromine are allowed to remain in contact. SPECIAL METHODS ON OIL ANALYSIS. 40. Bromine values of various oils. 59 / 1 p PB Bromine calculated from Hubl. Per cent of bromine absorbed. Bromine addition figure. Bromine substitution figure. Bromine from Hubl di- vided by bromine addi- tion figures. Raw linseed oil, several years old Raw linseed oil, several years old .... 1 9 166.9 157.3 105.2 99.1 98.4 99.2 95.4 92.0 1.5 3.6 1.103 1.000 Raw linseed oil ... Do 3 4 184.2 178.6 116.1 112.6 116.1 108.5 109.6 102.1 3.4 3.2 1.059 1.102 Do 5 185.9 117.2 113.2 109.2 2.0 1.072 Do 6 186.3 117.0 112.2 106.5 2.9 1.098 Do 7 104 5 99 9 2.3 Do s 115 1 109 5 2.8 Do q 114 6 109 4 2.6 Average omitting Nos. 1 and 2 Boiled linseed oil . . Do 1 2 183.8 180.4 183 3 115.7 113.7 115 5 112.0 106.0 110 8 106.6 100.8 105 8 2.7 2.6 2 5 1.083 1.126 1 091 Do 3 105 4 101 2 2 1 Do 4 110 103 2 3.4 Do Do Do ... 5 6 7 109.8 113.6 109 2 105.2 103.0 103 8 2.3 5.3 2.7 Do 8 110.8 101.0 4.9 Averages 109.5 103.0 3.2 Third run rosin oil . . Do 1 9 63 9 40 3 197.6 92 3 16.4 7 7 90.6 42 3 5 231 "Mystic" brand rosin oil 93 7 6 3 43 7 "Java" boiled rosin oil Corn oil 1 73.3 46.2 101.9 76.2 8.3 73.8 46.8 1.2 5.685 Do ?, 75.8 73.2 1.3 Do 3 75.4 71.6 1.9 Averages 75.8 72.9 1.5 60 ANALYSIS OF MIXED PAINTS. 41. Estimation of rosin in mixtures of linseed oil and mineral oil. Twitchell's method. A weighed portion of the sample is saponified by boiling with alcoholic potash; the alcohol is driven off by prolonged boiling after diluting with water. The unsaponifiable matter is shaken out with petroleum ether as previously described under Lin- seed Oil. The remaining soap solution made acid yielding a mixture of fatty and rosin acids. Heat until the fatty acids have separated on top. Cool, break the cake of fatty acids with a glass rod, pouring off the aqueous solu- tion. Treat the acids again with boiling water, cool, remove to a porcelain dish, and dry at 100 C. until freed from all traces of water. Two to three grams of the mixed fatty and rosin acids are weighed off accurately and dissolved in a flask in ten times their volume of absolute alcohol, and a current of dry hydrochloric acid gas passed through for about forty-five minutes or until the gas ceases to be absorbed. Allow 'to stand one hour, then dilute it with five times their volume of water and boiled until clear. From this point the analy- sis may be completed volumetrically or gravimetrically. 42. Volumetrically. The contents of the flask are transferred to a separatory funnel and the flask rinsed out several times with ether. After vigorous shaking the acid layer is run off and the remaining ethereal solution contain- ing the rosin acids washed with water until the last trace of acid is removed. Fifty c.c. of alcohol are added and the solution titrated with standard caustic potash, using phenolphthalein as an indicator. The rosin acids com- bine at once with the alkali, whereas the ethylic esters remain unchanged. The number of c.c. of normal alkali used multiplied by 0.346 will give the amount of rosin in the sample. 43. Gravimetrically. The contents of the flask are SPECIAL METHODS ON OIL ANALYSIS. 61 mixed with a little petroleum ether, boiling below 80 C., and transferred to a separating funnel, the flask being washed out with the same solvent. The petroleum ether layer should measure about 50 c.c. After shaking, the acid solution is run off and the petroleum ether layer washed once with water, and then treated in the funnel with a solution of 0.5 gram of potassium hydroxide and 5 c.c. of alcohol in 50 c.c. of water. The ethylic esters dis- solved in the petroleum ether will then be found to float on top, the rosin acids having been extracted by the dilute alkaline solution to form rosin soap. The soap solution is then run off, decomposed with hydrochloric acid, and the separated rosin acids collected as such, or preferably dissolved in ether and isolated after evaporat- ing the ether. The residue, dried and weighed, gives the amount of rosin in the sample. 44. Determination of the free fatty acids in linseed oil. Ten grams of oil are weighed into a suitable sized Erlen- meyer flask and 50 c.c. of neutral, aldehyde-free alcohol added. The mixture is heated to about 60 C. for a minute or two, then cooled and titrated with tenth-normal alcoholic potash, using phenol phthalein as an indicator. Oil made from mouldy seed, or seed contaminated with mustard oil, or oil containing rosin, will have a high acid figure. Pure raw oil should have a low acid figure, boiled oil will have a slightly higher figure. Free mineral acid in bleached oil is determined by washing a definite weight of oil with water, separating the water, and titrating the dissolved mineral acid present. Preparation of aldehyde, free alcohol for alcoholic potash solution. Dissolve 1.5 grams of silver nitrate in about 3 c.c. of water and add to a litre of alcohol in a glass-stop- pered cylinder, mixing thoroughly. Dissolve 3 grams of pure potassium hydroxide in 10 to 15 c.c. of warm alcohol. 62 ANALYSIS OF MIXED PAINTS. Cool, pour slowly into the alcoholic silver nitrate solution, without shaking. The silver oxide is precipitated in a finely divided condition. Allow to stand until the pre- cipitate has completely settled. Siphon off the clear liquid and distil. The distillate will be neutral and free from aldehydes, and will not darken when used as a sol- vent for potash. 45. Determination of the saponification value. This value is also spoken of as the Koettstorfer number and Saponification number. In each case it is equivalent to the number of milligrams of potassium hydroxide neces- sary to saponify one gram of the oil. Two grams of the oil are weighed out into a small Erlen- meyer flask and saponified with 25 c.c. of half-normal alcoholic potash, by heating gently on a water bath, a funnel being inserted in the flask. When the saponification is complete a few drops of phenolphthalein are added and the excess of alkali titrated with half-normal hydrochloric acid. A blank determination of the strength of the alcoholic potash should be made at the same time. 46. Determination of the flash point of linseed oil. For exact flash-point figures, rather expensive and com- plicated testers are needed; but for commercial tests that yield approximately the same figures, a very simple appa- ratus may be used, consisting of a two-ounce crucible, a thermometer reading at least 300 C., and a small gas jet attached to a rubber tube, a flame about the size of a pea being used. The cup is filled two-thirds full of oil, the bulb of the thermometer suspended in it, and the oil slowly heated. The determination should be carried on in a place entirely free from draughts. At short intervals the gas flame is brought close, but not touching, to the surface of the oil, with a slow, sweeping motion. The first distinct puff of pale blue flame that shoots across the SPECIAL METHODS ON OIL ANALYSIS. 63 surface of the oil indicates the flash point of the oil, and the temperature at which this occurs is noted. 47. Hurst states that linseed oil, whether raw or boiled, flashes about 243 C. ; but these figures are considerably lower than those obtained in this laboratory, the raw oils flashing in the vicinity of 300 C., and the pure boiled oils from 275 to 300 C. Volatile oils used in the drier added to the oil, lower the flash point considerably, 4 or 5 per cent of volatile oil lowering the flash point to about 250 C. The other vegetable oils, as corn and cotton-seed oils, flash at nearly the same temperature as linseed oil. Min- eral oils, such as would be used for adulteration, flash at 193 to 216 C., rosin oils at 140 to 167 C. The presence of rosin oil would also be indicated by the strong odor of rosin given off during the heating. Benzine and turpen- tine when present in linseed oil rapidly lower the flash point according to the percentage present, having a flash point themselves but little above that of room temperature. 48. Correction to be applied to the thermometer reading. Let N = Length of exposed thread of mercury expressed in degrees. T = observed boiling point. t = temperature of the auxiliary thermometer, the bulb of which is midway between ends of the exposed mercury thread. 0.000154 = apparent coefficient of expansion of mercury in glass. C = the correction in degrees. Then C = N (T - t) X 0.000154. 49. Evaporation test. This test will show very closely the amount of benzine added along with the drier in the preparation of boiled linseed oil. 64 ANALYSIS OF MIXED PAINTS. Five grams of the oil to be tested are weighed into a small flat-bottomed evaporating dish and allowed to remain undisturbed at a temperature of 150 C. for three hours. The dish is then removed, cooled quickly, and immediately weighed. The loss in weight represents usually the greater portion of mineral oils, rosin oils or other volatile matters present in the sample. J. Hortvet, state chemist for Minnesota, states that, " Of fifteen samples represented as raw linseed oil, when subjected to this test, eleven showed no loss in weight, while four gave losses amounting to less than 0.3 per cent. Of one hundred and ten samples represented as boiled oils, sixty gave losses above 2 per cent, thirty- two showed no loss in weight, and of the remaining eigh- teen the loss was slight, seldom approaching 2 per cent. Forty-seven of the sixty samples which gave over 2 per cent loss were found to vary in specific gravity from 0.8835 to 0.9310. All samples not found adulterated by the usual tests showed a specific gravity of from 0.9310 to 0.9425, with the exception of one sample which had a specific gravity as low as 0.930, but by the other tests appeared to be straight raw linseed oil." 50. Determination of flash point and fire test of petro- leum products, turpentine, etc. Covered testers. New York State Board of Health Tester. This instrument consists of a copper oil cup holding about 10 ounces heated in a water bath over a small flame. The cup is provided with a glass cover, holding a thermometer. This cover also has a hole for the insertion of the testing flame. The test should be applied as follows : * " Remove the oil cup and fill the water bath with cold water up to the mark on the inside. Replace the oil cup 1 Report New York State Board of Health, 1882, p. 495. SPECIAL METHODS ON OIL ANALYSIS. 65 and pour in enough oil to fill it to within one-eighth of an inch of the flange joining the cup and the vapor-chamber above. Care must be taken that the oil does not flow over the flange. Remove all air bubbles with a piece of dry paper. Place the glass cover on the oil cup, and so adjust the thermometer that its bulb shall be just covered by the oil. "If an alcohol lamp be employed for heating the water bath, the wick should be carefully trimmed and adjusted to a small flame. A small Bunsen burner may be used in place of the lamp. The rate of heating should be about two degrees per minute, and in no case exceed three degrees. " As a flash torch, a small gas jet one-quarter of an inch in length, should be employed. When gas is not at hand employ a piece of waxed-linen twine. The flame in this case, however, should be small. 51. " When the temperature of the oil in the case of kerosene has reached 85 F., the testings should commence. To this end insert the torch into the opening in the cover, passing it in at such an angle as to well clear the cover, and to a distance about half-way between the oil and the cover. The motion should be steady and uniform, rapid, and without any pause. This should be repeated at every two degrees' rise of the thermometer, until the ther- mometer has reached 95, when the lamp should be re- moved and the testings should be made for each degree of temperature until 100 is reached. After this the lamp may be replaced if necessary, and the testings continued for each two degrees. " The appearance of a slight bluish flame shows that the flashing point has been reached. " In every case note the temperature of the oil before introducing the torch. The flame of the torch must not come in contact with the oil. 66 ANALYSIS OF MIXED PAINTS. " The water bath should be filled with cold water for each separate test, and the oil from a previous test care- fully wiped from the oil cup." 52. Open testers. Tagliabue's open tester. This instru- ment is similar to the preceding, except that it is smaller, the oil cup being of glass and without a cover. The water bath is filled as before. The oil cup is filled to within three-thirty-seconds of an inch of the top. The heating flame is regulated to three-fourths of an inch in height, or at such height that the temperature of the oil is raised two and a half degrees per minute until 97 F. is reached, when the test flame is applied and the testings made every two degrees until the flash point is reached. 53. Fire test. The fire test is the temperature at which an oil will give off vapors, which when ignited will burn continuously. The cover is removed in the case of the closed tester, the heating being continued as described above. The flame may be extinguished by the use of a piece of asbestos board. 54. Specifications for various oils. It often devolves upon the paint chemist to examine various oils, some of which cannot be considered as paint oils, hence the follow- ing specifications adopted by the Treasury Department at Washington, 1907, of various oils will be of interest. 55. Linseed oil. It must be thoroughly strained and settled, transparent, free from suspended matter, and have the properties of a well-aged oil. The oil shall conform to the following physical and chemical tests: specific gravity at 15.5 C., not less than .933; flash point (open cup) not less than 280 C.; viscosity at 20 C., as determined by Engler viscosimeter (water being 100), not less than 750; iodine absorption number as determined by Wijs' method (time of absorption 2 hours), not less than 175; to be entirely free of all acids except fatty acids, of which not SPECIAL METHODS ON OIL ANALYSIS, 67 more than 2 per cent calculated as linolic acid should be present; when heated to 300 C., and allowed to cool, the oil should show no suspended matter or deposit ; and must show excellent drying qualities, as demonstrated by the Livache method. 56. Deodorized benzine. Should be a purified petroleum distillate, free from sulphur; specific gravity between .725 and .735 at 15.5 C. 57. Engine oil. Free running oil is required, consist- ing of 90 per cent refined petroleum, and 10 per cent pure acidless lard oil. The specific gravity should not be less than .905 at 15.5 C.; viscosity by Engler viscosimeter should not be less than 1550, and flash point less than 200 C. Samples that comply with the above require- ments will be subjected to a practical test. 58. High pressure cylinder oil. An oil is required con- sisting of 90 per cent refined petroleum stock and 10 per cent of acidless tallow; specific gravity should not be less than .870 at 50 C.; flash point not less than 285 C.; vis- cosity by Engler viscosimeter should not be less than 2000 at 50 C., and not less than 350 at 97 C. The mixture should be neutral, free from adulterations, and suitable for use on engine cylinders with steam pressure of 125 pounds per square inch. Samples that comply with the above requirements will be subjected to a practical test. 59. Lithographic varnish. No. 0. Should be a varnish of the best quality of linseed oil and with a specific gravity of .940 at 25 C., and be suitable for making fine typo- graphic inks. No. 1. Requirements same as for No. 0, but with a specific gravity of .945 at 25 C. No. 3. Requirements same as for No. 0, but with a specific gravity of .965 at 25 C. 60. Kerosene oil. Under this specification is required 68 ANALYSIS OF MIXED PAINTS. refined petroleum, water white, specific gravity .790 to .810 at 15.5 C., and flash point not lower than 45 C. 61. Lard oil. Should contain the least possible quantity of free acid ; should show a cold test of not over 4 C. ; be free from adulterations, and have specific gravity of .914 to .916 at 15.5 C. The oil should be made from fresh lard, be free from admixture with other oils, and should respond to no test for cotton-seed oil. 62. Sperm oil. Should be pure winter-strained sperm oil, free from admixtures of any kind; specific gravity to be .875 to .884 at 15.5 C., and flash point 250 C.; viscosity as determined by Engler viscosimeter to be: at 20 C., not less than 495; at 50 C., not less than 220; and at 90 C., not less than 133. 63. Gasoline. Should be a refined petroleum product of .680 to .705 specific gravity at 15.5 C. CHAPTER V. ANALYSIS OF WHITE LEAD. 64. Color. The two samples are weighed out in gram lots on to a large glass plate, twelve drops of bleached linseed oil added to each and rubbed up thoroughly, and matched up on a microscope slide, the color being judged from both sides of the glass. After comparing the color, place the slide in the steam oven for two hours. This will give some idea as to the amount of yellowing that will occur when the lead is used in painting. This defect is particularly marked in pulp leads. 65. Lead acetate. The presence of lead acetate may be detected by pouring a few drops of a 10 per cent solution of potassium iodide upon the dry lead. If it turns yellow it contains acetate, w r hile a well-washed sample will remain unchanged. 66. Opacity. Two grams each of the sample and standard are very carefully rubbed up with .01 gram of ultramarine blue and twenty-four drops of oil as described under the section on the Determination of the Tinting Strength of Colors. The more strongly the lead is colored, the weaker it is in hiding power or opacity. Adding we\q;hed amounts of lead until the colors are of equal depth will show the ratio between the two. 67. Painting test. The painting value is best judged by painting test boards as described under the section on the Comparison of Paints for Covering Power, and after- wards exposing them under suitable conditions. 68. Sandy lead. One hundred grams of the paste lead are thinned with benzine and run through a fine bolting 69 70 ANALYSIS OF MIXED PAINTS. cloth, thoroughly stirred, and allowed to settle slightly for a short time only. The benzine portion is decanted and the sediment washed with benzine in a similar man- ner, until the benzine comes off nearly clear, leaving the sand alone as a residue. Sandy lead, while present in nearly all commercial lead, should be below 2J per cent, but will sometimes be present in quantities as large as 10 per cent. 69. Foreign .pigments. White lead is often adulterated with less expensive pigments, such as barytes (barium sulphate), zinc oxide, calcium carbonate, calcium sulphate, and the various kinds of silicates. On treating a small portion of the sample with acetic acid and diluting, the white lead and calcium salts will go into solution, leaving any lead sulphate, barytes, silica and silicates undis- solved. Barytes is tested for by the flame test. Zinc is recognized by adding a few drops of potassium ferro- cyanide to a portion of the clear acetic acid solution, a whitish precipitate of zinc ferrocyanide being obtained. Hydrogen sulphide is passed through the remainder of the acetic acid solution until all of the lead, and any zinc, are precipitated. Filter, and treat the filtrate with ammo- nium oxalate and leave in a warm place. A white precipi- tate indicates the presence of calcium compounds. If the white lead is found to contain other pigments, the analysis is conducted as described under Analysis of White Paints. 70. Estimation of carbon dioxide. The amount of carbon dioxide in white lead may be estimated easily and accurately by means of Knorr's Apparatus or Scheibler's Apparatus. ANALYSIS OF WHITE LEAD. KNORR'S APPARATUS. 71 (1) Description of apparatus. This apparatus (Fig. 4) employs only ground-glass joints, and may be quickly made ready for use or taken to pieces and packed away. FIG. 4. KNORR'S APPARATUS. On the other hand, it is inflexible and must be carefully handled. A is distilling flask fitted to condenser by a ground-glass stopper; B, reservoir containing acid; C, soda-lime tube; D, condenser; E, calcium chloride tube; F, U-tube filled with pumice stone moistened with sul- phuric acid, followed by a calcium-chloride tube G. The three soda-lime tubes H, H, H are followed by a calcium chloride tube K, which is connected with an aspirator at L. The calcium chloride and soda lime employed should be finely granulated and freed from dust with a sieve. 71. One gram of the sample to be examined is placed in the distilling flask, which must be perfectly dry. The flask is closed with a stopper carrying the tube connecting with the absorption apparatus and also with the funnel tube. The tubes in which the carbon dioxide is to be absorbed are weighed and attached to the apparatus. In case two Liebig bulbs are employed, one for potassium 72 ANALYSIS OF MIXED PAINTS. hydroxide and the other for sulphuric acid, to absorb the moisture given up by the potassium hydroxide solution, it will be necessary to weigh them separately. If soda-lime tubes are employed it will be found advantageous to weigh them separately and fill the first tube anew when the second tube begins to increase in weight materially. The tube B is nearly filled with hydrochloric acid (sp. gr. 1.1), and the guard tube C placed in position. The aspirator is now started at such a rate that the air passes through the Liebig bulbs at the rate of about two bubbles per second. The stopper of the funnel tube is opened and the acid allowed to run slowly into the flask, care being taken that the evolution of the gas shall be so gradual as not to materially increase the current through the Liebig bulb. After the acid has all been introduced, the aspiration is continued, when the contents of the flask are gradually heated to boiling, the bulb in tube B being closed. While the flask is being heated the aspirator tube may be removed, although many analysts prefer when using ground-glass joints to aspirate during the entire operation. The boiling is continued for a few minutes after the water has begun to condense in D, when the flame is removed, the valve in the tube B, opened, and the apparatus allowed to cool with continued aspiration. The absorption tubes are then removed and weighed, the increase in weight being due to carbon dioxide. 