LIBRARY UNIVERSITY OF CALIFORNIA. Class ft FIG. 1. CONVEYING TAN-BARK. ENGLISH MANUFACTURE OF WHITE LEAD. THE LEAD AND ZINC PIGMENTS BY CLIFFORD DYER HOLLEY, M.S., PH.D. CHIEF CHEMIST ACME WHITE LEAD AND COLOR WORKS FIRST EDITION FIRST THOUSAND OF THE UNIVERSITY Of NEW YORK JOHN WILEY & SONS LONDON: CHAPMAN & HALL, LIMITED 1909 r\^ COPYRIGHT, 1909, BY CLIFFORD DYER HOLLEY (Entered at Stationers' Hall) Stanhope ipress F.H. GILSON COMPANY BOSTON. U.S.A INTRODUCTION. POSSIBLY in no other country has the art of pigment and paint making reached as high a level as in the United States. Certainly in no other country has the paint industry developed as rapidly during the last forty years as it has in America. The making of one hundred and fifty thousand tons of lead pigments and over seventy thousand tons of zinc pigments, resulting in the manufacture of over one hundred million gallons of paint besides the enormous sales of lead in oil, constitutes an industry that is to be counted among the important industries of the country. And yet until the passage of the first efficient and vigor- ous paint law in 1905, enacted by the state of North Dakota, and the court proceedings attendant thereto for the determining of the constitutionality of that law, those interested in the subject of pigments and paints were com- pelled to turn to English books for information, as our own literature was noticeable only for its meagerness. New pigments have come into use during the last ten years, new processes have been developed for the manu- facture of the older pigments, new combinations of pig- ments have been worked out that have secured results hitherto unattainable. Yet up to the time mentioned above, except for short articles in some of the trade papers, these improvements and innovations remained practically unnoticed. Since public attention has been directed to the paint industry by the enactment of the various state laws regarding the sale of paint materials, several excellent 20547;! yi INTRODUCTION. American works have been written on this subject, but the majority of them have been directed more particularly toward the compiling of analytical methods and data than to the manufacture and uses of the various pigments. In this work the author has attempted to record the progress made in the United States in the manufacture of the more important pigments, and hence but little space has been given to European methods and processes except for comparison, as they have been discussed in detail in various English and European works. The writer wishes to express his appreciation for the valuable information and data furnished him by Mr. Willson H. Rowley, who for many years has been promi- nently identified with the white lead industry and who has done much to place it on a more sanitary, scientific, and economical basis. DETROIT, MICH., July 1, 1908. CONTENTS. CHAPTER I. PAGE WHITE LEAD IN ANCIENT TIMES 1 1. Importance of white lead industry; 2. Composition; 3. Historical; 6. Essential conditions for manufacture of white lead; 10. Early improvements; 11. Effect of the revival of learning; 13. Development of the lead industry by the Dutch; 14. Early adulteration of white lead; 16. Manufacture of white lead in seventeenth century; 18. The Dutch method of manufacture; 20. English method of manufacture. CHAPTER II. DEVELOPMENT OF THE WHITE LEAD INDUSTRY IN THE UNITED STATES 14 21. Early use of white lead; 23. First white lead plant; 25. Effect of War of 1812; 26. Other early manufacturers; 27. Adoption of uniform scale of prices; 29. Formation of new companies; 30. Effect of the Civil War; 31. Patents issued; 33. Improvements. CHAPTER III. DEVELOPMENT OF THE WHITE LEAD INDUSTRY IN THE UNITED STATES (Continued) 23 34. Formation of National Lead Trust; 35. Absorption of other companies; 36. Dissolution of National Lead Trust; 37. Formation of National Lead Company; 39. Different branches of National Lead Company; 40. Operation of factories; 41. Independent companies; 42. The Bailey process; 44. The United Lead Company; 46. Growth of United Lead Company; 47. Acquisition of the United Lead Company: 48. Number and location of lead plants in the United States. vU Vill CONTENTS. CHAPTER IV. PAGE BRANDS, PRODUCTION AND PRICES OF WHITE LEAD 34 49. Brands; 50. Short weight packages; 51. Annual pro- duction of white lead; 52. Sale of dry white lead; 53. Dif- ferential between pig lead and white lead. CHAPTER V. THE MODERN APPLICATION OF THE DUTCH PROCESS IN THE UNITED STATES 42 54. Present importance of the Dutch Process; 55. Processes in use; 56. Grade of pig lead required; 57. Casting the buckles; 58. Building the stack; 59. Reactions involved in the process; 61. Conditions required for successful corrosion; 62. Taking down the stack; 64. Sandy lead. CHAPTER VI. THE MODERN APPLICATION OF THE DUTCH PROCESS IN THE UNITED STATES (Continued) 56 66. Disintegrating the buckles; 67. Washing the lead; 68. Importance of thorough washing; 69. Drying the lead; 71. Loss of lead in washing; 72. Effect of sandy lead in paints; 73. Cost of a stack operation; 75. Econ- omy of process; 76. Variation in quality; 77. Lack of proper grinding of white lead; 78. Changes that may take place in grinding; 79. English methods of grinding; 80. Combination leads; 82. Pulp ground lead; 83. Char- acteristics of pulp lead. CHAPTER VII. THE CARTER PROCESS 74 85. History; 86. Adams White Lead Company; 87. Omaha White Lead Company; 88. Formation of the Carter Com- pany; 90. Underlying principles; 91. Granulating the lead: 92. Corrosion; 94. Washing and floating; 95. Chem- ical composition; 96. Characteristics; 97. Success. CONTENTS. IX CHAPTER VIII. PAGE THE MILD PROCESS (Rowley) 85 98. Derivation of name; 100. Early attempts; 101. Solu- tion by W. H. Rowley; 102. Early training; 103. Atom- ization with superheated steam; 104. Growth of process; 105. Simplicity of process; 106. Atomizing the lead; 107. Oxidizing and hydrating; 109. Carbonating; 110. Control; 111. Advantages of process; 112. Not a precipitation process. CHAPTER IX. MATHESON PROCESS 101 114. Nature of process; 115. Development in the United States; 116. Characteristics of Matheson lead; 117. Manu- facture; 119. Uses. CHAPTER X. THE SUBLIMED LEAD PIGMENTS 108 120. Sublimed white lead; 121. Early developments; 123. Sublimation of the ore; 124. Condensation of the fume; 125. Bag-room; 126. Uniformity of product; 127. Chemical constitution; 128. Yearly production; 129. Physical characteristics; 131. Uses of sublimed white lead; 132. Chalking; 133. Comparative whiteness; 134. Inertness toward tinting colors; 135. Sublimed blue lead; 136. Properties; 137. Composition; 138. Sublimed lead oxide. CHAPTER XI. WHITE LEAD MANUFACTURE IN EUROPE 122 139. Comparative Costs of manufacture, English regulations'; 142. English methods; 143. Characteristics of English white lead; 144. German chamber process; 145. Klagen- furth modification; 147. Present German methods; 149. Effecting the corrosion; 151. Rapidity of corrosion; 153. Lack of success in the United States; 157. Present French practice. X CONTENTS. CHAPTER XII. PAGE PROPERTIES OF WHITE LEAD 133 158. Composition; 160. The higher carbonates; 161. Ageing of white lead; 163. Free fatty acids; 164. Fineness of particles; 165. Action of white lead on linseed oil; 167. Stability of white lead toward heat; 169. Reactions with acids; 170. Solubility; 171. Action of sulphur compounds; 172. Chalking of white lead; ,173. Effect of residual ace- tates; 174. Protracted oxidation; 175. White lead specifi- cations. CHAPTER XIII. LEAD POISONING 143 179. The English White Lead Commission; 180. Lead poisoning in the United States; 182. English regulations; 183. Duties of occupiers; 184. Duties of persons employed ; 185. English Statistics; 186. Precautions adopted by the French; 188. Recent improvements; 190. Restrictive legislation; 191. Danger to women; 192. Symptoms of lead poisoning; 194. Effect on the nervous system; 195. Chronic lead poisoning; 196. Absorption through the skin. CHAPTER XIV. MANUFACTURE OF ZINC OXIDE 152 197. Ancient history; 198. Production on a commercial scale; 199. Work of LeClaire; 200. LeClaire's Process; 201. Present French process; 202. Composition; 204. Processes in use in the United States; 205. Work of Jones and Wetherill; 206. Zinc oxide plants in United States; 207. Development of the New Jersey zinc mines; 209. Controversey regarding the ownership of the deposits; 210. Composition of Franklinite ore; 213. Chemical com- position; 214. Preliminary treatment of the ore; 216. The oxide furnaces; 218. Collection of the fume; 219. Palmer- ton plant ; 220. Purity of New Jersey zinc oxide ; 222. Fur- nace assays; 224. Spiegeleisen; 225. The Mineral Point works. CONTENTS. Xl CHAPTER XV. PAGE PROPERTIES AND USES OF ZINC OXIDE 175 226. Properties; 227. Solubility; 228. Composition of com- mercial grades; 229. Analyses of zinc oxide made from the ore; 230. Analyses of zinc oxide made from spelter; 231. Analyses of mineral point zinc oxides; 232. Analyses of zinc oxide Scott; 234. Sulphur dioxide and zinc sul- phate; 235. Imported zinc oxides; 236. Comparative prices; 237. Lack of affinity for moisture; 238. Zinc oxide as a paint pigment; 241. Production and value of zinc oxide. CHAPTER XVI. MANUFACTURE OF LEADED ZINC 182 242. History; 243. Comparison with Eastern methods; 244. Process of manufacture; 246. Characteristics; 248. Zinc sulphate; 249. Result on the life of the paint. CHAPTER XVII. ZINC-LEAD WHITE 188 250. Source; 252. Early manufacture; 253. Absorption by United States Smelting Company; 254. Standard of com- position; 255. Sublimation of fume; 256. Collection of fume; 257. Final treatment; 258. Production; 259. Phys- ical properties; 260. Recent improvements; 261. Use in house paints; 262. Use in the manufacturing trades; 264. Chemical composition; 265. Zinc sulphate; 266. Washing. CHAPTER XVIII. THE OXIDES OP LEAD 200 267. Classification; 269. Lead suboxide; 270. Litharge; 271. Early confusion regarding nature of litharge; 272. Development of litharge industry; 273. Manufacture; 274. Cupellation process; 275. Other processes; 276. Properties; 278. Commercial classification; 280. Produc- tion of litharge in United States; 281. Imports, Xll CONTENTS. CHAPTER XIX. PAGE THE OXIDES OF LEAD (Continued) 207 282. Early history of red lead; 283. Early methods of preparation; 285. Development of the industry; 287. Early manufacture in the United States; 288. Present methods of manufacture; 289. Furnace temperature; 291. Dressing; 292. Coloring; 294. Modern improve- ments; 295. The nitrate process; 297. Properties; 298. Adulteration; 299. Selection for vermilions; 301. Orange mineral; 302. Production and imports of red lead; 303. Production and imports of orange mineral. CHAPTER XX. THE LEAD CHROMATES 217 304. Varieties; 305. Tinting strength; 306. Presence of lead sulphate; 307. Raw materials; 308. Sodium bichromate; 309. Precautions to be observed; 310. Secret formulas; 312. Practical formulas; 313. Precipitation; 314. Orange chrome yellows; 315. Addition of the calcium oxide; 317. American vermilion; 319. Preparation; 320. Care in grinding. CHAPTER XXI. LlTHOPONE 225 321. Early history; 323. Zinc sulphide; 324. Preparation of zinc sulphate; 325. Preparation of barium sulphide; 327. Precipitating and calcining; 328. Physical properties of lithopone; 329. Reductions; 332. Comparison with white lead; 333. Grades of lithopone; 334. Manufacturers; 335. Production. CHAPTER XXII. PHYSICAL PROPERTIES OF WHITE LEAD 230 336. Amorphous character of white lead; 337. Color; 338. Cautions to be observed; 339. Opacity; 341. Oil require- ments and reductions; 343. Laboratory tests for opacity and covering power; 344. Microscopical measurements; 345. Determination of specific gravity; 349. Displace- ment in oil; 350. "Bulking" figure; 351. The determina- tion. CONTENTS. xiii CHAPTER XXIII. PAGE PRACTICAL TESTS 238 352. The North Dakota paint tests; 353. Reductions; 354. Red Seal, Eagle, Carter and Sublimed Lead white; 355. Matheson White lead; 356. Zinc-lead white; 357. Mild process white lead; 358. New Jersey zinc oxide; 359. Covering tests; 360. Hard pine boards; 361. Soft pine boards; 362. Cedar clapboards; 363. White pine clapboards; 364. Conclusion. CHAPTER XXIV. THE ART OF GRINDING WHITE LEAD, PASTES AND PAINTS 246 365. Importance of careful grinding; 366. Careless grind- ing; 367. Conditions to be observed; 368. Mixing and chasing; 369. Proper selections of stones; 371. Sources of millstones; 372. Domestic stones; 373. Stone dressing; 375. Types of mills; 376. Best method of dressing stones; 377. Adjustment of grooves; 378. Grinding pastes; 379. Use of mill picks; 380. Pneumatic dressing; 381. Frequency of dressing; 383. Types of dressing; 384. Speed of mills. CHAPTER XXV. ANALYSIS OF COMMERCIALLY PURE WHITE LEADS 258 385. Sulphur dioxide; 387. Sandy lead; 388. Determina- tion; 389. Tan-bark; 391. Metallic lead; 392. Lead sul- phate; 393. Determination; 394. Volumetric estimation of lead, Method I; 395. Potassium bichromate solution; 396. Silver nitrate solution; 397. Method II; 399. Molyb- date solution; 400. Tannic acid solution; 401. Carbon dioxide; 405. Acetic acid in white lead; 408. Determina- tion; 410. Conclusions. CHAPTER XXVI. ANALYSIS OF THE ZINC PIGMENTS 268 411. Moisture; 412. Silica; 414. Sulphur dioxide; 415. Iodine solution; 416. Sodium thiosulphate; 417. Starch paste; 418. Standardizing the thiosulphate solution; 419. Standard of acceptance; 420. Reaction with rosin xiv CONTENTS. ANALYSIS OF THE ZINC PIGMENTS (Continued) PAGE products; 421. Zinc sulphate; 423. Effect; 424. Lead; 425. Method I; 426. Method II; 427. Method III; 428. Total Zinc; 429. Potassium ferrocyanide method; 430. Standard zinc solution; 431. Standard potassium ferrocyanide solution; 432. Uranium nitrate solution; 433. Standardizing the ferrocyanide solution; 435. Titra- tion of sample; 436. Precipitation of zinc as carbonate; 437. Precipitation of zinc as phosphate; 438. Combined sulphuric acid; 441. Calculations; 442. Estimation of arsenic and antimony in zinc-leads; 447. Preparation of iodine solution; 449. Antimony; 450. Methods in use at Canon City; 451. Method I; 455. Method II. CHAPTER XXVII. ANALYSIS OF WHITE LEAD AND PAINTS IN OIL 282 457. Securing a fair sample; 458. Variations from formula; 459. Chemical changes in grinding; 462. Obtaining an average sample; 464. Inaccurate methods of analysis; 465. Extraction of the vehicle; 466. Removal of the vehicle for examination; 467. Use of centrifuge; 470. Use of volatile petroleum thinners; 472. Characteristics; 473. Reporting results. CHAPTER XXVIII. ESTIMATION OF WATER IN WHITE LEADS AND PAINTS 290 474. Occurrence; 475. Detection; 476. Estimation; 479. Estimation of water with amyl reagent; 480. Preparation of amyl reagent; 481. Determination; 482. Practical example. CHAPTER XXIX. QUALITATIVE ANALYSIS OF COMBINATION WHITE LEADS AND PASTES 295 483. Classification; 484. Inert pigments; 485. Barium sulphate; 486. Blanc Fixe; 487. Barium carbonate; 488. Calcium carbonate; 491. Calcium sulphate; 493. Alumi- nium silicate; 494. Magnesium silicate; 495. Silica; 497. Carbonates; 498. Barytes; 499. Sulphates; 500. Lead; 501. Zinc; 502. Calcium; 503. Magnesium. CONTENTS. XV CHAPTER XXX. PAGE QUANTITATIVE ANALYSIS OF COMBINATION WHITE LEADS AND PAINTS 302 504. Total lead; 511. Zinc oxide; 512. Standard potassium ferrocyanide solution; 513. Uranium nitrate solution; 514. Standardizing the ferrocyanide solution; 516. Titra- tion of sample; 519. White lead; 520. Insoluble residue; 521. Barium sulphate; 522. Silica; 523. Alumina; 524. Calcium and magnesium oxides; 525. Hydrofluoric acid treatment. CHAPTER XXXI. LABORATORY EQUIPMENT AND MANIPULATION 310 530. Weight per gallon; 531. Specific gravities; 532. Rapid extraction pigment; 533. Estimation of water in paints; 534. Estimation of volatile oils; 535. Rapid drying; 536. Filtering by suction; 537. Use of Gooch crucible; 539. Bottles for Standard solutions. APPENDIX 317 540. Atomic weights; 541. Formulas and molecular weights; 542. Factors for gravimetric analysis; 543. Specific grav- ities corresponding to degrees Baum for liquids lighter than water; 544. Table for liquids heavier than water; 545. Specific gravity and weights per gallon; 546. Speci- fic gravity of acetic acid; 547. Specific gravity of nitric acid; 548. Specific gravity of hydrochloric acid; 549. Sul- phuric acid; 550. Measures, weights and temperatures. ILLUSTRATIONS. 1. Conveying Tan-bark English Manufacture of White Lead . 2. Wetherill White Lead Works, 1808 16 3. Lead Buckle 21 4. Lead Fibers Bailey Process 28 5. Hammar Brothers' White Lead Works 30 6. Facsimiles of Leading Brands of National Load Company. . . 36 7. Facsimiles of Leading Brands of National Lead Company. . . 37 8. Pig Lead and Sections of Corroding Pots Containing New and Corroded Buckles 43 9. Buckle Casting Machine 45 10. Electric Crane for Conveying Tan-bark 47 11. Filling the Corroding Pots National Lead Company 48 12. A Layer of Corroding Pots in Position Eagle Company. . . 50 13. Completed Stack Hammar Brothers 51 14. A Finished Corrosion, Showing Position of Flues National Lead Company 52 15. Taking down a Stack Eagle Company 54 16. Crushing Rolls Hammar Brothers 55 17. Water Grinding Mills Hammar Brothers 57 18. Drag and Washing Box 58 19. Agitating and Washing Tubs National Lead Company .... 59 20. Drying Pans Eagle Company 61 21. Truck Dryer Philadelphia Textile Machine Company 63 22. White Lead Mixers Eagle Company 65 23. Oil Grinding Mills Eagle Company 68 24. English Type of White Lead Mill 70 25. Plants of Carter White Lead Company 75 26. Conveyer and Melting Kettle Carter Process 77 27. Corroding Cylinder Carter Process 79 28. Corroding Room Carter Process 81 29. Chaser and Mixers Carter Process 83 30. Plant Rowley Lead Company 86 31. Plant Mild Process Lead Company 88 32. Atomizing Apparatus Mild Process 90 33. Blow Chamber Mild Process 92 xvii xviii ILLUSTRATIONS. PAGE 34. Oxidizers Mild Process 94 35. Float System Mild Process 96 36. Carbonators Mild Process 97 37. Battery of Drying Pans Mild Process 99 38. Melting Room Matheson Process 102 39. Corroding Tanks Matheson Process 102 40. Washing Presses Matheson Process 104 41. Settling Tanks Matheson Process 104 42. Vacuum Driers and Filling Machine Matheson Process. . . . 106 43. Pulp Mill Matheson Process 106 44. Picher Sublimed Lead Works 109 45. Sublimed Lead Furnaces Ill 46. " Goose Necks " Picher Lead Company 112 47. Bag- room Picher Lead Company 114 48. Collecting Hoppers Picher Lead Company 116 49. Building the Stack English Method 124 50. Taking down the Stack English Method 126 51. Particles Old Dutch Process Lead 135 52. Particles Mild Process Lead 135 53. Particles Precipitated Lead 137 54. Particles Sublimed White Lead 137 55. Required Costume of English White Lead Worker 145 56. Palmerton Works New Jersey Zinc Company 157 57. Oxide Furnaces Palmerton Works 161 58. Stock Trestle Palmerton Works . . 163 59. Blower Room Palmerton Works 165 60. Bag- room Building Palmerton Works 167 61. Bag-room Palmerton Works 169 62. Blast Furnace for Spiegeleisen Palmerton Works 170 63. Spelter Plant Palmerton Works 172 64. Plant of Mineral Point Zinc Company 173 65. Pipe Line Coffeyville Plant 184 66. Furnaces Coffeyville Plant 184 67. Zinc Sulphate on Paint Film 186 68. Zinc-Lead Plant U. S. Smelting Company 190 69. Furnace Room U. S. Smelting Company 192 70. Refining Furnaces U. S. Smelting Company 193 71. Bag-room U. S. Smelting Company 195 72. Barrel Packer and Mixers U. S. Smelting Company 197 73. Oxide Works Matheson & Co 201 74. Oxide Furnaces National Lead Company 203 75. Oxide Furnaces Eagle 210 76. Exposure Fences, North Dakota (West Side) 239 77. Exposure Fences, North Dakota (East Side) 242 ILLUSTRATIONS. XIX PAGE 78. Dressing for a Paint Mill 252 79. Adaption of Grinding Surfaces 252 80. Adjustment of Furrows 253 81. Dressing for Heavy Grinding 254 82. Dressing for 20-inch Mill 255 83. Knorr's Apparatus 263 84. Extraction Apparatus 285 85. Estimation of Water 291 Of THE UNIVERSITY Of THE LEAD AND ZINC PIGMENTS. CHAPTER I. WHITE LEAD IN ANCIENT TIMES. 1. Importance of White Lead Industry. The lead prod- ucts industries are to be reckoned among the most impor- tant industries of the country. Of the 331,000 tons of lead produced in 1907, it is estimated that over 135,000 tons were used in the manufacture of white lead, red lead and litharge, an amount equivalent to over 40 per cent of the entire lead consumption. The conversion of this amount of metal into chemical products represents a large outlay of capital and the employment of a large number of workmen, in the nearly fifty plants producing these pigments in the United States. The production of litharge and red lead is small, however, as compared with white lead, which required during the year referred to about 100,000 tons of metallic lead. 2. Composition. White lead is perhaps the best known of all the white pigments and has been in general use from very ancient times. Chemically white lead is a basic carbonate of lead. A large number of analyses of the best samples indicate a constitutional formula of 2 PbC0 3 -Pb(OH) 2 , in which there are two molecules or equivalents of lead carbonate to one of hydroxide, the l 2 THE LEAD AND ZINC PIGMENTS. combination being represented by the following structural formula : p b ( OH White lead may be made to vary a good deal in com- position according to the method and conditions of making, and many writers in comparing the more modern pigments, such as sublimed white lead and zinc-lead white, with white lead have commented much on these variations; but white lead as manufactured to-day, whether by the Old Dutch process or by the quick processes that have been found by experience to be economically successful, varies but comparatively little in composition as regards the ratio of carbonate to hydroxide. 3. Historical. White lead was known to the ancients under the Greek name of psmithium and the Roman name of cerussa. Perhaps the earliest definite and reliable account of its manufacture is given in Theophrastus' " History of Stones," written about 300 years before Christ, in which the author describes the method of manu- facture substantially as follows: " Lead is placed in earthen vessels over sharp vinegar, and after it has acquired some thickness of a sort of rust, which it commonly does in about ten days, they open the vessels and scrape it off, as it were, in a sort of foul- ness; they then place the lead over vinegar again, repeat- ing over and over again the same method of scraping it till it has wholly dissolved. What has been scraped off they then beat to powder and boil for a long time, and what at last subsides to the bottom of the vessel is ceruse. " 1 1 Theophrastus, History of Stones, p. 223. WHITE LEAD IN ANCIENT TIMES. 3 4. Vitruvius, writing in the first century before Christ, says: " It will be proper to explain in what manner white lead is made. The Rhodians place in the bottom of large vessels a layer of vine twigs, over which they pour vinegar, and on the twigs they lay masses of lead. The vessels are covered to prevent evaporation, and when, after a cer- tain time, they are opened the masses are found changed into white lead." l 5. Pliny, the historian, living in the first century A. D., mentions a native ceruse (cerussite) found in Smyrna which the ancients made use of for painting their ships, but adds that" all ceruse is prepared from lead and vinegar/' 2 and the most esteemed, he adds, comes from Rhodes. These and other descriptions by the ancient writers and historians can only be regarded as imperfect and crude statements of processes they personally knew little or nothing about, and it is natural that their descriptions should be lacking in many essential details. Their methods if followed exactly as described would produce only lead actate, which, besides being very soluble in water, possesses but little opacity or hiding power. 