72. Scheibler's apparatus. One-half gram of the sample is weighed into the flask A (see illustration), and 10 c.c. of dilute hydrochloric acid (sp. gr. 1.1) pipetted into the globe funnel M. A considerable number of glass beads should be added to the flask. The stop-cock G is opened and the water in F forced up into the tubes L and N by pressing on the bulb H. Bring the water slightly above the zero mark at the top, and by ANALYSIS OF WHITE LEAD. 73 opening the pinch-cock bring the water in the tubes to a level on the zero mark. The apparatus is now ready for the determination. Open the stop-cock B and allow the acid to flow slowly into the flask. The gas immediately begins to come off and pass into the rubber balloon E, which causes the water FIG. 5. SCHEIBLER'S APPARATUS. in AT to be depressed and that in L to be correspondingly elevated. The pinch-cock G is opened and the water in L is allowed to flow out sufficiently fast to keep L and N as nearly on the same level as possible. When the water 74 ANALYSIS OF MIXED PAINTS. ceases to be depressed in N, the pinch-cock G is closed and the apparatus allowed to stand five minutes, then the flask A is shaken three times at suitable intervals. At the end of half an hour all of the carbon dioxide should be expelled. The water in the tubes is brought to the same level and the burette reading made. A barometer reading should also be taken and the temperature of the ther- mometer on the instrument noted in order to correct for pressure and temperature. By referring to the following tables the per cent of carbon dioxide may be easily cal- culated. EXAMPLE. Weight of sample 0.5 gram. Burette reading 30.3 c.c. Barometer reading 750. m.m. Thermometer reading 24 C. Correction for absorption . . . 5. 09 c.c. Gas evolved . 30.30 c.c. Total gas liberated 35. 39 c.c. Weight of 1 c.c. of carbon dioxide at 750 m.m. pressure and 24 C. = .001731 g. 35.39 X .001731 = .06126 g. 0.5 : 0.06126 : : 100 : x x =-- 12.25 per cent carbon dioxide in sample. NOTE. In determining the amount of carbon dioxide in such products as "mineral primer" made from dolomitic limestone, the evolution of carbon dioxide is incomplete without boiling. 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S^^^^ 8g^>S| aotf[5?H S^SiS&giijSaS^ 140 ANALYSIS OF MIXED PAINTS. 205. Tuscan reds should contain about 60 per cent ferric oxide, and are often brightened up by having pre- cipitated on them an organic red. Another class of oxides, carrying about the same amount of iron oxide as Tuscan reds, is "Prince's metallic." The variation of iron content is shown in the following analyses: No. Ferric Oxide. I 44.07 II 38.17 III 68.45 IV 49.58 V 39.35 A complete analysis gave the following : Per cent. Volatile 3 .33 Ferric Oxide 40 .91 Alumina 3 .49 Calcium Oxide 2 .00 Insoluble 49 .57 Undetermined 0.70 100.00 206. Ochres, of which the French ochres are considered the best, to pass inspection by the various service depart- ment scientists of the United States Government, must be of good bright color, contain at least 20 per cent sesqui- oxide of iron and not over 5 per cent of lime in any form. A good grade of yellow ochre to pass this inspection would analyze about as follows : Per cent. Silica 52.14 Alumina 12.89 Ferric oxide 22.42 Calcium oxide . 36 Combined water 10.16 Hygroscopic water 2.03 100.00 ANALYSIS OF INDIAN REDS. 141 t-i O ^ O5 O O5 CO Oi O CO Tfi CO CO CO CO rt< r-i -H CO C^ C^ (N -i 00 . CO 00 W C^l CO ^ O5 CO iO -TJI -' I C^TfrllOCO'O'l'O'-H''^ O5 ^ i I I CN o c o b s -r _r o G CO O >O O O O "5 CO Tf G ^ oo * o rt* o 1-1 I-H co oo COCOT* t^iOt^^COt^rJi -00 -O -OfNlN CO Oi 00 O5 CO 00 Tt< T}< -co CO O H QQ ^ ^S OOOOOOOCOOO^HOOOO fe.Jg 142 ANALYSIS OF MIXED PAINTS. Specifications for Venetian Red. (Bureau of Supplies and Accounts, Navy Department, 1902). 208. Red, Venetian. I. Red, Venetian (bright). The dry pigment must contain at least 20 per cent of sesqui- oxide 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. II. Red, Venetian (deep). The dry pigment must contain at least 30 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. III. Red, Venetian (medium). 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. CHAPTER XII. ANALYSIS OF BLACK AND BROWN PIGMENTS AND PAINTS. 209. Composition. The ordinary black pigments, lamp- black, vegetable black, bone black, ivory drop black, gas black, graphite, etc., contain carbon as their essential con- stituent, and while all of these products are said to be of a black color, they vary greatly in shade and still more so in tinting strength. 1. Lampblack and vegetable black are essentially soot blacks, being the soot deposited from the combustion of oily bodies such as dead oil. Lampblack has a distinct gray tint as may be shown by comparison with ivory black. These blacks are apt to contain varying quanti- ties of oil, owing to the nature of their manufacture. Less than 1 per cent of oil often being sufficient to retard seriously the drying of lampblack paints. Vegetable blacks are more voluminous than lampblacks and are usually of a jet black color. 2. Carbon black is usually produced from the incom- plete combustion of natural gas. While its tinting power is very great its use has been largely abandoned owing to its tendency to produce a streaky color when used in tinting paints. 3. Bone black is as its name indicated, obtained by the charring of bones in retorts. The carbon content varies usually between 12 and 22 per cent, the balance consisting of moisture, phosphate of calcium and car- bonate of calcium. The best grades of bone black are made from selected sheep bones. An exceedingly intense 143 144 ANALYSIS OF MIXED PAINTS. black is made by digesting selected bones in hydrochloric acid until all of the mineral matter is dissolved, leaving the carbon in a flocculent state. This black is often sold under the name of black toner, and is one of the highest priced blacks. 4. Animal black is a name sometimes given to bone black but is also used to designate a wide variety of blacks prepared in the same way as bone black from waste animal products of all kinds, as leather scrap parings, horn trim- mings, etc. 5. Frankfort black, drop-black and German black are terms used to designate blacks made from a variety of organic materials, such as vine twigs, refuse of wine-making, peach stones, bone shavings, etc. These blacks vary in hue from a bluish-black to a reddish-black. 6. Graphite while not used to any extent in house- paints is largely used in bridge, elevator, and warehouse paints. It is rarely used by itself for these purposes, silica, calcium carbonate and iron oxide pigments, zinc and lead being the other usual constituents. It may be tested for qualitatively in the extracted pigment by rub- bing a portion of the sample between the palms, which soon assume the characteristic appearance produced by stove polish. Of all the black pigments graphite alone gives this test. 7. Charcoal black and vine black are produced by the charring of wood products, and contain besides carbon the ash ingredients common to wood. Charcoal blacks are usually made from maple, willow and bass wood, and vine blacks from the charring of the grape vine. Paints con- taining considerable quantities of these blacks are liable to saponify badly owing to the moisture and potash salts present. BLACK AND BROWN PIGMENTS. 145 8. Mineral black which is still occasionally used is black slate finely ground. 210. Moisture. Dry 2 grams at 105 C. for 3 hours. Loss in weight represents approximately the amount of moisture present. 211. Oils. Extract 2 grams with ether in a fat extrac- tion apparatus. After removing the ether and drying, any increase in weight represents the amount of oily matter present. 212. Ash. Two grams are weighed into a crucible and heated over a Bunsen burner until all the carbon is burned off. If the ash constitutes only a small per cent, it may be cooled and weighed directly. Otherwise the residue is moistened with a solution of ammonium carbonate, heated gently, and weighed. The object of this operation is to restore the carbon dioxide which may have been expelled from the bases by the strong heat to which they have been subjected. 213. Carbon. The carbon is usually estimated by difference, by adding together the moisture, oil and ash, and subtracting from 100. 214. Calcium. Digest the residue from 212 in a mix- ture of 25 c.c. of concentrated hydrochloric acid and 5.c.c. of concentrated nitric acid on the hot plate for one-half hour, dilute, filter, and make up to 250 c.c. in a graduated flask. Any appreciable residue on the filter may indicate addition of barytes, silica, clay or alumina. Determine the calcium and magnesium in an aliquot portion of the solution by adding ammonia in small quantities until a precipitate is formed, then acetic acid in excess until redissolved, except for traces of iron which may be re- moved by filtration. Ammonium oxalate is added, and the calcium precipitate treated in the usual manner. 215. Phosphoric acid. Take an aliquot portion of 146 ANALYSIS OF MIXED PAINTS. the solution prepared above, neutralize with ammonia, and clear with a few drops of nitric acid, add about 5 grams of dry ammonium nitrate or a solution containing that amount. To the hot solution add 50 c.c. of molybdic solution for every decigram of phosphoric acid that is present. Digest at about 65 for an hour, filter and wash with cold water, or preferably ammonium nitrate solution. Test the filtrate for phosphoric acid by renewed digestion and addition of more molybdic solution. Dissolve the precipitate on the filter with ammonia and hot water, and wash into a beaker to a bulk of not more than 100 c.c. Nearly neutralize with hydrochloric acid, and add mag- nesia mixture from a burette; add slowly (about 1 drop per second), stirring vigorously. After 15 minutes add 30 c.c. of ammonia solution of density 0.96. Let stand for some time; 2 hours is usually enough. Filter, wash with 2.5 per cent ammonia, ignite to whiteness or to a grayish white, and weigh as magnesium pyrophosphate. 216. Preparation of reagents. Molybdic solution. Dis- solve 100 grams of molybdic acid in 400 grams or 417 cc., of ammonia, specific gravity 0.96, and pour the solution thus obtained into 1,500 grams or 1,250 c.c. of nitric acid, specific gravity 1.20. Keep the mixture in a warm place for several days, or until a portion heated to 40 deposits no yellow precipitate. Decant the solution from any sediment and preserve it in glass-stoppered vessels. Magnesia Mixture. Dissolve 110 grams of crystallized magnesium chloride, 280 grams of ammonium chloride, in 700 c.c. of ammonia of specific gravity, 0.96, and suffi- cient water to make 2000 c.c. 217. Magnesium. The filtrate, from which the calcium has been precipitated, is evaporated to a small bulk and made alkaline with ammonia. After standing several, hours the magnesium precipitate is filtered, ignited, and BLACK AND BROWN PIGMENTS. 147 weighed, and calculated to magnesium by multiplying by 21.88. 218. Calculations. The magnesium is calculated to magnesium phosphate, and the remainder of the phos- phoric acid to calcium phosphate. Any calcium remain- ing is calculated to calcium carbonate. Genuine ivory black, made by carbonizing waste frag- ments and turnings of ivory, is often adulterated with bone black, which is somewhat similar in composition, but contains only a small amount of magnesium phosphate as compared with the ivory black. 219. Specifications for drop black. (Navy Department, May, 1903). 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. The pigment must be of the best quality, free from all adulterants, and equal in all respects to the standard sample. The paste must be ground in pure raw linseed oil only, to a medium stiff paste, which will break up readily in thinning. 220. Specifications for carbon black, etc. (Treasury Department, 1907). Carbon black must be pure gas carbon with not more than 0.5 per cent of ash, that is, 97.5 per cent of pure carbon and the balance moisture, ash, etc. Hard black; should be suitable for making the highest class of plate printing inks; and other factors being equal, a color having chemical and physical properties adapted for that purpose and which produces an ink having the most satisfactory working qualities will be selected. The black now in use has the following chemical analysis: Per cent. Ash 48.3 Moisture 3.7 Carbon 48.0 Ash insoluble in hydrochloric acid 11.4 per cent. 148 ANALYSIS OF MIXED PAINTS. Soft Black. Requirements same as for hard black, black in use has the following chemical analysis: Per cent. Ash 56.1 Moisture 2.5 Carbon (by diff.) 41.4 100.0 Ash insoluble in hydrochloric acid 36.3 per cent. The 221. COMPOSITION OF IVORY AND BONE. IVORY (Uncalcined). Calcium phosphate, including slight amount of calcium fluoride . Calcium carbonate Magnesium phosphate Soluble salts Organic matter BONE (Uncalcined). Calcium phosphate . . Calcium carbonate . . Magnesium phosphate. Organic matter . . . . I. Per cent. 38.48 5.63 12.01 0.70 43.18 100.00 I. Per cent. 61.4 8.6 1.7. 28.3 100.00 II. Per cent. 46.48 3.86 7.84 0.77 41.05 100.00 II. Per cent. 62.4 7.9 1.7 28.0 100.00 222. TYPICAL ANALYSES BY THE AUTHOR OF THE VARIOUS BLACKS. Moisture Oil . . . Ash. . . Carbon . I. Ivory Drop Black Per cent. 0.14 0.22 15.23 84.41 100.00 II. Lamp Black Per cent. 2.24 0.35 0.32 97.09 100.00 III. Lamp Black Per cent. 2.18 0.19 0.10 97.53 100.00 BLACK AND BROWN PIGMENTS. 149 I. II. III. Ivory Black 1 Per cent. German Ivory Black Per cent. Ivory Black ' Per cent. 0.75 0.17 88.98 .42 2.33 0.22 84.82 2.59 0.14 84.70 32 77 .51 77, ,82 6 .51 5 ,60 10.10 .38 12.63 96 12.57 100.00 100.00 100.00 Moisture Oil Ash Insoluble ... 0.88 Calcium phos- phate . . .73.72 Calcium carbon- ate 14.00 Magnesium phos- phate .... 0.38 Carbon Analysis of Mixed Paints Tinted with Black and Oxide of Iron Pigments. 223. Carbon. One gram of the pigment is dissolved in hydrochloric acid as described under white pigments, and the residue filtered through an ashless filter, that has been dried in the hot water oven and weighed. After washing the residue with boiling water the filter and contents are dried and weighed, then ignited until all the carbon is burned off, and weighed again. The percentage of carbon is obtained by difference. Where the per- centage of color is small, it is often estimated by difference, adding together the determined constituents and sub- tracting from 100. 224. Ferric oxide. If the filtrate from the insoluble residue is of an appreciable yellow color it indicates that the tint has been " warmed up " by the addition of an ochre or oxide. In which case the lead is precipitated and estimated as described under analysis of white pig- ments, the filtrate from the lead sulphide heated until all of the hydrogen sulphide has been expelled and the iron 1 Not true ivory blacks. 150 ANALYSIS OF MIXED PAINTS. and alumina precipitated with ammonia after having been oxidized by boiling with a few drops of nitric acid, filtered and ignited and weighed in a porcelain crucible, the residue fused with bisulphate of potassium, dissolved in water with the aid of a little hydrochloric acid, heated to boiling, reduced with stannous chloride; mercuric chloride and manganous sulphate solution added and titrated with permanganate in the manner described under analysis of Venetian Reds. 225. Alumina. The alumina is calculated by difference from the data obtained under 224. 226. Zinc oxide. The filtrate from the iron and alumina precipitate and the filtrate from the lead sulphate precipi- tate, the alcohol having been removed by evaporation, are mixed, made distinctly alkaline with ammonia and the zinc precipitated with hydrogen sulphide. The liquid containing the zinc sulphide precipitate is heated to boil- ing, and about 5 grams of solid ammonium chloride added, which renders the precipitate easier to filter. Settle, filter, and wash thoroughly. Pierce filter, wash through into a clean beaker with water, dissolving the residue on filter with dilute hydrochloric acid and wash with hot water. Dilute, heat to expel hydrogen sulphide arid titrate with ferrocyanide as previously described. If iron is absent in the paint the zinc may be estimated directly as described under analysis of white paints. 227. Calcium and magnesium. Estimate as usual in the filtrate from the zinc sulphide. 228. Residue insoluble in hydrochloric acid. Fuse with sodium carbonate as previously described. Dissolve in water and filter. Iron not previously dissolved will remain on the filter as ferric oxide along with any barium that may be present. This residue after thorough washing is dis- solved with the aid of a small quantity of hydrochloric BLACK AND BROWN PIGMENTS. 151 acid, the barium precipitated as usual and the iron esti- mated in the filtrate from the barium sulphate. The silica and alumina are estimated as usual. 229. Lead sulphate. Determine the combined sulphuric acid as described under analysis of white paints and calcu- late to lead sulphate in the absence of calcium sulphate. If calcium carbonate and calcium sulphate are both present the nitric acid-alcohol separation should be used. 230. ANALYSES BY AUTHOR OF PAINTS TINTED WITH BLACKS, OCHRE AND IRON OXIDES. I. II. Light Drab. Drab. Net weight, Ibs. and oz. 6:6 6:12 Capacity of can, qts 2.06 2.03 Contents qts 1.93 1.92 Per cent. Per cent. Pigment by weight . 56 . 6 56 . 9 Vehicle . 43.4 43.1 ICO. 00 100.00 ANALYSIS OF VEHICLE. Per cent. Per cent. Linseed oil 92.9 92.0 Turpentine drier 7.0 6.2 Water 0.1 1.8 100.00 100.00 ANALYSIS OF PIGMENT. Per cent. Per cent. White lead 26.57 27.73 Lead sulphate . . 0.78 2.39 Zinc oxide 62.34 57.12 Color 10.31 12.76 Clay and silica 5 . 56 7 . 74 Iron oxide 3 . 02 3 . 89 Carbon and undetermined . 1.73 1.13 100.00 100.00 152 ANALYSIS OF MIXED PAINTS. Vandyke-Brown. Composition. 231. Vandyke-Browns vary widely in composition according to the method of preparation. Some are obtained from natural deposits of an organic nature, such as peat, decayed vegetable matter, etc. ; or by the slight calcining of cork-cuttings, bark and twigs of trees; while some of the more common varieties are prepared by mixing lampblack or other black pigments with sufficient red oxide and ochre to give the desired shade. 232. Analyses of two Vandyke-Browns by the author gave the following results. I. II. Organic matter and moisture . . 90.95 91.10 Ash 9.05 8.90 Silica 1.90 2.61 Alumina and ferric oxide ... 1 . 43 1 . 50 Calcium carbonate 4 . 98 3 . 28 Soluble salts .... . 74 1.51 100.00 100.00 Analysis of Umbers and Siennas. 233. Hygroscopic moisture. Heat 2 grams at 105 C. for 3 hours. Loss in weight represents hygroscopic moist- ure. 234. Combined water. Transfer above sample to a weighed platinum crucible and heat for 1 hour over an ordinary lamp, or better in a muffle. Loss in weight indi- cates amount of combined water. Carbonates and organic matter render the results inaccurate. In which case con- tinue the ignition at bright red heat for several hours, and weigh again. Determine the carbon dioxide in another portion of the sample and estimate the combined water by difference. 235. Silica and barium sulphate. One gram of the pig- ment is intimately mixed with 6 to 8 grams of potassium BLACK AND BROWN PIGMENTS. 153 bisulphate and fused in a large porcelain crucible, the cover of which is small enough to set inside the top of the crucible, at not too high a temperature for one-half hour. Finally heating the side of the crucible to finish the conversion of any material adhering to the cover and upper portion of the crucible. The iron, manganese, aluminum, calcium, and magnesium are converted into sulphates, the barytes remains unchanged and the silica is completely dehydrated. After cooling, the entire contents of the crucible may be shaken loose and dissolved in sufficient water and a little hydrochloric acid. Filter and make up to 250 c.c. 236. The residue remaining on the filter, which should be white, a red or brownish color indicating incomplete fusion with potassium bisulphate, in which case the sample must be fused again, is ignited and weighed in a platinum crucible. The residue is tested for barium sulphate by the flame test, if absent the residue is reported as silica; if present the residue is treated in the crucible with hydro- fluoric acid until a thin paste is formed. The mixture is stirred with a platinum wire and digested at a gentle heat, finally two or three drops of sulphuric acid are added, and the temperature gradually raised until no further loss in weight takes place, indicating that the silica has been com- pletely expelled. The residue is weighed as barium sul- phate and the loss in weight represents the silica. 237. Ferric oxide. An aliquot portion of the solution from 235 is heated nearly to boiling and stannous chloride solution added cautiously until the yellow color has disap- peared, and then a slight excess added. All at once with vigorous shaking of the flask 50 c.c. of mercuric chloride solution is added, then 50 c.c. of the manganous sulphate solution. Dilute with cold fresh boiled water and titrate with permanganate solution. Calculate iron found to ferric oxide. 154 ANALYSIS OF MIXED PAINTS. 238. Manganese. Digest 0.5 grams of the sample with 15 c.c. of concentrated hydrochloric acid until all of the iron and manganese has dissolved, then add 5 c.c. of sul- phuric acid diluted with 10 c.c. of water, and evaporate on the hot plate until all of the hydrochloric acid is expelled as shown by copious evolution of sulphur trioxide fumes. Cool, dissolve in about 25 c.c. of water, and heat carefully with occasional shaking until all of the anhydrous sulphate of iron has dissolved. Transfer to a 250 c.c. graduated flask and add an excess of zinc oxide emulsion, obtained by mixing C. P. zinc oxide with water. Avoid a large excess, but sufficient to precipitate all the iron, so that on standing the solution begins to settle clear and some zinc oxide can be seen in the bottom of the flask. Cool and make up to the mark. 239. Transfer an aliquot portion to a beaker or flask, and add an excess of a saturated solution of bromine water and about 3 grams of sodium acetate. One c.c. of a saturated solution of bromine water will precipitate about 0.01 gram of manganese. Boil for about 2 minutes. Filter and wash with hot water. The filtrate must be perfectly clear. Place the filter containing the washed precipitate back in the beaker or flask in which the precipitation was made. All traces of bromine must be entirely expelled. 240. Add an excess of standard oxalic acid solution and about 50 c.c. of dilute sulphuric acid (1:9) and heat nearly to boiling with gentle agitation until the precipitate is entirely dissolved. Dilute to about 200 c.c. with hot water, and titrate with standard permanganate. Standard oxalic acid solution. Dissolve 12.6048 grams of chemically pure oxalic acid in freshly boiled water and make to 1000 c.c. in a graduated flask. One c.c. of this solution = .0055 gram of manganese. The oxalic acid solution should be standardized against BLACK AND BROWN PIGMENTS. 155 the standard permanganate solution and the correction factor calculated. Example: Wt. of sample taken = 0.5 gram. Volume of solution = 250 c.c. Aliquot portion used == 100 c.c. = 0.2 gram. 1 c.c. of permanganate sol. = 0.499 c.c. of oxalic acid. 1 c.c. of oxalic acid sol. = 0.0055 gram of manganese. Permanganate solution used in titrating excess of oxalic acid solution = 13.2 c.c. 13.2 c.c. = 6.59 c.c. of oxalic acid. Oxalic acid solution used, 10.00 c.c. Excess, 6.59 c.c. Consumed, 3.41 c.c. 3.41 X .0055 = .018755 g Mn. Mn : Mn0 2 : .018755 : x. x = .02967 g. MnO r .02967 -5- 0.2 - 14.84 per cent Mn0 2 . 241. Alumina. Fifty c.c. of the 250 c.c. solution pre- pared in 235, is treated with about 20 grams of solid ammo- nium chloride, made just alkaline with ammonia, heated, allowed to settle, decanted, filtered and washed. The precipitate is dissolved on the filter with hydrochloric acid and after washing with small portions of boiling water, the iron and aluminum is re precipitated, solid ammonium chloride being added as before. The precipitate is washed by decantation, filtered and the filtrate collected in the beaker containing the first filtrate. This treatment frees the iron and aluminum from any manganese and the precipitate may be dried, ignited and weighed in the usual manner, the alumina being obtained by difference. It is often advisable to make another reprecipitation of the iron and alumina, using but a small amount of ammonium chloride. 156 ANALYSIS OP^ MIXED PAINTS. 242. Calcium and magnesium. The combined filtrates from the iron and alumina are treated with colorless ammonium sulphide in such a manner as to form the green sulphide of manganese which is very much easier to filter than the pink sulphide. The colorless ammonium sulphide may be prepared as follows: Saturate one-half of a solution of 100 c.c. of water and 50 c.c. of ammonia (sp. gr. 0.90) with hydrogen sul- phide, and then add the other half of the solution. For the precipitation of the manganese, 25 c.c. of the ammonium sulphide solution and 10 c.c. of ammonium chloride solution containing 3 grams of the dry salt, are placed in a 50 c.c. Erlenmeyer flask, the solution diluted to about 100 c.c. and heated. As soon as it comes to a boil, the combined filtrate from the iron and alumina is added and the beaker rinsed with a little water. The flask is shaken vigorously and the solution kept nearly at the boiling point. After alternate shaking and heating, the pink sulphide of manganese turns green and settles readily, leaving a clear supernatent liquid. If the ammo- nium sulphide is of the proper strength and a sufficient amount be used, there should be no difficulty in obtaining the green sulphide in proper condition for filtering. After filtering off the manganese, the filtrate is evapo- rated to a syrupy consistency and 20 c.c. of nitric acid (sp. gr. 1.2,) added in small portions, evaporating each time. Sufficient hydrochloric acid is added and heat applied, until the brown fumes cease to be given off. This treatment which removes the excess of ammonium salts is not necessary if magnesium is known to be absent. The solution after the removal of the nitric acid is diluted with water, made alkaline with ammonia and the calcium and magnesium, separated and estimated in the usual manner, both being calculated to the oxides. BLACK AND BROWN PIGMENTS. 157 The calcium may have been -present as carbonate or sul- phate or both. Hence an estimation of the combined sulphuric acid present in the original sample is necessary. For this purpose 1 gram is dissolved in 30 c.c. of strong hydrochloric boiled 10 minutes, diluted with 50 c.c. of water heated to boiling, filtered, and washed with hot water. Neutralize the filtrate with ammonia then make just distinctly acid with hydrochloric acid, boil, add 10 c.c. of barium chloride solution, continue boiling for 10 min- utes, filter, wash, ignite and weigh as barium sulphate. Calculate combined sulphuric acid by multiplying weight of precipitate by 0.343. Calculate the combined sulphuric acid found to calcium sulphate and the remaining calcium to oxide. 243. ANALYSES OF UMBERS AND SIENNAS BY THE AUTHOR. I. II. Raw Burnt Sienna. Sienna. Moisture 0.42 0.44 Loss on ignition 12.28 12.67 Silica 36.85 19.55 Ferric oxide 45.18 62.75 Alumina 3.00 1.66 Calcium oxide 1.09 2.52 Magnesium oxide . 85 . 00 Sulphur trioxide 0.15 0.20 Manganese dioxide 0.13 0.17 Undetermined 0.05 0.04 100.00 100.00 III. IV. Raw Burnt Umber Umber. Moisture 1.78 2.01 Loss on ignition 13.64 3.94 Silica 20.60 24.21 Ferric oxide 42.60 51.04 Alumina 2.90 6.80 Calcium oxide 3 . 68 1 . 95 Magnesium oxide 2.16 Sulphur trioxide 0.36 0.22 Manganese dioxide 11.95 9.79 Undetermined 0.33 O.O 4 100.00 100. uu 158 ANALYSIS OF MIXED PAINTS. Analysis of Mixed Paints Containing Umbers, Siennas and Ochres. 244. Determine the manganese in a separate sample as determined under the analysis of umbers. Determine the lead as in white paints, using the filtrate from the lead sulphide for the estimating of the iron, which must be oxidized by boiling with a little nitric acid before precipi- tating. Determine aluminum, zinc, calcium, and mag- nesium as described under analysis of umbers and siennas. The zinc being precipitated as the sulphide after the removal of the iron, and aluminum, is contaminated with manganese sulphide. Dissolve the mixed sulphides in dilute hydrochloric acid, boil until odor of hydrogen sulphide is expelled. Cool. Add excess of sodium hydroxide and filter off the precipitated manganese hydroxide, washing thoroughly. The filtrate containing the zinc in solution as sodium zincate, is acidified with hydrochloric acid, heated to about 80 C. and titrated with potassium ferrocyanide in the usual manner. Any barytes, silica and insoluble silicates are separated and estimated as usual. CHAPTER XIII. ANALYSIS OF BLUE PIGMENTS AND PAINTS. Analysis of Prussian Blues, Chinese Blues, etc. 245. Hygroscopic moisture. Heat 2 grams to 105 C. for 3 hours. Loss in weight represents hydroscopic mois- ture. 246. Water of combination. The water of combination, so called, cannot with advantage be determined directly, but can be approximated by subtracting the total per cent of constituents determined hygroscopic moisture, cyanogen, iron, aluminum, alkali metal, alkaline sulphate and inert base, if any - - from 100 per cent. 247. Iron. Ignite one gram at a temperature sufficient to decompose the last trace of the blue, but not so high as to render the oxide of iron difficult of solution. Dissolve in 25 c.c. of hydrochloric acid and 25 c.c. of water with aid of heat. Filter, making up nitrate to 250 c.c. Titrate 50 c.c. with potassium permanganate, after adding stan- nous chloride, mercuric chloride and manganous sulphate solution in the usual manner. Calculate to metallic iron. 248. Aluminum. Precipitate the iron and aluminum from 50 c.c. of the iron solution. Filter, ignite and weigh, estimating the alumina by difference. It probably exists in the Prussian blue as aluminum ferrocyanide. Calcu- late to metallic aluminum. 249. Calcium. Calcium compounds are very rarely found in Prussian blues. If the Prussian blue is precipi- tated on barytes, the latter is liable to contain a small 159 160 ANALYSIS OF MIXED PAINTS. amount of calcium carbonate as an impurity. Treat the nitrate from 248 with ammonium oxalate. Settle, filter, ignite and weigh as calcium oxide. Calculate to calcium carbonate. 250. Alkali metal and alkaline salts. The filtrate from 249 is evaporated to dryness in a weighed evaporating dish, the ammonium salts completely volatized, the alkaline salts weighed, and the chlorine therein determined by titration with standard silver nitrate solution. The alkali metal, is, almost without exception, entirely sodium or potassium and not a mixture of the two, and may be iden- tified by the flame test using a small fragment of the weighed alkaline salt. The sulphuric acid is estimated, in 50 c.c. of the solution prepared under 247, by precipita- tion with barium chloride, in the usual manner. The amount obtained is calculated to sodium sulphate or potassium sulphate as the case may be. The potassium or sodium chemically combined with the Prussian blue is calculated from the amount of chlorine found and reported as metallic sodium or potassium. 251. Cyanogen. Estimate the nitrogen in 1 gram of the sample by the Kjeldahl-Gunning method. Multiply the nitrogen obtained by 1.86 to convert it into cyanogen. 252. Barytes, silica, clay, etc. The insoluble portion remaining on the filter paper in 247 is ignited and weighed. Fuse with sodium carbonate and estimate the barytes, silica, alumina, etc., as described under analysis of white paints. 253. Calculations. The amount of Prussian blue may be calculated approximately by multiplying the iron con- tent by 3.03 or the nitrogen content by 4.4. These factors are not exact as Prussian blues have varying compositions. A Prussian blue to be considered pure should contain at least 20 per cent of nitrogen and 30 per cent of iron ANALYSIS OF BLUE PIGMENTS. 161 calculated on the dry matter and after burning should be entirely soluble in hydrochloric acid. A dry blue should contain less than 7 per cent moisture and the sulphuric acid in the Kjeldahl nitrogen determination should not be blackened which would indicate organic adulteration. 254. ANALYSES OF Moisture (lost at 100 C.) . . Water of combination, etc. . Cyanogen ......... Iron ........... Aluminum ........ Alkali metal (Na) ..... Alkaline sulphate ... PURE" I. 5.61 15.46 37.72 29.48 1.82 PRUSSIAN BLUES. 1 II. 3.54 18.18 41.10 32.16 .52 III. 5.36 6.22 42.97 34.27 7.60 (K) 4.50 (K)7.72 2.31 3.46 IV. 5.45 13.07 37.90 30.32 3.17 (K)2.25 7.84 100.00 100.00 100.00 100.00 Moisture (lost at 100 C. ) . Water of combination, etc. Cyanogen Iron Aluminum Alkali metal (Na) Alkaline sulphate V. 74 . 53 3.08 10.64 7.97 .72 VI. 5 . 32 7.86 39.91 30.94 1.00 VII. 5 . 56 14.60 40.19 31.94 1.43 (K)1.06 (K)11.31 Na 2.52 VIII. 5.61 16.93 40.86 31.25 1.52 .76 2.00 3.66 3.76 Na 3. 07 100.00 100.00 100.00 100.00 255- ANALYSES OF CHINESE BLUES BY AUTHOR. I. II. III. . . . 2.49 3.45 2.04 . . . 12.69 18.12 8.75 . . . 45.78 36.51 46.09 35.87 32.34 35.86 Nal.'57 (K)4'.89 Nas'.SO . . . 1.50 3.61 3.35 . . . 0.10 1.08 0.11 100.00 100.00 100.00 Moisture (lost at 100 C.) Water of Combination, etc Cyanogen Iron Aluminum Alkali metal Alkaline sulphate Silica. Analysis of Mixed Paints containing Prussian Blue, Chinese Blue, etc. 256. Weigh 1 gram into a 250 c.c. beaker, add 30 c.c. of concentrated hydrochloric acid, boil 5 minutes, add 50 1 Parry and Coste, The Analyst, Vol. XXI., page 227. 162 ANALYSIS OF MIXED PAINTS. c.c. of hot water, boil 10 minutes, filter. Wash thoroughly with boiling water. Ignite, filter and precipitate gently, so as to destroy the blue color but not at a sufficiently high temperature to render the iron oxide difficultly soluble in acid. Cool digest in moderately concentrated hydrochloric acid until the iron is all dissolved. Dilute, filter, adding this filtrate to the first filtrate. The insoluble residue is ignited, weighed and fused with sodium carbonate, the barium, silica and alumina separated as described under analysis of white paints. The lead, iron, soluble alumi- num, zinc and any calcium and magnesium compounds separated and estimated as described under analysis of mixed paints containing blacks and oxide of iron pigments. 257. If the paint in question is free from other iron pig- ments the percentage of Prussian blue may be calculated by multiplying the iron content by 3.03. If other iron pigments are present the nitrogen content must be deter- mined; this multiplied by 4.4 will give the approximate amount of Prussian blue present. Analysis of Ultramarine. ' 258. Properties. Ultramarine is a compound of silica containing alumina, soda, sulphur and combined sulphuric acid. It has been often stated that ultramarine cannot be mixed with white lead, because of the sulphur content of the ultramarine, but the author has ascertained that a great many paint manufacturers use it in tinting mixed paints where the percentage of white lead does not exceed that of the zinc, without any harmful results following. Ultramarines that are to be used in the manufacture of paper should be tested for their power of resisting the action of alum, by boiling 5 grams in a 5 per cent alum ANALYSIS OF BLUE PIGMENTS. 163 solution. As found on the market ultramarines vary much in tint, brilliance and coloring power. 259. Moisture. Heat 2 grams at 1.05 C. for 3 hours, cool and weigh. 260. Silica. Digest 1 gram in a casserole provided with a beaker cover, with 30 c.c. of concentrated hydrochloric acid. Evaporate to complete dryness, cool, add 2 c.c. of concentrated hydrochloric acid, evaporate to dryness, and heat gently for 15 minutes. Take up in 100 c.c. of hot water add 10 c.c. of hydrochloric acid. Filter, ignite and weigh as silica. 261. Alumina. The filtrate from the silica is made just sufficiently alkaline with ammonia to precipitate the alu- minum, heat gently, filter, ignite and weigh as alumina. 262. Sodium oxide. The filtrate from the alumina is neutralized with sulphuric acid in a porcelain evaporating dish, evaporated to dryness, the residue treated with a little sulphuric acid, evaporated to dryness again, treated with water, evaporated to dryness, and ignited at low red heat, cooled and weighed. Wt. sodium sulphate X 0.4366 = wt. of sodium oxide. 263. Total sulphur. Fuse 1 gram in a large crucible with a mixture of potassium nitrate and potassium chlorate for about half an hour. Dissolve the fused mass in dilute hydrochloric acid and boil the solution with strong nitric acid for half an hour, filter off the silica and precipitate the sulphuric acid with barium chloride in the usual man- ner. Filter, ignite, and weigh as barium sulphate. From the weight of barium sulphate thus obtained deduct the weight found in 264, the difference is the amount due to sulphur present in the blue as sulphide. Wt. barium sulphate X 0.1373 = wt. sulphur. 264. Combined sulphuric acid. Dissolve 1 gram in dilute hydrochloric acid. Filter off the silica, make filtrate 164 ANALYSIS OF MIXED PAINTS. alkaline with ammonia and then just distinctly acid with hydrochloric acid and treat with barium chloride in the usual manner. The precipitated barium sulphate is fil- tered, ignited, and weighed as usual. Wt. barium sulphate X 0.3434 = wt. of sulphur tri- oxide. 265. ANALYSES OF ULTRAMARINES BY THE AUTHOR. Ultra- Ultra- Ultra- marine marine marine Blue. Blue. Blue. I. II. III. Silica 39.26 39.45 41.92 Alumina 25.60 25.81 26.21 Sulphur 11.69 12.02 10.82 Sulphur trioxide 3.10 2.33 1.93 Sodium oxide 19.87 19.73 18.40 Water 0.48 0.66 0.72 100.00 100.00 100.00 266 ANALYSES OF ULTRAMARINES BY HURST. Silica Alumina ~ . Sulphur . . . Sulphate. 49.69 23.00 9 23 Soap Makers. 40.65 25.05 12.95 Calico Printers. 40.89 24.11 13.74 Paper Makers. 45.42 21.15 11 62 Sulphur trioxide .... Soda Water 2.46 12.49 3.13 4.81 14.26 2.28 3.05 15.61 2.60 5.58 9.91 6.32 100.00 100.00 100.00 100.00 Analysis of Cobalt Blue. 267. This pigment which is essentially a compound of the oxides of alumina and cobalt has largely gone out of use, but that it still finds a limited application is evidenced by the fact that the author receives occasional samples for analysis. Certain shades of ultramarine blue are often sold under the name of cobalt blue. 268. Moisture. Determine as usual. ANALYSIS OF BLUE PIGMENTS. 165 269. Alumina. Fuse 1 gram with potassium bisulphate as described under analysis of Indian reds and Venetian reds. Dissolve in water and hydrochloric acid, filter and make up to 250 c.c. in a graduated flask. Any residue remaining on the filter paper is ignited and weighed as silica, unless barium sulphate is present which would be shown by the flame test. An aliquot portion of the solution is treated with an excess of ammonium chloride, and then made just dis- tinctly alkaline with ammonia. Filter, dissolve on the filter with hydrochloric acid and re precipitate. Filter again, combining the two filtrates. Wash thoroughly, ignite and weigh as alumina. 270. Calcium and magnesium. The combined filtrates from the alumina are saturated with hydrogen sulphide, filtered and any calcium and magnesium estimated in the filtrate in the usual manner. 271. Cobalt oxides. The oxides of cobalt present are best estimated by difference, by substracting the deter- mined constituents from 100. It is stated by Hurst that phosphoric acid is occasionally used in the manufacture of cobalt blues, in which case it should be removed before estimating the aluminum, calcium and magnesium. The several samples examined by the author were found to be free from phosphoric acid. CHAPTER XIV. ANALYSIS OF YELLOW, ORANGE, AND RED CHROME LEADS, ANALYSIS OF VERMILIONS. 272. Composition. The lemon yellow chromes usually contain sulphate of lead, sometimes carbonate of lead. The red chromes, known by the various names of scarlet chrome, chrome red, Chinese red, American vermilion, and vermilion substitute may be considered as basic chro- mates of lead. Often these basic chromes are brightened up by having precipitated on them an organic color; this may be tested for by treating a portion of the pigment with alcohol, which will dissolve the organic color, giving a strongly colored solution. See analysis of vermilions. 273. Hygroscopic moisture. Heat 2 grams at 105 C. for 3 hours. Loss in weight represents hygroscopic mois- ture. 274. Barytes, silica and clay. One gram of the pigment is boiled for 5 minutes with 30 c.c. of concentrated hydro- chloric acid in a covered beaker. While boiling add half a dozen drops of alcohol one at a time. Fifty c.c. of water is added and the boiling continued for 10 or 15 minutes. Filter, wash thoroughly with boiling water, ignite and weigh. The insoluble residue is fused with sodium car- bonate and the barium, silica and alumina separated as described under analysis of white paints. 275. Lead. The filtrate from the insoluble residue is neutralized with dilute ammonia until the further addition of another drop would cause the formation of a permanent 166 ANALYSIS OF LEADS. 167 precipitate, diluted to about 250 c.c. to 300 c.c., and hydro- gen sulphide passed in for 10 minutes. Solutions containing large amounts of chromium if neutralized with ammonia until a permanent precipi- tate appears, seem to require an excess of hydrochloric acid for their resolution, sufficient to prevent the satis- factory precipitation of the lead with the hydrogen sulphide. Allow the precipitate to settle thoroughly as it renders the filtering much easier, filter, wash with hydrogen sul- phide water. Boil, filter, and precipitate with dilute nitric acid, until all of the lead has .dissolved, filter with aid of suction, washing thoroughly with hot water. Add 5 c.c. of concentrated sulphuric acid, diluted with an equal volume of water to the filtrate. Evaporate on hot plate until the white fumes of sulphur trioxide appear. Cool, dilute with water, add an equal volume of alcohol, filter, washing with dilute alcohol, ignite gently, and weigh as lead sulphate. Save filtrate. 276. Chromium. The alcoholic filtrate from the lead sulphate is evaporated nearly to dryness to expel alcohol, and the filtrate from the lead sulphide heated until the hydrogen sulphide is expelled. The two filtrates are mixed, diluted if necessary, and made just perceptibly alkaline with ammonia; boil, settle, filter, wash thoroughly, ignite and weigh as chromic oxide. Wt. chromic oxide X 1.3137 = wt. chromic anhydride. Occasionally these pigments contain a small quantity of iron, which should be tested for qualitatively in a separate portion of the pigment. If found to be present the precipi- tate of ferric and chromium hydroxides is dissolved on the filter with hydrochloric acid, the filter washed thoroughly with hot water, and the iron and chromium in the filtrate reprecipitated with ammonia and treated with sodium 168 ANALYSIS OF MIXED PAINTS. peroxide to dissolve the chromium as described under the analysis of chrome greens. 277. Calcium. The filtrate from the chromium is treated with ammonium oxalate, allowed to stand in a warm place for an hour or so, filtered, washed thoroughly, strongly ignited and weighed as calcium oxide. 278. Magnesium. The magnesium is estimated in the filtrate from the calcium in the usual manner. 279. Combined sulphuric acid. The combined sulphuric acid may be estimated by either of the two methods given in paragraph 170, analysis of white paints. In fact, the latter method may be used for the rapid analysis of a chrome lead, the insoluble lead carbonate being filtered off, the chromium precipitated as the hydroxide in the usual manner, and the combined sulphuric acid estimated in the filtrate from the chromium. Wt. barium sulphate X 0.3433 = combined sulphuric acid. 280. Calculations. If calcium is absent, or present as carbonate, the combined sulphuric acid is calculated to lead sulphate, the chromic anhydride to lead chromate, and excess of lead to lead oxide. If calcium sulphate and carbonate of lead are present, the carbon dioxide must be determined and the amount of calcium present as sulphate estimated by Thompson's method as described under analysis of white paints. Wt. comb, sulphuric acid X 3.788 = wt. lead sulphate. Wt. chromic anhydride X 3.230 = wt. lead chromate. Wt. lead chromate X 0.6406 = wt. lead. Wt. lead X 1.0773 = wt. lead oxide. The specifications for chrome leads issued by the U. S. Treasury Department, 1907, state that a color containing lead sulphate is to be preferred to one containing white lead. ANALYSIS OF LEADS. 169 281. ANALYSES OF CHROME LEADS BY AUTHOR. Light Deep Chrome Orange Yellow. Chrome Yellow. Moisture 0.04 0.03 Lead chromate 68.65 40.56 Lead oxide 47.24 Lead sulphate 31.21 5.49 Silica ... . 74 Alumina ... 0.44 Organic color ... 4 . 87 Undetermined 0.10 0.63 100.00 100.00 Analysis of Mixed Paints Containing Chrome Yellows and Ochres. 282. Barytes, silica and clay are estimated as described under analysis of chrome leads. 283. Lead, both as sulphate and carbonate, is estimated as described under chrome leads, the filtrate from the lead sulphate being saved as before. 284. Iron. The filtrate from the lead sulphide is heated until all o'f the hydrogen sulphide has been expelled and added to the filtrate, from the lead sulphate, from which the alcohol has been expelled by boiling. A few drops of nitric acid are added and the solution boiled for a minute or two, then made just distinctly alkaline with ammonia, boiled, settled and filtered. Dissolve on the filter with hot dilute hydrochloric acid, wash with hot water. Cool. Reprecipitate with ammo- nia, avoiding excess, without waiting for the precipitate to settle, carefully add a sufficient quantity of sodium peroxide (1 gram is usually sufficient) keeping the beaker covered meanwhile. Digest until all of the chromium and aluminum have passed into solution, adding more peroxide if necessary. The iron remains undissolved while the chromium and aluminum go into solution, filter, wash 170 ANALYSIS OF MIXED PAINTS. thoroughly, ignite strongly and weigh as ferric oxide, or dissolve in dilute hydrochloric acid and titrate. The treatment with peroxide is preferably performed in a porcelain evaporating dish. 285. Chromium. The filtrate from the iron is made up to 250 c.c. in a graduated flask. An aliquot portion is rendered acid with acetic acid and a slight excess of lead nitrate solution added, allowed to remain on the hot plate until thoroughly settled, filtered on to a weighed Gooch crucible, washed, dried and weighed as lead chromate. 286. Aluminum. An aliquot portion of the 250 c.c. solution is made just acid with hydrochloric acid, and then just distinctly alkaline with ammonia, allowed to settle, filtered on to a Gooch crucible, ignited and weighed as alumina. 