6. Essential Conditions for Manufacture of White Lead. Three conditions are essential for the proper manufacture of white lead from metallic lead and vinegar or acetic acid: 1. The placing of the lead above the acid so that it would not come in contact with it. 2. A long continued gentle heat, such as would be obtained by the use of horse manure or by the fermentation of moist tan-bark. 3. The presence of carbon dioxide in considerable quantities. 1 Vitruvius, p. 186. 2 Pliny, Natural History, Book XXXV, Chap. IX. 4 THE LEAD AND ZINC PIGMENTS. 7. That the ancients were well acquainted with the first requisite is evidenced by the descriptions already given. Pliny also in describing the manufacture of white lead says, "It is made from very fine shavings of lead placed over a vessel filled with the strongest vinegar." * Discorides, writing in the first or second century, states : " Having poured vinegar . . . into a broad -mouthed pitcher, or an earthen jar, fasten firmly a mass of lead near the top of the jar upon a mat of reeds previously stretched beneath." 2 In another place he explains more in detail, " Having suspended a stick of wood about the middle of the jar, place the mat of twigs before mentioned upon it, in such a manner that it may not touch the vinegar." 8. The second requirement, that of a gentle but long continued source of heat, while not mentioned by some of the earlier writers, is specifically mentioned by at least two. Discorides states that the manufacture of white lead can be carried on in the winter as well as in the summer, " if you place the jar over braziers, cauldrons or furnaces; for heat applied to it shows the same effect as the sun," thus indicating that advantage was taken of the sun's rays as a source of heat. Galen, writing in the second century, says that white lead is made by dissolving litharge in vinegar, burying the vase containing these substances in dung for forty days. 3 Here we also have a probable source of heat mentioned. 9. In regard to carbon dioxide, the third requisite necessary for the proper manufacture of white lead, it can be said that none of the ancient writers mention any means of securing its presence or in any way indicate that 1 Pliny, Natural History, Book XXXIV, Chap. LIV. 2 Discorides, De Materia Medica. 8 Hoffmann, Das Blei, p. 42. WHITE LEAD IN ANCIENT TIMES. 5 carbon dioxide or any gas was necessary for the preparation of ceruse. This omission on their part has led some modern writers to doubt that the ancients were acquainted with what we know as white lead. However, if we con- sider the exceedingly imperfect knowledge that the ancients had regarding the chemistry of the various pro- cesses they used in their manufactures, this omission is not to be wondered at, especially when we consider the impure nature of the vinegar or acetic acid in use in early times, due to the crude and imperfect methods of manufacture, which necessarily resulted in a considerable amount of grape skins and pulp passing into the expressed juice. These impurities naturally evolved considerable carbon dioxide in the course of their decomposition, an amount sufficient at least to carbonate a considerable quantity of lead. This method of producing carbon diox- ide being so closely associated with the natural fermen- tation of the grape juice into vinegar, might well pass unnoticed and uncommented upon by the ancient experi- menters and historians. In support of this contention, Pulsifer cites the following statement from Gentele's Lehrbuch der Farbenfabrikation regarding the modern manufacture of white lead at Klagenfurth, in Carinthia: " The acetic acid and the carbon dioxide being simulta- neously produced by the fermentation of the extract of ied grapes or raisins, or of the residuum of grapes after pressing. Water-tight boxes are prepared into which the raisins or the residuum is placed; to this is added a quantity of vinegar. When subjected to heat, the vinous fermentation begins in the sweetish liquor, producing alcohol and carbon dioxide, and the acetic fermentation also occurs in the alcohol, producing acetic acid." Viewing the matter in this light, the presence of carbon dioxide can be satisfactorily accounted for in the processes 6 THE LEAD AND ZINC PIGMENTS. used by the ancients, and the product obtained by them was a true white lead; although probably badly contami- nated with both the normal and the almost insoluble basic lead acetates. It is quite certain that white lead was made in notable quantities at the beginning of the Christian era. Accord- ing to the historians, Rhodes was the most important seat of manufacture, although the industry was sufficiently notable in Corinth and Lacedemonia to be mentioned by Pliny. 10. Early Improvements. Little practical advancement was made in the art of making white lead for many hun- dred years after the beginning of the Christian era. This is not to be wondered at when we consider the decay of learning and the dismemberment of the Roman Empire. Such knowledge as survived was locked up in the various monasteries, and it is to the various manuscripts written by the monks that we must look for our information. Many of the references that have been found regarding methods or recipes for the manufacture of white lead were evidently copied from still earlier writings, which in turn may have been and in fact probably were, taken from the manuscripts of the Greek and Roman historians already referred to. Some of the manuscripts, however, seem to be more than copies and really serve as a connecting link between the methods used by the ancients and those in use at the present time, and indicate certain noteworthy improvements in the art. Especially are the writings of Theophilus and Eraclius of interest, as they imply that decomposing horse dung came into use during this period as a source of gentle heat for carrying the reaction through to completion and also unwittingly perhaps as a source of carbon dioxide gas. Also both writers mention the use of linseed oil as a vehicle for preparing paints. Theophi- WHITE LEAD IN ANCIENT TIMES. 7 lus in particular gave elaborate directions for the prepa- ration of linseed oil and the grinding of white lead in oil. 11. Effect of the Revival of Learning. The revival of learning in Europe, beginning in the eleventh century, was accompanied by a renewed activity in manufactures and scientific pursuits, and the manufacture and use of white lead became an item of importance throughout western Europe and Great Britain, although its use was confined almost entirely to paintings and church decorations. History relates that the chapel of Saint Stephen in England was rebuilt in 1352 and that all of the painters in the sur- rounding country were employed in its decoration. Among the items for material were the following : l 8 d 19 pounds white lead for priming at 4d 6 4 4 flagons of painter's oil 16 62 pounds red lead at 5d 1 5 10 J pound red lead 8 And again: Item : To John Lightgrave s d 51 pounds white lead at 2Jd 10 ?i 53 pounds white lead at 3Jd 15 5 43 pounds red lead at 4d 16 6 3 pounds white lead 1 The considerable variations in price might indicate that the use of reduced or adulterated white lead was by no means uncommon even at that time, a fact which was severely commented upon by various writers at a slightly later date. 12. The methods of manufacture described in the various authentic documents of the period, while indicating that the 1 Pulsifer, History of Lead, p. 243. 8 THE LEAD AND ZINC PIGMENTS. manufacture was carried on on a more extended scale and with a continual improvement in technical knowledge, still followed closely the principles recorded by Vitruvius, Pliny, Theophilus, and others, except that the advantages resulting from the use of stable manure as a source of heat were now fully recognized. 13. Development of the Lead Industry by the Dutch. It is almost universally believed that the Dutch were the inventors or originators of 'the process of manufacturing white lead by which the larger part of our white lead is made to-day, viz., the " Dutch process," the usual date given for the establishing of the industry in Holland being 1622. As has been clearly shown, however, the industry did not originate with the Dutch, but was in general use throughout western Europe prior to that date; in fact, as Pulsifer points out in his " History of Lead," that " the description in the manuscript of Theophilus varies in no important par- ticular from that used by the Dutch in the seventeenth century, even to the use of stable litter. Objection may be made to the statement that The0philus did not secure the necessary carbon dioxide from the decomposing dung, neither did the Dutch in the seventeenth century depend upon the decomposition of the ferment for this element, but added to the vinegar in the pots wine lees, bits of marble, and other substances capable of producing this necessary factor." He states further in the same connection, " it is impossible, therefore, that the Dutch invented a process which is clearly described in manuscripts written before the foun- dation of Amsterdam, and it is unlikely that they borrowed from the Arabs in Spain a method which had been prac- ticed for more than three hundred years in the Italian cities with which their neighbors, the Flemings, had been in con- stant communication." WHITE LEAD IN ANCIENT TIMES. 9 14. Early Adulteration of White Lead. Nevertheless credit must be given the Dutch for developing the industry along broad commercial lines. In fact their very eagerness to monopolize the white lead industry of Europe and under- sell their competitors, especially the Venetians, undoubtedly led them to adulterate their products with chalk and similar materials, to the detriment of the entire industry. Zedler in his Lexicon states " that the painter bought the Holland ceruse because it was cheaper, but contained much chalk, whereas the Venetian was pure, of great enduring qualities, and kept white until the last." Pomet, chief druggist to the French king, Louis XIV, in his complete "History of Drugs," says that they " used little else in France than ceruse de Holland, which was cheaper, and was much esteemed by the painter, but in this they were wrong, as the Dutch ceruse had so much chalk in it that it was of no long duration." 15. Von Justi, writing in 1758, states, " white lead is in much greater demand than one would suppose; the man- ufacture is not enough to supply the demand in this Prus- sian kingdom. It is best not to falsify white lead, but to prepare it pure. In Holland and England we find that a good proportion of chalk is added, and so we have been obliged to do this that we may sell it at the same price. Only the Venetian is wholly pure and on that account it is much sought after and is sold at a higher price." 16. Manufacture of White Lead in Seventeenth Century. Sir Philiberto Vernatti, writing in 1678, describes with much skill and accuracy the process used by the Venetians at that time for making white lead. His description indicates that they had reached a high state of skill in the art, such as could only have been obtained by many years of intelli- gent and continued activity in the industry, and which should be conclusive evidence that they were well versed 10 THE LEAD AND 2INC PIGMENTS. in the manufacture of white lead prior to the date ascribed to the Dutch. It is also to be noted that Vernatti's descrip- tion differs in no important detail from the process now known as the Dutch process. He says: " First, pigs of clean and soft lead are cast into thin plates a yard long, six inches wide, and to the thickness of the back of a knife. These are rolled with some art round, but so as the surfaces nowhere meet to touch, for where they do, no ceruse grows. Thus rolled, they are put each in a pot just capable to hold one, up-held by a little bar from the bottom, that it comes not to touch the vinegar which is put into each pot to effect the corrosion. Next a square bed is made of new horse- dung, so big as to hold twenty pots abreast and to make up the number four hundred in one bed. Then each pot is covered with a plate of lead, and lastly all with boards, as close as conveniently can be. This repeated four times makes one 'heap' so called, containing sixteen hundred pots. After three weeks the pots are taken up, the plates unrolled, laid upon a board, and beaten with battledoors till all the flakes come off, which if good, prove thick, hard and weighty; if otherwise, fuzzy and light, or sometimes black and burned if the dung prove not well ordered; and sometimes there will be none. From the beating table the flakes are carried to the mill, and with water ground between mill-stones until they be brought to an almost impalpable fineness; after which it is moulded into small parcels and exposed to the sun to dry until it be hard, and so fit for use." 17. " Accidents to the work are; that two pots alike ordered, and set one by the other, without any possible distinction of advantage, shall yield, the one thick and good flakes, the other few and small or none, which happeneth in greater quantities, even over whole beds sometimes. Sometimes the pots are taken up all dry and so some- times prove best; sometimes again they are taken up wet. WHITE LEAD IN ANCIENT TIMES. 11 Whether this arises from the vapors coming from below, or by the moisture that is squeezed out by the weight of the pots, we cannot discover. This we observe, that the plates which cover the pots yield better and thicker flakes than do the rolls within ; and the outsides next the planks, bigger and better than the insides." 18. The Dutch Method of Manufacture. The above description indicates that the Venetians were cognizant of the same obstacles and drawbacks that confront the corroder to-day, and that the above method is very closely similar to the Dutch process as described by the Dutch writer, Jars, approximately one hundred years later. Jars is accredited as a most careful and intelligent observer, and his statements as given by Pulsifer, 1 probably repre- sented very closely the methods followed by the Dutch at that time. " The lead was first cast in thin sheets which were rolled in a spiral and placed in earthen pots, seven to eight inches high and four to five inches in diameter, made wider at the top than at the bottom. To prevent the lead from falling to the bottom, they placed inside the pot, and at about one- third of its depth, a piece of wood, cut the length of the diameter of the pot. This was the Rotterdam method. At Amsterdam, the manufacturers had moulded in the inside of the pot, and at about one-third its height, three little points which served, instead of wood, to support the lead. The stacks were built in one range of four, each being about fifteen feet square. After the pots had been filled up to an indicated point with vinegar, and the spiral of lead placed in position in each pot, they were arranged in rows in the stack upon a bed of dung, four feet thick; the pots were placed together as closely as possible, and when the bed was covered with the pots, plates of lead were 1 Pulsifer, History of Lead, p. 267. 12 THE LEAD AND ZINC PIGMENTS. laid upon them and the whole covered with boards. These boards were then covered with dung, and another tier of pots placed as before, filled with vinegar and lead, and covered in the same manner. This was repeated until five tiers, or layers, were built up. The lead was left in the stacks from four to five weeks according to the season and the quality of the dung. In one of the layers which Jars saw opened, he remarked that the action did not appear to be equally satisfactory. In some the sheets of lead were entirely corroded, in others the operation was partial only, while in a few the surface of the sheets was only slightly attacked. This unequal action he attributed to the dung heating more in some parts than in others. The sheets covering the pots formed a crust or scale, harder and more compact, and were put to one side to be used in the manu- facture of blanc de plomb. When the dung had been used several times, it was replaced by new; that rejected was sold to be used as a fertilizer. The sheets which were par- tially converted were taken from the pots and placed upon heavy tables, and beaten with mallets to separate the white lead from the unconverted, care being taken to sprinkle it with water from time to time to abate the dust. The ceruse was now removed to the mills where in Amsterdam it was twice, and in Rotterdam three times ground in water, the mills being placed one above another, the lead falling from the upper mill directly to the one below it, finally passing to a tub placed below to receive it. 19. " The workmen having in charge the grinding of the lead fed the ceruse from the tubs with a ladle into the eye of the stone, adding from time to time chalk in desired proportions to form the mixture. This mixture formed the ceruse. The blanc de plomb, which was white lead, was ground without the admixture of any substance, and being harder and requiring to be finer and ground with WHITE LEAD IN ANCIENT TIMES. 13 more care, the mills could produce but ten quintals per day, while of the ceruse fifteen quintals were turned out. "The last operation, drying, was managed as follows: the ceruse in a pulpy state was filled into unglazed earthen pots, in shape like a section of an inverted cone; these pots were placed upon long wooden shelves, in a long and narrow building, in the sides of which a great number of doors were provided to open and close at pleasure, to shield the ceruse from sun and rain which would impair its fcolor. After five or six weeks the pots were removed, and the ceruse was turned out, the contents of each pot forming a conical mass or loaf; when perfectly dry this was trimmed, tied up in blue paper and packed in barrels for market." 20. English Method of Manufacture. The methods employed for the manufacture of white lead in England were substantially the same as those in use in Holland. In 1787, however, one Richard Fishwick obtained a patent for the use of spent tan-bark in the place of stable manure, claiming that the tan-bark communicated a more equable and uniform degree of heat to the lead and vinegar. This date undoubtedly approximately marks the introduction of this important improvement which may be considered the link connecting these earlier methods with the Dutch process as conducted to-day. CHAPTER II. DEVELOPMENT OF THE WHITE LEAD INDUSTRY IN THE UNITED STATES. 21. Early Use of White Lead. Pulsifer in his " History of Lead " * clearly explains the attitude of the early Amer- ican colonists toward the use of white lead and of paints in general. " There was but little need for the establishment of white-lead factories in the United States until after the Revolution. The simple habits of the first settlers, their poverty and their struggles for subsistence prohibited the use of paints for decorative purposes, while the abundance of timber rendered it unnecessary to be at any great expense to preserve it from the destructive action of the elements. The use of paint, therefore, was discour- aged by the early settlers. Bishop relates the case of the Rev. Thomas Allen, of Charlestown, near Boston, who was ' called to account ' in 1639 for having paint about his dwelling. The reverend gentleman secured immunity from correction by assuring the authorities of his condem- nation of the practice of using paint, and by proving that the offensive substance had been applied by a former proprietor, and was there when he took possession of the premises. 22. "The dwellings of the early settlers were generally of wood, unpainted on the outside and inside. The interior walls were occasionally whitewashed, but beyond this no decoration was to be observed. The first church in Boston (destroyed by fire in 1711) was never painted, 1 Page 313. 14 DEVELOPMENT OF WHITE LEAD INDUSTRY. 15 it is said, inside or outside. In 1705, according to Bishop, the coat of arms of Queen Anne, in the Court House at Salem, Mass., was ordered to receive a ' coloured cover- ing/ which is said to be the first reference to art in that quarter. A list of mechanics made in 1670, in Massachu- setts, fails to show the name of a single painter. Painters' colors, however, were for sale in Boston in 1714." 23. The First White Lead Plant. It is not surprising, therefore, that the development of the white lead industry was delayed for a great many years after numerous other industries had secured a foothold in the colonies. Even the actual date of the establishment of the first white lead plant is uncertain. Credit for the introduction of the industry into this country is ascribed to Samuel Wetherill & Sons, who in 1777 or shortly after had established a factory in Philadelphia for the manufacture of chemical products and were known as importers and dealers in dye- stuffs, various chemicals, and white and red lead. Mr. W. H. H. Wetherill, a descendant of the fourth generation, fixes the date of domestic production and the actual establishment of the industry by Wetherill & Sons at 1804. History relates that the factory was burned shortly after it began operation by an Englishman who sailed for London the day following the fire. The factory was rebuilt in 1808 or 1809, despite the threats of English white lead agents that they would crush the enterprise, and which history relates they endeavored to accomplish until the war of 1812 forced them to retire from the American markets and assured the prosperity of the enterprise. Wetherill & Sons undoubtedly used the Dutch process, and utilized horse dung as the source of heat and carbon dioxide. Pulsifer records that they took out several patents and made numerous improvements in both the white and red lead industries. 16 THE LEAD AND ZINC PIGMENTS. DEVELOPMENT OF WHITE LEAD INDUSTRY. . 17 24. Coxe in an official report to the Secretary of the Treasury in 1810 states that there was only one lead factory in operation at that date and that 369 tons were produced in that year. This report undoubtedly refers to the Wethcrill plant. 25. Effect of the War of 1812. The war of 1812 made the white lead industry a very profitable one, and it is only natural that the industry developed rapidly. The second plant was built in Philadelphia about 1812 by an English- man by the name of Smith, who was succeeded in 1813 by one Joseph Richards, who in 1819-20 disposed of the con- trolling interest to M. Lewis & Co. John Harrison, a chemical manufacturer, also of Philadelphia, began the corroding of white lead by the Dutch process almost immediately after the rebuilding of his chemical works which were destroyed by fire in 1806. The actual date of operation, however, is unknown. 