287. Zinc. The filtrate from the chromium, iron and aluminum hydroxides, under iron is mixed with the filtrate from the lead sulphate from which the alcohol has been expelled, and the mixed solution saturated thoroughly with hydrogen sulphide, boiled with the addition of solid ammo- nium chloride to render the precipitate less slimy, and filtered. The zinc sulphide dissolved with hydrochloric acid, boiled to expel hydrogen sulphide and titrated with standard ferrocyanide of potassium as described under analysis of white paints. 288. Calcium, magnesium and combined sulphuric acid are estimated as described under analysis of Chrome Leads and the calculations made as there described. Analysis of Vermilion. 289. Properties. Vermilion is a bluish scarlet powder, having a specific gravity of 8.2. It is insoluble in any single acid such as hydrochloric or nitric acid and in the alkalies. Heated in contact with the air it burns with a ANALYSIS OF LEADS. 171 pale blue lambent flame. Pure vermilion will burn away entirely or at least leave but a small fraction of 1 per cent of ash. This is a reliable test for it, as other adulterants would be left behind on heating. The most common adulterants of vermilion are red lead, oxide of iron, lead chromes, vermilionette lakes, para reds, and alizarine reds. 290. Detection of vermilionettes, para and alizarine reds. (a). Boil a little of the dry color with water, settle and filter. Vermilionettes give a deep red solution, para reds a pale brownish or orange, and the alizarine reds a colorless solution. (6). Boil a little of the dry color with a mixture of methyl and ethyl alcohol, filter, heat and settle. Vermil- ionettes give a bright red solution, usually having a yellow bloom, para reds an orange red solution, alizarine reds a practically colorless solution. (c). Boil another portion of the dry pigment with some freshly distilled aniline, settle, and filter. Vermilionettes give a purple-red, alizarine lakes a pale brow r n, and the para reds an intense orange-red solution. (d). Boil some of the dry color with a solution of caustic soda. Vermilionettes give a red solution with a green " bloom," para reds a bluish-red solution, while alizarine reds yield a characteristic deep violet solution. 291. Barytes, silica and clay. Dissolve 1 gram in 30 c.c. of concentrated hydrochloric acid, 50 c.c. of water with the aid of 1 to 2 grams of potassium chlorate added in small portions and warming. Evaporate to dryness on water-bath. Take up in 50 c.c. of water acidulated with hydrochloric acid, heat to boiling to dissolve any lead chloride, filter, wash with boiling water, ignite and weigh any insoluble residue. Fuse with sodium carbonate and 172 ANALYSIS OF MIXED PAINTS. estimate the barium sulphate, silica and alumina as described under analysis of white paints. 292. Lead. If lead is present, calcium compounds being absent, the nitrate is treated with sulphuric acid, evaporated carefully to expel excess of hydrochloric acid, diluted with water and alcohol, the lead sulphate filtered off on a Gooch crucible in the usual manner. 293. Mercuric sulphide (vermilion). The filtrate from the insoluble residue, if lead is absent, or the filtrate from the lead sulphate, is heated with a little sulphurous acid to reduce any iron present to the ferrous condition, made neutral with ammonia, and then fust acid to litmus with hydrochloric acid. The solution is diluted to about 350 c.c. and hydrogen sulphide passed in for 10 minutes. The mercuric sulphide is filtered off on a weighed Gooch crucible, washed with FIG. 11. hydrogen sulphide water, the crucible removed to another holder and washed with alcohol and carbon bisulphide to remove sulphur, dried in steam-oven and weighed. 294. Estimation of lead and mercury, calcium com- pounds present. The filtrate from the insoluble residue from 291 is precipitated with hydrogen sulphide as de- ANALYSIS OF LEADS. 173 scribed under 293, collected on a weighed filter and dried at 100 C., weighed and mixed uniformly. An aliquot part is introduced into the bulb of Fig. 11. A slow stream of washed chlorine gas passed through it, and a gentle heat applied to the bulb, increasing this gradually to faint redness. The escaping chlorine is conducted into a flue. First, sulphur chloride distils over, which decomposes with the water in E and F. The mercuric chloride formed volatilizes, condensing partly in E, partly in 0. Cut off that part of the tube, rinse the mercuric chloride into E and mix the contents of the latter with the water in F. Mix the solution with excess of ammonia and warm gently until no more nitrogen is evolved, acidify with hydrochloric acid, fil- ter and determine the mercury in the filtrate as under 293. 295. Ferric oxide. The filtrate from the sulphides is heated until all of the hydrogen sulphide has been expelled and the iron chromium and alumina precipitated with ammonia, filtered and separated as described under analy- sis of chrome greens. 296. Zinc oxide. The filtrate from the iron and alu- mina precipitate is made distinctly alkaline with ammonia and the zinc precipitated with hydrogen sulphide. The liquid containing the zinc sulphide precipitate is heated to boiling, and about 5 grams of solid ammonium chloride added, which renders the precipitate easier to filter. Settle filter, wash thoroughly. Pierce filter, wash through into a clean beaker with water, dissolving the residue on filter with dilute hydrochloric acid, and washing with hot water. Dilute, heat to expel hydrogen sulphide and titrate with ferrocyanide as previously described. If iron is absent in the paint, the zinc may be estimated directly as described under analysis of white pigments. 174 ANALYSIS OF MIXED PAINTS. 297. Calcium and magnesium. Estimated as usual in the filtrate from the zinc sulphide. 298. Calculations. If chromium is present it is calcu- lated to basic lead chromate, and any excess of lead above that required to form the chromate is calculated to red lead. 299. ANALYSES OF VERMILIONS BY THE AUTHOR. I. II. III. English English Vermilion. Vermilion Vermilion. Deep. Pale. Sulphide of Mercury .... 99.53 99.61 99.61 Ash 0.47 0.39 0.39 100.00 100.00 100.00 I. II. Vermilion. Radium Vermilion. Moisture 0.16 0.06 Red lead 80.08 97.99 Barytes 16.83 Alumina . 77 Organic color 2.16 1.95 100.00 100.00 I. II. Light Deep Vermilion. Vermilion. Moisture 1.33 0.15 Lead chromate 50.16 53.60 Lead oxide 41.20 40.88 Lead sulphate 6.15 4.97 Ferric oxide . 37 . 33 Soluble salts . 33 trace Undetermined . 0.46 0.07 100.00 100.00 300. Antimony vermilion and orange. These two pig- ments have the same composition, corresponding to the formula of antimony trisulphide. They are insoluble in dilute acids, but soluble in strong hydrochloric acid. It is seldom necessary to make a complete analysis of these ANALYSIS OF LEADS. 175 pigments. Adulteration will be indicated by the pigment not being completely soluble in strong hydrochloric, though a trace of sulphur may remain undissolved, floating on top of the acid. 3ooa. Analysis of Red Lead. 1 Solutions required : Ti iodine solution, stannous chloride solution (14.1 g. in 1000 c.c.), starch paste solution. Pipette 25 c.c. of the stannous chloride solution into an .Erlenmeyer flask, add 40 c.c. hydrochloric acid, boil one minute, add 100 c.c. cold water, cool rapidly and titrate with the iodine solution, using starch paste as an indicator. Weigh 1 gram of the sample red lead into a similar Erlenmeyer flask, moisten with water, add 25 c.c. stan- nous chloride and 40 c.c. of hydrochloric acid, boil until all of the lead is in solution, and titrate with iodine solution as above. The difference in c.c. of iodine solution u^ed in the blank and in the determination give the number of c.c. of iodine solution to which the available oxygen in the red lead is equivalent. 1 c.c. iodine sol. = 0.8 m.g. oxygen. Available oxygen X 42.73 = amount of red lead. 1 J. H. Wainwright, Engineering Chemistry. CHAPTER XV. ANALYSIS OF CHROME GREENS AND EMERALD GREENS. Analysis of Chrome Greens. 301. Hygroscopic moisture. Heat 2 grams of the sample at 105 C. for 3 hours. Cool and weigh. 302. Organic color. Occasionally chrome greens are brightened up by treatment with an organic color. Boil a portion of the sample with alcohol ; a green colored solu- tion not due to suspended particles indicates the addition of an organic color. 303. Barytes, silica, clay, or other silicates. Weigh 1 gram into a porcelain crucible, heat gently, so as to destroy the Prussian blue, but not at a temperature suffi- ciently high to fuse the lead chromate or render the iron difficultly soluble in acid. Cool. Boil gently with 30 c.c. of concentrated hydrochloric acid in a covered beaker until all of the iron and lead have gone into solution. A few drops of alcohol added one at a time may assist the solution. Add 50 c.c. water; boil for 15 minutes. Filter hot, wash thoroughly with boiling water, ignite and weigh. Fuse with sodium carbonate and estimate the barytes, silica and alumina as described under analysis of white paints. 304. Lead. The filtrate from the barytes, silica and alumina is made just alkaline with ammonia, and then just acid to litmus, with hydrochloric acid ; dilute to about 300 c.c. and pass in a current of hydrogen sulphide for 10 minutes. Allow the precipitate to settle thoroughly. 176 ANALYSIS OF GREEN PIGMENTS. 177 Filter, wash with hydrogen sulphide water. Digest pre- cipitate and filter in a covered beaker with dilute nitric acid until the lead is entirely dissolved, filter on suction funnel, wash with hot water. Add 5 c.c. of concentrated sulphuric acid diluted with an equal volume of water to the filtrate; evaporate on sand bath until white fumes of sulphur trioxide appear. Cool, dilute with 50 c.c. of water, add 75 c.c. of alcohol and allow to stand for up- wards of an hour with occasional stirring. Filter on to Gooch crucible, washing with water containing 2 per cent sulphuric acid, finishing with 50 per cent alcohol; dry, heat gently, and weigh as lead sulphate. Reserve, filtrate. 305. Iron. The filtrate from the lead sulphide is heated to expel the hydrogen sulphide and added to the filtrate from the lead sulphate, which has been boiled until all of the alcohol has been expelled. A few drops of nitric acid are added, the solution boiled for a minute or two and then made just distinctly alkaline with ammonia, filtered and washed. Dissolve on the filter with hot dilute hydrochloric acid, wash with hot water, cool. Re- precipitate with ammonia, avoiding excess, without wait- ing for the precipitate to settle; carefully add a sufficient quantity of sodium peroxide (1 gram is usually sufficient) keeping the beaker covered meanwhile. Digest until all of the chromium and aluminium have passed into solu- tion, adding more peroxide if necessary. The ferric hydroxide remains undissolved and is filtered off, washed thoroughly, ignited, and weighed as ferric oxide. 306. Chromium. The filtrate from the ferric hydroxide is made up to 250 c.c. in a graduated flask, and an aliquot portion is rendered acid with acetic acid, a slight excess of lead nitrate added, and heated on the hot plate until the precipitate has thoroughly settled. Filter on to a weighed Gooch crucible, dry, and weigh as lead chromate, 178 ANALYSIS OF MIXED PAINTS. or, the precipitate may be heated gently over an ordinary flame, so as not to fuse the chromate. 307. Aluminium. An aliquot portion of the 250 c.c. solution is made just acid with hydrochloric acid, and then just distinctly alkaline with ammonia. The precipi- tate of aluminium hydroxide allowed to settle, filtered, ignited and weighed as alumina. 308. Calcium and magnesium are estimated in the filtrate from the iron, aluminium and chromium hydrox- ides as usual. 309. Cyanogen. One gram of the sample is digested with sulphuric acid and the nitrogen estimated as under analysis of Prussian blues. Wt. nitrogen X 1.86 = wt. Cyanogen. 310. Combined sulphuric acid. Heat gently 1 gram of the pigment so as to destroy the Prussian blue, dissolve in 30 c.c. of strong hydrochloric acid in a covered beaker. Dilute with 50 c.c. boiling water, boil 5 minutes, filter, make nitrate neutral with ammonia, then slightly acid with hydrochloric acid, bring to boiling, add 15 c.c. barium chloride, boil 10 minutes, filter, wash with hot water, ignite, and weigh, Wt. barium sulphate X 0.3433 = combined sulphuric acid. 311. Calculations. The amount of Prussian blue present may be calculated, either by multiplying the iron content by 3.03 or the nitrogen content by 4.4. The chromium is calculated to lead chromate and the combined sulphuric acid, in the absence of calcium sulphate, to lead sulphate excess of lea-d over that required for the lead chromate and lead sulphate, calculated to lead oxide, unless the basic car- bonate of lead were present, which is very rarely the case. NOTE. In making an analysis of a mixed paint tinted with a green, it should be borne in mind that the Prussian blue is occasionally replaced with an ultramarine blue. ANALYSIS OF GREEN PIGMENTS. 179 312. ANALYSES OF CHROME GREENS BY THE AUTHOR. I. II. Light Medium Chrome Chrome. Green. Green. Moisture 0.20 0.10 Lead chromate 16.57 16.67 Lead sulphate Prussian blue 5.80 5 98 5.29 6.80 Barytes 68 . 22 66.72 Alumina 1.40 1.94 Silica 1.71 1.66 Undetermined 0.12 0.82 100.00 100.00 Emerald Green, Paris Green and Arsenic Insecticides. 313. Properties. The chief use of emerald green, better known as Paris green, is as an insecticide, but little being used as a paint pigment owing to its poisonous qualities. As a pigment it is very opaque, has good covering power and is fairly permanent. It is completely soluble in ammonia, turning it to an intense blue color. This test, however, is not conclusive, since white arsenic and a number of other substances used in adulterating Paris green are soluble in ammonia and would escape detection if this method alone were depended on. Under the terms of the North Dakota law regulating the sale of Paris green it shall be deemed adulterated if it contains less than 50 per cent of total arsenious oxide, or more than 4 per cent of free or uncombined arsenious oxide. In most cases the determination of water soluble and total arsenious oxides is sufficient. 314. Water soluble arsenious oxide. One-half gram of the sample is weighed into a 250 c.c. Erlenmeyer flask, 180 ANALYSIS OF MIXED PAINTS. 100 c.c. of distilled water added. The flask is agitated by shaking every few minutes during a working period of 8 hours, keeping the temperature between 25 to 30 C. The next day, after pouring off the clear liquid, 100 c.c. of distilled water is again added, and the shaking treat- ment repeated. The clear solution is again poured off, and the operation repeated with a fresh portion of 100 c.c. of distilled water. The three 100 c.c. leachings are com- bined and filtered through a double filter and titrated with tenth-normal iodine, using starch as an indicator as follows: Add 20 c.c. of a saturated solution of sodium bicar- bonate to every 0.1 gram of arsenious oxide and titrate as usual. 1 c.c. tenth-normal iodine = 0.00495 arsenious oxide. 3 15. Total arsenious oxide. Weigh 1 gram of the sample into a side-neck distilling flask, and add 5 grams of ferrous sulphate. Connect with a condenser, the other end of which dips below the surface of about 100 c.c. of distilled water, which is kept cooled. Fifty c.c. of hydrochloric acid are added to the flask containing the sample, which also has a glass tube leading nearly to the bottom, the other end of which is connected with a flask, in which hydrochloric acid gas is generated. This gas is very readily obtained by allowing concentrated sulphuric acid to drop into concentrated hydrochloric acid saturated with sodium chloride. The flask containing the arsenic solution is cooled nearly to zero, by immersing the flask into a vessel containing cracked ice. Pass in the hydro- chloric acid gas; when no more is absorbed, the ice is removed and the solution brought to a boil. The stream of hydrochloric acid gas is allowed to flow and the distil- lation continued until the volume of the solution is reduced to about 25 c.c. The distillate is just neutralized with a ANALYSIS OF GREEN PIGMENTS. 181 solution of sodium hydroxide or sodium carbonate, a sufficient amount of sodium bicarbonate added, the whole solution made to a definite volume and an aliquot part titrated with tenth-normal iodine and starch. 316. ANALYSES OF PARIS GREENS, BY E. F. LADD. Laboratory Number. Free Arsenious Oxide. Total Arsenious Oxide. 101 .. 3 46 52 38 102 .... 7 41 54 36 103 1 73 45 46 104 6 17 57 32 105 1 98 57 32 106 1 48 56 34 107 7 41 59 72 108 18 77 51 39 109 5 93 52 18 110 98 50 01 111 3 70 An inspection of the above shows that five of the samples contained excessive amounts of free arsenious oxide ranging from 9.93 to 18.77 per cent, while one of the samples contained a total of 45.46 per cent of arsenious oxide instead of 50 per cent prescribed as a minimum. If a complete analysis is desired, the following scheme may be used. 317. Moisture. Heat 2 grams at 105 C. for 2 hours, cool and weigh. 318. Aniline color. Treat a portion of the sample with alcohol, after settling. If the solution remains distinctly green, an aniline color is present. 319. Insoluble residue. Digest 1 gram with dilute nitric acid, filter and wash with hot water. Residue may consist of lead sulphate, barium sulphate, silica, and clay. Digest residue with a strong solution of acid ammonium 182 ANALYSIS OF MIXED PAINTS. acetate in order to dissolve the lead sulphate; filter, wash with hot water. To the filtrate add dilute sulphuric acid, evaporate nearly to dryness. Cool and take up with water, filter on Gooch crucible, wash with 50 per cent alcohol, ignite, and weigh as lead sulphate. The residue from the ammonium acetate treatment is fused with sodium car- bonate, and the barium, alumina and silica separated as usual. 320. Lead chromate. The nitric acid filtrate is treated with 1 c.c. of sulphuric acid, evaporated nearly to dryness, cooled, taken up with water, any lead sulphate present filtered off and calculated to lead chromate. 321. Copper. Dilute the filtrate from the lead sul- phate to about 200-250 c.c. Pass hydrogen sulphide through the liquid for half an hour, maintaining the tem- perature at 70 C. Settle, filter, wash with hydrogen sulphide water. Transfer filter and contents to a 250 c.c. beaker, add excess of strong solution of sodium sulphide, digest for 30 minutes at a gentle heat. Filter. The residue which consists of copper sulphide is dissolved in dilute nitric acid freed from sulphur by filtration, and the copper determined electrolyticalty or by the iodide method. Calculate to cupric oxide. 322. Arsenic. The arsenic is best determined as de- scribed above under the estimation of total arsenious oxide. 323. Chromium and zinc. The filtrate from the copper and arsenic sulphides is boiled to thoroughly expel the hydrogen sulphide, ammonia added until alkaline. A greenish precipitate indicates chromium, a white precipi- tate, zinc hydroxide. In the latter case add sufficient ammonia to redissolve the zinc. Heat, filter, ignite and weigh as chromium oxide. The filtrate from the chro- mium, or the solution if chromium was absent, is saturated ANALYSIS OF GREEN PIGMENTS. 183 with hydrogen sulphide to precipitate the zinc as sulphide, boil, adding 5 grams of solid ammonium chloride to ren- der the precipitate less slimy. Dissolve in hydrochloric acid and titrate with standard potassium ferrocyanide as described under analysis of white pigments. 324. Calcium. The filtrate from the zinc is boiled to expel hydrogen sulphide made more strongly alkaline with ammonia, and the calcium precipitated with ammonium oxalate and estimated as usual. A determination of sul- phates should be made so as to ascertain whether the calcium was present as carbonate or sulphate. 325. Magnesium. If a considerable quantity of cal- cium is present the filtrate from the calcium is tested for magnesium, which if found is estimated as usual. 326. Acetic acid. The acetic acid may be obtained by difference, or if desired estimated by C. Mohr's process as described in Button's Volumetric Analysis. 327. ANALYSES OF A PARIS GREEN BY HURST. Water 0.90 Copper oxide 32 . 55 Arsenious acid 57.31 Acetic anhydride 6.63 Sulphur trioxide 1 67 Undetermined . 0.94 100.00 CHAPTER XVI. EXERCISES IN COLOR MAKING. 328. The following formulas for the preparation of the more common colors are intended only for the analyst who may wish to acquire a little insight into the principles underlying the manufacture of colors by making a few experiments for himself. The formulas used by color makers are kept as secret as possible, and probably each manipulator has his own modifications which enable him to manufacture colors of greater strength and permanence to light than any novice may hope to do in a set of beakers in the laboratory. 329. Para-nitroaniline lake. Seven grams of para-nitro- aniline is added to 15 grams of pure concentrated hydro- chloric acid and 200 c.c. of water. Heat until all of the para-nitroaniline is dissolved. Cool to below 40 F. and then slowly and with constant stirring add 5 grams of sodium nitrite dissolved in 20 c.c. of water, keeping the solution cool with ice. Allow to stand one-half hour. Then add 15 grams of sodium acetate dissolved in 100 c.c. of water and 100 grams of inert base, like blanc fixe, which has been thoroughly freed from lumps. In the meanwhile 7 grams of beta-naphthol are dis- solved in 3 grams of sodium hydroxide and 175 c.c. of boiling water. Cool to below 45 F. and then add slowly and with constant stirring to the preparation of para- nitroaniline, keeping the particles of blanc fixe* in thorough 184 EXERCISES IN COLOR MAKING. 185 suspension. The lake forms at once. Wash by decanta- tion, filter, and dry at a low temperature. If a bluer shade is desired use beta-naphthol R. 330. Crimson red lake. For the preparation of this lake use 7 grams of alphanapthylamine instead of the para-nitroaniline, and conduct the process exactly as described under the manufacture of para-nitroaniline lake, using the same ingredients and the same amounts. 331. Emerald green. Dissolve 25 grams of cojDjper sul^ phate in 200 c.c. of water; add 7 grams sodium. crystals or 3.5 grams of the dry carbonate. This will precipitate part of the copper as copper carbonate. Then add just sufficient acetic acid to dissolve the copper carbonate. In a separate beaker dissolve 15 grams of arsenious acid and 22 grams of soda crystals, or 9.5 grams of dry carbonate, in 150 c.c. of water. Heat both solutions to boiling and pour the arsenic solution slowly and evenly into the copper solution with constant stirring. Wash by decantation, filter and dry. 332. Pale lemon chrome. 1. Lead solution. Lead ace- tate 50 grams in 150 c.c. of water. 2. Bichromate solution. Dissolve 8 grams of sodium bichromate in 100 c.c. of water. 3. Sulphuric acid. Dilute 8 grams of sulphuric acid with 25 c.c. of water. Add the diluted sulphuric acid to the sodium bichromate solution and run the mixture slowly from a separating funnel into the lead acetate solution, with constant stir- ring. Settle, wash by decantation 4 times, filter, dry and grind. 333. Medium chrome yellow. 1. Lead solution. Dis- solve 50 grams lead acetate in 125 c.c. of water. 2. Bichromate solution. Dissolve 9 grams of sodium bichromate in 75 c.c. of water. 186 ANALYSIS OF MIXED PAINTS. 3. Sulphuric acid. Dilute 6 grams of sulphuric acid with 25 c.c. of water. Precipitate and treat as described under pale lemon chrome. Interesting results may be obtained by experimenting with an excess of each ingredient, precipitating at dif- ferent temperatures and with different concentrations. 334. American vermilion basic lead chromate. 1. Lead solution. Dissolve 50 grams of lead nitrate in 150 c.c. of water. 2. Bichromate solution. Dissolve 17 grams of pow- dered sodium bichromate in 100 c.c. of water. 3. Slaked lime. Carefully slake 6 grams of fresh lime; reduce to a thin paste in a mortar until free from lumpy particles. Place the bichromate solution in a separating funnel and allow to run slowly into the lead nitrate with constant stirring. Settle, pour off the supernatent liquid. Add the lime and heat to boiling, with constant stirring, until the required shade has fully developed. Settle, wash four times by decantation, filter, dry and grind. 335. CHINESE BLUE. NUMBER I. Grams. Potassium ferrocyanide 25 Ferrous sulphate 25 Potassium bichromate 2 Sulphuric acid 12 Potash alum . . 3 Dissolve the ferrous sulphate and alum in 200 c.c. of water. Dissolve the ferrocyanide in 200 c.c. of water and run the iron solution into it with constant stirring. Run in the dichromate dissolved in 25 c.c. of water, and then add the acid with constant stirring. Settle, wash by decantation three times, filter and dry. EXERCISES IN COLOR MAKING. 187 336. CHINESE BLUE. NUMBER II Grams. Potassium ferrocyanide 25 Ferrous sulphate 25 Chloride lime 5 Sulphuric acid 3 Hydrochloric $ Dissolve and mix the ferrous sulphate and ferrocyanide as described above. Settle. Draw off the supernatent liquid, and add the chloride of lime, dissolved in 75 c.c. of water, through a fine sieve. Finally add the sulphuric acid, stir, settle, decant three times, filter and dry. 337. CHINESE BLUE. NUMBER III. Grams. Potassium ferrocyanide 25 Ferrous sulphate 26 Potassium chlorate 4 Sulphuric acid . . 29 Prepare as described under Chinese Blue. Number I. 338. Brunswick greens. These greens are prepared by precipitating the yellow first, usually on an inert base like barytes, and then precipitating the blue over the yellow. Pale green. Precipitate 35 grams of chrome yellow on 100 grams of barytes, and precipitate 1.5 grams of Prus- sian blue on the yellow, with vigorous stirring in each case. Medium green. 35 grams chrome yellow, 100 grams barytes and 2.5 grams of Prussian blue. Deep green. 35 grams of chrome yellow, 100 grams of barytes and 5 grams of Prussian blue. CHAPTER XVII. ANALYSIS OF JAPANS AND DRIERS. 339. At the present time the terms " Japan " and " drier " are interchangeable and refer to the same line of products, manganese linoleate, lead lineolate, resinate of manganese, resinate of lead, or mixtures of these com- pounds. Originally Japan contained a considerable quan- tity of dissolved resin, constituting a preparation that on drying gave a film of considerable hardness and lustre, but this distinction has largely disappeared. These com- pounds should not be confused with baking Japans, which represent an entirely different class of products and which will not be discussed at this time. Japans and driers are usually made by heating the oxides of lead and manganese or borate of manganese with linseed oil or the various resins, and dissolving the melted mass in turpentine, benzine or mixtures of both. 340. Determination of the drying salts. The salts generally used are Litharge, PbO Red lead, Pb 3 3 Oxide of manganese, Mn0 2 Borate of manganese, MnB 2 4 occasionally Zinc sulphate, ZnS0 4 , and Zinc oxide, ZnO. Weigh 25 grams of the drier into a 250 c.c. Erlenmeyer flask and dilute with 25 c.c. of a mixture of equal parts of benzine and turpentine. Add 50 c.c. of dilute hydro- 188 ANALYSIS OF JAPANS AND DRIERS. 189 chloric acid (1.10 sp. gr.) Allow to stand 1 hour, shaking thoroughly at intervals of 10 minutes. Immerse the flask in a beaker of hot water, at a considerable dis- tance from the flame. When the contents of the flask are hot, shake with a circular motion, avoiding undue pressure in the flask. Allow to stand until cool, so as to be sure that the drier has been wholly dissolved. Pour into a separatory funnel, draw off the aqueous layer into a casserole, wash the oil portion twice with warm water, adding the washings to the casserole and evaporate to dryness under the hood. Dissolve in dilute nitric acid with the aid of heat, filter into a 250 c.c. graduated flask and after washing thoroughly make up to the mark. 341. Lead. To an aliquot portion add 5 c.c. of dilute sulphuric acid and evaporate on the hot plate until white fumes of sulphur trioxide appear. Cool, add cautiously 50 c.c. of water, heat to boiling, cool slightly, and add 50 c.c. of alcohol. Allow to stand one-half hour, filter on to a Gooch crucible, wash with 50 per cent alcohol, dry, heat gently and weigh as lead sulphate. 342. Manganese. To an aliquot portion of the sample add 5 c.c. of sulphuric acid dilute with 10 c.c. of water, and evaporate on the hot plate until all of the hydrochloric acid is expelled as shown by copious evolution of sulphur trioxide fumes. Cool, dissolve in about 25 c.c. of water and heat carefully with occasional shaking until all of the anhydrous sulphate of iron has dissolved. Transfer to a 250 c.c. graduated flask and add an excess of zinc oxide emulsion, obtained by mixing C. P. zinc oxide with water. Avoid a large excess, but sufficient to precipitate all the iron, so that on standing the solution begins to settle clear and some zinc oxide can be seen in the bottom of the flask. Cool and make up to the mark. Transfer an ali- quot portion to a beaker or flask and add an excess of a 190 ANALYSIS OF MIXED PAINTS. saturated solution of bromine water, and about 3 grams of sodium acetate. One c.c. of a saturated solution of bromine water will precipitate about 0.01 gram of manganese. Boil about 2 minutes. Filter and wash with hot water. The filtrate must be perfectly clear. Place the filter con- taining the washed precipitate back in the beaker or flask in which the precipitation was made. All traces of bro- mine must be entirely expelled. Add an excess of standard oxalic acid solution and about 50 c.c. of dilute sulphuric acid (1:9) and heat nearly to boiling with gentle agitation until the precipitate is entirely dissolved. Dilute to about 200 c.c. with hot water and titrate with standard permanganate. 343. Zinc. Zinc sulphate and zinc oxide are but little used at present in driers. If present zinc may be esti- mated in the filtrate from the lead sulphate, as described under the analysis of mixed paints containing umbers and siennas. 344. Calculations. The color of the drier gives a clue as to the combinations used, borate of manganese being used in light colored driers, oxide of manganese in dark driers, and the oxides of lead in medium colored driers. By far the most common combination is a mixture of borate of manganese and litharge. 345. Determination of the volatile oils. Five grams of the drier is quickly weighed into a flat-bottomed dish, a petri-plate is the most suitable, dried for 3 hours at 150 C., cooled and weighed. Loss in weight represents very closely the amount of volatile thinner present, and in the samples analyzed by the author the volatile thinners constituted 63 to 68 per cent by weight. 346. Separation of benzine and turpentine. About 100 grams of the drier is distilled to the point of incipient decomposition, the distillate redistilled and the benzine ANALYSIS OF JAPANS AND DRIERS. 191 estimated by the Sulphuric Acid Number, as described under the analysis of volatile oils, Chapter IV. 347. Detection of rosin. About 1. c.c. of the drier is dissolved in 15 c.c. of acetic anhydride, warming until the solution is complete. Cool, filter, place a few drops of the filtrate on a crucible cover and add a drop of sulphuric acid, so that it will mix slowly. If rosin is present a charac- teristic fugitive violet color results. Lineolate driers sometimes give a color resembling that of rosin driers, and it is better to evaporate a portion of the drier to a syrup consistency, treat with alcohol, and test the alcoholic extract. 348. Practical tests. The chemical analysis of a Japan will give very little information regarding its efficiency, since the latter is largely dependent upon the conditions of manufacture. The. following specifications, 1 as adopted and used by the Philadelphia and Reading Railroad, give very excellent methods for determining the efficiency of a Japan. "The material desired consists of a pure turpentine hardener and oil drier, conforming to the following: 1st. When equal parts by weight of the Japan and of pure turpentine are thoroughly mixed and poured over a slab of glass, which is then placed nearly vertical at a tem- perature of 100 Fahrenheit, with a free access of air, but not exposed to draught, the coating shall be hard and dry, neither brittle nor sticky, in not exceeding 12 minutes. 2d. When thoroughly mixed with pure raw linseed oil at the ordinary temperature in proportions of 5 per cent, by weight of Japan to 95 per cent by weight of raw linseed oil, no curdling shall result, nor any marked separation or settling on standing. 1 Practical Testing and Valuation of Japan, by Robert Job, Chem- ical Engineer, Vol. IV., No. 5. 192 ANALYSIS OF MIXED PAINTS. 3d. When the above mixture is flowed over a slab of glass, which is then placed nearly vertical, at a temperature of 100 Fahrenheit, with free access to air, but not exposed to draught, the coating shall dry throughout, neither brittle nor sticky, in not exceeding 2 hours. 4th. When five cubic centimetres of the Japan are poured into 95 cubic centimetres of pure turpentine at the ordinary temperature, and thoroughly shaken, a clear solution shall result, without residue, on standing 1 hour. 5th. After evaporation of the turpentine, the solid resi- due must be hard and tough, and must not ' dust ' when scratched with a knife. 6th. Benzine or mineral oil of any kind will not be permitted. Shipments which are not closely in accordance with these specifications, or which are not of uniform quality throughout, will be returned at the expense of the shipper. " 349. The temperature of 100 F. is obtained by the use of a suitable oven. The strips of glass used being 4 inches long by 2 inches wide. They are so placed in the oven that there is free access of air, but no draught. The bulb of the thermometer is placed beside the glass strips and the dry- ness of the film tested opposite the bulb of the thermo- meter. The addition of rosin renders the dry film brittle and hence will " dust " when scratched with a knife. The majority of driers used for house and barn paints are weak driers, and will not meet the above requirements. However, if the chemist will test out a few high-class driers by the above specifications, he will have but little trouble in estimating the value of the cheaper and inferior driers. The United States Treasury specifications for manganese borate require that it be free from by-products, and that, ANALYSIS OF JAPANS AND DRIERS. 193 other properties being satisfactory, preference will be given to the article containing the least amount of alkali. Another practical test much in vogue among practical painters and shop foremen is to make a semi-paste with moisture-free litharge and the drier. High-class driers will remain three to four days before showing a decided ten- dency to thicken or harden; cheap rosin driers will begin to harden in a comparatively short time. CHAPTER XVIII. ANALYSIS OF SHELLAC AND SPIRIT VARNISHES. Analysis of Shellac. 350. The most common adulterant of shellac is common rosin or colophony. Sabin, in his Technology of Paint and Varnish, says that, " It is reported and probably true, that large quantities of common rosin are shipped to India and used as an adulterant of gum shellac." 351. Detection of rosin. About 1 gram of the sample is dissolved in about 15 c.c. of acetic anhydride, warming gently until the solution is complete. Cool thoroughly under the tap. The rosin will remain in solution while the greater part of the shellac will separate out. Filter. Place a few drops of the filtrate on a porcelain crucible, cover, and add by means of a stirring rod one drop of sul- phuric acid (34.7 c.c. sulphuric acid and 35.7 c.c. water) so that it will mix slowly. If rosin is present a charac- teristic violet fugitive color results. A pure shellac should give no coloration. 352. Estimation of rosin. The amount of rosin present is best estimated by means of the iodine number. For this purpose the Hanus method is to be preferred to the Hubl or Wijs method. The Hubl for a long time has been the official method, but it has several faults which affect its accuracy. It rapidly loses strength and is so slow in its reaction with some oils, such as linseed oil, that a serious error is brought about by the change in strength of the solution during the reaction. Another objection to the 194 ANALYSIS OF SHELLAC AND SPIRIT VARNISHES. 195 Hubl method is that practically each chemist uses a mod- ification of his own as regards the time necessary for the solution to remain in contact with the substance to be tested. In their workings the Hanus and Wijs methods are very similar, but the Hanus solution is much easier to prepare and the results obtained more nearly correspond to those obtained by the Hubl method. As most of the published data relating to the iodine numbers of oils, fats, etc., has been obtained by the use of the Hubl method, this fact is of considerable importance in making comparisons. 353. The Hanus solution is prepared and used as described in Chapter IV. 0.2 gram to 0.3 gram of the ground sample is introduced into a 250 c.c. Erlenmeyer flask; 20 c.c. of glacial acetic acid added, and the mixture warmed until the solution is complete, except for the wax. 10 c.c. of chloroform is added, the solution cooled to room temperature, and 25 c.c. of Hanus solution added, the flask stoppered, allowed to remain in the dark or in diffused light for 1 hour, with occasional shaking. 10 c.c. of potassium iodide solution is then added, 100 c.c. of water and titrated with tenth- normal thiosulphate, using starch as an indicator in the usual manner. Blank determinations should be made each time. EXAMPLE: Wt. of sample = 0.4 gram. A blank of 25 c.c. of Hanus solution required 55 c.c. of thiosulphate. One c.c. of thiosulphate = .0125 gram of Iodine. Titration of unabsorbed iodine = 49.5 c.c. thiosulphate. 55.0 49.5 = 5.5 c.c. of thiosulphate equivalent to iodine absorbed. 196 ANALYSIS OF MIXED PAINTS. (5.5 X 100 X .0125) -f- 0.4 = 17.2 per cent iodine absorbed. 354. Iodine Numbers of shellacs obtained from the leading wholesalers and jobbers of the United States, sup- posed to be strictly pure: 1 No. Variety. Iodine No. Color Reaction. 2 1 2 3 Orange shellac Unbleached shellac Orange shellac . . 31.06 15.85 12 68 Rosin present. Rosin absent. Rosin absent 4 Ralle standard shellac .... 16 80 Rosin absent 5 Star brand shellac 14 90 Rosin absent 6 13 H. N. superior shellac Orange shellac 12.99 22.27 Rosin absent. Rosin present 14 15 16 17 Orange shellac Orange shellac Orange shellac Orange shellac 20.36 16.54 20.36 13.36 Rosin absent. Rosin absent. Rosin absent. Rosin absent. 7 8 9 10 12 Bone Dry bleached shellac Refined bone dry bleached shellac Bleached shellac Bleached shellac Bleached shellac 8.87 12.34 6.34 8.87 13.36 Rosin absent. Rosin absent. Rosin absent. Rosin absent. Rosin absent Analysis of Shellac Varnish. 355. Composition. A varnish having the proper con- sistency is prepared by dissolving 45 parts of shellac in 55 parts of grain alcohol of 94 per cent strength or about 5 pounds of shellac per gallon of alcohol. In place of the expensive grain alcohol, some manufacturers substitute wood alcohol or Columbian spirits, which is rectified wood alcohol. The poisonous properties of wood alcohol are well known, and on account of its injurious effects great care should be exercised in the use of varnishes containing it. Shellac varnish is often adulterated with rosin, thus producing a product of an inferior quality. The sophis- 1 Analyses by author. 2 Libermann-Storch Reaction. ANALYSIS ON SHELLAC AND SPIRIT VARNISHES. 197 tication of varnish with this substance is well described by Langmuir: 1 " Starting out with an adulterated shellac, the varnish maker, secure in his belief that rosin cannot be detected in the solution, proceeds to add still more rosin. What has been said in regard to adulteration of shellac fades into insignificance in comparison with that practice in the manufacture of shellac varnishes. Shellac varnishes are sold containing no shellac. ' Pure ' shellac varnishes, grain alcohol, may be purchased at less cost than the alcohol." 356. Determination of the body of shellac varnishes. Three to 5 grams of the well stirred sample is weighed into a weighed flat-bottomed petri-dish and evaporated to a constant weight in the steam oven. The result is calcu- lated in pounds per gallon. If a platinum evaporating dish be used and the evaporation conducted over a water bath, the amount taken should not be over 1 gram. Tak- ing the weight of a gallon of wood alcohol at 60F. as 6.75 pounds, the pounds per gallon may be ascertained by means of the following table : 2 Per cent. Pounds Residue. per Gallon. 30.77 3.0 34.15 3.5 37.20 4.0 40.00 4.5 42.55 5.0 44.90 5.5 47.06 6.0 49.05 6.5 50.91 7.0 52.63 7.5 54.23 8.0 357. Determination of the strength of the alcohol used. The strength of the alcohol may be calculated, knowing the 1 Determination of Rosin in Shellac, J. Soc. Chem. Ind., January 1, 1905. 2 Determination of Rosin in Shellac, J. Soc. Chem. Ind., January L 1905. 198 ANALYSIS OF MIXED PAINTS. per cent of residue as determined above and the specific gravity of the varnish. The calculation is best illustrated by the following example: 5 grams of varnish yielded a residue of 2.300 grams. The specific gravity of the varnish was 0.9445 at 15.5 C. 100 grams of the varnish gave 2.300 X 20 = 46.00 grams of residue or 46.00 per cent. The alcohol by difference 100.00 - 46.00 = 54.00 grams or 54.00 per cent. Average specific gravity of shellac itself = 1.145. The volume taken up by the shellac in the varnish would be 46.00-5-1.145 = 40.17 c.c. in 100 grams of varnish. The specific gravity of the varnish was 0.9445. 100 c.c. would weigh 94.45 grams and hence 100 grams would occupy 105.9 c.c. 105.9 c.c. 40.17 c.c. = 65.73 c.c., the volume occu- pied by 54.00 grams of alcohol solvent. 54.00 + 65.73 - 0.8215, the specific gravity of the alcohol. From the alcohol tables this will be found to correspond to 90.5 per cent of grain alcohol. If desired a portion of the varnish may be distilled until the decomposition point is reached and the strength of the alcohol determined from the specific gravity of the distillate. 358. Examination of the solvent. One hundred grams of the varnish is carefully distilled to the point of incipient decomposition. If necessary the distillate may be re- distilled. 359. Detection of benzine. Dilute a portion of the dis- tillate with three or four volumes of water. If benzine is present it will separate out. 360. Columbian spirit and wood alcohol. The test for acetone, which is always to be found in wood alcohol, will distinguish between Columbian spirit and wood alcohol. ANALYSIS OF SHELLAC AND SPIRIT VARNISHES. 199 361. Detection and estimation of wood alcohol in mixtures with grain alcohol. Qualitatively, the methyl alcohol may be detected by the following method : Dilute a portion of the distillate until the liquid con- tains approximately 12 per cent of alcohol by weight. Oxidize 10 c.c. of the liquid in a test tube as follows: Wind copper wire 1 m.m. thick upon a rod or pencil 7 to 8 m.m. thick in such a manner as to enclose the fixed end of the wire and to form a close coil 3 to 3.5 cm. long. Twist the two ends of the wire into a stem 20 cm. long and bend the stem at right angles about 6 cm. from the free end, or so that the coil may be plunged to the bottom of a test tube, preferably about 16 m.m. wide and 16 m.m. long. Heat the coil in the upper or oxidizing flame of a Bunsen burner to a red heat throughout. Plunge the heated coil to the bottom of the test tube containing the diluted alcohol. Withdraw the coil after a second 's time and dip it, in water. Repeat the operation from three to five times, or until the film of copper oxide ceases to be reduced. Cool the liquid in the test tube meanwhile by immersion in water. 362. Add 1 c.c. of strong ammonia to the oxidized liquid in a casserole and expel the acetaldehyde by boiling gently over a direct flame until the vapor ceases to smell of ammonia. Add 2 to 3 drops of strong hydrochloric acid to set free the formaldehyde which has been retained as hexamethyltetramin, and brmg the liquid momentarily to a boil; cool promptly by immersion of the casserole in water and test for formaldehyde by the modified resorcin test, as follows: Adc? to the liquid remaining 1 drop of a solution con- taining 1 part of resorcin in 200 parts of water, and pour the mixture cautiously into a test tube containing 3 c.c. of concentrated sulphuric acid, holding the tube in an 200 ANALYSIS OF MIXED PAINTS. inclined position in such a manner that the two liquids shall not mix. Allow it to stand 3 minutes, then sway the tube slowly from side to side in such a manner as to produce a gentle rotary motion of the two layers. Persist in this operation, if necessary, for a minute or more, using a piece of white paper for a background, and producing only a very gradual and partial mixing of the acid and water. Nearly half of the acid should remain as a dis- tinct unmixed layer at the end. When methyl alcohol is present, the shaking causes the separation of more or less voluminous flocks of a very characteristic rose-red color. The appearance of colored zones or flocks of other hues, even when tinged with red, or of a rose-red solution without flocks, should never be considered proof of the presence of methyl alcohol. However, if the flocks are reddish brown, or if the upper layer has a pronounced red, it is often well to repeat the test. By this method for the removal of acetaldehyde 10 per cent of methyl alcohol may be readily detected, and an experienced operator may detect with certainty a less amount. 