26. Other Early Manufacturers. The manufacture of white lead was begun in Pittsburg not far from 1810-12 by Bielin & Stevenson, and at about the same time by Trevor, Pettigrew & Provost, who, however, did not remain in business long. In 1815 a factory was established in Cin- cinnati by the Cincinnati Manufacturing Company. Bishop in his " History of American Manufactures "states that a corroding plant was established in New York in 1820, but does not state the name of the company. The Brook- lyn White Lead Works was incorporated not far from 1825. This firm first endeavored to manufacture white lead by a quick process said to have been devised by a Dr. Vanderberg of Albany, who was the originator of the company. The process, like many later ones, proved unsuccessful and was abandoned for the old Dutch process about 1830, horpe manure being used as the fermenting material. In 1832 Mr. Augustus Graham, an active part- 18 THE LEAD AND ZINC PIGMENTS. ner of the company, went to England and there secured employment as an ordinary workman in one of the best equipped corroding plants and learned their process and methods in detail and which were introduced in his own plant on his return to this country, the most important improvement being the substitution of tan-bark for horse manure. 27. Adoption of Uniform Scale of Prices. The establish- ment of numerous other white lead plants and the opening up of new lead ore fields caused a big decline in the price of both metal and white lead, and Pulsifer relates that " In 1830 the manufacturers of the Eastern cities of the United States found it necessary, owing to very strong competition, and probably overproduction, to enter into an agreement for the purpose of maintaining uniform and profitable prices. By the terms of this agreement each factory (there were eight at that time east of the Alleghanies) had the privilege of appointing an agent in eleven principal markets in the Eastern States, from Portland to New Orleans. These agents were to receive a commission of five per cent. The prices and terms fixed by this agree- ment were as follows: Dry white lead 8 cents per pound Pure lead, ground in oil 9 cents per pound Potters' red lead 6 cents per pound Glassmakers' red lead 7| cents per pound * The terms were : For quantities amounting to Less than $300, 6 months. From $300 to $500, 6 months and 1 per cent discount. From $500 to $800, 6 months and 2 per cent discount. From" $800 and upwards, 6 months and 3 per cent dis- count. DEVELOPMENT OF WHITE LEAD INDUSTRY. 19 " It was stipulated that these amounts were to be pur- chased at one time to entitle the buyer to these terms. 28. "The parties to this agreement bound themselves in the sum of two thousand dollars, to be considered and treated as stipulated damages, for the full and faithful performance of the agreement, and ninety days' notice was required to be given of an intention to withdraw. " The signers of this agreement were Lewis & Company, Wetherill & Sons, Harrison Brothers, of Philadelphia; Hinton & Moore, of New York, who were possibly selling agents for the Union Company, the Brooklyn White Lead Company, of Brooklyn, New York; and Francis Peabody, and the Salem Lead Manufacturing Company of Salem, Massachusetts." The production of white lead at this date had reached about three thousand tons and in 1840 to about five thou- sand tons. 29. Formation of New Companies. Between 1840 and 1850 the white lead industry increased rapidly. The follow- ing companies were established at about this period: Eckstein White Lead Company, Cincinnati, 1837. Atlantic White Lead Company, of New York, 1842. Jewett Lead Works, of New York, 1844. Ulster White Lead Company, Saugerties, N. Y., Fahnestock White Lead Works, Pittsburgh, 1844. Eagle White Lead Works, Cincinnati, The Collier White Lead and Oil Works, St. Louis, 1851. It is probable that the annual production of white lead in 1850 was about nine thousand tons. Between 1850 and 1860 there was little development in the industry as far as the building of new plants was concerned. The practice of adulterating white lead had grown to such an extent that but little room was left for substantial increase 20 THE LEAD AND ZINC PIGMENTS. in the manufacture of white lead, notwithstanding the increase in population and wealth of the country, and the I/ production by 1860 was only about fifteen thousand tons. 30. Effect of the Civil War. The enormous demand for metallic lead at the beginning of the Civil War checked the growth of the white lead industry for a time, although the differential between pig lead and white lead reached almost ten cents in 1864. This enormous profit stimulated the erection of several new plants toward the close of the war, and the period immediately following was marked by a great development of the industry. Among the more important plants erected during this period are : S. B. Cornell & Son, Buffalo, 1861. St. Louis Lead and Oil Company, St. Louis, 1865. Southern White Lead Company, St. Louis, 1866. D. B. Shipman White Lead Works, Chicago, 1865. Western White Lead Company, Chicago, Davis Chambers Lead Company, Pittsburgh, 1866. Beymer, Bauman & Co., Pittsburgh, 1867. J. H. Morley White Lead Works, Cleveland, 1867. Bradley White Lead Works, Brooklyn, Salem Lead Works, Salem, Mass., 1868. 31. Patents Issued. Pulsifer states that not less than forty patents were issued during this decade (1860-1890) for improvements in the manufacture of white lead, most of them modifications of the Dutch process or precipi- tation processes. None of them, however, as far as can be learned proved to be of any economic value. The ^/production of white lead in 1870 has been estimated at 35,000 tons. 32. Between 1870 and 1880 the industry continued to show a healthy development, but was along the lines of expansion and increase of facilities in the plants already DEVELOPMENT OF WHITE LEAD INDUSTRY. 21 FIG. 3. LEAD BUCKLE. 22 THE LEAD AND ZINC PIGMENTS. established rather than in the building of new plants. Thirty-five patents were issued for improvements in the manufacture of white lead during this decade, fifteen of which were for new processes the majority of which were tried out on a commercial scale but like the preceding inven- tions were unsuccessful and were abandoned after entailing more or less loss upon the promoters. Since that date there have been comparatively few attempts to develop new processes on a commercial scale, although two at least have proven highly successful and are being carried out on a large scale, viz., the Carter process and the Mild process, formerly known as the Rowley process, both of which, together with the Matheson process and the Bailey process, will be discussed at length in subsequent chapters. 33. Improvements. Since the substitution of tan-bark for stable litter in 1832 by Graham there have been very few improvements made in the methods or details of the Dutch process, and these few relate chiefly to improve- ments in the washing, screening, and drying of the white lead rather than in the principles or details of corrosion. One or two companies are attempting to separate the corrosions from the metallic cores by a dry process with- out washing the lead at all and the residual acetates remaining in the white lead are given a treatment with ozonized air to convert them into a less active form. One of the newest attempted innovations is the use of glass corroding pots. CHAPTER III. DEVELOPMENT OF THE WHITE LEAD INDUSTRY IN THE UNITED STATES (Continued). 34. Formation of National Lead Trust. In 1887 there was formed an organization known as the National Lead Trust, capitalized at $90,000,000, which according to the agreement and by-laws was organized for the purpose of securing intelligent cooperation in the business of smelt- ing, refining, corroding, manufacturing, vending, and dealing in lead and all its products and canying on all other business incident thereto. The corporations form- ing the trust were : The Bradley White Lead Company. Anchor White Lead Company. The St. Louis Smelting and Refining Company. The St. Louis Lead and Oil Company. Brooklyn White Lead Company. Jewett White Lead Works. The J. H. Morley Lead Company. 35. Absorption of Other Companies. Within three years from the time the National Lead Trust was formed there had been drawn into and absorbed by the trust accord- ing to the evidence in the case of the National Lead Com- pany v. S. E. Grote Paint Store Company, Supreme Court of Missouri, 1898, in addition to those enumerated above: The National Lead and Oil Company of New York, Ulster Lead Company. Union Lead Company. 23 24 THE LEAD AND ZINC PIGMENTS. S. G. Cornell Lead Company. Atlantic White Lead Company. Davis Chambers Lead Company. National Lead and Oil Company of Pennsylvania. Armstrong-McKelvey Lead Company. Fahnestock White Lead Company. John T. Lewis & Brothers. Eckstein White Lead Company. Kentucky Lead Company. Maryland White Lead Company. McBirney- Johnson Company. Salem Lead Company. Collier White Lead and Oil Company. Missouri Lead and Oil Company. Red Seal Castor Oil Company. Southern White Lead Company of Missouri. W. H. Gregg White Lead Company. 36. Dissolution of National Lead Trust. In 1891 the National Lead Trust was dissolved. President Thompson testified that the reasons which led to the dissolution and termination of the trust were: " Mainly l because there had been laws passed by the United States and a number of States that were inimical to that form of organization and a great public prejudice had been aroused which seriously affected the value of the shares of a trust. . . . Besides the capitalization of the National Lead Trust was excessive." 37. Formation of National Lead Company. In December of that year (1891) the National Lead Company was organized with a capital of $30,000,000. President Thomp- son's report to the stockholders of the National Lead 1 Statement, briefs, and opinion of the Court, National Lead Com- pany v. S. E. Grote Paint Store Company, St. Louis Court of Appeals, p. 3. I T DEVELOPMENT OF WHITE LEAD INDUSTRY. 25 Company, February 16, 1893, states that " This company was organized for the purpose of taking over all the assets of the National Lead Trust." 38. According to the testimony in the case above cited (redirect examination of President Thompson, page 30) the certificate holders of the National Lead Trust sur- rendered their trust certificates in the National Lead Trust and received in exchange therefor stock in the National Lead Company, the certificate holders receiving one share of common stock and one share of preferred stock in the National Lead Company for every six certificates in the National Lead Trust and thirty cents cash. 39. Different Branches of the National Lead Company. The report also shows that the National Lead Company had the following branches : * Atlantic Branch, New York City, proprietors of - Atlantic White Lead and Linseed Oil Works. Jewett White Lead Works. Brooklyn White Lead Works. Bradley White Lead Works. Union White Lead Works. Lenox Smelting Works. Ulster Lead Works. Boston Branch, Boston, Mass., proprietors of Salem Lead Works. Buffalo Branch, Buffalo, N. Y., proprietors of- Cornell Lead Works. Baltimore Branch, Baltimore, Md., proprietors of Maryland W T hite Lead Works. Cleveland Branch, Cleveland, Ohio, proprietors of J. H. Morley Lead Works. 1 Statements, briefs, and opinion of the Court, National Lead Com- pany v. S. E. Grote Paint Store Company, St. Louis Court of Appeals, p. 5. Also Appellants Abstract of the Record, Appeal from the Circuit Court, pages 83 to 91. 26 THE LEAD AND ZINC PIGMENTS. Cincinnati Branch, Cincinnati, Ohio, proprietors of Eckstein White Lead Works. Anchor White Lead Works. Louisville Branch, Louisville, Ky., proprietors of , Kentucky Lead and Oil Works. American White Lead Works. Chicago Branch, Chicago, 111., proprietors of Southern White Lead Works. D. B. Shipman White Lead Works. St. Louis Branch, St. Louis, Mo., proprietors of St. Louis Lead and Oil Works. Collier White Lead and Oil Works. Southern White Lead Works. Red Seal Castor Oil Works. John T. Lewis & Brothers Company, Philadelphia. Western White Lead Company, Philadelphia. National Lead and Oil Company of Pennsylvania, Pitts burg, proprietors of - Armstrong-McKelvey Lead and Oil Works. The Beymer-Bauman Lead Works. Davis Chambers Lead Works. Fahnestock White Lead Works. Pennsylvania White Lead Works. American Oxide Works. Also St. Louis Smelting and Refining Company, St. Louis, Mo., proprietors of - St. Louis Smelting and Refining Works, St. Louis, Mo. Harrison Reduction Works, Leadvilie, Colo. Rio Grande Smelting Works, Socorro, New Mexico. St. Louis and Zacatecas Ore Company, Jiminez, Mexico. 40. Operation of Factories. This report goes on to state that " White lead factories disadvantageously located, or DEVELOPMENT OF WHITE LEAD INDUSTRY. 27 unable from any cause to make their goods on an economic basis, have been discontinued, while others have been greatly enlarged, so that the capacity for production of all classes of goods manufactured by the company has been decidedly increased." 41. Independent Companies. While the National Lead Company owned or controlled a large majority of the white lead plants of this country, there were several which main- tained an independent existence, the more important of which were the Wetherill plant of Philadelphia; the Carter Company of Omaha and Chicago; Nevin, of Pittsburg; the Eagle Lead Company of Cincinnati, Ohio; the Gebhardt Company, of Dayton, Ohio; and the Pioneer of San Fran- cisco. Several of these however, were of veiy small capacity. 42. The Bailey Process. In 1901 the Union Lead and Oil Company of New York was organized and a plant of an intended yearly capacity of 15,000 tons was built, which was to manufacture white lead by the Bailey process, and represented an investment, it is said, of not far from one million dollars. 43. The essential features of this process were the exten- sion of the surface exposed to attack by the corroding vapors. " In this process the melted lead was forced by its own gravity through a perforated plate of thin steel, which forced it into threads or hairs about one one- thousandth of an inch in diameter. The lead solidified and cooled almost as soon as it passed the plate, and was piled on long, shallow trays with slat bottoms. Each of these trays as it received its charge was run back automatically into place in a suitably constructed bin or rack. When all the trays in this rack had been charged with the fibrous lead the process of corrosion began. Mingled vapors of acetic acid, moisture, air, and purified carbonic acid gas were blown in through 28 THE LEAD AND ZINC PIGMENTS. FIG. 4. LEAD FIBRES. BAILEY PROCESS. DEVELOPMENT OF WHITE LEAD INDUSTRY. 29 suitable openings at the bottom and sides of the rack, and after circulating freely through the mass, finally escaped. The temperature meanwhile was maintained automatically at the degree most favorable to satisfactory corrosion." Corrosion was completed in about three days. The product was disintegrated, separated from the uncorroded lead, washed and dried in the usual manner. 44. The United Lead Company. Before the plant was operated at full capacity it was taken over at a much higher figure by an organization known as United Lead Company, a corporation organized in June, 1904, which in substance w r as a subsidiary corporation of the American Smelting and Refining Company, who presumably desired more suitable or at least other outlets for the pig lead obtained in their smelting operations. The United Lead Company also acquired the Gebhardt plant, the recently built plant of the Boston-Chadwick Company, the Selby plant of San Francisco, and the McDougall White Lead Company of Buffalo, formerly known as the Kellogg & McDougall Company, which operated under what was substantially the Carter process. 45. The Bailey plant apparently proved a colossal failure, as it was shortly afterwards abandoned. This left the United Lead Company with an outlet for only about one- half of the tonnage capacity anticipated, and did not render them the formidable rival of the National Lead Company that was anticipated. 46. Growth of United Lead Company. Further means were, taken by the United Lead Company by securing some of the highest talent in the white lead industry with a view of constructing enormous Dutch process corroding plants in different sections of the country, as there were no more independent plants that could be acquired at anything like reasonable figures, the Sterling and Davis white lead com- 30 THE LEAD AND ZINC PIGMENTS. panies having been purchased by the National Lead Com- pany. A site was secured at Perth Amboy, N. J., and the construction of the largest white lead plant in the world was begun. This plant was to have a producing capacity of 20,000 tons yearly, and it was rumored that as soon as completed it was to be followed by the erection of an equally large plant in East St. Louis, for which the site had already been secured, and subsequently by another plant in Chicago. This policy if carried out would have resulted in an overproduction of white lead, as the National Lead Com- pany was not then operating all of its plants, and this naturally would have led to a bitter competitive warfare for the supremacy of the white lead markets. 47. Acquisition of the United Lead Company. Appar- ently the National Lead Company did not care to enter j- MfHk FIG. 5. WHITE LEAD WORKS. HAMMAR BROTHERS. into the struggle, as even before the Perth Amboy plant was entirely completed they acquired control of all of the properties of the United Lead Company, the sale taking place March 8, 1906. This substantially gave the National Lead Company control of approximately eighty per cent of the white lead manufactured in this county and it has DEVELOPMENT OF WHITE LEAD INDUSTRY. 3l been strongly intimated that the National Lead Company shortly afterwards obtained a large or controlling inter- est in the Carter Company, 1 the independent concerns being represented by the Matheson Lead Company, Wetherill & Sons, Harrison Brothers, the Eagle White Lead Company, which had developed a capacity of over twelve thousand tons, the Hammer White Lead Com- pany of about five thousand tons, the Pioneer, and the Rowley, now known as the Mild Process Company, which has recently built a new five thousand ton plant. These companies represented at that time an aggregate capacity of about thirty thousand tons of white lead and oxides. 48. The following is a list of the white lead plants in the United States with their locations and estimated capacities. Those not in operation, as near as the writer can learn, are indicated by leaving the capacity blank. The completion of the Perth Amboy plant in 1907 has doubtless resulted in the closing down of some of the more antiquated plants and probably in reducing the pro- duction of several others, as the total estimated tonnage capacity is considerably in excees of the amount of white lead produced. These figures cannot be regarded as exact and can be only considered estimates, as definite informa- tion along these lines is very difficult to secure. 1 See Mineral Industry, 1906, page 520. 32 THE LEAD AND ZINC PIGMENTS. ex- 6 ^D ^D CD ^D ^D ^D ^D O OOOO OO ojoo^-g^ojoooocooooco : :rac : : : o o o o g ... 000 02 03 oo G X) pq *~ o T3 ^ c3 ^ _ ^ c3 l ill 1 ^ a? .^ y >^t^ ^ ^w ^ : ^J a) ^ _S S-3 .O ~4 l*U HM P^ rr^ S _i^ ro c3 o t^s -^ S^s ' T-5 * tH o ooooooooo i i i i . 2 > s o c S a PQ S L l o Q^ 2 ^ (P ^ CHAPTER IV. BRANDS, PRODUCTION, AND PRICES OF WHITE LEAD. 49. Brands. The following arc facsimiles (pages 36 and 37), of the chief brands of white lead offered for sale by the National Lead Company, which are now being somewhat unified by the use of the accompanying " Dutch Boy " label. Many of these brands have a national reputation, others have attained their greatest reputation in certain locali- ties because of supposedly distinct qualities and properties possessed by them. In other words, each brand originally had a distinctive and individual significance to the master painter using it. Now, however, as these brands are con- trolled by a single corporation, there is in the opinion of many no satisfactory assurance that they are any longer made in the same plants as originally. In fact the writer understands that certain brands of white lead each bearing the name of the original manufacturing company and its location are still being offered for sale when as a matter of fact the plants of these former companies have been either abandoned or dismantled. The author does not, however, wish to be understood as stating that the lead offered under these brands possesses less merit than formerly. 50. Short-weight Packages. The adulteration of white lead was exceedingly widespread and attained its greatest prevalence prior to the Civil War. The establishment of several large plants shortly after the close of the war gave a decided impetus to the production and sale of strictly pure white lead. This movement has been steadily growing ever since, and at the present time the writer does not know of a company whose business is strictly the manu- 34 BRANDS, PRODUCTION, AND PRICES OF WHITE LEAD. 35 facture of white lead that offers for sale any white lead but what is strictly free from adulteration. It has, how- ever, been practically a universal custom for many years to offer white lead for sale in short-weight packages, that is, a 50 -pound keg of lead weighing 50 pounds gross weight instead of 50 pounds net. In a number of actual determi- nations made by the writer in 1900 the following shortage in weights was observed: Number. Assumed weight. Net weight. Shortage. Lbs. Lbs. Oz. Lbs. Oz. I 50 46 3 4 II 12* 11 13 11 III 12* 10 6 2 2 IV 12* 10 7 2 1 V 25 21 12 3 4 VI 25 22 7 2 9 VII 12* 10 2 8 VIII 12* 11 1 8 Since the passage of laws in several states regulating the sale of paints and paint products, which require net weights and measures to be stated on the label, all or nearly all of the corroders are offering their leads in full-weight packages. 51. Annual Production of White Lead. Annual produc- tion of white lead in the United States, 1 1884 to 1907. Year. Quantity. Value. Year. Quantity. Value. Short tons. Dollars. Short tons. Dollars. 1884 65,000 6,500.000 1896 88,608 8,371,588 1885 60,000 6,300,000 1897 95,658 9,676,815 1886 60.000 7,200,000 1898 96,048 9,400,622 1887 70,000 7,560,000 1899 110,197 11,317,957 1888 84,000 10,080,000 1900 98,210 10,657,956 1889 80,000 9,600,000 1901 100,787 11,252,653 1890 77,636 9,382,967 1902 114,658 11,978,174 1891 78,018 10,454,029 1903 113,886 12,837,647 1892 74,485 8,733,620 1904 117,292 13,026,954 1893 72,172 7,695,130 1905 136,676 15,738,649 1894 76,343 6,662,307 1906 132,081 16,929,250 1895 90,513 8,723,632 1907 127,251 16,448,324 > Mineral Resources of United States, 1884-1907. 36 THE LEAD AND ZINC PIGMENTS. R.LI,NG ITE LEAD COHPASt ^ -i - FIG. 6. FACSIMILES OF LEADING BRANDS OF NATIONAL LEAD COMPANY. BRANDS, PRODUCTION, AND PRICES OF WHITE LEAD. 37 FIG. 7. FACSIMILES OF LEADING BRANDS OF NATIONAL LEAD COMPANY. 38 THE LEAD AND ZINC PIGMENTS. 