363. Quantitatively the methyl alcohol may be esti- mated by the method of Thorp and Homes. This method depends upon the fact that in the presence of potassium dichromate and sulphuric acid in a closed vessel at 100, ethyl alcohol is converted into its theoretical equivalent of acetic acid, while with methyl alcohol, the product resulting from the oxidation is always carbon dioxide and water. It has, however, been found that for each gram of ethyl alcohol present in the solution 0.01 'gram of carbon dioxide may be formed, and this correction should be made in all determinations. The specific gravity is determined by means of a pycno- meter. The total per cent of the alcohol is practically the ANALYSIS OF SHELLAC AND SPIRIT VARNISHES. 201 same as the per cent of ethyl alcohol of the same specific gravity. 364. The methyl alcohol is determined by converting it into carbon dioxide by means of sulphuric acid and potassium dichromate in the Knorrs' apparatus described under the estimation of carbon dioxide in white lead. Weigh into the flask 20 grams of potassium dichro- mate, connect the apparatus after having weighed the soda-lime tubes. Introduce through the stop-cock funnel an exact volume of the alcohols not to exceed 4 grams of the mixed alcohols, and an amount of water equal to 50 c.c. less the number of c.c. of alcoholic solution, 80 c.c. of sulphuric acid (made by diluting one volume of concentrated acid with four volumes of water) are added, well shaken and allowed to stand 18 hours. Dissolve 10 grams of potassium dichromate in 50 c.c. of water, add through the funnel, then add 50 c.c. of concen- trated sulphuric acid and heat the contents of the flask to boiling for about ten minutes, the carbon dioxide being carried off by a current of air through the apparatus. The heat is now removed and the current of air continued for a few minutes longer. Disconnect and weigh the soda-lime tubes. Calculate the methyl alcohol from the proportion 1.373 : 1 : : wt. C0 2 obtained : x x = wt. methyl alcohol, the theoretical oxidation of 1 gram methyl alcohol pro- ducing 1.373 grams of carbon dioxide. EXAMPLE. Specific gravity of sample, 0.7992 Weight of sample used, 1.0118 grams Weight of carbon dioxide, 1.3810 grams 202 ANALYSIS OF MIXED PAINTS. 1.373:1 : : 1.3810 : x x = 1.006 grams methyl alcohol. 1.0118 : 1.006 : : 100 : y y = 99.4 per cent methyl alcohol. 365. If ethyl alcohol is present, the correction previously referred to, of 0.01 gram carbon dioxide for each gram of ethyl alcohol, should always be applied. The weight of the methyl alcohol subtracted from the weight of the mixed alcohols (calculated from the sp. gr.) gives the weight of the ethyl alcohol, approximately. The weight obtained by 0.01 gives correction to be deducted from the total carbon dioxide, for the recalculation of the weight of methyl alcohol. It is obvious that a very slight error is thus introduced, but the writer believes that it is so small that it may be safely neglected. 366. Detection and estimation of rosin. The residue remaining after the drying of the varnish in the determi- nation of the " body " may be used for the detection of rosin as described under the examination of shellac. If much rosin is present, it is not safe to take the residue after evaporation for the quantitative estimation as has been shown by Langmuir. " A little rosin (iodine value 224.3) was dissolved in alcohol, evaporated on the water bath and heated 5 hours. It then showed a value of 148.2. Similarly, a dark rosin 175.7 fell to 131." A quantity of the varnish sufficient to yield 0.2 to 0.4 gram of residue is weighed from a small vial, provided with a perforated stopper carrying a shortened 1 c.c. pipette, into a 200 c.c. Erlenmeyer flask; the weight of the sample used being thus obtained by difference. The sam- ple in the flask is carefully evaporated at a low temperature until pasty and then dissolved in the requisite amount of acetic acid and chloroform and the iodine number then ANALYSIS OF SHELLAC AND SPIRIT VARNISHES. 203 determined in the usual manner. The error due to the action of the small amount of alcohol remaining in the pasty mass on the thiosulphate is negligible. In calculating the per cent of rosin the iodine values of 150 l for rosin, 16 * for unbleached and II 1 for bleached shellac may be used. If other resins are present, as san- darac, etc., these can only be calculated in the terms of rosin. 367. Estimation of rosin, Mannhardt's method. 2 Five grams of gum shellac or 10 grams of shellac varnish are weighed into a casserole or flask, and the solvent expelled on the water-bath. The residue is saponified with alcoholic potash, the alcohol expelled, and the residue taken up in 100 c.c. of hot water. At this point any wax present may be extracted with benzine (sp. gr. .730), the benzine evaporated off, and the residue weighed. The solution of the soaps is treated with 50 c.c. benzine (sp. gr. .730), shaken vigorously, and, before the emulsion has time to separate out, add dilute sulphuric acid in slight excess. The shellac acids immediately coagulate, and all rosin acids go into the benzine, which is readily separated, filtered and evaporated in a weighed beaker. The shellac acids are absolutely insoluble in benzine. Damar and possibly sandarac will behave like rosin. 368. Practical test for brewers' varnish. Varnishes for brewers' purposes should be made from pure shellac and grain alcohol 94 per cent strength. They may be tested out by varnishing a strip of wood 6 inches long by 3 inches wide, and a quarter of an inch in thickness, and after drying immerse half of the strip in 4 per cent alcohol for 48 hours. A varnish made from impure shellac or alcohol of less than the proper strength will soon turn white. 1 Average values obtained by author. 2 Hans Mannhardt, Chemist, Heath & Milligan Mfg. Co. 204 ANALYSIS OF MIXED PAINTS. 369. ANALYSES OF SHELLAC VARNISHES. 1 No. Variety. Iodine Number. Percentage of Gum. Calculated Percentage Rosin. 18 Orange shellac . . . 40.5 49.8 18.3 19 Orange shellac .... 13.4 42.2 23 Orange shellac .... 26.2 37.1 7.6 2 25 Orange shellac .... 16.2 35.9 . . . 26 Orange shellac .... 15.2 21.0 . 27 Orange shellac .... 37.4 13.3 16.6 29 Orange shellac .... 23.3 40.5 5.4 2 31 Orange shellac .... 15.0 39.8 20 White shellac .... 40.8 44.1 2i!4 30 White shellac .... 37.8 22.4 19.3 21 White shellac .... 13.3 41.0 22 White shellac .... 16.2 37.6 28 White shellac .... 17.5 42.0 370. Damar varnish. The following specifications adopted by the Navy Department, May, 1904, will serve for the practical testing and valuation of damar varnish. Damar varnish must be made from the very best quality of damar gum in a solution containing at least 50 per cent of gum and 45 per cent of turpentine, the gum to be digest- ed cold and well settled. The varnish must be as clear as and not darker than the standard sample, and must be free from benzine, rosin, lime, or other mineral matter. Its specific gravity at 60 F. must be about 0.950, and its flash point between 105 and 115 F. It must set to touch in not more than 20 minutes, and when mixed with pure zinc oxide must show a smooth glossy surface equal to that shown by the standard sample. 371. Tests. Besides chemical tests to determine the above qualities, and practical tests to determine its quali- ties of finish, a board properly coated with a mixture of 1 Analyses by author. 2 Liebermann-Storch reaction produces a somewhat different color than that usually given by rosin, hence these samples may be adulter- ated with other gums. ANALYSIS OF SHELLAC AND SPIRIT VARNISHES. 205 zinc and the liquid will be exposed to the weather for a period of 1 month, and at the end of this time must have stood 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. Another sample, similarly prepared, will be exposed in a dark room at ordi- nary temperature for a, period of 1 month and at the end of this time must not have turned darker to any appre- ciable degree than the standard sample. CHAPTER XIX. ANALYSIS OF OIL VARNISHES. 372. Analysis of oil varnishes. As stated by Hurst, " The analysis of oil varnishes is one of great difficulty, as it is quite impossible to separate all the ingredients from one another. J; However in spite of the unsatisfactory state of our present knowledge of varnish analysis, a dis- tillation and separation will give an approximate idea of the quantity and kind of volatile solvents used. Treating the residue by Twitchell's method , will give approximately the amount of oil and the amount of gum present in the varnish and an examination of the physical and chemical properties of the separated gum may give an approximate idea of its hardness, and throw some little light on its probable source. The presence of lime, color produced by the Liebermann-Storch reaction, acid figure and iodine absorption will indicate the presence of rosin and to some extent the amount present. With these tests, in conjunc- tion with the solubility of the separated gum, the original character of the varnish, e.g., the pouring of a portion of the sample on a sheet of glass, noting how it flows, dries, the kind of film produced, its resistance to abrasion, to moisture, its elasticity, etc., and a comparison made with varnishes of known composition and similar properties, a very shrewd guess can be made as to how the varnish under consideration must be duplicated, or in other words, the approximate amounts of the different gums required to produce a similar product. 373. On the other hand, a proximate analysis of a var- 206 ANALYSIS OF OIL VARNISHES. 207 nish furnishes us with but a small amount of helpful infor- mation, as the gloss, working qualities, and durability depend largely on the quality of gum used, the quality and treatment of the oil, the quality of the driers used, and especially as to how the varnish was prepared, as regards heat, method of cooking, ageing, filtering, etc. On these essential points a chemical analysis tells us but little. That greater light will eventually be thrown on the problems involved, the author has not the slightest doubt, but meanwhile interpretations based solely on chemical analyses are liable to be more or less misleading; but taken in connection with physical tests, carefully made, the value of varnishes can be determined with considerable accuracy. 374. Specific gravity. The determination of the specific gravity is of considerable importance and should be made with a pycnometer at 15.5 C. 375. Viscosity. The determination of the viscosity of a varnish will throw considerable light on its working qualities. Any of the standard types of viscosimeters may be used for varnish work, but the Doolittle Torsion Viscosimeter offers several advantages over the others. 376. Separation, identification, and estimation of the volatile oils. Seventy-five grains of a uniform sample of the varnish is weighed into a 500 c.c. distilling flask, pro- vided with a tube leading very nearly to the bottom, the other end of which is connected with a steam supply. The flask is also provided with a thermometer, the bulb of which dips below the surface of the varnish, and the flask then connected with a rather long condenser. By means of an oil bath the varnish is heated to 130 C., and a cur- rent of steam passed through, until about 500 c.c. of water has passed over, or until the steam ceases to carry over any more volatile oil. It is advisable to collect the dis- 208 ANALYSIS OF MIXED PAINTS. tillate directly in a separating funnel. When the volatile oil has completely settled out, the water is drawn off and the oil transferred to a weighed flask, weighed, and the percentage calculated. The aqueous distillate will con- tain a small quantity of the volatile oil equal to about 0.4 gram per hundred c.c. This correction should be made in calculating the percentage. The constituents of the volatile oil and the amount of petroleum products present may be determined exactly as described in the chapter on the Analysis of the Vehicle of Mixed Paints. 377. Separation of the resin gums from the oil, Twitchell's method. The flask containing the residue of oil and gum is connected with a return condenser, 150 c.c. of normal alcoholic potash added, the flask heated care- fully on a water bath to avoid bumping and finally heated over a free flame for about an hour. The solution is then cooled and separated from the residue, which is again treated with alcoholic potash, and the process continued until as complete a saponification as possible has been made; usually a small residue of about 1 per cent remains. The different alcoholic solutions are united, neutralized with hydrochloric acid, the excess of alcohol evaporated off, and the fatty acids and gums removed with succes- sive portions of ether. The ethereal solution is distilled to remove the ether, a small quantity of absolute alcohol added, and the flask again heated gently, the alcohol carrying off the last traces of water. About 10 volumes of absolute alcohol are added to the dry gums and acids, the solution being kept cold by ice and dry hydrochloric acid gas is passed in until the solution is saturated. This will usually take from 30 to 45 minutes. The flask and contents are allowed to stand for about an hour, then diluted with about 5 volumes of hot water, and boiled ANALYSIS OF OIL VARNISHES. 209 until clear; the heating being conducted gently to avoid frothing. 378. The contents of the flask are mixed with a little petroleum ether, boiling below 80 C. and transferred to a separating funnel, the flask being washed out with the same solvent. The petroleum ether layer should measure about 50 c.c. After shaking, the acid solution is run off and the petroleum ether layer washed once with water, and then treated in the funnel with a solution of 2.5 grams of potassium hydroxide and 20 c.c. of alcohol in 200 c.c. of water. The cthylic esters dissolved in the petroleum ether will then be found to float on top, the rosin acids having been extracted by the dilute alkaline solution to form rosin soap. The soap solution is then run off, decom- posed with hydrochloric acid, and the separated rosin acids collected as such, or preferably dissolved in ether, and the whole evaporated in a small weighed beaker on the water bath. A small quantity of absolute alcohol is added, and the evaporation repeated. Finally, cool in the desiccator and weigh. This will give approximately the amount of gums present in the varnish. Any residue insoluble in the 10 volumes of absolute alcohol above mentioned is weighed up and its weight added to the weight of resin gum. 379. Separation of the gums from the oil, Scott's Method. 1 In separating the gum, by this method, it is necessary to know whether the sample is a Long Oil or Short Oil Varnish, i.e., whether it contains a large or small amount of linseed oil. Hard oil finishes, interior varnishes, and rubbing varnishes are usually shot oil varnishes, while carriage and similar varnishes are long oil varnishes. In order to determine to which class a varnish belongs, 1 Drugs, oils, and paints, XV., No. 4, p. 132, and No. 6, page 219. 210 ANALYSIS OF MIXED PAINTS. about 10 c.c. of the sample is poured into a beaker and 50 c.c. of benzine, previously cooled to about 5 C., added. If the sample be short oil varnish the gums will be partially precipitated, while a long oil varnish will show but little change. The color of the precipitated gum may be con- sidered as another indication, a light colored precipitate denoting a short oil, and a dark colored preciptate, a long oil varnish. 380. Short oil varnishes. A beaker of about 150 c.c. capacity, provided with a stirring rod, is carefully weighed, and about 10 grams of varnish weighed into it. Cool to below 10 C. Fifty c.c. of petroleum ether that has pre- viously been cooled to below 3 C. is poured into the beaker and the contents stirred. The beaker is placed in a freezing mixture for about an hour, or until the precipi- tated gums have settled. 381. Place a filter paper that has been dried in the oven, in the suction funnel. Moisten and suck the filter free from surplus moisture, pour in the gasoline, retaining as much of the resins as possible in the beaker. Add another 50 c.c. of ice cold petroleum ether, and allow to stand as before in the freezing mixture. Meanwhile pour 25 c.c. of ice cold water on the filter paper, allowing it to run into the petroleum ether filtrate, which is then vig- orously shaken up so as to thoroughly mix the water and petroleum ether, which causes the gum held in solu- tion by the ether to precipitate, and on refiltering is retained. The second ether solution that has been cool- ing is now poured on to the filter along with the precipitate, rinsing out the beaker with ice cold petroleum ether. Treat with 25 c.c. of ice cold water, shaking and refiltering, as described above. Repeat this operation twice, trans- fer the filter, and precipitate to the weighed beaker, and dry in the hot air oven at 105 to 115 C. and weigh. ANALYSIS OF OIL VARNISHES. 211 Increase in weight, over that of the beaker, stirring rod and filter, represents the weight of the gum. The petroleum ether solution containing the varnish oils is poured into a weighed beaker, the excess of petro- leum ether evaporated off with due precautions, and the beaker placed in the hot air oven for 3 hours at 150 C., cooled and weighed. The residue represents the fixed oils in the varnish. 382. Long oil varnishes. Distil ofT the thinners from a portion of the sample. Weigh out 10 grams of the gum and oil into a weighed beaker as described above, cool down below 15 C. and add 50 c.c. of petroleum ether cooled below C. Set in the freezing mixture for an hour and finish exactly as described under short oil var- nishes. The separation of the total gum in long oil var- nishes is quite difficult and requires considerable patience and experience. According to the experience of the author, Scott's method gives somewhat low results, espe- cially as rosin is quite soluble in cold petroleum ether. 383. Determination of the so-called insoluble and soluble gums. This method is somewhat similar to the above, and, in the hands of a careful chemist, when run alongside of standard varnishes, will throw considerable light on the nature of the sample in question. Weigh 2 grams of the sample into a weighed 6-oz. wide- mouth flask, add 2 c.c. of chloroform, 100 c.c. of 80 petroleum ether, gradually and with constant shaking so as to avoid any preciptation, until 15 c.c. are added, allow to stand over night. The precipitated gums adhere to the bottom of the flask. Decant and wash with a little petroleum ether. Dry to constant weight as insoluble gum. The petroleum ether extract should be decanted into a weighed beaker, the petroleum ether evaporated off and 212 ANALYSIS OF MIXED PAINTS. the beaker dried at 100 for seven to eight days to con- stant weight. All linseed oil should now be in the form of linoxyn. Digest over night with chloroform, which will dissolve the gum, and leave the linoxyn undissolved. Filter through cotton wool. Evaporate off the chloroform, dry to constant weight in the steam oven and weigh as soluble gum. A varnish to meet with the requirements of the United States Treasury Department, among other things, should contain not less than 25 per cent of best quality imported gums, and must not contain rosin or petroleum products. Varnishes containing wood oil are liable to give mis- leading results by the above method, as the whole or a considerable portion of the wood oil will be precipitated by the petroleum ether, depending on the length of time and temperature to which the oil has been heated. 384. Detection and estimation of rosin in varnishes. Qualitatively rosin may be detected as follows: Pour about 5 c.c. of the varnish into a small separatory funnel, add about 5 c.c. of carbon bisulphide, shake and add 10 c.c. of acetic anhydride. Allow to stand until complete separation takes place. Draw off the lower layer, which is the acetic anhydride. Pour 1 or 2 c.c. of the acetic anhydride portion into an inverted crucible cover, add carefully, by means of a stirring rod, one drop of sulphuric acid (34.7 c.c. of sulphuric acid to 35.7 c.c. of water) to the edge of the cover, so that it will mix slowly with the acetic anhydride, if rosin is present a characteristic fugitive violet color will result. 385. The quantitative estimation of rosin in the pres- ence of other varnish gums is a problem of especial diffi- culty. Gill, 1 suggests a method based on comparative ester values. The ester value being obtained by sub- 1 J. Amer. Chem. Soc. XXVIII., No. 12, page 1723. ANALYSIS OF OIL VARNISHES. 213 tracting the free acid value from the saponification value. The gums are separated from the oils by Twitchell's method, the last traces of moisture being removed by drying over sulphuric acid. Gill obtains the following values for rosin and kauri. Gum. Saponifi- cation. Free Acids. Ester. Aver- age. Pure rosin , No. 1 182.3 160.1 22.2 Pure rosin , No. 6 . . 185.7 161.7 24.0 23.1 Kauri, No . 1 ... 124.2 41.0 83.2 Kauri, No . 2 .... 129.7 45.0 84.7 84.0 By the use of the usual formula 100 (7 - n) x = m n the percentage of adulteration may be approximated, as described in the chapter on the Analysis of the Vehicle, in discussing cotton-seed oil. 387. Gill's method is open to considerable criticism, as he directs that the Free Acid Value be obtained by direct titration, and the Saponification Value by saponifying in practically an open flask. Dietrich l has shown that direct titration gives acid values far too low for all resin, because the complete neutralization of the rosin acid proceeds slowly. As an illustration of this point, Worstall * gives the following experiment: " Several portions of a sample of Kauri, whose acid number has been accurately determined as 103, were weighed out arid the acid number determined by indirect 1 Analyse der Harze, Balsane, und Gumminharze. 2 Chemical Constants of Fossil Resins, J. A. Chem. Soc. XXV., page 860. 214 ANALYSIS OF MIXED PAINTS. titration at different intervals of time, as follows: The results were Time. Acid No. 5 minutes 82 1 hour 92 3 hours 96 6 hours 101 12 hours 102 18 hours 103 388. Regarding open saponification Worstall states that " from the researches of Tschirch and his pupils, it appears that the copals consist of ' resenes ' - - neutral compounds containing oxygen and possibly of an aldehyde nature and of the resin acids. Other investigators have noted the fact that the copals will absorb oxygen, and evidently the increase in acid number and decrease in iodine absorption is due to the oxidation of these * resenes/ by contact with the air, to resin acids. . . . That this increase in the acid number is actually due to oxidation, the following experiments will illustrate : "A number of samples of Kauri were selected, each one finely powdered, and its acid and iodine numbers deter- mined. These samples were then left four months in open bottles exposed to the air, and the .powdered resins stirred from time to time to promote oxidation. At the end of this time their constants were again determined with the following results. No. Before Acid. Oxidation Iodine. After Acid. Oxidation Iodine. Acid Increase. Iodine Decrease. 1 72 154 87 133 15 21 2 76 159 111 121 35 38 3 77 140 93 115 16 25 4 72 170 107 110 35 60 5 97 109 104 99 7 6 105 113 109 112 4 1 ANALYSIS OF OIL VARNISHES. 215 " Samples 1, 2, 3 and 4 were hard, ' bold ' gum of highest quality, while samples 5 and 6 were of a soft, spongy, lowest grade Kauri, in which oxidation had already made much progress before the experiment was carried out. " This oxidation proceeds rapidly in presence of alkalies, so that open saponification with alcoholic caustic potash gives acid numbers that are much too high. Doubtless this fact, in connection with the impossibility of obtaining correct acid numbers by direct titration, has led to the reporting of ester values in resins where no esters exist. That Kauri is free from esters was shown by saponifying several samples in flasks with return condensers, digesting for one hour on the steam bath. In every case the saponi- fication number thus found was the same as the indirect acid number." 389. From the above data it is evident that in order to approximate the percentage of rosin in a varnish by the so-called ester values according to Gill's method, each analyst must establish his own set of figures, under certain definite working conditions, obtaining his data from var- nishes of known composition. Any variation of these conditions, either in time, factor or condition of the gums, is certain to give different results. Little that is reliable has been written concerning the detection of the other varnish gums. Certain resins, how- ever, give some indication of their presence. For instance, Kauri imparts a reddish stain to a varnish. Damar, if present in considerable quantity, can be detected by its smell, especially in the dried varnish. It is seldom found in varnishes intended for outside use. 390. In closing, a word should be said concerning wood oil. This product, the properties of which are but little understood by the majority of chemists, is finding a wide use among varnish manufacturers. It is claimed by var- 216 ANALYSIS OF MIXED PAINTS. nish manufacturers that by the use of wood oil, varnishes containing a large amount of rosin may be prepared, pos- sessing satisfactory wearing qualities and free from the objectionable features of ordinary rosin varnishes. How- ever, in light of the rather heavy losses encountered by a number of varnish firms in endeavoring to prepare a satis- factory rosin-wood oil varnish, the above claims of the varnish manufacturers may be questioned somewhat. As to the analysis of this type of varnish the author is not aware of any suitable published method. It is said, how- ever, that it may be detected qualitatively by practical varnishers, in quantities as low as five per cent by the characteristic odor given off in sandpapering a coat which has barely dried. 391. Navy specifications for interior varnish for naval vessels, 1906. To be of the best quality and manu- facture and equal in all respects including body, cov- ering properties, gloss, finish and durability to the standard samples in the general storekeeper's office, navy- yard, New York. 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. The varnish must flash above 105 F., set to touch in from 6 to 8 hours, and dry hard within 24 hours in a temperature of 70 F. It must stand rubbing with pumice stone and water within 36 hours without sweating, and must polish in 72 hours with rotten stone and water. To be as clear and not darker than the standard sample, and to be equal to it in all respects as above specified. 392. Navy specifications for black asphaltum varnish, 1906. Black asphaltum varnish must be of pure, high- grade asphaltum of the very best quality, pure linseed oil, pure spirits of turpentine and lead manganese driers, and ANALYSIS OF OIL VARNISHES. 217 to be free from all adulterants or other foreign materials, and must contain not less than 20 gallons of prepared lin- seed oil to 100 gallons of varnish. It must not flash below 105 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. It must set to touch in from 1J to 2 hours, and dry hard in less than 20 hours at 70 F. When dry and 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. CHAPTER XX. THE PRACTICAL TESTING OF VARNISHES. 393. The thorough practical testing of varnishes is an exceedingly difficult matter for the average chemist, as it requires long familiarity with the direct application of varnishes under a large variety of circumstances and con- ditions. However, there are several practical tests which can be made without special difficulty, and which will throw considerable light on the character of the varnish, especially if the chemist be supplied with a standard set of varnishes which he can run along with the sample to be tested, and have constantly by him to enable him to check up his judgment by comparison. 394. Smell. The smell of a varnish will often tell much concerning its value. A good, wholesome, gummy odor usually indicates a varnish made from good materials, while a strong, raw, pungent odor is often the sign of a cheaper grade of goods. Markedly inferior articles can almost witnout exception be detected in this manner. Occasionally the true odor of the varnish is masked by a strong turpentine odor, in which case allow a sample of the varnish to drain out of a beaker for 3 to 5 minutes and then note the smell of the portion adhering to the sides of the beaker, i.e., the " after smell," as it is called. 395. Consistency. The consistency of a varnish is to a considerable degree regulated according to the work for which it is to be used, and should be judged accord- ingly. There is a marked tendency, at the present time, to make varnishes altogether too thin. This may in part 218 THE PRACTICAL TESTING OF VARNISHES. 219 be due to the insistent demands made by contractors and other varnish users for goods that will " work fast " and dry quickly, but it should be remembered that such varnishes do not afford the measure of protection to the surface that is regarded necessary by the best practical users of varnish. 396. Working and flowing. The working qualities of the varnish under the brush will at once show whether the chemist is dealing with a " long oil " or a " short oil " varnish. A test board having been suitably surfaced and filled either with thin shellac, or with the varnish reduced with 25 per cent of turpentine, dried and sandpapered down smooth, is given an even, uniform coat of the varnish to be tested. The length of time the varnish can be worked under the brush, before it exerts a characteristic " pull " on the brush, is indicative of the character of the varnish. If it permits of sufficient time for thorough brushing out so that a large panel could be coated and worked out smooth, before it begins to pull on the brush, i.e., " set up," the sample would be considered a long oil varnish, while if it begins to pull under the brush almost at once, it would be considered a short oil varnish. Naturally, there are varnishes which do not exhibit these extremes, but usually the classification can be made without difficulty. 397. Special notice should be taken of the way the varnish flows out into a uniform surface, whether it does so \\ith ease, or slowly and with difficulty. In apply- ing the final coats the working and flowing can be studied with greater exactness. Some varnishes will work easily, others will work " tough," some " greasy," etc.; with a little experience the chemist can grade them with con- siderable accuracy. As mentioned in a preceding para- graph, there are many varnishes on the market which are altogether too thin. Such varnishes will work and flow 220 ANALYSIS OF MIXED PAINTS. with great ease because of their excessive thinness, and hence the consistency must be taken into account when passing on the working and flowing qualities. 398. Time of drying. The time a varnish requires to dry properly, i.e., to harden thoroughly, is regulated according to the purpose for which the varnish is to be used. For instance, floor varnishes are supposed to dry hard over night, while the average spar varnish will require a much longer time. Hence the samples tested should be com- pared with the accepted standards of those types of varnishes, both on the wood test surface and on a sheet of glass, on which samples of the varnishes have been placed and then set in a dust-free but unconfined place at an angle of about 30 degrees from the perpendicular. The best results are secured by resting the glass on a couple of small hooks, which permits the varnish to drain freely. The rapidity of the drying should be noted at regular intervals. When dry, the tests should be saved for further examination. 399. The sponge test. After the requisite number of coats have been applied to the test boards and the finish- ing coat has hardened thoroughly, a sponge made of several thicknesses of felt is thoroughly moistened and laid on the varnished surface and allowed to remain for a stated number of hours, undisturbed. A high-grade varnish will either show no discoloration at all, or will regain its color on dry- ing, provided, of course, that it has been suitably applied. A varnish containing a large amount of rosin will be more or less badly corroded and will remain permanently white and discolored. With a little practice by working with varnishes of known composition the chemist can make a pretty shrewd guess as to the approximate amount of rosin present by the degree of discoloration. Right here the author wishes to state that the use of cheap inferior rosin varnishes has caused untold damage. There is probably THE PRACTICAL TESTING OF VARNISHES 221 more rosin varnish sold than all other grades put together. It is claimed by high-class manufacturers that the addition of three or four per cent of hardened rosin will enable the varnish maker to melt his gums at a somewhat lower heat and without darkening, thus making a better and lighter- colored varnish; but the addition of rosin has passed this point so far that a three or four per cent addition is a very minor consideration indeed. 400. Another modification of the above test is to varnish a clean strip of tin, and after thorough drying immerse it under water and note the rapidity and extent of corrosion and discoloration. 401. Toughness and elasticity. In order for a varnish to be durable and give entire satisfaction, it must have the desired toughness and elasticity as well as the requisite hardness. A varnish which is brittle, although it may have the required hardness, will be easily cracked or crushed by a very moderate blow. Some varnishes are required to be tougher and more elastic than others, as in the case of floor finishes. 402. The varnish having thoroughly dried on the test glass alongside of the standard sample, its toughness may be determined to a certain extent by its behavior under the thumb-nail, and the results obtained compared with a similar examination on the varnished test board. Also the films of the thoroughly dried varnish on the test glass may then be scratched with a sharp instrument. A small, sharply pointed knife-blade is excellent for this purpose. A first-class varnish having suitable toughness and elasticity will show a smooth, even scratch, no scaling or " dusting " being observable ; and if the knife be held in the proper position, a small uniform, coherent ribbon of varnish will be ploughed off. If the varnish is deficient in elasticity and toughness, it will scale away under the knife-point, 222 ANALYSIS OF MIXED PAINTS exhibiting a ragged, irregular scratch. Varnish films con- taining rosin when tested with the knife-point will usually " dust " more or less badly, i.e., fly away from the knife- point in the form of a fine powder, settling on the glass at a considerable distance from the scratch. The fact that varnishes vary greatly in consistency should be taken into account in making these tests, as the films on the glass will vary in thickness according to the consistency of the varnish. 403. In judging the brittleness of a varnish on a test board, especially if it is hard wood, the effect of the material used for the first coat must be taken into con- sideration. This may be readily shown by taking a hard- wood board, coating a portion of it with shellac, another portion with an average cheap liquid filler, and the remain- ing portion with the varnish itself. After applying two coats of varnish over the entire surface and allowing it to harden thoroughly, it will be found on testing the surface with a knife that the varnish over the liquid filler is very brittle, that over the shellac somewhat brittle, while the straight varnish-filled surface will remain tough and elastic. Another method of testing the elasticity, is to varnish a strip of tin, and, after thorough drying, bend the tin and note the extent which the varnish gives under the strain to which it is subjected. In making these various tests, the chemist must be certain that the varnish is thoroughly dry, as many of the cheaper varnishes harden slowly, and, if examined too soon, will show greater tough- ness and elasticity than would be obtained in actual practice. 404. Hardness, A varnish may have the toughness and elasticity required of first-class goods, but may be deficient in hardness. In order to report on the hardness, the chemist should have some means of giving this quality a numerical value. An instrument for this purpose has been THE PRACTICAL TESTING OF VARNISHES 223 devised by Dr. A. P. Laurie and F. G. Baily of Heriot Watt College, Edinburgh, the essential features of which are a central rod sliding easily in a vertical direction through holes in two brackets. The upper portion of the rod has a screw thread, on which is a running nut. By means of a milled head at the top the rod is twisted round, and the nut caused to travel up and down on the thread. A spring is attached at its upper end to the travelling nut and at the lower end to the lower bracket. To the lower end of the rod" is attached a hardened blunt steel point, and the varnished plate to be tested is placed under this point, and the point brought to the surface of the varnish. The test surface is drawn slowly under the point, the pressure being increased until a white scratch is observed, at which point the reading is noted on the scale. The machine reads to a maximum of 2000 grams. Spirit varnishes break down at a pressure of about 100 grams, rosin varnishes 200 to 400 grams, fairly good common varnishes at about 700 grams, and fine carriage varnishes at 1200 grams and upwards. The inventors claim that the best oil varnishes take twelve months to reach their maximum hardness, and that the rate of drying and the ultimate hardness can be measured with accuracy by their instrument. 405. Classification of varnishes. The varnish industry has from its beginning been conducted with as much secrecy as possible, and but little has been published that would enable the average chemist to pass judgment on the different grades and varieties of varnish, and for this reason a short discussion of some of the principal classes of varnish may not be amiss. 406. Floor varnishes. x Goods of this class should have a medium consistency. If heavy they will require a longer time to dry and harden than is desirable, and would be apt to become marred from usage before thoroughly hardened; 224 ANALYSIS OF MIXED PAINTS. if too thin they will not afford the desired protection to the wood. In price they are about the same as for first-class interior varnishes, ranging usually from $2.00 to $2.50 per gallon wholesale. Floor varnishes are usually " long oil " goods, as a high degree of elasticity is required. 407. Interior varnishes. Varnishes for interior work should be of fairly heavy consistency, so as to stand rubbing. For the best class of work they should be " long oil," although " short oil " goods may be used for the under- coats. In price they usually range from $2.00 to $2.50 per gallon wholesale. Often, especially in contract work, " No. 1 Coach " goods are used. This term means absolutely nothing, as it stands for no specific grade or quality of varnish. Sold under this name varnishes are put on the market for $0.90 to $1.10 per gallon, or even less, and are usually high in rosin and benzine or heavier petroleum- products. Polishing varnishes, such as are used for pianos, high-class furniture, etc., are usually of excellent quality, averaging in price from $2.50 to $2.75, although the very best grades may run as high as $3.50 wholesale. 408. Interior varnishes being subjected to less strenuous usage than floor finishes, carriage or exterior goods, the tendency has been to lower the standard of quality, until perhaps low grade, inferior goods are the rule, and really high-grade finishes the exception, on the market at the present time. Neither is the size of the company any guarantee that the product is of high value, for many of the best grades of varnishes are made by small concerns who depend on the quality of their goods rather than on extensive advertising for their sales. 409. Exterior varnishes. These should always be " long oil " goods. Spar varnishes, which are the usual type of exterior varnishes, should be of medium consistency, tough and elastic, and not easily scratched. In price they THE PRACTICAL TESTING OF VARNISHES. 225 usually range from $3.00 to $3.75 per gallon wholesale. Carriage varnishes bring the highest price of all varnishes, and their successful manufacture is accomplished by only a comparatively small number of concerns, and but few domestic brands are rated equal to the best imported English goods. Domestic carriage varnishes range from $4.75 to $5.75 wholesale, and the best imported English goods at about $7.25 per gallon. 410. Short volume. It is a lamentable fact that varnish manufacturers almost invariably defraud the consumer by putting out their packages short in volume. Of eleven samples purchased by the author on the open market, in the original package none were full measure. The amount of shortage is given in the following table : No. Description. Per Cent Short- age of Contents. 1 Floor Varnish 3 2 2 Floor Varnish 4 2 3 Floor Varnish . 2 1 4 Interior Varnish 3 2 5 Exterior Varnish 2 1 6 Coach Varnish 2.1 7 Interior Varnish 8.4 8 Floor Varnish 3 2 9 Exterior Varnish 4 2 16 Floor Varnish 9 5 18 Floor Varnish 13 3 Average . . ... ... 5.0 Five per cent shortage in measure represents a very fair profit to the manufacturer in itself. 411. Significance of lime in varnishes. The addition of five to six per cent of quicklime to melted rosin makes it considerably harder. The compound formed easily dissolves in linseed oil (at the present time wood oil is largely used), and when properly thinned forms the base of about all the cheap varnishes on the market. Such 226 ANALYSIS OF MIXED PAINTS. varnishes are characterized by giving a brilliant surface, easily scratched, and in a short time liable to crack badly. The relation between the percentage of lime (CaO) in the varnish and its toughness and elasticity is not marked enough to enable the chemist to pass judgment on its working qualities from the amount of lime it contains. 412. Sixteen of the leading varnishes on the market were tested out for toughness and elasticity, and then the amount of calcium oxide determined in each, the results obtained being given in the following table. No. Kind. Per Cent of Calcium Oxide in Varnish. Elasticity and Toughness. 2 Floor Varnish 868 Good 3 Floor Varnish 246 Good 4 Interior Varnish 0.200 Good 5 6 7 9 Exterior and Interior Varnish No. 1 Coach Varnish . . .' Interior Exterior 0.178 0.313 0.195 Medium Good Poor Medium 11 13 No. 1 Coach Varnish . . . Interior Varnish . . 0.265 0.271 Poor Very Poor 14 Interior Varnish .... 0.161 Poor 15 0.800 Medium 17 0.158 Medium 19 Interior Varnish .... 0.158 Good 21 Interior Varnish 0.212 Good 23 25 Interior Coach Varnish . . Interior Varnish 0.532 0.281 Poor Poor 413. Of twelve brands of floor varnishes examined by the author, four were altogether too thin for the purpose intended; and of fourteen interior finishes, four were ex- ceedingly thin, and several of the remainder were below average in this respect. Of a total of twenty-six of the leading brands of floor, exterior and interior varnishes tested out by the author, seven were considered first class in all respects, eight were medium or just fair quality, while eleven were unquestion- THE PRACTICAL TESTING OF VARNISHES. 227 ably poor and inferior both as regards working and the quality of the film after drying. Of the above eleven, eight were interior finishes. 414. The twenty-six with but two exceptions flashed at room temperature, a fact which is worthy of considerable attention on the part of the consuming public as regards fire risk. 228 ANALYSIS OF MIXED PAINTS. APPENDIX. 415. TRADE NAMES OF THE PRINCIPAL PAINT PIGMENTS WITH CHEMICAL NAMES. BLUE PIGMENTS. Trade Name. Composition. Antwerp blue Chinese blue Cobalt blue . Prussian blue Ultramarine Potassium ferric ferrocyanide. tt u ' A compound of the oxides of alumina and cobalt. Potassium ferric ferrocyanide. Exact constitution unknown. RED AND YELLOW PIGMENTS. Trade Name. Composition. American vermilion Chinese vermilion . Chrome yellow . . English vermilion . Indian red . . . Litharge Lemon chrome . . Ochre Orange chrome . . Para vermilion . . Permanent vermilion Radium vermilion . Tuscan red .... Venetian red Usually basic chromate of lead, sometimes an cosine vermilionette on red lead. Sulphide of mercury. Lead chromate usually containing lead sulphate. Sulphide of mercury. Natural oxide of iron about 90 per cent or more, pure. Lead monoxide. Usually a mixture of lead chromate and lead sulphate. Earthy base carrying about 20 per cent hydrated ferric oxide. Lead chromate. An organic red precipitated on an inert base. Red lead coated with organic color. A more or less impure oxide of iron brightened with organic color. Usually a mixture of oxide of iron and calcium sulphate. APPENDIX. WHITE PIGMENTS. 229 Trade Name. Composition. Barytes Barium sulphate. Blanc fixe Precipitated barium sulphate China clay Corroded lead Hydrated silicate of aluminum. Basic lead carbonate English white Gypsum Lithopone Calcium carbonate. Hydrated calcium sulphate. A combination of barium sulphate zinc Magnesite oxide and zinc sulphide. Magnesium carbonate Marble dust Calcium carbonate Paris white Calcium carbonate Ponolith . . Silex Similar to lithopone. Silica Silicate of magnesia . . . Silver white Spanish white . ... Magnesium silicate, aluminum, and cal- cium are usually present. Silica. Calcium carbonate Standard zinc lead white . Sublimed white lead . . . Terra alba Lead sulphate and zinc oxide in about equal amounts. Apparently a basic sulphate of lead with about 5 per cent zinc oxide. Hydrated calcium sulphate. White lead Basic carbonate of lead. Whiting White mineral primer . . White ochre Calcium carbonate. Calcium carbonate. Calcium carbonate Wood filler Zinc white Silica. Zinc oxide Zinc oxide (leaded) . . . Zinc oxide containing a varying amount of lead sulphate. I ILACK PIGMENTS. Trade Name. Composition. American gas black . . . Animal charcoal . . . Bone black Very nearly pure carbon. Carbon and calcium phosphate. Carbon and calcium phosphate Drop black Carbon and varying amount of ash Frankfort black Carbon and varying amount of ash Graphite Hydrocarbon black . . . Ivory black Natural carbon and mineral ash. Very nearly pure carbon. Carbon calcium and magnesium phos- Lampblack Mineral black . phate. Very nearly pure carbon. Ground slate 230 ANALYSIS OF MIXED PAINTS. GREEN PIGMENTS. Trade Name. Composition. Brunswick green Chrome green Emerald green Usually Prussian blue and chrome yel- low on an inert base. Aceto-arsenite of copper. 