52. Sale of Dry White Lead. White lead is sold by the manufacturers to the wholesale and retail trade ground in about eight per cent of linseed oil or in dry form to the mixed paint manufacturers for use in prepared paints. In order that the reader may gain an idea of the increase in the sale of prepared or mixed paints and its effect upon the sale of white lead in oil the following figures are given, being taken from the United States Geological Records. These figures also serve to show the influence of paint legislation and public agitation along these lines. The effect has not been particularly noticeable in the sale of mixed or prepared paints but rather in the sale of reduced or combination white lead, as at the present date (1908) the writer know r s of several large paint manufacturers whose sales of combination white lead have fallen off nearly seventy-five per cent. It is possible, however, that other influences have contributed to produce these results in part. Year. White lead in oil. Dry white lead. Tons. Tons. 1895 76,000 15,000 1903 62,674 51,212 1904 58,332 65,014 1905 62,767 73,909 1906 93,763 38,318 1907 92,216 35,035 53. Differential between Pig Lead and White Lead. The following table showing the variations in price between pig lead and white lead will be of interest. BRANDS, PRODUCTION, AND PRICES OF WHITE LEAD. 39 RANGE OF PRICES PER HUNDRED POUNDS OF PIG LEAD AND WHITE LEAD. 1 Year. Pig lead. Dry white lead. White lead in oil. 1783 9 50 12 50 1784 1785 9.82 11 90 11.90 11 67 1786 1787 1788 1789 1790 1791 1792 1793 1794 1795 9.92 9.82 9.82 10.27 9.82 9.82 9.82 9.82 10.71 11 90 11.43 11.43 11.10 11.10 10.71 10.71 10.96 11.16 13.84 13 39 1796 11.16 12.86 1797 11.30 13.32 1798 11 90 11 68 1799 12.50 14.29 1800 12 50 14 29 1801 14 29 14 29 1802 12 50 13 39 1803 12 50 14 29 1804 13 98 14 88 1805 1806 13.98 13 '.IS 14 73 15.00 16 27 1807 16 74 16 91 1808 16 96 17 32 1809 16 29 17 28 1810 14 29 16 97 1811 14 29 16 97 1812 1813 11.16 17.86 21 43 21.43 24 12 1814 20 54 21 88 1815 1816 17.86 21.43-35.71 10 71 21.43-35.71 14 29 1817 10 71 13 39 1818 10 71 12 50 1819 1820 1821 1822 1823 1824 1825 1826 1827 6.70 6.36 6.63 6.35 5.36 6.39 7.59 6.75 6.14 11.61 11.61 10.71 10.71 10.71 10.71 10.71 10.71 10.27 12.50 12.50 12.50 12.50 12.50 11.61 11.61 11.61 11.61 Mineral Industry, 1894, p. 408. Mineral Resources, 1894-1907, 40 THE LEAD AND ZINC PIGMENTS. RANGE OF PRICES. Continued. Year. Pig lead. Dry white lead. White lead in oil. 1828 5.39 9.82 11.61 1829 3.75 7.59 9.49 1830 3.75 7.37 8.60 1831 4.56-6.00 8.24-8.73 9.21 1832 5.94 9.50 10.66 1833 5.91 9.50 10.66 1834 5.13 9.35 10.16 1835 6.50 9.86 10.84 1836 6.38 10.00 11.50 1837 5.96 11.12 12.00 1838 5.29 10.75 11.50 1839 5.83 10.25 11.00 1840 4.89 9.75 10.25 1841 4.50 9.00 9.25 1842 3.81 8.00 8.25 1843 3.58 7.75 8.25 1844 3.90 7.25 8.25 1845 4.03 7.50 8.00 1846 4.73 7.00 8.00 1847 4.37 6.90 7.20 1848 4.26 6.18 6.83 1849 4.78 7.31 7.45 1850 4.80 7.00 7.22 1851 4.85 6.75 7.28 1852 4.80 6.31 7.06 1853 6.45 8.75 9.50 1854 6.57 8.50 9.25 1855 6.87 8.75 9.02 1856 6.59 8.37 9.09 1857 6.18 8.25 9.00 1858 5.94 8.50 8.77 1859 5.50 7.25 8.00 1860 5.65 7.25 8.00 1861 5.25 7.27 8.07 1862 6.10 8.20 8.47 1863 6.25 10.44 12.17 1864 7.10 16.72 16.81 1865 6.60 15.58 15.88 1866 6.90 13.41 16.13 1867 6.50 12.73 14.34 1868 6.50 12.19 13.60 1869 6.45 13.27 12.00 1870 6.25 9.64 10.85 1871 6.10 9.68 11.30 1872 6.35 9.41 11.33 1873 9.30 10.62 11.83 1874 6.00 10.50 11.25 1875 5.95 10.00 10.84 1876 6.05 10.00 10.50 BRANDS, PRODUCTION, AND PRICES OF WHITE LEAD. 41 RANGE OF PRICES. Continued. Year. Pig lead. Dry white lead. White lead in oil. 1877 5.45 9.30 9.81 1878 3.60 7.50 8.08 1879 4.18 7.00 7.46 1880 5.06 8.00 8.54 1881 4.89 6.58 7.03 1882 4.91 6.17 6.67 1883 4.32 6.18 6.68 1884 3.74 5.50 6.00 1885 3.95 4.98 5.48 1886 4.63 4.88 5.38 1887 4.50 5.87 6.37 1888 4.42 5.16 5.66 1889 3.93 4.89 5.39 1890 4.48 5.43 5.93 1891 4.35 5.80 6.30 1892 4.05 6.50 6.75 1893 3.69 5.75 6.38 1894 3.29 4.50 5.26 1895 3.23 4.25 5.00 1896 3.03 4.38 4.90 1897 3.64 4.63 5.00 1898 3.79 4.50 5.08 1899 4.53 5.00 5.35 1900 4.55 5.07 5.57 1901 4.21 5.39 5.87 1902 4.21 5.09 5.62 1903 4.23 5.25 6.12 1904 4.42 5.13 6.12 1905 5.28 6.25 6.50 1906 5.83 6.32 6.86 CHAPTER V. THE MODERN APPLICATION OF THE DUTCH PROCESS IN THE UNITED STATES. 54. Present Importance of the Dutch Process. By far the larger proportion of white lead manufactured to-day is still made by the old Dutch process, so called, and while some of the newer processes have been very successful in their operation, producing high grades of white lead at a cost not exceeding that of old Dutch process white lead, and one or two of them at a very much less figure, yet by reason of the fact that it has meant the introduction of new brands on the market, competing against well-known brands of long standing, the development and expansion of these newer processes has been slow, but at the same time more or less sure, and it is more than probable that within a very few years they will -constitute as important factors in the white lead industry as the Solvay and elec- trolytic processes have in the soda industry. 55. Processes in Use. Confining our discussion at the present time to the white lead industry of the United States and neglecting the large number of experimental and patented processes that for one reason or another have not proven successful in actual commercial practice, the follow- ing may be considered as the processes by which white lead is made in this country at the present time : 1. Old Dutch process. 2. Carter process. 3. Matheson process. 4. The Mild process (Rowley) 42 MODERN APPLICATION OF THE DUTCH PROCESS. 43 44 THE LEAD AND ZINC PIGMENTS. Several electrolytic processes have been devised, but the writer is not aware that they have yet been developed on a successful commercial scale. As conducted in this country at the present time the old Dutch process is substantially as follows : 56. Grade of Pig Lead Required. The pig lead used must be a double refined lead, which usually commands a price at least ten cents above the best grades of ordinary 'refined lead. The following analysis is typical of a good grade of corroding lead : Constituents. Per cent. Silver 0.0006 Arsenic .0050 Antimony trace Tin 0.0003 Copper .. none Bismuth 0.0100 Iron 0.0015 Zinc trace Manganese < . none Nickel and cobalt none Impurities . 0174 Lead by difference 99.9826 100.0000 The commercial impurity which is the cause of the greatest trouble is bismuth, a lead becoming " common " when it contains as much as 0.0800 per cent of bismuth. 57. Casting the Buckles. The pig lead is melted in a large iron kettle and allowed to flow continuously on to an endless double belt of molds, which form the lead into perforated disks of about one pound each, these disks being commonly known as buckles, due to the fanciful resem- blance to the large metallic buckles used as ornaments on MODERN APPLICATION OF THE DUTCH PROCESS. 45 I' 46 THE LEAD AND ZINC PIGMENTS. shoes in the earlier times. It is absolutely necessary that these buckles be cast, as a rolling process would harden or change the crystalline nature of the lead to such an extent that it would be impossible to corrode it. It is therefore extremely necessary that all the parts of the casting sys- tem must work in entire harmony the temperature of the molten lead, the speed with which the chain of molds travels, and length of the mold belt in order to secure the best results. A double line of molds will cast about eighty buckles per minute. The heat of the molds and the temperature at which the lead is run upon them has a very decided influence upon the ease of corrosion. The buckles are conveyed, generally by wheelbarrows, to the corroding houses, which are compartments square or nearly so, twenty or twenty-five feet each way, located in a large building or shed usually one story in height. 58. Building the Stack. Usually sixteen to eighteen buckles are placed in each corroding pot, about one pint of commercial, number eight acetic acid, diluted to three per cent of true acetic acid, having been placed in the well of the pot. The pots are strongly built of earthenware, the only glazed portion being the well. The loaded pots are then placed side by side on a layer of tan -bark and horse manure about two and one-half feet in depth, and an outer layer about one foot in breadth between the walls of the stack and the pots. About one- third fresh tan -bark is used each time, the other two-thirds being that used in the previous corrosion, sixty to seventy bushels of manure being used to about seven hundred bushels of tan-bark. The tan -bark used is that obtained from tanneries, and in the most modern Dutch process plants it is conveyed from the yard to the stack by means of electric cranes or carriers. The layer of pots is then covered over with a double layer of boards on which is placed more tan-bark, the upper layers MODERN APPLICATION OF THE EUTCH PROCESS. 47 usually being about one foot in depth. More pots are placed on the tan-bark, and in this manner the " stack " so called is built up layer after layer, and when finished is usually ten or twelve layers high, and contains from sixty to one hundred and twenty tons of lead, one hundred tons probably being a fair average. This operation requires the services of four men for about three days. Each layer of pots is connected by a flue or vent leading to the roof, FIG. 10. ELKCTRIC CRANE FOR CONVEYING TAN-!>ARK. HAMMAR BROS. which permits the gares due to the decomposition of the moistened mixture of tan-bark and manure to escape. The temperature and smell of the escaping gases and steam and their apparent volume furnish the cnly means of judg- ing the conditions inside of the stack and progress of the corrosion, and also the only possible means of regulating these conditions by closing or partially closing the flues, thus controlling to some extent the reactions imdile. the stack. The temperature if too low will check the corro- THE LEAD AND ZINC PIGMENTS. MODERN APPLICATION OF THE DUTCH PROCESS. 49 sion or retard it entirely ; if too high will cause the forma- tion of a crystalline or sandy white lead or even a yellow product which is largely oxide. 59. Reactions Involved in the Corrosion. The stacks are allowed to remain undisturbed for one hundred to one hundred and twenty days. The tan-bark and manure, hav- ing been carefully tempered prior to their introduction into the stack, rapidly ferment, the temperature rising rapidly to 160 to 175 F., a temperature sufficient to vaporize the acetic acid and the moisture in the tan-bark. The mixed vapors attack the metallic lead, forming first a basic lead acetate. A large amount of carbon dioxide is also liber- ated during the fermentation, which reacts with the basic acetate, forming a basic lead carbonate, or what is com- monly known as white lead. The transformation of the lead may be represented by the following equations: 1. Pb + 2C 2 H 4 2 = H 2 + Pb(C 2 H 3 O 2 ) 2 . 2. 3 Pb(C 2 H 3 2 ) 2 + 2 H 2 O = 2 Pb(C 2 H 3 O 2 ) 2 . Pb(OH) 2 + 2C 2 H 4 2 . 3. 2 Pb(C 2 H 3 2 ) 2 Pb(OH) 2 + 2 C0 2 -f 2 H 2 O = 2 PbC0 3 Pb(OH) 2 +4 C 2 H 4 2 . Several authorities consider the liberation of hydrogen as improbable and believe the reactions proceed as follows : 1. Pb+H 2 + = Pb(OH) 2 . 2. Pb(OH) 2 +2 C 2 H 4 2 = Pb(C 2 H 3 2 ) 2 + 2 H 2 0. 3. Pb(C 2 H 3 2 ) 2 + 2 Pb(OH) 2 = Pb(C 2 H 3 2 ) 2 - 2 Pb(OH) 2 . 4. 3 [Pb(C 2 H 3 2 ) 2 2 Pb(OH) 2 ]+4 C0 2 = 3 Pb(C 2 H 3 2 ) 2 +2 [Pb(OH) 2 2 PbCOj +4 H 2 O. 60. These reactions indicate that the acetic acid or the neutral lead acetate is continually regenerated, attacking more of the metallic lead, and the reaction becoming cyclic until the larger portion of the lead is converted into white 50 THE LEAD AND ZINC PIGMENTS. MODERN APPLICATION OF THE DUTCH PROCESS. 51 lead, the operation becoming slower and slower as the crust or coating of white lead on the metal increases in thickness, usually coming to a standstill when 70 to 80 per cent of the metal has become converted. The horse dung acts as the starter for the tan-bark, causing the fer- mentation to begin more quickly and proceed more rapidly in the initial stages. If it were not for the discoloration of the white lead, due to the action of hydrogen sulphide and other sulphur compounds, the horce dung would be used in much larger quantities, as its action is very much more rapid and complete than that of the tan-bark. 61. Conditions Required for Successful Corrosion. The FIG. 13. COMPLETED STACK. HAMMAR BROTHERS. correct tempering of the tan -bark is the most important part of the process. If an excessive amount of water is used, or the water is too hot, or the heap of bark allowed to overheat, the tan will be " killed/' as it is termed, i.e., 52 THE LEAD AND ZINC PIGMENTS. MODERN APPLICATION OF THE DUTCH PROCESS. 53 the principle which causes the fermentation is checked. Whether this principle is a form of bacteria or an enzyme is not definitely known, but on its proper cultivation depends the success of the corrosion. 62. Taking Down the Stack. At the expiration of the allotted time the stack is taken down in the same manner as erected, except of course the operations are reversed. A considerable number of the pots will be found to be broken, due to the weight of the stack. As long, how- ever, as the well of the pot remains intact it can be used to advantage, because in such instances the corrosion is more nearly complete, as the gases and vapors have freer access to the buckles. The buckles, if the corrosion has been conducted properly, will be found to have become changed into a white hard porcelain-like mass of the same general shape as the original buckle but warped and swollen and usually containing a portion of uncorroded lead in the center. The completeness of the corrosion will vary not only with different stacks but in different portions of the same stack. 63. Very slight amounts of impurities such as bismuth, antimony, arsenic, and zinc will retard the conversion or cor- rosion very seriously. Great care must also be exercised in the moistening and tempering of the tan-bark. Improper tempering may cause the stack to'" die, "resulting in a very low percentage of corrosion. Occasionally the fermenta- tion of the tan-bark may be so rapid as to dehydrate the white lead as fast as formed into a yellow oxide. With due care these undesirable results may be avoided, but there are other less troublesome results arising from obscure conditions which cannot be readily controlled, such as soft and fluffy corrosions which require more oil in grinding and have less hiding power. 64. Sandy Lead. If the pig lead or the stack conditions have not been suitable the buckles on being broken will 54 "THE LEAD AND ZINC PIGMENTS. MODERN APPLICATION OF THE DUTCH PROCESS. 55 show a grainy, glistening, crystalline structure due to crystals of neutral lead carbonate. This results in a white lead of diminished hiding power which is very difficult to grind and settles out as a useless sandy lead when thinned down to painting consistency. Notwithstanding every precaution taken by an experi- enced corroder, a variable percentage of such lead will be found in eveiy corrosion. 65. The labor item in taking down the stack is very FIG. 1G. CRUSHING ROLLS. nearly equal to that of putting it up, as the boards have to be taken up carefully in order to avoid getting bits of tan-bark into the pots of corroded lead, and either con- veyed to the yard or placed on pegs projecting from the wall. The tan-bark is wheeled or conveyed to the yard; the contents of the pots are also wheeled to the crushing and grinding mill. CHAPTER VI. THE MODERN APPLICATION OF THE DUTCH PROCESS IN THE UNITED STATES (Continued). 66. Disintegrating the Buckles. In order to separate the crust of white lead from the metal core the buckles are crushed between large steel grooved rollers and passed through a coarse screen which retains the larger pieces of metallic lead. The portion passing through the screen, which still contains considerable metallic lead, is run through the flattening rolls, which further disintegrate the corroded lead and flatten out the metallic particles so that they are retained on a finely meshed screen. The white lead passing through is ground with water in large stone mills, the grinding surfaces of which have to be frequently recut and dressed, due to the hardness of the white lead particles. In order to remove the metallic lead which often clogs the mills by filling the grooves in the stone, common salt is often put in the hopper in con- siderable quantities. 67. Washing the Lead. From the grinding mills the white lead is conveyed to the float table or drag box, where the coarser and more crystalline particles are settled out to be reground. The lighter particles are floated off and washed thoroughly in a series of agitator tubs with an increased amount of water to remove as much of the acetic acid and the more or less insoluble basic acetates of lead as possible, the purified white lead finally passing through a fine silk bolting cloth to re- move any particles of tan-bark and metallic lead remain- ing in it. 56 MODERN APPLICATION OF THE DUTCH PROCESS. 57 . 17. WATEK GRINDING MILLS. HAMMAB BROTHERS. 58 THE LEAD AND ZINC PIGMENTS. 68. Importance of Thorough Washing. The washing of the white lead must needs be thorough, as nearly all the acetic acid used is present in the white lead buckles when removed from the corroding pots, as solid acetate of lead constituting one-half to one per cent of the weight of the buckle and if not properly removed seriously affects the FIG. 18. DRAG AND WASHING Box. service value of the white lead. An eminent paint chemist in discussing this matter says that " slight traces of ace- tate in the ground lead in oil render it not only far more readily attacked by the blackening influence of the sulphur fumes and sulphuretted hydrogen of the air, but also act upon the linseed oil with which it is mixed, so that it reaches the final state of oxidation and perishes much more quickly than would otherwise be the case, resulting UNIVERSITY OF MODERN APPLICATION OF THE DUTCH PROCESS. 59 60 THE LEAD AND ZINC PIGMENTS. in the rapid chalking of the lead. Under the influence of moisture and the carbonic acid gas of the air complete corrosion and change of the basic carbonate into the trans- parent crystalline normal carbonate may also take place when acetate of lead is left in the finished product." 69. Drying the Lead. After having been pumped to large settling tanks, where the excess of water is drawn off, the white lead paste, carrying fifty to sixty per cent of water, is pumped on to large copper drying pans usually arranged in series three to four pans high. The dimensions of the pans will vary in the different plants; eight feet in width by about sixty feet in length is a very common size. Each pan is jacketed and so constructed as to withstand considerable pressure, the steam circulating from one pan to the next in the same series. 70. The paste lead is usually pumped on to the pans to a depth of about six inches, and as soon as it has dried to a solid consistency it is marked off into squares, which ultimately causes the formation of cracks as the lead shrinks and thus hastens the drying. About six to eight days are required to dry the pasty mass moisture free. The lead is removed as soon as thoroughly dry, as over- drying tends to the formation of a crust which is hard to grind. It is then taken from the pan with the aid of wooden shovels and packed dry in barrels by means of a mechanical barrel packer or sent to the mills to be ground in oil. 71. Loss of Lead in Washing. The large volume of wash waters used in this process entails a considerable loss of lead, a portion of which is recovered by the more careful corroders by precipitating out with sodium carbonate; even with this precaution and the use of large settling tanks a considerable amount ultimately finds its way annually into the sewer. MODERN APPLICATION OF THE DUTCH PROCESS. 61 62 . -: THE LEAD AND ZINC PIGMENTS. 72. Effect of Sandy Lead in Paints. The utility of white lead for certain purposes depends quite largely on the care exercised in freeing it from " sandy " lead, i.e., the dense, hard grains of crystalline carbonate due to over- corrosion or unequal distribution of the corroding agencies. In interior brush work or in dipping paints where the white lead is thinned with a considerable amount of turpentine or benzine the sandy lead will rapidly settle out as a useless sediment, and it is the firm belief of the writer that the majority of old Dutch process white lead would be considerably better for the removal of at least three to five per cent of crystalline lead. 73. Cost of a Stack Operation. The following figures as to cost and yields are believed by the writer to be fairly representative, as they are obtained from a run of a one- hundred -ton stack for the usual corroding period, with average conditions and prices. These figures are exclu- sive of all costs and expenses outside of the stack. Materials composing stack. Cost. 210,000 buckles equivalent to 200,000 pounds of lead at $6 per hundredweight $12,000 . 00 10,000 corroding pots 600 . 00 4,000 pounds acetic acid 80 . 00 Lumber (portable) 130.00 100 cords tan-bark 350.00 Labor setting up stack 40 . 00 Labor taking down stack 30 . 00 Miscellaneous. . 20.00 $13,250.00 MODERN APPLICATION OF THE DUTCH PROCESS. 63 64 THE LEAD AND ZINC PIGMENTS. Products obtained. Value. 178,000 pounds white lead at 6 cents per pound $10,680. 00 50,000 pounds uncorroded 3,000.00 6,000 pounds tailings 210.00 Lumber fit to reuse 120.00 Pots less breakage 565 . 00 Tan-bark, two-thirds to be used over 233.00 $14,808.00 Increase in value $1,558.00 Increase in product 200,000 Ibs lead set 50,000 Ibs. lead uncorroded 150,000 Ibs. lead corroded = 178,000 Ibs. white lead, 6,000 Ibs. tailings. 184,000 Ibs. total yield. 184,000 Ibs. 150,000 Ibs. 34,000 Ibs. chemical increase = 22.7 per cent. Theoretical chemical increase = 24.8 per cent. 74. It should be stated that these figures were obtained during a. year in which there was practically no difference between the price of pig lead and dry white lead, this being an exceptional occurrence, as there is generally a marked difference between the two, resulting in a much greater profit, which can be readily calculated by inserting the prevailing market values. 75. Economy of Process. While it is probable that labor- saving devices and appliances have not J>een utilized L to the greatest extent possible, in the majority of old Dutch cor- MODERN APPLICATION OF THE DUTCH PROCESS. 65 66 THE LEAD AND ZINC PIGMENTS. roding plants, the nature of the process itself is not con- ducive to mechanical economies. Nevertheless the art is much more advanced in this country with respect to labor- saving appliances and the preservation of health among the workmen than in Europe. This is especially true with regard to the washing and drying of the white lead. 76. Variation in Quality. There has been considerable controversy during the past few years, especially among the master painters, as to whether the old Dutch process white lead of to-day is the equal of that produced by the same process in less recent years. In this country, as explained in a previous chapter, the large majority of the white lead plants are under the control of a single corpo- ration having a central office which receives the regular routine reports of the various factories as regards labor, materials used, yields and details of process, and it is only natural that each plant would endeavor to obtain the greatest percentage of corrosion with the least expense, and with a process which admittedly does not give a uni- form product at all times, it is easy to see how quality may at times be sacrificed for quantity. It was formerly the custom of the most careful corroders to sort and separate out the imperfect corrosions, and in addition age their lead by storing in large bins for a considerable length of time before grinding in oil, and the writer understands that this custom still prevails among the conservative English man- ufacturers to-day. 77. Lack of Proper Grinding of White Lead. While the practice discussed above may have a considerable bearing on the question, the present-day practice of grinding white lead by the manufacturers of this country has, in the opinion of the writer, very much more to do with the ser- vice or wearing value of white lead than most investi- gators and writers have been led to believe. The writer MODERN APPLICATION OF THE DUTCH PROCESS. 