416. ATOMIC WEIGHTS OF THE MORE COMMON ELEMENTS. 0= 16. Atomic Weight. Symbol. Aluminum 27.1 Antimony 120.2 Arsenic 75.0 Barium 137.4 Bromine 79.96 Cadmium 112.4 Calcium 40.1 Carbon 12.0 Chlorine 35.45 Chromium 52 . 1 Cobalt 59.0 Copper 63.6 Hydrogen 1.008 Iodine 126.85 Iron 55.9 Lead 206.9 Magnesium 24.36 Manganese 55.0 Mercury 200.0 Molybdenum 96.0 Nitrogen 14.04 Oxygen : 16.0 Phosphorus 31.0 Platinum 194.8 Potassium 39.15 Silicon 28.4 Silver . . 107.93 Sodium 23.05 Sulphur 32.06 Zinc . 65.4 Al Sb As Ba Br Cd Ca C Cl Cr Co Cu H I Fe Pb Mg Mn Hg Mo N O P Pt K Si Ag Na S Zn APPENDIX. 231 417. FACTORS FOR GRAVIMETRIC ANALYSIS. Determined as. Required. Factor. A1 2 3 Al 0.5303 As 2 S 3 As 0.6093 As 2 S 3 As 2 3 0.8043 Mg 2 As 2 7 As 2 3 0.6372 BaSO 4 Ba 0.5885 BaSO 4 PbSO 4 1.3004 BaS0 4 CaS0 4 0.5837 BaS0 4 CaS0 4 2H 2 0.7382 BaSO 4 S0 3 0.3433 BaSO 4 SO 2 0.2747 CaO Ca 0.7143 CaO CaCO 3 1.784 CaCO 3 CaO CO 2 CaSO 4 2H 2 O 0.440 3.0715 CaSO 4 2H 2 O C0 2 Cr 2 3 S0 3 2PbC0 3 Pb(OH) 2 PbCr0 4 0.4561 8.8068 4.2288 Cr 2 O 3 CrO 3 1.3137 Cr 2 3 PbCrO 4 PbO 7.1438 Fe0 3 Fe 0.7000 JtVoOV/^ K 0.4491 K 2 PtCL K 0.1612 K 2 PtCl r M&PA K 2 Mg 0.1941 0.2188 Mg 2 P 2 7 MgO 0.3624 Mg 2 P 2 O 7 MgC0 3 0.7575 Na-jSO, Na 0.3243 N a2 SO 4 Pb0 4 Na 2 Pb 0.4368 0.6832 PbS0 4 PbO 0.7359 PbS0 4 PbSO 4 Pb,0 4 2PbC0 3 Pb(OH) 2 0.7536 0.8526 PbSO 4 PbCrO 4 1.0676 sof 2 7 Pf>SO 4 0.6376 3.788 Zn 3 ZnSO 4 2.478 Zn ZnO 1.2462 ZnS0 4 ZnO 0.503 232 ANALYSIS OF MIXED PAINTS. 418. MEASURES, WEIGHTS AND TEMPERATURES. One Imperial gallon One wine gallon One wine gallon One wine gallon One quart One quart One liter One cubic foot One cubic inch One cubic centimeter One pound Avoirdupois One ounce Avoirdupois One gram One inch One foot One yard One meter 277 . 27 cubic inches. 231 . cubic inches. 3. 7854 liters. 8.3389 pounds water at 40 C. 57 . 88 cubic inches. . 9464 liter. 1 . 0567 quart. 28315 cubic centimeters. 16.38 cubic centimeters. .061 cubic inch. 453 . 6 grams. 28.35 grams. 15. 432 grains. .0254 meter. .3048 meter. ^.. .91438 meter. 39. 3708 inches. Fahrenheit degrees Centigrade degrees 9 C. + 32 5 5 (F. - 32) 9 INDEX. Atomic weights, 230. Benzine, 67. Black pigments, analysis of, 145. Analysis of paints tinted with, 149. Composition of, 143. Specifications for, 147. Typical analyses of, 148. Blue paints, composition of, 33. Blue pigments, 169. Analysis of cobalt blue, 164. Analysis of blue mixed paints, 161. Analysis of Prussian blues, 159. Typical analyses of, 161, 164. Analysis of ultramarine, 162. Brown paints, composition of, 34. Calcium carbonate pigments, analy- sis of, 93. Cheapened mixed paints, 130. Chinese blue, 169, 186. Chrome green, analysis of, 176. Typical analyses of, 179. Chrome leads, analysis of, 166. Analysis of paints containing, 169. Composition of, 166. Typical analyses, 169. Chrome yellow, analysis of, 166. Clays, analysis of, 96. Typical analyses of, 100. Composition of colored paints, 32. Comparison of paints for covering power, 103. Corn oil, 44. Cottonseed oil, 43. Crimson red lake, 186. Covered testers, 64. Damar varnish, 204. Specifications for, 204. Driers, 188. Determination of lead in, 189. of manganese in, 189. of volatile oils in, 190. of zinc in, 190. Practical tests, 191. Rosin in, 191. Separation of benzine and tur- pentine, 190. Emerald green, 179. Analysis of, 179. Typical analyses, of, 181, 183. Estimation of petroleum products, 49. Estimation of rosin in .linseed and mineral oils, 60. Evaporation test, 63. Factors, 231. Free fatty acids, 61. Fineness of pigments, 102. Fire test, 66. Fish oil, 44. Flash point, 64. Gasoline, 68. Gravity and volume of pigments, 106. Gray paints, composition of, 35. Green paints, composition of, 34. 233 234 INDEX. Indian reds, analysis of, 135. Inside paints, 129. Iodine number, 194. Determination of, 54, 194. of oils, 56, Preparation of reagents for, 54. Iron oxides, analysis of, 136. Analysis of paints containing, 149. Specifications for, 142. Typical analyses of, 139, 141. Kerosene, 67. Labels that mislead, 19. Leaded-zinc paints, 129. Linseed oil, 39. Determination of flash point of, 62. Extraction from paint, 39. From inferior seed, 45. Specifications for, 47, 66. Tests for purity of, 40. Lithographic varnish, 67. Lithopone, 92. Mcllhiney's method, 56. Mineral oils, 41. N. D. Paint law, 6. Ochers, analysis of, 135. Oils, specifications for, 66. Oil varnishes, analysis of, 206. Classification of, 223. Consistency of, 218. Determination of soluble and insoluble gums in, 211. Drying of, 220. Estimation of rosin in, 212. Hardness of, 222. Long oil, 211. Separation of rosin gums, 208, 209. of volatile oils, 207. Short oil, 210. Oil varnishes continued. Short volume of, 225. Smell, 218. Specifications for, 216. Specific gravity, 207. Sponge test, 220. Toughness and elasticity, 221. Viscosity, 207. Working and flowing, 219. Open testers, 66. Paints, 107. Application of middle coat, 115. of paste leads, 116. of priming coat, 112. of third coat, 115. Driers in, 117. Oil reductions in, 113. Testing of, 107. Test structures for, 107. Turpentine reductions, 113. Para iiitroaniline lake, 184. Paris green, 179. Paris white, 93. Paste wood filler, 100. Ponolith, 92. Preparation of samples, 29. Ratio of pigment to vehicle, 31. Red lead, 175. Red oxides, 135. Red paints, composition of, 32. Relation of lead to zinc, 24. Rosin and rosin oils, 44. Saponification value, 62. Separation of mineral oil from rosin oil, 42. Separation of vehicle from pig- ment, 29. Shellac, 194. Detection of rosin in, 194. Estimation of rosin in, 194. Iodine numbers of, 196. INDEX. 235 Shellac varnish, 196. Body of, 197. Brewer's test, 203. Composition of, 196. Detection of benzine in, 198. Determination of strength of al- cohol used, 197. Estimation of rosin, 202. Estimation of wood alcohol in, 199. Maunhardt's method for rosin, 203. Typical analyses of, 204. Short measure and weights, 24. Silica, analysis of, 96. Sublimed lead, analysis of, 81. Composition of, 82. Identification and estimation in mixtures, 83. Paints, 128. Specific gravity of oils, 40. Spot test, 41. Table of atomic weights, 230. Tinting strength of colors, 104. Trade names of pigments, 228. Ultramarine, 162. Umbers and siennas, analysis of, 152. Analysis of paints containing, 158. Typical analyses of, 157. Vandyke-brown, 152. Venetian red, analysis of, 135. Vermilion, analysis of, 170. Antimony vermilion, 174. Vermilion continued. Detection of vennilionettes, 171. Properties of, 170. Typical analyses, 174. Volatile oils, estimation of, 39, 49. Excessive use of, 62. Identification of, 48. Water, detection in paint, 36. Estimation of, 37. Occurrence in paints, 36. White lead, acetic acid in, 78. Color of, 69. Estimation of carbon dioxide in, 70. Foreign pigments in, 70. Lead acetate in, 69. Opacity of, 69. Painting tests with, 69. Sandy lead, 69. Short weights, 79. Typical analyses of, 78, 79. White mineral primer, 93. White ocher, 93. White paints, 119. Analyses of, 125, 128. Cost of, 126. Qualitative analysis of, 119. Quantitative analysis of, 120, 131. Why paints fail, 1. Yellow paints, composition of, 33. Zinc oxides, analysis of, 84. Classification of, 86. Arsenic and antimony in, 88. Typical analyses, 87. OF THE * I UNIVERSITY } OF SHORT-TITLE CATALOGUE OF THE PUBLICATIONS OF JOHN WILEY & SONS, NEW YORK, LONDON: CHAPMAN & HALL, LIMITED. ARRANGED UNDER SUBJECTS. Descriptive circulars sent on application. Books marked with an asterisk (*) are sold at net prices only. All books are bound in cloth unless otherwise stated. AGRICULTURE. Armsby's Manual of Cattle-feeding i2mo, Si 75 Principles of Animal Nutrition 8vo, 4 oo Budd and Hansen's American Horticultural Manual: Part I. Propagation, Culture, and Improvement I2mo, 50 Part II. Systematic Pomology I2mo, 50 Elliott's Engineering for Land Drainage i2mo, 50 Practical Farm Drainage I2mo, oo Graves's Forest Mensuration 8vo, oo Green's Principles of American Forestry 1 2mo, 50 Grotenfelt's Principles of Modern Dairy Practice. (Woll.) i2mo, oo Hanausek's Microscopy of Technical Products. (Winton.) 8vo, oo Herrick's Denatured or Industrial Alcohol 8vo, oo Maynard's Landscape Gardening as Applied to Home Decoration I2mo, 50 * McKay and Larsen's Principles and Practice of Butter-making 8vo, 50 Sanderson's Insects Injurious to Staple Crops 12 mo, 50 * Schwarz's Longleaf Pine in Virgin Forest i2mo, 25 Stockbridge's Rocks and Soils 8vo, 50 Winton's Microscopy of Vegetable Foods 8vo, 7 50 Woll's Handbook for Farmers and Dairymen i6mo, i 50 ARCHITECTURE. Baldwin's Steam Heating for Buildings I2mo, 2 50 Bashore's Sanitation of a Country House i2mo, i oo Berg's Buildings and Structures of American Railroads 4to, 5 oo Birkmire's Planning and Construction of American Theatres 8vo, 3 oo Architectural Iron and Steel 8vo, 3 5<> Compound Riveted Girders as Applied in Buildings 8vo, 2 oo Planning and Construction of High Office Buildings 8vo, 3 50 Skeleton Construction in Buildings 8vo, 3 oo Brigg's Modern American School Buildings. * 8vo, 4 oo Carpenter's Heating and Ventilating of Buildings 8vo, 4 oo 1 Freitag's Architectural Engineering 8vo. 3 50 Fireproofing of Steel Buildings 8vo, 2 50 French and Ives's Stereotomy 8vo. 2 50 Gerhard's Guide to Sanitary House-inspection i6mo, i oo Sanitation of Public Buildings i2mo, i 50 Theatre Fires and Panics .-. . . i2mo, i 50 *Greene's Structural Mechanics 8vo, 2 50 Holly's Carpenters' and Joiners' Handbook i8mo, 75 Johnson's Statics by Algebraic and Graphic Methods 8vo, 2 oo Kellaway 's How to Lay Out Suburban Home Grounds 8vo, 2 oo Kidder's Architects' and Builders' Pocket-book. Rewritten Edition. i6mo,mor., 5 co Merrill's Stones for Building and Decoration . .8vo, 5 oo Non-metallic Minerals: Their Occurrence and Uses 8vo, 4 oo Monckton's Stair-building 4to, 4 oo Patton's Practical Treatise on Foundations 8vo, 5 oo Peabody's Naval Architecture 8vo, 7 50 Rice's Concrete-block Manufacture 8vo, 2 oo Richey's Handbook for Superintendents of Construction i6mo, mor., 4 oo * Building Mechanics' Ready Reference Book : * Carpenters' and Woodworkers' Edition i6mo, morocco, i 50 * Cementworkers and Plasterer's Edition. 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(Mercur.) 8vo, half morocco, 7 50 Manual for Courts-martial i6mo, morocco, i 50 * Mercur's Attack of Fortified Places I2mo, 2 oo * Elements of the Art of War 8vo, 4 oo Metcalf's Cost of Manufactures And the Administration of Workshops. .8vo, 5 oo * Ordnance and Gunnery. 2 vols I2mo, 5 oo Murray's Infantry Drill Regulations i8mo, paper, 10 Nixon's Adjutants' Manual 24010, i oo Peabody's Naval Architecture 8vo, 7 50' * Phelps's Practical Marine Surveying 8vo, 2 50 Powell's Army Officer's Examiner . . i2mo, 4 oo Sharpe's Art of Subsisting Armies in War i8mo, morocco, i 50 * Tupes and Poole's Manual of Bayonet Exercises and Musketry Fencing. 24mo, leather, 50 Weaver's Military Explosives 8vo, 3 oo Wheeler's Siege Operations and Military Mining . . .8vo, 2 oo Winthrop's Abridgment of Military Law. ... . . 12010, 2 50 Woodhull's Notes on Military Hygiene i6mo, i 50 Young's Simple Elements of Navigation i6mo, morocco, 2 oo ASSAYING. 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Baker's Engineers' Surveying Instruments I2mo, 3 oo Bixby's Graphical Computing Table Paper 19^X24! inches. 25 Breed and Hosmer's Principles and Practice of Surveying 8vo, 3 oo * Burr's Ancient and Modern Engineering and the Isthmian Canal 8vo, 3 50 Comstock's Field Astronomy for Engineers 8vo, * CorthelTs Allowable Pressures on Deep Foundations I2mo, Crandall's Text-book on Geodesy and Least Squares 8Vo, Davis's Elevation and Stadia Tables 8vo, Elliott's Engineering for Land Drainage i2mo, Practical Farm Drainage i2mo, *Fiebeger's Treatise on Civil Engineering 8vo, 5 oo Flemer's Phototopographic Methods and Instruments .8vo, 5 oo Folwell's Sewerage. (Designing and Maintenance.) 8vo, 3 oo Freitag's Architectural Engineering. 2d Edition, Rewritten 8vo, 3 5<> French and Ives'S Stereotomy 8vo, 2 50 Goodhue's Municipal Improvements i2mo, i 50 Gore's Elements of Geodesy 8vo 2 So * Hauch and Rice's Tables of Quantities for Preliminary Estimates I2mo, i 25 Hayford's Text-book of Geodetic Astronomy 8vo, 3 oo. 6 Bering's Ready Reference Tables (Conversion Factors) i6mo, morocco, 2 50 Howe's Retaining Walls for Earth I2mo, i 25 Hoyt and Grover's River Discharge 8vo, 2 oo * Ives's Adjustments of the Engineer's Transit and Level i6mo, Bds. 25 Ives and Hilts's Problems in Surveying i6mo, morocco, i 50 Johnson's (J. B.) Theory and Practice of Surveying Small 8vo, 4 oo Johnson's (L. J.) Statics by Algebraic and Graphic Methods 8vo, 2 oo Laplace's Philosophical Essay on Probabilities. (Truscott and Emory.) . i2mo, 2 oo Mahan's Treatise on Civil Engineering. (1873.) (Wood.) 8vo, 5 oo * Descriptive Geometry 8vo, i 50 Merriman's Elements of Precise Surveying and Geodesy 8vo, 2 50 Merriman and Brooks's Handbook for Surveyors i6mo, morocco, 2 oo Nugent's Plane Surveying 8vo, 3 50 Ogden's Sewer Design I2mo, 2 oo Parsons's Disposal of Municipal Refuse. . .8vo, 2 oo Patton's Treatise on Civil Engineering 8vo half leather, 7 50 Reed's Topographical Drawing and Sketching 4to, 5 oo Rideal's Sewage and the Bacterial Purification of Sewage 8vo, 4 oo Riemer's Shaft-sinking under Difficult Conditions. (Corning and Peele.) . 8vo, 3 oo Siebert and Biggin's Modern Stone-cutting and Masonry 8vo, i 50 Smith's Manual of Topographical Drawing. (McMillan.) 8vo, 2 50 Sondericker's Graphic Statics, with Applications to Trusses, Beams, and Arches. 8vo, 2 oo Taylor and Thompson's Treatise on Concrete, Plain and Reinforced 8vo, 5 oo Tracy's Plane surveying I6mo, morocco, 3 oo * Trautwine's Civil Engineer's Pocket-book i6mo, morocco, 5 oo Venable's Garbage Crematories in America ., 8vo, 2 oo Wait's Engineering and Architectural Jurisprudence 8vo, 6 oo Sheep, 6 50 Law of Operations Preliminary to Construction in Engineering and Archi- tecture 8vo, 5 oo Sheep, 5 50 Law of Contracts 8vo, 3 oo Warren's Stereotomy Problems in Stone-cutting 8vo, 2 50 Webb's Problems in the Use and Adjustment of Engineering Instruments. i6mo, morocco, i 25 Wilson's Topographic Surveying 8vo, 3 50 BRIDGES AND ROOFS. Boiler's Practical Treatise on the Construction of Iron Highway Bridges. .8vo, 2 oo Burr and Falk's Influence Lines for Bridge and Roof Computations 8vo, 3 oo Design and Construction of Metallic Bridges 8vo, 5 oo Du Bois's Mechanics of Engineering. Vol. II Small 4to, 10 oo Foster's Treatise on Wooden Trestle Bridges 4to, 5 oo Fowler's Ordinary Foundations 8vo, 3 50 Greene's Roof Trusses 8vo, i 25 . Bridge Trusses 8vo, 2 50 Arches in Wood, Iron, and Stone 8vo, 2 50 Grimm's Secondary Stresses in Bridge Trusses. (In Press.) Howe's Treatise on Arches 8vo, 4 oo Design of Simple Roof-trusses in Wood and Steel. 8vo, 2 oo Symmetrical Masonry Arches 8vo, 2 50 Johnson, Bryan, and Turneaure's Theory and Practice in the Designing of Modern Framed Structures Small 4to, 10 oo Merriman and Jacoby's Text- book on Roofs and Bridges: Part I. Stresses in Simple Trusses 8vo, 2 50 Part II. Graphic Statics 8vo, 2 50 Part III. Bridge Design 8vo, 2 50 Part IV. Higher Structures 8vo, 2 50 7 Morison's Memphis Bridge 4to, 10 oo Waddell's De Pontibus, a Pocket-book for Bridge Engineers. . i6mo, morocco, 2 oo Specifications for Steel Bridges i2mo, 50 Wright's Designing of Draw-spans. Two parts in one volume 8vo, 3 50 HYDRAULICS. Barnes's Ice Formation 8vo, 3 oo Bazin's Experiments upon the Contraction of the Liquid Vein Issuing from an Orifice. (Trautwine.). , 8vo, 2 oo Bovey's Treatise on Hydraulics 8vo, 5 oo Church's Mechanics of Engineering 8vo, 6 oo Diagrams of Mean Velocity of Water in Open Channels ... paper, i 50 Hydraulic Motors. . 8vo, 2 oo Coffin's Graphical Solution of Hydraulic Problems i6mo, morocco, 2 50 Flather's Dynamometers, and the Measurement of Power i2mo, 3 oo Folwell's Water-supply Engineering 8vo, 4 oo Frizell's Water-power 8vo, 5 oo Fuertes's Water and Public Health i2mo. i 50 Water-filtration Works i2mo, 2 50 Ganguillet and Kutter's General Formula for the Uniform Flow of Water in Rivers and Other Channels. (Hering and Trautwine.) 8vo, 4 oo Hazen's Clean Water and How to Get It Large I2mo, i 5o Filtration of Public Water-supply 8vo, 3 oo Hazlehurst's Towers and Tanks for Water-works 8vo, 2 50 Herschel's 115 Experiments on the Carrying Capacity of Large, Riveted, Metal Conduits 8vo, 2 oo *Hubbard and Kiersted's Water- works Management and Maintenance.. .8vo, 4 co Mason's Water-supply. (Considered Principally from a Sanitary Standpoint.) 8vo, 4 oo Merriman's Treatise on Hydraulics 8vo, 5 oo * Michie's Elements of Analytical Mechanics 8vo, 4 oo Schuyler's Reservoirs for Irrigation, Water-power, and Domestic Water- supply Large 8vo , 5 oo * Thomas and Watt's Improvement of Rivers 4*0, 6 oo Turneaure and Russell's Public Water-supplies 8vo, 5 oo Wegmann's Design and Construction of Dams. 5th Edition, enlarged. . .4to, 6 oo Water-supply of the City of New York from 1658 to 1895 4to, 10 oo Whipple's Value of Pure Water Large i2mo, i oo Williams and Hazen's Hydraulic Tables 8vo, i 50 Wilson's Irrigation Engineering , Small 8vo, 4 oo Wolff's Windmill as a Prime Mover 8vo, 3 oo Wood's Turbines 8vo, 2 50 Elements of Analytical Mechanics 8vo, 3 oo MATERIALS OF ENGINEERING. Baker's Treatise on Masonry Construction 8vo, 5 oo Roads and Pavements 8yo, 5 oo Black's United States Public Works Oblong 4to, 5 oo * Bovey's Strength of Materials and Theory of Structures .8vo, 7 50 Burr's Elasticity and Resistance of the Materials of Engineering 8vo, 7 So Byrne's Highway Construction 8vo, 5 oo Inspection of the Materials and Workmanship Employed in Construction. i6mo, 3 oo Church's Mechanics of Engineering 8vo, 6 oo Du Bois's Mechanics of Engineering. Vol. I Small 410 7 50 *Eckel's Cements, Limes, and Plasters 8vo, 6 oo 8 Johnson's Materials of Construction Large 8vo, 6 oo Fowler's Ordinary Foundations 8vo, 3 50 Graves's Forest Mensuration 8vo, 4 oo * Greene's Structural Mechanics 8vo, 2 50 Keep's Cast Iron 8vo, 2 50 Lanza's Applied Mechanics 8vo, 7 50 Martens's Handbook on Testing Materials. (Henning.) 2 vols 8vo, 7 50 Maurer's Technical Mechanics 8vo, 4 oo Merrill's Stones for Building and Decoration 8vo, 5 oo Merriman's Mechanics of Materials 8vo, 5 oo * Strength of Materials I2mo, i oo Metcalf's Steel. A Manual for Steel-users I2mo, 2 oo Patton's Practical Treatise on Foundations 8vo 5 oo Richardson's Modern Asphalt Pavements 8vo, 3 oo Richey's Handbook for Superintendents of Construction i6mo, mor., 4 oo * Ries's Clays: Their Occurrence, Properties, and Uses 8vo. 5 oo Rockwell's Roads and Pavements in France I2mo, i 25 Sabin's Industrial and Artistic Technology of Paints acd Varnish 8vo, 3 oo *Schwarz's Longleaf Pine in Virgin Forest ., i2mo, i 25 Smith's Materials of Machines i2mo, i oo Snow's Principal Species of Wood 8vo, 3 50 Spalding's Hydraulic Cement 1 2mo, 2 oo Text-book on Roads and Pavements I2mo, 2 oo Taylor and Thompson's Treatise on Concrete, Plain and Reinforced 8vo, 5 oo Thurston's Materials of Engineering. 3 Parts 8vo, 8 oo Part I. Non-metallic Materials of Engineering and Metallurgy 8vo, 2 oo Part II. Iron and Steel 8vo, 3 50 Part IH. A Treatise on Brasses, Bronzes, and Other Alloys and their Constituents 8vo, 2 50 Tillson's Street Pavements and Paving Materials 8vo, 4 oo Turneaure and Maurer's Principles of Reinforced Concrete Construction. .8vo, 3 oo Waddell's De Pontibus. (A Pocket-book for Bridge Engineers.). . i6mo. mor., 2 oo * Specifications for Steel Bridges 121110, 50 Wood's (De V.) Treatise on the Resistance of Materials, and an Appendix on the Preservation of Timber 8vo, 2 oo Wood's (De V.) Elements of Analytical Mechanics 8vo, 3 oo Wood's (M. P.) Rustless Coatings: Corrosion and Electrolysis of Iron and Steel 8vo, 4 oo RAILWAY ENGINEERING. Andrew's Handbook for Street Railway Engineers 3x5 inches, morocco, i 25 Berg's Buildings and Structures of American Railroads 4to, 5 oo Brook's Handbook of Street Railroad Location i6mo, morocco, i 50 Butt's Civil Engineer's Field-book i6mo, morocco, 2 50 Crandall's Transition Curve i6mo, morocco, i 50 Railway and Other Earthwork Tables 8vo, I 50 Crockett's Methods for Earthwork Computations. (In Press) Dawson's "Engineering" and Electric Traction Pocket-book i6mo, morocco 5 oo Dredge's History of the Pennsylvania Railroad: (1879). . v Paper, 5 oo Fisher's Table of Cubic Yards Cardboard, 25 Godwin's Railroad Engineers' Field-book and Explorers' Guide. . . i6mo, mor., 2 50 Hudson's Tables for Calculating the Cubic Contents of Excavations and Em- bankments 8vo, i oo Molitor and Beard's Manual for Resident Engineers i6mo, i oo Nagle's Field Manual for Railroad Engineers i6mo, morocco, 3 oo Philbrick's Field Manual for Engineers i6mo, morocco, 3 oo Raymond's Elements of Railroad Engineering. (In Press.) 9 Searles's Field Engineering i6mo, morocco, 3 oo Railroad SpiraL i6mo, morocco, i 50 Taylor's Prismoidal Formulae and Earthwork 8vo, i 50 * Trautwine's Method of Calculating the Cube Contents of Excavations and Embankments by the Aid of Diagrams 8vo, 2 oo The Field Practice of Laying Out Circular Curves for Railroads. 1 2 mo, morocco, 2 50 Cross-section Sheet Paper, 25 Webb's Railroad Construction i6mo, morocco, 5 oo Economics of Railroad Construction Large i2mo, 2 50 Wellington's Economic Theory of the Location of Railways Small 8vo, 5 oo DRAWING. Barr's Kinematics of Machinery 8vo, 2 50 * Bartlett's Mechanical Drawing 8vo, 3 oo * " " " Abridged Ed 8vo, i 50 Coolidge's Manual of Drawing 8vo, paper, i oo Coolidge and Freeman's Elements of General Drafting for Mechanical Engi- neers v Oblong 4toj 2 50 Durley's Kinematics of Machines 8vo, 4 oo Emch's Introduction to Projective Geometry and its Applications 8vo, 2 50 Hill's Text-book on Shades and Shadows, and Perspective 8vo, 2 oo Jamison's Elements of Mechanical Drawing 8vo, 2 50 Advanced Mechanical Drawing 8vo, 2 oo Jones's Machine Design: Part I. Kinematics of Machinery. 8vo, i 50 Part II. Form, Strength, and Proportions of Parts 8vo, 3 oo MacCord's Elements of Descriptive Geometry 8vo, 3 oo Kinematics; or, Practical Mechanism 8vo, 5 oo Mechanical Drawing 4to v 4 oo Velocity Diagrams 8vo, i 50 MacLeod's Descriptive Geometry Small 8vo, i 50 * Mahan's Descriptive Geometry and Stone-cutting. . . . . 8vo, i 50 Industrial Drawing. (Thompson.) 8vo, 3 50 Moyer's Descriptive Geometry 8vo, 2 oo Reed's Topographical Drawing and Sketching 4to, 5 oo Reid's Course in Mechanical Drawing 8vo> 2 oo Text-book of Mechanical Drawing and Elementary Machine Design. 8vo, 3 oo Robinson's Principles of Mechanism. 8vo, 3 oo Schwamb and Merrill's Elements of Mechanism 8vo, 3 oo Smith's (R. S.) Manual of Topographical Drawing. (McMillan.) 8vo, 2 50 Smith (A. 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