67 has visited several of the largest white lead plants in the country, and found them grinding their white lead in oil in a double set of stone mills which were not water-cooled, with the obvious result that as the day progressed the mills became hotter and hotter, and after five or six hours of steady running the lead as it came from the mills averaged in three specific cases 262 F., 280 F. and 284 F., the tem- peratures were taken by the writer himself, and were from different mills and represented two different factories. These figures have been repeatedly verified by the writer in numerous plants, and temperatures as high as 300 F. have been noted at the close of the day's run, and yet according to the records of the operator of the mill no temperature higher than 125 F. was recorded. It is not an easy matter to ascertain accurately the temperature of the lead just as it emerges from the mill, and it was much easier for the workman to take the temperature of the lead as it dropped into the keg, some little distance from the mill, and by that time the lead was fairly cool and his figures not far from correct. This practice of grinding hot lead is much more general, the writer believes, than most paint authorities imagine. 78. Changes that may take place in Grinding. Two of the most powerful aids in producing a chemical reaction or combination, where the tendency of the substances to com- bine is not pronounced, are heat and pressure, and in a large, uncooled white lead mill running steadily for ten hours, the above-mentioned conditions are certainly attained to a high degree, and a more or less pronounced combination of white lead and linseed oil must inevitably take place with the formation of a lead soap, possibly accompanied by further structural changes in the white lead molecule. This, in the opinion of the writer, is the reason why much of the white lead manufactured in this country chalks 68 THE LEAD AND ZINC PIGMENTS. MODERN APPLICATION OF THE DUTCH PROCESS. 69 more readily and does not possess the wearing qualities of the more carefully ground English leads. One of the fore- most authorities on the manufacture of white lead, in a letter to the writer, confirms this view with the following statement : " I do not feel that it is safe to heat white lead over 150 F., preferably not over 125 F., as, if it is heated above the higher temperature, saponification is apt to ensue, with toughening of the mixture, discoloration and actual change in the nature of the material." 79. English Methods of Grinding. The method still followed by the more conservative English manufacturers of using roller mills for incorporating the lead with oil has much to commend it in avoiding these difficulties. A lead- ing English authority, in discussing this subject with the writer, stated that " many of our large English firms have tried the American water-cooled mills, but with very dis- appointing results. Two London firms, in < particular, installed six of these mills, but have thrown them out and are using the English combination roller mills." The writer believes that the cooling effect of the water-cooled mill has been overrated, as the stones are sueh. exceed- ingly poor conductors of heat that the grinding face of the stone may be exceedingly hot, and yet the other sur- face which is in contact with the water may be compara- tively cool; in other words, the cooling effect of the water is really very slight, unless there is, as often is the case, a ten- dency for the mill to heat up very hot, 260 to 300 F., in which case the water will exert a considerable cooling effect, but with temperatures around 200 F. and below, the cool- ing effect is almost negligible, especially during the sum- mer months. The degree of heating will of course depend on how " tight" the mill is set. The writer has repeatedly observed temperatures as high as 255 F. in the most approved types of water-cooled mills, when a " close grind " 70 THE LEAD AND ZINC PIGMENTS. MODERN APPLICATION OF THE DUTCH PROCESS. 71 was required, and that, too, as early as two o'clock in the afternoon. 80. Combination Leads. Neither are the manufacturers of combination white leads, so-called, always exempt from the above criticisms, and many of the ills ascribed to the use of combination leads, such as hardening in the keg, are more often due to the practice of grinding in hot mills than to the inert materials employed, although some inert pigments, notably silica, tend materially to aggravate the heating of the mill. 81. The English mills have a much greater capacity than is conceded them by the advocates of the American system of grinding. The type of mill illustrated in this connection, having a 7-foot chasing pan and fitted with 33-inch by 16-inch tandem triple granite rolls is capable of turning out from 8 to 10 tons of white lead per day, while a 40-inch American mill will seldom exceed 3 tons. 82. Pulp Ground Lead. Another means of incorporat- ing white lead with oil has come into use during the last fifteen or twenty years and affords a product which has obtained much favor in the Eastern section of the country. The writer refers now to " pulp " ground lead. In this process the paste of lead and water which would other- wise be pumped onto the dry pan is pumped into a care- fully measured and weighed box placed on stationary scales, and the actual weight of white lead present in the paste determined, the correct amount of oil added and the contents of the box dumped into a tall, very narrow upright mixer. Owing to the greater affinity of the oil for the lead a continuous separation of water takes place, which rises to the top, while the stiff paste of lead and oil works to the bottom and is carried off by a screw conveyor either to a grinding mill or is filled directly into the kegs. If the latter, the percentage of water will usually be over 72 THE LEAD AND ZINC PIGMENTS. 0.5 per cent, while if it has been ground in a mill, sufficient heat is usually generated to bring the water content below 0.5 per cent. Prepared as described above, " pulp " ground lead may contain a considerable amount of acetate of lead. 83. Characteristics of Pulp Lead. The easy working of this lead under the brush and its apparently great white- ness has led to its being received with much favor, espe- cially in the East. However, Hooker, in discussing the value of pulp ground lead, expresses the writer's own views on the subject when he states: "A critical comparison between pulp ground lead and regularly ground lead would not seem to justify this use of pulp lead when durability and per- manence of color are. concerned." " Pulp lead " is usually distinguished from regular lead by rather a flat, dull look and a little whiter color than the other lead; it will also stand a little more oil in first thinning, but " breaks " suddenly when thinned too far. A small amount rubbed upon a palette or glass with the addition of just a trifle of dry eosine (an aniline dye insoluble in oil) shows at once a bright pink color, due to the production of an eosine lake by the acetate of lead solution present. True, this acetate of lead does not represent to exceed one per cent ordinarily of the lead, but it has a strong bearing upon the saponification of the oil and consequent durability of the paint. A comparison with regularly ground lead shows no such reaction. Now place the two leads, " regu- lar and pulp " ground, upon a glass, and note the effect, when they are rather rapidly dried, as would be the case when the glass is left for a time on the top of a heated radiator. The pulp lead turns rapidly yellow, showing the yellowing effect of the heat on the saponified oil in the pulp lead. The action of gases such as sulphuretted hydrogen present in the atmosphere, particularly of cities, MODERN APPLICATION OF THE DUTCH PROCESS. 73 is very generally known, so far as the blackening of white lead is concerned, but the marked difference between different white leads as regards susceptibility to this influence is not generally known. Placing a little pulp lead in oil upon glass beside regularly ground lead in oil, and subjecting both to the influence of this gas diffused in air, it will be seen that the pulp lead is badly blackened before the action is scarcely appreciable upon the other, showing plainly how much more susceptible to discolor- ation the pulp ground lead is than the other. 84. The points which have created a certain demand for pulp ground lead are, first, its color, which is fictitiously white, in that it loses this when the water evaporates, besides discoloring more readily than any other; the extra thinners which it will carry and still retain a certain peculiar brushing quality; the seemingly greater covering, which proves false when entirely dry, and the readiness with which it can be used to produce a certain " flat " finish for inside work. The last might be worth some consider- ation were it not that it is so greatly offset by the sensitive- ness of the lead to discoloration, and the rapidity with which it acts upon linseed oil, due, doubtless, to the acetate that was not removed, thus causing the paint to chalk and perish far more rapidly than would a regularly ground lead. Such lead should never be used and be expected to stand any length of time. CHAPTER VII. THE CARTER PROCESS. 85. History. Numerous efforts have been made and much money spent in attempting to shorten the time required for the manufacture of white lead by the old Dutch process, but the various quick processes as they were termed did not possess all of the elements of success and after a short trial were given up as impracticable or unprofitable on a large scale. The Carter process, how- ever, was the first in this country to prove the exception to the rule, and at the date of writing, the two plants of the Carter Company in the United States have an aggregate yearly tonnage of approximately twenty thousand tons. 86. Adams White Lead Company. The original patents of what is commonly known as the " Carter Process >r were taken out by McCreary & Adams in the early seventies who formed a corporation and operated a small plant in Baltimore, Md., under the name of the Adams White Lead Company. The plant was operated for only a short time. A little later another attempt was made at Washington, Pa., which was likewise unsuccessful, owing to imper- fections in the process and crudeness in operation, and also to lack of sufficient capital. 87. Omaha White Lead Company. In 1878, S. E. Locke secured a license from the Adams White Lead Company to operate a plant in Omaha, Nebr., and to this end organ- ized the Omaha White Lead Company which was com- posed of a number of Omaha capitalists. Besides the manufacture of white lead the company dealt in glass and painters' supplies. 74 THE CARTER PROCESS. 75 76 THE LEAD AND ZINC PIGMENTS. A banker by the name of H. W. Yates, being one of the largest owners, placed his nephew, S. B. Hayden, in charge of the company. Owing, however, to the lack of experi- ence the company became financially embarrassed. 88. Formation of the Carter Company. Levi Carter, at this time a member of the firm of Coe & Carter of Omaha, large railroad contractors, saw the possibilities of the process and secured in 1885 a controlling interest in the plant which then had a capacity of about four hundred tons yearly. The reorganized company, the name of which had been changed to the Carter White Lead Com- pany, encountered exceedingly bitter competition from the then recently consolidated white lead interests but, due to the indomitable character and perseverance of Mr. Carter, the company managed to keep the plant in operation with a continued improvement of the products produced until it was destroyed by fire in 1890. Profiting by the experi- ence obtained, new capital was secured and a plant of about seven thousand tons yearly capacity was immediately built in East Omaha by Mr. Carter, which began operation in the fall of 1892. 89. The success with the new plant was immediate, the enterprise proving so profitable that the building of a large plant in Chicago was decided upon, and which was com- pleted and put in operation in 1896, having a capacity of about fourteen thousand tons. Later a plant of about five thousand tons capacity was built in Montreal with the aid of Canadian capital. 90. Underlying Principles. The principles underlying this process are the same as in the old Dutch process, but by increasing the area of attack and the use of a more concen- trated supply of carbon dioxide, and the continued removal of the crust of white lead from the metal, the corrosion into white lead is accomplished in approximately twelve days, THE CARTER PROCESS. 77 78 THE LEAD AND ZINC PIGMENTS. whereas as the old Dutch process requires one hundred to one hundred and twenty, and the percentage of converted lead is eighty-five to ninety per cent as against about seventy-five per cent in the older process. 91. Granulating the Lead. The lead, which is of the same nature and grade as used in the Dutch process, is melted in a large kettle holding about ten thousand pounds, the pigs of lead being conveyed and dumped into the kettle by means of an endless chain. The stream of molten lead as it flows from the kettle encounters a jet of high pressure steam which disintegrates it into a coarse granular powder, which collects in the hopper-shaped bottom of the large blow room and is discharged into truck cars placed underneath. By the use of a slight vacuum any fine particles of lead dust are conveyed to a dust collector, thus avoiding danger to health in the loading of the cars. Charges of about four thousand pounds of this " blown lead " are placed in large wooden drums ten or twelve feet long, and about five or six feet in diameter. Around the tub at each end is a heavy iron hoop resembling a car-rail; these rest on roller bearings; around the center of the tub is another hoop, containing gear-teeth, which in turn mesh into the gears from the large driving shaft which runs the entire length of the corroding room, which contains nearly three hundred of these tubs or drums. The drums revolve slowly, making about six revo- lutions per hour, which causes the lead to continually shift position, that which is carried up the side of the drum rolling again to the bottom. This exposes each granule to the action of the corroding agencies and also by abrasion wears off the coating of white lead as fast as it forms, continually exposing fresh metal to be acted upon. 92. Corrosion. Dilute acetic acid and water are sprayed into the drums at intervals during the first three days, 30 per cent acetic acid being used, which has been reduced THE CARTER PROCESS. 79 80 THE LEAD AND ZINC PIGMENTS. one part with four parts of water. The amount used dur- ing the corrosion being one and three-quarters to two pounds of 30 per cent acetic acid per hundred pounds of metallic lead, considerably more than used in the Dutch process. A current of purified flue gas containing eight to ten per cent of carbon dioxide is passed through the cylinders, entering through the center of one end and coming out at the other. This gas is obtained by burning a very high grade of coke, low in sulphur, under the boilers, and is puri- fied by passing it through a compartment filled with bog iron ore, which removes all traces of sulphur, and also gives an opportunity for any soot particles to deposit. The tem- perature of the gas will vary between 150 and 200 F., as it is delivered to the drums. In order to secure an even and uniform corrosion the partially corroded mass is removed from the drums about the sixth day, and run through a pulverizer to reduce any lumps or balls that may have been formed. 93. The disintegrated material is then replaced in the drums and the conversion finished, the entire corroding process taking about twelve days. Great care must be exercised in not adding too large quantities of water or acid, or granulating the lead too fine in the first place, as in such instances the mass becomes so pasty as not to work prop- erly in the drums, or is " drowned out " as the workmen term it, which results in an almost entire cessation of chemical action, and can only be " started " again by mixing with a large amount of fresh lead and recorroding. The chemical actions that take place are entirely similar to those of the old Dutch process and in fact, the Carter process differs not at all in the fundamental principles from' the older process. 94. Washing and Floating. The finished product on removal from the drums is run into large tanks, where it is THE CARTER PROCESS. 81 82 THE LEAD AND ZINC PIGMENTS. agitated with water and then washed through a rotary screen to remove coarse particles, the finer material is then passed through a drag and float system to remove the last trace of blue lead and as much of the crystalline lead as possible. The separated white lead is washed thoroughly to free it from acetic acid, and the more or less insoluble acetates of lead, which are afterwards precipitated from the wash waters with carbonate of soda. The washed lead is allowed to settle in large tanks, the supernatent water drawn off, and the thick paste pumped onto copper drying pans and dried in the usual manner. 95. Chemical Composition. In chemical composition the ratio of carbonate to hydroxide is fairly constant, the following table showing the composition every two weeks for a period of twelve months. Carbonate. Hydroxide. May 31 1906 73 59 26 41 June 15, 1906 75 23 24 77 June 30, 1906 July 15, 1906 July 31, 1906 76.26 71.89 73 23 23.74 28.11 26 77 Aug. 15, 1906 69.65 30 35 Aug. 31, 1906 72.86 27.14 Sept 15 1906 71 16 28 84 Sept 30 1906 73 84 26 16 Oct 15 1906 75 11 24 89 Oct 31 1906 . . 72 50 27 50 Nov. 15, 1906 75 29 24 71 Nov. 30, 1906 '. Dec. 15, 1906 74.68 77.41 25.32 22.59 Dec. 31, 1906 76.81 23.19 Jan 15 1907 74 44 25 56 Jan 31 1907 74 93 25 07 Feb 15 1907 ... 75 77 24 23 Feb. 28 1907 77 11 22.89 Mar. 15, 1907 75.65 24.35 Mar. 31, 1907 74.62 25.38 Apr. 15, 1907 76.32 23.68 Apr 30 1907 77 72 22 28 Average 74 61 25.39 THE CARTER PROCESS. 83 84 THE LEAD AND ZINC PIGMENTS. It will be noted that the percentage of carbonate is slightly higher than in the average grades of old Dutch white lead, which together with its freedom from blue lead explains its clearness of tone. In the practical paint tests, made by the writer, little or no difference has been observed in its wearing or service value, as compared with the best brands of old Dutch lead; in application it works slightly easier under the brush, and remains in suspension better in the oil. 96. Characteristics. As produced by this process, Carter lead is usually whiter than old Dutch white lead, the parti- cles are much finer and of a more nearly uniform size, and, therefore, 100 pounds of Carter lead in oil will cover a con- siderable larger area of surface than 100 pounds of old Dutch lead when reduced alike with oil. The body or hid- ing power, however, is not at all times quite equal to that of the older lead, although the surface is distinctly a cleaner, clearer white. 97. Success. This process having proven very successful financially, a plant was built along similar lines by Harrison Brothers & Company, Philadelphia, in which the Carter Company was interested in a way, and assisted towards the construction of the plant. Shortly afterwards another plant was built at Buffalo, by Kellogg & McDougall, of about three thousand tons capacity, with the assistance of the same engineer who constructed the Harrison plant. Both of these plants have been eminently successful. -' CHAPTER VIII. THE MILD PROCESS (ROWLEY). 98. , Derivation of Name. The " Mild Process " for manu- facturing white lead is the only one in practical operation in this country which does not require the use of strong acids, alkalies, or other chemicals in the process of manu- facture, every trace of which must be removed from the finished product, necessarily involving certain purifying processes which in themselves are expensive and costly and if incomplete will cause a marked deterioration in the quality of the lead produced. 99. This process derives its name from the very fact that it is the mildest, simplest, most natural process possi- ble for the manufacture of white lead metallic lead, air, water and carbon dioxide gas being the only substances required. This process results in the production of one uniform product, a strictly pure basic carbonate of lead of approved chemical and physical constitution and of a whiteness, density and covering power not exceeded by that of any other make of white lead. 100. Early Attempts. The proposition of reducing gran- ulated lead by attrition in the presence of water and car- bonating the product obtained is a comparatively old idea and numerous attempts have been made and several patents have been taken out embodying this idea, not only in England and on the Continent but in this country as well. Pulsifer in his History of Lead records the attempts of Welch and Evans of Philadelphia in 1814 who patented a quick process of making white lead, by which granulated 85 THE LEAD AND ZINC PIGMENTS. THE MILD PROCESS (ROWLEY). 87 lead was placed in lead-lined barrels, which were made to revolve. The barrels were partly filled with water, and the particles of lead removed by attrition were oxidized by oxygen from the air, and this oxide carbonated by the introduction of carbon dioxide produced from burning charcoal. Also that of Smith Gardner, of New York, who took out a patent in 1840, for a process by which " granu- lated or small pieces of lead were introduced into vessels lined with sheet lead, and partially filled with water, and so arranged that they could be revolved or manipulated in such a manner as to subject the lead to continual attri- tion. The vessels were kept closed, and during the process carbon dioxide and air were introduced." 10 1. Solution by W. H. Rowley. Owing to a lack of knowledge of the correct principles by which this process must be conducted in order to be successful all of these earlier attempts failed when put to practical test on a commercial scale and it remained for Mr. Willson H. Rowley of St. Louis, Mo., to overcome the difficulties encountered by his predecessors and put this type of process into successful operation on a large scale. 102. Early Training. Unlike the majority of inventors who have worked along the line of attempting to render the process of white lead manufacture more rapid and economical, Mr. Rowley had the advantage of many years experience in the white lead industry, having been connected with the Carter White Lead Company, besides having had a close acquaintance with the old Dutch Process of manu- facture through employment with the Southern White Lead Company with which his father, Mr. G. A. Rowley, was connected for some years. 103. Atomization with Superheated Steam. Mr. Rowley's predecessors had been able to obtain only a coarsely granulated lead to start with, which could be reduced to 88 THE LEAD AND ZINC PIGMENTS. THE MILD PROCESS (ROWLEY). 89 oxides or basic hydroxides only with great difficulty by attrition in the presence of water and air. His experi- ments, however, led him to conceive the idea of atomizing or disintegrating the lead with the aid of a current of high pressure superheated steam. His experiments along this line which were carried out on an extensive scale were completely successful and the several patents covering the processes of manufacture were granted Mr. Rowley in 1902 and 1903. 104. Growth of Process. Immediately thereafter a plant of approximately 1000 tons annual capacity was equipped and placed in operation early in the same year. The product found immediate consumption and by 1907, the sales having outgrown the producing capacity of the plant, it was found necessary to enlarge the factory or build a new one. The latter proposition was the one decided upon as the most feasible and resulted in the building of the present plant in Detroit, additional capital having been interested in the enterprise, and the name changed from the Rowley White Lead Company to the Mild Process White Lead Company, affiliated with the Acme White Lead & Color Works. The present plant is one of the largest and most modern equipped white lead factories in the world, having when fully equipped an annual capacity of over 5000 tons. The mechanical de- vices installed for reducing the amount of labor to a min- imum in the handling and conveying of the lead in the different stages of manufacture render this process the most economical of any in use and at the same time the most sanitary. 105. Simplicity of Process. The process by which this simple and progressive conversion from metallic lead into white lead is accomplished is extremely simple. The cor- roder is not obliged to use the extremely highly refined 90 THE LEAD AND ZINC PIGMENTS. THE MILD PROCESS (ROWLEY). 91 lead used by the Dutch process, but may use an ordinary good grade of lead; some of the hard grades of lead, how- ever, do not suffer conversion as easily as the softer vari- eties, although there is apparently little or no difference in the color and quality of the product obtained. 106. Atomizing the Lead. The lead is melted in large kettles holding 5,000 pounds each from the bottom of which it is conveyed through heated pipes to the " atomizers, " which are similar in principle to the ordinary laboratory blast lamp. In the atomizers the molten lead comes in contact with a current of steam superheated to a temper- ature higher than the melting point of the lead. The expansive force of the steam disintegrates the lead into exceedingly minute particles, which immediately solidify. Each of the four atomizers in the present plant has a capacity of 1,500 pounds of atomized lead per hour. The streams of atomized lead are directed downward in a large steel room some two stories in height, in the bottom of .which are about two feet of water. By means of a drag- and -screw conveyor the lead, in the form of a very heavy mud, is delivered from the blow-basin to the pump-feeder, which keeps the particles suspended in the water so that the material can be handled by a rotary pump, which forces the lead and water through a pipe line to the float boxes, where the lead is deposited in the desired compart- ments, the water flowing back to the blow-basin again, which insures against any loss of lead. There are five float boxes in each of the two lines, and when filled each line has a capacity of 250,000 pounds of lead. 107. Oxidizing and Hydrating. By means of gate valves the lead is discharged into the oxidizers directly under- neath, six to ten thousand pounds to the oxidizer as desired. The requisite amount of water is added, a current of air under low pressure from a fan introduced and the 92 THE LEAD AND ZINC PIGMENTS. THE MILD PROCESS (ROWLEY). 93 contents agitated mechanically for twenty-four to thirty- six hours. The particles of lead during the atomizing process have already become coated with a thin pellicle of suboxide which renders the lead very active chemically, so that within a very few hours after the beginning of the agitation a strong chemical action sets in accompanied by a marked rise in temperature, resulting in the formation of any of several basic hydroxides of lead as may be desired, which will vary in color from greenish yellow through the different shades of yellow orange, to a brownish orange, these results being secured by varying the amount of water, air, agitation and control of the temperature. Some of these basic hydroxides are much more suitable for white lead making than others. At the expiration of the twenty- four to thirty-six hours, according to the size of the charge, about eighty to ninety per cent of the lead will have been converted and the oxidizers are discharged into a trough emptying into the float system, where by means of an inclined drag, two agitator tubs and a float-table the metal- lic lead is separated from the basic oxide and returned to the float boxes, to be added to a fresh charge of atomized lead in the oxidizers. 1 08. The separated basic hydroxide is conveyed by means of another rotary pump to the fourth floor where it is deposited in a series of large tanks, the water being returned to the separating system again thus avoiding any mechanical loss of lead. 109. Carbonating. The above-mentioned tanks also act as a storage for the basic hydroxide, which is drawn as required into the carbonators located on the floor below. The carbonators are large cylinders somewhat similar to the oxidizers in construction but of less capacity; in them the basic hydroxide of lead is agitated in the presence of flue gas containing about eighteen per cent of carbon 94 THE LEAD AND ZINC PIGMENTS. THE MILD PROCESS (ROWLEY). 95 dioxide. By means of scrubbers the flue gases are thor- oughly cooled, desulphurized and freed from soot particles. For the first twenty-four hours no apparent change is noticed in the color but in the next twelve hours the change is very rapid and is accompanied by a remarkable swelling or increase in volume of the mass, the carbonators requiring to be watered at short intervals, both on account of the swelling of the mass and the combining of the water with the lead. In approximately thirty-six hours the carbonation is complete 4 , resulting, if the operation has been properly conducted, in an exceedingly white basic carbon- ate of lead of very closely the theoretical composition. As there are no impurities present, no washing or floating is necessary, and on withdrawal from the carbonators the white lead is pumped directly onto the dry pans arid dried in the usual manner; when dry it crumbles instantly under the slightest pressure into a very fine powder and there- fore does not have to be run through a disintegrating mill before it is barreled dry. no. Control. The " Mild Process " is under a much more complete control than any of the other processes, as any slight variations that may take place in the chem- ical actions involved can be easily corrected and counter- balanced. At first thought it might seem that a white lead produced in this manner would consist largely of a mixture of hydroxide and normal carbonate, but such is not the case as may be demonstrated both by a micro- scopical examination and by a close study of the process of formation of the white lead. The composition of the basic hydroxide formed indicates a hydration of ten to twelve per cent, or about one-third of the amount to be found in the finished white lead. Therefore the larger part of the hydroxide portion of the molecule is formed during the carbonating process and this has much to do 96 THE LEAD AND ZINC PIGMENTS. THE MILD PROCESS (ROWLEY). 97 98 THE LEAD AND ZINC PIGMENTS. with the large apparent increase in volume, as it is possible by a long continued carbonation to form a very crystal- line carbonate containing very little hydroxide, the oper- ation being accompanied by a considerable diminution of apparent volume. in. Advantages of Process. From a manufacturing standpoint this process has much to commend it, espe- cially as regards the following items : 1. The process is not restricted to a specially refined lead. 2. It is under complete control. 3. It results in conversion into white lead of all of the metallic lead during the process, avoiding any metallic residues whatever. 4. The white lead produced is of a uniform grade no tailings or sandy lead. 5. No mechanical losses of lead as the same water is used over and over again, there being no impurities of consequence present. 6. Manual labor is reduced to a minimum, the conveying of the material in the process being accomplished entirely by gravity and pumps. 7. The process can be made entirely sanitary as the work- men need not come in contact with the lead in any part of the process, nor is there any dust produced that contains lead particles, except in the final barreling operations. 8. Nothing is required in the manufacture, aside from the machinery, power and labor, that involves any expense except the cost of lead itself. 112. Not a Precipitation Process. The Mild process should not be confounded with any of the so-called precipi- tation processes, as it bears no analogy to them, the lead not being in solution at any stage of the process. As com- pared with other white leads, Mild process white lead is THE MILD PROCESS (ROWLEY). 99 100 THE LEAD AND ZINC PIGMENTS. whiter than old Dutch white lead, being equal to Carter lead in this respect. The particles are of very uniform fine- ness, being slightly smaller than Carter, and much finer than old Dutch lead. Although very soft and chalky in appearance and " feel," it is as dense and does not require any greater quantity of oil in the grinding and little, if any, more in reducing to painting consistency, than old Dutch or Carter leads, and is sold in the same sized kegs. Under the brush it works easier, and owing to the uniform fineness of the particles, it covers more surface with an equal hiding power than any old Dutch process lead that the writer is familiar with. CHAPTER IX. MATHESON PROCESS. 113. Matheson white lead is the product of one of the newer methods of corroding, which are popularly but inaptly called " quick processes " in order to distinguish them from the older or Dutch process. 114. Nature of Process. In all of the so-called quick processes, the metal is reduced to smaller particles, and, therefore, exposes a greater surface to the action of the corrosive elements than is the case with the " buckle " used in the Dutch method, so that the corrosion of a given weight of metal is more quickly accomplished. However, the corrosion of so much lead as is exposed directly to the action of the corroding agents must progress substantially as rapidly in either method, and if the newer processes used the " buckle " instead of smaller units, their corrosion would be no quicker than by the Dutch method. Some of them, and notably the Matheson, would, however, still differ from the Dutch process in being practically continu- ous and permitting the recovery of the carbonate as rapidly as made, and to that extent they could justly be designated " quick " in contrast with the older method, in which more than one hundred days must elapse before the basic car- bonate of lead, or white lead (which has been accumulating on the buckles as the water and acetic acid vapors and car- bonic acid gas force their way through the outer layers of carbonate and continue to attack the inner core of metallic lead until they can no longer reach it) can be made avail- able for marketing. 101 102 THE LEAD AND ZINC PIGMENTS. FIG. 38. MELTIXG ROOM. MATHESON PROCESS. FIG, 39. CORRODING TANKS, MATHESON PROCESS. MATHESON PROCESS. 103 115. Development in United States. Another point of difference between the Matheson process and some of the older methods is that it is more controllable, and can thus be made to yield a product more uniform than is obtained by those methods which are not open to inspection or regu- lation while they are working. The process itself is modeled upon some of the processes in use in France, but was modified by Mr. Ellert W. Dahl, a Norwegian chemist, who introduced it into this country in about 1893, and who for a number of years marketed his product here under the name " Premier White Lead." In 1898, it was purchased by the William J. Matheson Company, and has since been known under their name. The process has been subjected to some changes in its mechanical detail which have been developed on the larger scale upon which it has been manu- factured, but the product upon analysis does not differ from its original composition, which conforms fairly closely to the accepted chemical formula for white lead, and its chemical behavior is comparative with that of any other hyd rated carbonate of lead that is properly made. 1 1 6. Characteristics of Matheson Lead. Its physical characteristics are widely different, however, as it is whiter and finer, and is free from the gritty particles of the Dutch process, which are the result of the long exposure to con- tinued action of the acid and gas, of the outer layers of car- bonate formed on the " buckles." In specific gravity, Matheson lead is somewhat lighter than Dutch process, its bulk being correspondingly greater and its oil carrying power exceeding that of the heavier leads by about 33 J per cent. In other words, 88 pounds of Matheson dry lead will require about 60 pounds of oil to put into the form of paint, properly reduced, and 92 pounds of Dutch process lead will require, 45 pounds of oil to make a paint of equal consis- tency. The resultant product measures over 9J gallons 104 THE LEAD AND ZINC PIGMENTS. FIG. 40. WASHING PRESSES. MATHESON PROCESS. FTG. 41. SETTLING TANKS. MATHESON PROCESS. MATHESON PROCESS. 105 with Matheson lead, to less than 8 gallons of the Dutch, or about 25 per cent more volume of paint, which is claimed by the manufacturers to cover at least a correspondingly greater surface with equal opacity. It should be remem- bered, however, that the above increase in volume is due to the increased amount of oil used. 117. Manufacture. In the Matheson process, the metallic lead is " feathered," or brought into a form resembling a sponge in structure, by running the molten metal into water. This lead is brought into contact with dilute acetic acid in large corroding tanks or tubs. In the presence of air and steam a basic acetate of lead is produced, this, in turn, being transformed into hydrated carbonate by con- tact with carbonic acid gas obtained from coke furnaces. The carbonate is then repeatedly washed, after which most of the water is removed by filter presses, and it is then dried in vacuum driers. The whiteness of the lead results from its complete corrosion, and the consequent absence of " blue " lead in the carbonate, as well as to its freedom from tan-bark or other organic matter. The grinding process does not differ from that employed with other leads, except as to the greater amount of oil required, to which reference has already been made. Special precautions must be observed in freeing the white lead from residual acetates, which if not completely removed will be more than likely to give serious trouble when used in paints. 118. During the corrosion of the lead by this process, there is produced a considerable quantity of a crystalline practically insoluble basic acetate, which the author under- stands is separated and calcined into litharge, together with a certain amount of metallics which are difficult of conversion affording a most excellent grade according to the samples examined by the writer. 106 THE LEAD AND ZINC PIGMENTS. FIG. 42. VACUUM DRIERS AND FILLING MACHINE. MATHESON PROCESS. FIG. 43. PULP MILL. M \THFSON PROCESS. MATHESON PROCESS. 107 119. Uses. Several examinations of Matheson - lead by the writer have shown it to be quite uniform in compositien, approximating 72.50 per cent carbonate to 27.50 per cent hydroxide. The product is of exceptional whiteness, and free from impurities other than basic acetates of lead. It not only takes a much larger amount of oil in grinding than other leads, but a much larger amount in reducing to paint- ing consistency. For these reasons the writer understands that it finds its larger use in mixed paints and semi-paste goods, where these features are desirable, rather than as strictly pure lead in oil. Its hiding power or opacity is excellent when its spreading qualities due to the large amount of oil required are considered. CHAPTER X. THE SUBLIMED LEAD PIGMENTS. 120. Sublimed White Lead. The invention of sublimed white lead is due to Mr. E. 0. Bartlett, who, while manager of the Keystone Zinc Company's works at Birmingham, Pa., in 1866, became impressed with the idea that a lead pigment could be made by the same process as that used for making zinc oxide, i.e., by sublimation of the ore in an oxidizing fire and collection of the condensed product in cloth filters or bags. 121. Early Development. In the latter part of the sixties he associated himself with the firm of John T. Lewis & Bros., of Philadelphia, for the purpose of carry- ing out experiments along that line. A small plant was built which was afterwards removed to Joplin, Mo., and enlarged under the financial backing of Mr. Lewis, and the experiments continued on a commercial scale. The loca- tion of Joplin was chosen because that city was in the heart of the enormously productive mining region of Southwestern Missouri, and also because the lead ores produced in that section were exceedingly free from other metals yielding volatile oxidation products which would contaminate the sublimate. The single exception was zinc which is, consequently, found as oxide in all sub- limed white lead at present on the market to the extent of approximately five per cent. 122. The first patent for the process was taken out in 1870 and since that time there has been an almost contin- uous series of patents for improvements in the process 108 THE SUBLIMED LEAD PIGMENTS. 109 110 THE LEAD AND ZINC PIGMENTS. taken out at short intervals. The pigment has been on the market commercially in this country for twenty-five years, although the quantity produced was relatively small until 1900. Since that date the production of sub- limed white lead has rapidly increased. 123. Sublimation of the Ore. The ore used in the manu- facture of sublimed white lead is a high grade of galena (native lead sulphide) which has been crushed and " jigged" so as to free it from accompanying rocks. This separation is complete as regards interfering compounds, except, as mentioned above, in the case of zinc. The finely pulver- ized ore is fed into the furnace along with the necessary amounts of fuel and fluxes. The furnaces are of a special type which is a compromise between the furnace employed for zinc oxide and the blast furnace used in smelting roasted lead ores. The fire box has a circular water jacket supplied with tuyeres which inject a powerful hot-air blast from all sides. The intense heat generated instantly volatilizes the lead sulphide in gaseous form, which, as it rises from the incandescent hearth, comes in contact with the oxygen of the air from the blast, and at the enormously high temperature, is oxidized to what the manufacturers claim is an oxysulphate, which, after rising several feet in the cylindrical furnace lined with fire brick, passes into a large transverse brick lined flue. 124. Condensation of Fume. The heat of the combus- tion and oxidation is so great that the furnace and trans- verse flue or chamber are completely filled with flame and hence it is difficult to decide at just what point the com- bination is complete. After traversing this long horizontal chamber, the vapor or " white fume " as it is usually called, passes through a series of large air-cooled iron pipes or flues and through what are termed the " goose- necks," which are so arranged that the coarser particles THE SUBLIMED LEAD PIGMENTS. Ill 112 THE LEAD AND ZINC PIGMENTS. FIG, 46. GOOSENECKS. PICHEB LEAD COMPANY. THE SUBLIMED LEAD PIGMENTS. 113 containing impurities settle out and the " white fume " itself floats along, aided by powerful suction fans, for a total distance of between 700 and 1000 feet when the gases and " fume " are sufficiently cooled to permit of the collection of pigment particles in fabric condensers, allow- ing the gases to escape through their meshes. 125. Bag Room. The condensers or collectors are in the form of long bags, hung perpendicular in a large build- ing known as the bag house. The bags are shaken at regular intervals to detach the pigment from the sides, the pigment collecting below the bags in large hoppers from which it is drawn into steel lined carts on the floor below and packed in barrels which hold about five hundred pounds. The atmosphere of the bag rooms is unbearable except for short intervals by reason of the sulphur dioxide in the escaping gases. 126. Uniformity of Product. Naturally, the ratio of the lead sulphate to lead oxide in sublimed white lead is dependent largely upon three factors, the nature of the ore fed into furnaces, i.e., whether it is entirely lead sulphide ore or whether other lead compounds are added; the amount of air which comes in contact with the ore ; and the temperature at which the reactions take place in the furnace. These conditions being under control of the manufacturer, the product can be kept quite uniform and of the desired composition under favorable furnace con- ditions, although it is probable that atmospheric changes exert more or less influence on the nature of the finished product. The range of variation in samples examined by the writer is as follows : Lead sulphate 75 to 80 per cent Lead oxide 20 to 14 per cent Zinc oxide 5 to 6 per cent 114 THE LEAD AND ZINC PIGMENTS. FIG. 47. BAGROOM. PICKER LEAD COMPANY. THE SUBLIMED LEAD PIGMENTS. 115 127. Chemical Constitution. As heretofore stated, sub- limed white lead is claimed to be a basic sulphate of lead. In substantiation of this claim it is argued that all of the lead oxides known to chemists are red or brown and a white oxide of lead is as yet unknown; further, that a mixture of sublimed white lead in oil dries normally in about the same length of time as required for corroded white lead, two days, while a mixture of lead sulphate, lith- arge (lead monoxide) and zinc oxide, in the same propor- tions as those shown by an analysis of sublimed white lead, dries in from ten to twelve hours. Recent work by Chevalier indicates that the fume from a furnace roasting lead sulphide has the formula Pb 3 S 2 9 , apparently a com- plex of two molecules of sulphate with one of oxide. The conditions of the production of the two fumes are not essentially different and it is claimed by the sublimed white lead makers that they have isolated this compound in a state of purity although not on a commercial scale. If the existence of this basic sulphate is a fact, then com- mercial sublimed white lead is a mixture of it with a vary- ing amount of neutral lead sulphate. These arguments, while presumptive, can hardly be accepted as entirely conclusive. The reactions and com- binations that take place at exceedingly high temperatures are but imperfectly understood and it is entirely possible that we may have aggregates formed at high temperatures in which the components are so intimately associated that they are apparently chemically combined without such actually being the case. 128. Yearly Production. Many improvements have been made in the process of manufacture during the past few years, which have resulted in an increased demand for sublimed white lead on the part of the paint manufac- turers as shown by the table on page 117. 116 THE LEAD AND ZINC PIGMENTS, THE SUBLIMED LEAD PIGMENTS. 117 Year. Production in i>oimds. Value. 1902 9,465,500 $449,611.00 1903 8,592,000 386,640.00 1904 12,954,000 550,589.00 1905 13,954,000 732,585.00 1906 15,974,000 958,440.00 1907 17,400,000 1,026,600.00 129. Physical Characteristics. As prepared at the present time, sublimed white lead is a very finely divided substance entirely amorphous in structure. In color it is not quite as white as a good white lead. This may in part be accounted for by the fact that it contains about 0.06 per cent of ferric oxide. Its specific gravity is slightly less than corroded white lead, being 6.2. The average diam- eter of the particles is about one thirty-five thousandth of an inch while those of white lead vary in the same sample between one four hundredth and one fifteen thousandth of an inch. It is for this reason, probably, that paints made wholly or largely of sublimed white lead show brush marks more plainly than white lead paints. It requires more oil in grinding than ordinary white lead but not sufficient to give it excessive spreading qualities. 130. After having once been packed together in barrels, it is much less poisonous than corroded white lead ; which fact is not of so great moment as formerly because with modern appliances for ventilation in the manufacturing and painting establishments and increasing cleanliness on the part of the workmen, lead poisoning has largely ceased to be the formidable evil that it once was in this country. 131. Uses of Sublimed White Lead. Because of the exceeding fineness of its particles, sublimed white lead is seldom ground straight in linseed oil but it is generally ground with other pigments, and hence finds its largest 118 THE LEAD AND ZINC PIGMENTS. use in the manufacture of mixed paints; and because this fineness allows the pigment to remain in suspension in the vehicle, it is a favorite constituent for dipping paints. Owing to its comparative inertness to sulphurous vapors and gases and having a hiding power substantially equal to white lead, sublimed white lead is rapidly coming into extensive use in railroad specifications. It is also finding a wide use in the structural iron and steel paints. 132. Chalking. The objections frequently urged against this pigment are that it chalks, that it is not equal in whiteness to white lead, and that paints containing it thicken up and work stiff and greasy in cool weather or during the cooler portions of the day. While chemist at North Dakota Experiment Station, the writer was closely associated with Professor E. F. Ladd in the conducting of a large number of practical exposure tests in which sub- limed white lead was applied straight and in a number of combinations. As a result of these and other practical tests the writer believes that sublimed white lead does chalk even more, possibly, than old Dutch process white lead, but the chalking is of an entirely different character. When ordinary white lead begins to chalk vigorously, it will be found that the paint film has lost its elasticity, and has become brittle and friable throughout; also, that the luster of the film under the chalk-like coating has entirely disappeared. A sublimed white lead film, on the other hand, retains much of its original elasticity under the chalk coating, indicating that the disintegration is con- fined to the surface, and it is possible that the retention of the " chalk " on the surface gives some protection to the unaffected coat below. When used with other pigments, the chalking of sublimed white lead is retarded and it behaves almost exactly like old Dutch process white lead under similar conditions. THE SUBLIMED LEAD PIGMENTS. 119 133. Comparative Whiteness. Sublimed white lead, when applied straight, is not of equal whiteness as compared with old Dutch white lead, having a slightly yellowish, creamy tone. After one year's exposure, however, the result is reversed. The sublimed white lead is then the whiter and has lost its creamy tint; while the old Dutch process white lead has taken on its customary grayish tone. Paints containing a large percentage of sublimed white lead, according to the experience of the writer, show a distinct tendency to thicken and work stiffer under the brush during cool weather. This may be due to the exceeding fineness of the particles. If so, the change is physical rather than chemical and hence not a serious matter when handled understandingly by the master painter and when it is considered that most painting is done in warm weather. 134. Inertness toward Tinting Colors. Due to the chemical stability of sublimed white lead, it has little injurious effect on the tinting colors which it may be ground with: as is well known, chrome yellow, chrome green, Prussian or Chinese blue and some organic colors do not give permanent tints when ground with white lead, due to chemical interaction between the color pigment and the white lead. Addition of chemically inert pigments lessen the action in the case of white lead but do not entirely inhibit it. For this reason sublimed white lead has come widely into use in mixed paints, especially in the tints replacing a portion of the white lead and thus increasng the permanence of the tint. 120 THE LEAD AND ZINC PIGMENTS. SUBLIMED BLUE LEAD. 135. Sublimed blue lead is a pigment finding considera- ble use as a protective coat for metallic surfaces. Its manufacture is by methods analogous to those employed for the manufacture of sublimed white lead, but in this case the sublimation is conducted in a reducing instead of an oxidizing atmosphere. 136. Properties. Because of the large amount of un- saturated sulphur compounds which it contains, the sublimed blue lead coat is quite different from that of any other paint made with linseed oil. Apparently the sul- phides and sulphites contained in it affect the oil so that, after drying, it is comparatively immune from action by coal gas. However useful the presence of these ingredients may be after the coat is applied, they are a considerable detriment in the eyes of the paint maker, as this material has a very great tendency to cause the paint to thicken, or liver, if allowed to stand after being thinned. For this reason, sublimed blue lead is not, as a rule, sold straight in liquid form, but is packed either as paste or else ground with a percentage of graphite or red lead. 137. Composition. In composition, sublimed blue lead varies somewhat, but the analysis is about as follows: Per cent. Lead sulphate 50 Lead oxide 35 Lead sulphide 5 Lead sulphite 5 Carbon 3 Zinc oxide . . 2 100 The production, in 1907, was 2,422,000 pounds, valued at $135,632. THE SUBLIMED LEAD PIGMENTS. 121 SUBLIMED LEAD OXIDE. 138. Sublimed lead oxide is a sublimate obtained as a by-product from the manufacture of litharge by the hearth or cupellation process. It is an exceedingly fine, sulphur- yellow material, and desirable for many purposes, particu- larly color making. Unfortunately, it is not, as yet, produced as a regular article of commerce on a large enough scale to attract atten- tion, although litharge manufacturers are working toward this end. CHAPTER XL WHITE LEAD MANUFACTURE IN EUROPE. 139. Comparative Costs of Manufacture. The manu- facture of white lead in England and on the Continent is conducted in a much different manner than in this country. The majority of European white lead plants are much smaller than the average plants in the United States, and, especially in England, are conducted on a much more con- servative scale with regard to labor-saving machinery and appliances; so, notwithstanding a lower European wage scale, American white lead plants undoubtedly enjoy a lower cost of production. Government regulations safe- guard as carefully- as possible the health of the employees, whereas in this country there are substantially no restric- tions, although there is at the present time a manifest tendency to legislate in this direction. 140. English Regulations. The following abstracts from the English regulations (1906), in addition to those quoted in the chapter on White Lead Poisoning, will afford some idea of the safeguards placed around the employees who work with lead products. " No dry lead color shall be placed in any hopper or shoot without an efficient exhaust draught and air guide, so arranged as to draw the dust away from the worker as near as possible to the point of origin." " Every person employed in a lead process shall be examined once each calendar month by the certifying sur- geon of the district, who shall have power to suspend from employment in any lead process." 122 WHITE LEAD MANUFACTURE IN EUROPE. 123 " Overalls shall be provided for all persons employed in lead processes, and shall be washed or renewed at least once every week." " No person shall be allowed to introduce, keep, prepare, or partake of any food, drink (other than medicines pro- vided by the occupier and approved by the certifying sur- geon) or tobacco in any room in which a lead process is carried on." 141. In England, the majority of white lead plants operate under the old Dutch process, although there are one or two plants which make use of modifications of the German Chamber process, which process will be discussed in a subsequent portion of this chapter. The Bischof process, used at Mond's Works at Brimsdown in Middlesex, has recently attracted considerable attention. The metallic lead is converted into an oxide by a simplified process and is then heated to 250 to 300 C., in a current of water gas, which reduces the lead to a black suboxide of unknown composition, which is treated with water, a yellow hydrate being formed and considerable heat being evolved. The hydrate is then converted into white lead by treatment with carbon dioxide gas. 142. English Methods. Many of the details of the old Dutch process, as carried out by the English, differ con- siderably from the practice in this country. Instead of using round buckles and placing them inside of the corrod- ing pots, the more usual English practice is to cast the lead into sheets or gratings, which are laid on top of the pots, which are much smaller than those in use in this country. The building of the stacks, which usually have a height of twenty-two to twenty-four feet, is usually done by women, who work barefoot, and who convey the tan-bark in bas- kets carried on their heads (see frontispiece). The lead is usually handled by cranes. The work of taking down the 124 THE LEAD AND ZINC PIGMENTS. WHITE LEAD MANUFACTURE IN EUROPE. 125 stacks is performed by men only, who wear a regulation costume (see Fig. 50), required by the Home-office to be worn by all workers in the white lead departments. The white lead must also be dampened before its removal from the stack rs attempted. This is in marked contrast with the practice in this country, where any sort of a costume is permitted, and in the several factories visited by the writer no attempt was made to keep down the dust in the stack operations. 143. Characteristics of English White Lead. As found on the market, English white lead in oil is much stiffer than the American product; this is due to the different method of grinding, where, instead of rotary buhrstone mills, powerful granite rolls moving at different speeds are used. The several English brands examined by the author showed evidence of most careful corrosion, resulting in great purity of color, almost theoretical chemical composition, and free- dom from crystalline or sandy lead. Newcastle-on-Tyne is one of the principal seats of manufacture. Other im- portant corroding centers are London, Glasgow, Chester, Bristol and Sheffield. 144. German Chamber Process. The more progressive German manufacturers use a modification of the Dutch process, which materially shortens the length of time required by the other process. The present method is probably an outgrowth of what was used at Klagenfurth, in Carinthia, for a great many years, dating back perhaps as far as 1835. White lead made by this process enjoyed a remarkably high reputation. This presumably was due, not so much to the method of manufacture, as to the very great purity of the lead used, which was produced from the mines at Bleiberg. 145. Klagenfurth Modification. The principal points of difference between the old Dutch process and the Klagen- 126 THE LEAD AND ZINC PIGMENTS. WHITE LEAD MANUFACTURE IN EUROPE. 127 furth modification consisted in the vaporizing of the vinegar or acetic acid by artificial heat and the production of the carbon dioxide by the fermentation of substances other than tan-bark or horse manure, usually grape skins or refuse from wine manufacture, the corrosion being effected in large closed chambers about one hundred feet in length, each chamber being divided into upper and lower compartments by a loosely constructed floor, through which warm air from below could readily pass. The lower compartments contained the furnace with flues leading to the room above. On the floor of the upper compartment were placed strongly constructed boxes containing the acetic acid or vinegar, and the fermenting material, such as grape skins, grape pulp, etc. 146. Above each box was a framework extending to the roof, containing numerous cross pieces, over which the sheets of lead were placed. The warm air from the furnace below, warming the contents of the boxes, not only vapo- rized the acetic acid, but also effected a vigorous fermen- tation of the grape pulp, liberating considerable amounts of carbon dioxide, which, with the water vapor arising with the acid, afforded all the requisites of the Dutch process. The lead being cast into considerably thinner sheets than was customary in the older process, and with a much more vigorous action of the corroding agents resulted in the shortening of the time of corrosion to six or eight weeks. The resulting white lead, after being freed from metal residues, ground, washed and dried, afforded a product of great whiteness, as this process assured entire absence of hydrogen sulphide with the attendant blackening of the lead. 147. Present German Methods. The present German chambers process may be regarded as the result of the gradual development of the Klagenfurth method, the 128 THE LEAD AND ZINC PIGMENTS. vaporization of the acid and the generation of the carbon dioxide being under direct control by the operator. The corroding rooms or stacks are approximately thirty feet long, twenty feet wide and fifteen feet high, the walls being covered with earthenware tiles for resisting the action of the acid vapors. The stacks are fitted with racks from which the strips of cast lead are hung as in the Klagenfurth process, six to eight tons being the usual stack charge. 148. The acetic acid is supplied in the form of vapor by evaporating diluted vinegar in iron covered pans set in brickwork, the vapors being conveyed in earthenware pipes to the stacks and distributed throughout the rooms by means of large perforated pipes. The carbon dioxide is produced by burning coke or charcoal in iron stoves, care being taken to secure as complete combustion as possible, the resulting gas being introduced into the stacks through the perforated pipes that disseminate the acid vapors, thereby securing a uni- form mixture of acid and gas. 149. Effecting the Corrosion. The formation of an amor- phous basic carbonate of lead, substantially free from neutral carbonate or crystalline carbonates, by the chamber process depends on the formation of a true basic acetate on the sheets of lead before the conversion into carbonate is begun. In order to secure the most desirable condi- tions, great care must be exercised in regulating the amounts and strength of the acid admitted, in the introduction of proper quantities of air, and in maintaining the proper temperature in the stack room. During the first twenty- four hours, acetic acid of five to six per cent strength may be distilled into the stack room; the second twenty-four hours the strength should be reduced to about one per cent, in order to prevent a too vigorous action on the lead due WHITE LEAD MANUFACTURE IN EUROPE. 129 to the increased warmth of the chamber. On the third and following days the strength of the acid should be further reduced, depending on the conditions observed in the stack. 0.5 to 0.7 per cent strength represents the more usual practice. 150. When distinctly perceptible drops of dissolved basic acetate have formed on the lead sheets, carbon dioxide should be admitted and the supply of atmospheric air reduced correspondingly. The formation of white lead proceeds rapidly, and in a short time the strips of lead are covered with a white coating. The best results are obtain- able by introducing the acetic acid, water vapor, and carbon dioxide in such amounts as will maintain a damp or slightly pasty feeling to this coating, necessitating entrance to the chamber at regular intervals, which, owing to the high temperature, often 60 to 80 C., will require the use of protective clothing and a means of artificial respiration on the part of the examiner. 151. Rapidity of Corrosion. As before stated, the success of the operation depends on the formation of a basic acetate of lead first, which is converted into basic carbon- ate and neutral acetate by the carbon dioxide and air. The neutral acetate reacts in turn with the metallic lead, forming more basic acetate with the assistance of the water vapor, which is converted into a further quantity of white lead or basic carbonate with a further quantity of carbon dioxide, more neutral acetate being formed. This cyclic reaction explains the diminution of acetic acid vapor required after the process is well under way. 152. The corrosion will be most rapid near the inlet openings for the vapors in the chamber and, therefore, the action will be completed near the bottom and center of the room before the strips near the walls and upper portion of the chamber are more than one-half or two-thirds corroded; 130 THE LEAD AND ZINC PIGMENTS. and, in order to secure the most desirable grade of white lead, the operation is stopped before complete conversion is secured in all parts of the chamber in order to avoid over- corrosion, entailing conversion into crystalline carbonates on the strips most vigorously acted upon. Under improved conditions the operation requires five to seven weeks, eighty to ninety per cent of the metallic lead being con- verted into white lead. The crushing, screening, grinding and washing operations are entirely similar to those in the old Dutch process. 153. Lack of Success in United States. Although the chamber process has been very successful in Germany and in the adjoining countries, attempts at introduction into the United States have failed entirely. Two reasons may be assigned for this; first, lack of intimate knowledge on the part of the promoters of all the fine points to be observed in controlling the corrosion, resulting in a product not at all uniform in composition, while, on the other hand, the long experience of the German chamber manufacturers has enabled them to control the details of their process successfully; second, lack of economy of the chamber pro- cess as compared with the Dutch process in this country, the latter undoubtedly being on a much more economical basis here than in Europe. 154. In Montreal, Canada, a white lead plant has recently been built which operates under a modified form of the chamber process, and as there is only one other white lead in Canada, it should at least be moderately successful. 155. The French, or Thenard's Process. The practica- bility of this process was first demonstrated about 1801 by Thenard, a French chemist, who discovered that if carbon dioxide was passed into a saturated solution of basic lead acetate that white lead or basic carbonate of WHITE LEAD MANUFACTURE IN EUROPE. 131 lead was precipitated and a certain amount of neutral lead was regenerated which could again be converted into basic acetate, the process being exemplified by the follow- ing equations : 2 PbO(litharge) +Pb(C 2 H 3 2 ) 2 (lead acetate) = Pb(C 2 H 3 2 ) 2 2 Pb(OH) 2 (basic lead acetate) 3 Pb(C 2 H 3 2 ) 2 2 Pb(OH) 2 +4 C0 2 = 2 [2 PbC0 3 Pb(OH) 2 ] (white lead) +3 Pb(C 2 H 3 2 ) 2 (neutral acetate) + 4 H 2 156. The lead acetate may be obtained by treating granulated lead with acetic acid in the presence of air or by treating litharge with acetic acid; the latter method is easier and more rapid but the higher price of litharge offsets these advantages. The carbon dioxide must be used in a more concentrated state than in the chamber process and is usually prepared by heating limestone with burning coke in a specially constructed furnace and is forced into the solution of basic acetate under a slight pressure. The precipitation usually requires about ten to twelve hours. After removal, the white lead is washed thoroughly to free it from acetate salts. The product obtained is of exceeding whiteness, but, owing to a some- what crystalline nature, has less opacity or hiding power than white lead made by the other processes. For this reason and because of the comparatively high cost of production, this process has not come into the general use that was formerly anticipated. The Matheson process, which is a much improved modification of the Thenard principle, is the only one of this type in successful oper- ation in this country. 157. Present French Practice. In fact, Thenard's process has practically passed out of use, the old Dutch process having taken its place. The procedure of the French, old 132 THE LEAD AND ZINC PIGMENTS. Dutch process corroders is very similar to that of the Eng- lish. In some factories the lead is cast in sheets and then rolled into a spiral, which is placed inside the pot; in other works, the lead is cast in the form of gratings which are placed on top of the pots. While the majority of French factories have discarded manure for tan-bark, a number of the more conservative plants still depend on horse manure as the source of heat and carbon dioxide, as the corrosion is completed in nearly half the time required by tan-bark. The grinding, washing and drying operations correspond closely with the English practice. CHAPTER XII. PROPERTIES OF WHITE LEAD. 158. Composition. White lead of accepted grade is a white, earthy, heavy amorphous powder which appears under the microscope to consist of round globules of irregular size. White lead prepared by the newer processes is usually whiter than that made by the Dutch pro- ~^ cess. pb ' 159. Chemically, it may be considered as a >CO basic carbonate of lead. The best grades of Pb white lead approximate very closely the form- >C0 3 ula 2 PbC0 3 . Pb(OH) 2 , which may be graphi- Pb cally represented as follows : According to this formula, there are about sixty-nine parts of lead carbonate to thirty-one parts lead hydroxide. This constitutes an increase of about twenty-five per cent of white lead on the basis of the metallic lead used. In other words, 100 pounds of metallic lead produces approxi- mately 125 pounds of white lead. There are, however, other basic carbonates of lead, among which is 3 PbC0 3 . Pb(OH) 2 , represented by the graphic formula: /OH Pb >C0 3 Pb >C0 3 Pb >C0 3 Pb \OH 133 134 THE LEAD AND ZINC PIGMENTS. 1 60. The Higher Carbonates. These higher carbonates increase the yield of white lead, and there is a notable tendency, especially with the newer processes, to work in this direction, as the added increase may amount to from one to two per cent of the weight of the pig lead used. This gain, however, is at the expense of the opacity, as the higher carbonates possess less hiding power. White lead which has been overcorroded will be more or less crys- talline instead of amorphous, due to the presence of the crystals of the normal carbonate. Such leads are markedly inferior in their hiding power. 161. Ageing of White Lead. The ageing of white lead, both in the dry state and in oil, has been a fruitful subject for discussion. As to the precise nature of the changes undergone, but little information that is really satisfactory is obtainable. That certain changes take place in both cases is undeniable, as an experienced painjber can almost invariably pick out an aged lead from among unaged leads of similar manufacture. The author has observed that a tank of wet white lead not quite up to standard whiteness will, on standing for eight to ten weeks, improve materi- ally in whiteness. This change is apparently due to molecular rearrangements tending to a uniform relation between hydrate and carbonate, and is apparently assisted by the pressure due to the weight of the contents of the tank. 162. Salvador! 1 is of the opinion that the ordinary basic carbonate is fully as stable, if not more so, than the normal carbonate, and that the latter is easily converted into the former by boiling with water or even by heating under water for several hours at 70 C. It is certain, however, that under other circumstances a reverse action will take place resulting in the formation of a crystalline 1 Gaz Chim Ital. 34, 87. PROPERTIES OF WHITE LEAD. 135 FIG. 51. OLD DUTCH PROCESS WHITE LEAD. Magnification 500 diameters. '-, ' } r* '- FIG. 52. MILD PROCESS WHITE LEAD. Magnification 500 diameters. 136 THE LEAD AND ZINC PIGMENTS. normal carbonate. From these operations, however, and remembering that pressure is a powerful aid to chemical transformations, it is not at all strange that a substance of as complex a nature as white lead, in bulk either wet or dry, will undergo various molecular rearrangements which an ordinary chemical analysis will not indicate. 163. Free Fatty Acids. In the case of white lead ground in oil, the problem is complicated by the temperature and pressure of grinding and the amount of free fatty acids contained in the linseed oil. Such changes as will occur under these conditions will reach a consummation much more rapidly, probably, than in the previous instances, and these changes probably terminate within a few weeks after the lead has been ground. 164. Fineness of Particles. White lead varies greatly with regard to the fineness of the particles of which it is composed. Mild process white lead particles are uniformly fine, while old Dutch process white lead is composed of fine and comparatively coarse particles intimately mixed. The following table prepared by the Paint Manufacturers' Association, 1 gives some idea as to the size of the various pigment particles under average conditions of grinding. No. Name. Diameter in inches. Small. Average. Large. 1 2 3 4 5 6 7 8 9 10 11 Dutch process lead Quick process lead .00002 .00002 .000014 .00002 .000014 .00003 .00006 .00014 .00003 .00009 .00015 .00007 .00012 .00007 .00007 .00007 .00007 .00036 .00044 .00014 .00026 .00018 .00014 .00014 .00014 Picher lead Zinc oxide Zinc lead . Beckton white Barytes .0021 .0022 .0003 .025 .49 Gypsum Blanc fixe China clay Abestine First Annual Report, Scientific Section. PROPERTIES OF WHITE LEAD. 137 FIG. 53. PRECIPITATED WHITE LEAD. Magnification 500 diameters. FIG. 54. SUBLIMED WHITE LEAD. Magnification about 500 diameters. 138 THE LEAD AND ZINC PIGMENTS. 165. Action of White Lead on Linseed Oil. Much has been written concerning the action of white lead on linseed oil. Hannay and Leighton, in the Proceedings of the Chemical Society, No. 124, have questioned the frequently made statement " that saponification takes place when white lead is ground with linseed oil, giving rise to peculiar working properties, which other pigments do not have. They show that no such combination between the lead and oil takes place, and that a very small trace of oleate of lead in the oil will cause serious blackening under the influence of the small amount of sulphuretted hydrogen in the air, when pure white lead would hold its color, showing that such saponification would be decidedly deleterious." 1 66. The conclusion drawn was that dry white lead produced slow oxidization, but no saponification of the oil, since saponification implied hydrolysis, and could only take place in the presence of moisture. A. H. Hooker confirms these statements, and calls atten- tion that " in wet or pulp ground leads alone we find a partial saponification to take place and that such lead is vastly more susceptible to the blackening influence of sulphuretted hydrogen than ordinary lead." 167. Stability of White Lead toward Heat. White lead is riot a very stable pigment. It begins to lose its com- bined water at 110 to 130 C. Several of the quick-process leads break down much more easily than old Dutch process lead. By keeping the temperature below 150 C., all of the combined water can be driven off in six to eight hours, with very slight loss of carbon dioxide. 1 68. A slightly higher heat breaks down the white lead at once into an oxide, high temperature giving litharge, and a continued lower temperature an oxide which absorbs oxygen, forming the product known as orange mineral, which may be considered a debased form of red lead. In PROPERTIES OF WHITE LEAD. 139 actual practice the crystalline tailings or sandy lead is largely used for this purpose. 169. Reactions with Acids. Owing to the weakness of the chemical linkage between radicals composing white lead, it is extremely susceptible toward acids and alkalies, being readily soluble in acetic and nitric acids, and hot hydro- chloric acid, the lead chloride formed separating out on cooling. Hence when hydrochloric acid is used as a sol- vent for lead compounds in mixtures, such solutions should be filtered boiling hot, else crystals of lead chloride will form in the pores of the filter paper, which will be dissolved out with difficulty, even with boiling water. Sulphuric acid converts lead compounds into an insoluble sulphate. This operation is much made use of in the quantitative analysis of lead compounds. However, in the presence of even slight amounts of nitric, hydrochloric or acetic acids the lead sulphate is sufficiently soluble to introduce quite a serious error in the determination. The addition of alcohol will overcome this difficulty to a considerable extent, although it is best to expel any free nitric, acetic, or hydro- chloric acid by evaporation. 170. Solubility. Solubility of lead compounds in 100 c.c. pure water at room temperature: Compound. Grams Soluble. Lead Carbonate . 00011 Lead Sulphate 0.00410 Lead Chromate 0.00002 Lead Chloride 1.08 Lead Acetate 50.0 Lead Nitrate 56.0 171. Action of Sulphur Compounds. As is well known, white lead is easily attacked by sulphuretted hydrogen and gases containing sulphur compounds, pulp ground leads being more susceptible than leads previously freed from 140 THE LEAD AND ZINC PIGMENTS. water before being ground in oil. This blackening or darkening is one of the leading objections to its use as the base of white paints. In fact, for interior work, but little strictly pure lead is used ; generally a mixture of zinc oxide and white lead is used, in which the zinc oxide is in pre- ponderance, as the effect of sulphur compounds on zinc oxide is not noticeable, zinc sulphide being white. In cities where large quantities of soft coal are burned, the darkening of white lead is especially rapid. This is due not only to the sulphurous gases in the atmosphere, but also to the soot particles which lodge on the comparatively rough surface of the lead paint film, and through the agency of moisture, the sulphur and other corrosive substances in the soot act directly on the paint film. 172. Chalking of White Lead. The principal objection brought against white lead as a paint pigment is that it " chalks or flours." This chalking may begin within four months after application or may not be apparent at the end of twelve to fifteen months. Many reasons have been ascribed for this defect, for defect it is, of white lead. In many instances the oil is undoubtedly at fault, especially oils which either by treatment or long standing have become high in free fatty acids, and will cause a rapid dis- integration of the paint film. Again, the temperature at which the lead is ground in the mill has much to do with its chalking. The low temperature at which white lead begins to break down certainly renders any undue heating of the mill a serious consideration. Many grinders even to-day are using uncooled buhr mills. Even with a water- cooled mill operated as efficiently as possible, it is often difficult to keep below the danger temperature, especially after the mills have been running six or seven hours. In many instances the result is so pronounced that the lead hardens in the package within 36 hours after grinding. PROPERTIES OF WHITE LEAD. 141 173. Effect of Residual Acetates. Another important cause of chalking, and one that the author believes should merit special attention on the part of chemists, is the pres- ence in greater or less quantity of acetate of lead, which is to be found in all white leads made through the instru- mentality of acetic acid. In numerous tests which have come under the observation of the writer, white leads pre- pared without the use of acetic acid " chalk " very much slower, and to a much less extent than the other leads. That these more or less basic acetates of lead exert an influ- ence all out of proportion to the amount present seems certain. In fact their action may be regarded as of a cata- lytic nature, and the author is firmly convinced that many abnormal cases of u chalking," if carefully traced, would have shown the presence of an abnormal quantity of acetate of lead present in the white lead used. 174. Protracted Oxidation. It is also a well-known fact, as Hooker states, " that white lead promotes the slow oxidization or drying of the oil and the ultimate product of this oxidization is a dry powder without life or elasticity. White lead hastens this end of completed drying much more rapidly than any other pigment, except of course red lead and litharge, and so unless some means is used to retard the action, the oil perishes and the dry lead alone is left to wash or chalk off. However, the chalking of white lead while objectionable is not entirely so, since it leaves the surface in an excellent condition to receive a fresh coat of paint." 175. White Lead Specifications. One of the best speci- fications that has come under the observation of the author covering the use of white lead is the one in use by the Rock Island Lines of the St. Louis and San Francisco Railroad Company. The following are the points covered : 142 THE LEAD AND ZINC PIGMENTS. 176. " Material. White lead must be furnished in paste form and must contain nothing but oil and pigment, in the following proportions by weight: Oil, not less than 7 per cent nor over 10 per cent. Pigment, not less than 90 per cent nor over 93 per cent, the paste to contain not over one per cent by weight of volatile matter, at 212 F., and must be free from skins and mix readily for spreading, and when made into a paint it must not be deficient in opacity, and must be of maxi- mum whiteness, work freely under the brush, and when thinned down ready to use it must not settle into a hard mass on standing overnight." 177. " Oil. The pigment must be ground in pure linseed oil, well clarified by settling and age, and must otherwise meet the requirements of this company's standard speci- fication for raw linseed oil. " Pigment. The pigment desired is the pure, fully- hydrated basic carbonate of lead, which must not be crystalline in structure or contain more than 0.15 per cent acetic acid, and must approach closely the following com- position : Lead carbonate, not less than 67 per cent nor over 80 per cent. Lead hydrate, not less than 20 per cent nor over 33 per cent. "The pigment must not contain more than one-half of one per cent of lead sulphate." 178. The only objection the writer would raise against these requirements is the high per cent of, carbonate per- mitted. Seventy-six per cent should be regarded as the highest desirable amount, as above this point the lead begins to lose in opaqueness or body. CHAPTER XIII. LEAD POISONING. 179. The English White Lead Commission. In England, and also on the continent, especially in France, there has been a very pronounced agitation against the manufacture and use of white lead as a paint pigment, due to the alleged harmful effect on the employees of the white lead works and the painters who use the product. This agita- tion led to the formation of the White Lead Commission in England, in 1898, whose report was instrumental in introducing many improvements in the industry. In France the white lead industry has been made the object of special legislation restricting and regulating the sale and use of white lead. 180. Lead Poisoning in United States. In the United States the question of white lead poisoning has remained practically unnoticed. To the casual reader this may seem strange, but when we compare the condition of the industry abroad and at home, the reasons why it has attracted so slight attention at once becomes apparent. Two reasons primarily may be advanced as an explana- tion for this state of affairs : 1. Superiority of American methods and workmen. 2. Absence of female labor in this industry in America. 181. In the United States the white lead, after having been ground in the water mills and subjected to the usual washing, is pumped on large copper steam-heated drying pans, some of which are nearly one hundred feet in length by nearly ten or more feet in breadth, while in England 143 144 THE LEAD AND ZINC PIGMENTS. until very recently the thick paste was placed in large earthenware bowls which were carried by women to drying compartments known as " stoves," which were essentially rooms heated by a stove or steam coils and provided with a large number of shelves arranged around the sides. Until 1898, the " filling " and " drawing " of the stoves was very largely done by women, and, as Sir Thomas Oliver 1 has pointed out, this part of the process " has been the cause of a larger number of severe and fatal cases of lead poisoning than any other department in a white lead factory." " The work was found to be so detrimental to female life that the White Lead Commission recommended that no woman or girl should be allowed to work in the stoves." At the present time while the use of copper dry- ing pans is becoming more common in England and on the continent, the practice has by no means become universal. 182. English Regulations. In 1899, the Chief Inspector of Factories issued special rules for white lead works. These were modified again slightly in 1901, and the following are the essential requirements as stated in Factory Acts of 1901. 183. Duties of Occupiers. 1. No person shall be em- ployed in drawing Dutch stoves on more than two days per week. 2. No woman shall be employed or allowed in the white beds, rollers, washbecks, or stoves, or in any place where dry white lead is packed, or in other work exposing her to white lead dust. 3. The occupier shall provide and maintain sufficient and suitable respirators, overalls and head coverings, and shall cause the same to be worn. 4. A supply of a suitable sanitary drink, to be approved by the appointed surgeon, shall be kept for the use of the workers. 1 Dangerous Trades, page 289. LEAD POISONING. 145 FIG. 55. REQUIRED COSTUME OF ENGLISH WHITE LEAD WORKER. 146 THE LEAD AND ZINC PIGMENTS. 5. The occupiers shall provide and maintain lavatories for the use of workers, one lavatory basin for every five persons employed, to which must be supplied a constant supply of hot and cold water. 6. Before each meal, and before the end of the day's work, at least ten minutes in addition to the regular meal times should be allowed to each worker for washing. 7. The occupier shall provide and maintain sufficient baths and dressing-rooms for all persons employed in lead processes, with hot and cold water, soap, and towels, and shall cause each such person to take a bath once a week at the factory. A bath register shall be kept containing a list of all persons employed in lead processes, and an entry of the date when each person takes a bath. 184. Duties of Persons Employed (Briefly Stated). 1. No person, after suspension by the appointed surgeon, shall work in a lead process without his written sanction. 2. Every person employed in a lead process shall take a bath at the factory at least once a week, and wash in the lavatory before bathing; having done so, he shall at once sign his name in the bath register with the date. 3. No person employed in a lead process shall smoke or use tobacco in any form or partake of food or drink elsewhere than in the dining-room. 4. No person shall obtain employment under an assumed name, or under any false pretenses. 185. English Statistics. That these regulations adopted in 1899 were justified is amply shown by the official reports on lead poisoning for the three years preceding. Year. Cases. 1896 357 1897 370 1898 480 LEAD POISONING. 147 These figures indicate that one in every seven to eight employees suffered from lead poisoning. The drying stoves furnished two and one-half times as many cases of plumbism as the corroding beds. 186. Precautions Adopted by the French. In France even more rigid precautions are prescribed against lead poisoning than in England. Those in use at the corrod- ing works of M. Expert-Besangon may be taken as repre- sentative of the care exercised with French white lead workers. As the best preventative of plumbism, regular rations of milk are prescribed which the workmen are required to take at six o'clock and nine o'clock in the morning and three o'clock in the afternoon. To the nine o'clock ration is added hyposulphite of soda, about one and a half pounds to the gallon. It is also to be noted that the workmen are not permitted to drink their milk or partake of food in any of the rooms where any lead products are handled or are in process. The men are required to wash their face and hands and rinse out their mouths before eating or drinking their milk and on leaving the factory at the close of the day. Frequent baths are also required. The time required for all of these operations is considered a part of the day's work and for which the workmen are paid. 187. As a final precaution each workman is inspected at least once a week by a doctor who keeps a complete record of the health of each man. When indications of lead poisoning are observed, cessation from work is ordered by the doctor until recovery is complete, at which time a certificate is issued permitting him to return to work. 188. Recent Improvements. Since 1901, conditions have materially improved in England, as in 1900 the total cases notified in the Northeastern Division of England was 197, in 1901 there were 98 cases notified, and in 1902 148 THE LEAD AND ZINC PIGMENTS. only 69 cases were notified. On the Continent methods have been introduced to some extent for incorporating the lead with oil without drying out the water, similar in prin- ciple to the white lead pulping mills used in this country, thus avoiding danger from white lead dust common to this part of the process. In this country mechanical barrel packers and the strict use of respirators have reduced this danger to a minimum, there being much more lead sold dry than abroad. 189. The taking down of the corroding beds is perhaps the most dangerous part of the process in this country, as it is an operation in which manual labor cannot with ad- vantage be supplanted by mechanical devices. The incor- poration of the dry lead oil by means of " chasers" is also a serious source of lead poisoning, unless, as is the practice in some plants of placing the chasers in small rooms, the workmen remaining outside until the incorporation of the lead and oil is complete. 190. Restrictive Legislation. Even when all reasonable precautions have been adopted, there is always danger of the employees acquiring lead poisoning in a corroding plant, especially one in which the old Dutch process is used, but in the opinion of the writer the danger is not nearly serious enough to warrant restriction by legislation against the manufacture and use of white lead. While it is true that painters suffer more or less from lead poisoning, it is usually due to lack of even ordinary cleanliness, for the painter who is scrupulously neat is very seldom affected. Much of the complaint regarding the various forms of kidney diseases with which many painters are troubled, especially those working under cover, is due essentially to the irritating and toxic effect of the turpentine used. Carriage painters are perhaps more seriously affected by this class of troubles than any others, and yet the LEAD POISONING. 149 amount of white lead applied by them is very small as compared with the amount applied by the ordinary house painter. 191. Danger to Women. The different forms and mani- festations of lead poisoning, such as " wrist drop/' " lead colic/' are more or less well known, but the more serious aspects which this affliction may assume should be more generally known and recognized, and effectual measures taken to prevent development into a chronic or acute stage. The effect of lead poisoning is very much more serious on women than on men. This has been amply demonstrated by Oliver/ who states that " where the two sexes are as far as possible equally exposed to the influence of lead, women probably suffer more rapidly, certainly more severely, than men." " Children of female lead workers almost invariably die of convulsions shortly after birth or during the first twelve months. If the child is the offspring of parents both of whom are lead workers, it is puny ami ill nourished, and is either born dead, or dies a few hours after birth." Fortunately in this country female labor is not employed in white lead factories. 192. Symptoms of Lead Poisoning. In discussing white lead poisoning, Oliver states in the same connection, that : " The symptoms of plumbism are manifold. Usually easy of recognition, they are sometimes so obscure as to render the malady difficult of detection, even by a careful physi- cian. One of the earliest signs is pallor of the countenance. There is developed a degree of anaemia which gradually increases until the features become altered and expression- less, a form of bloodlessness which, since it is characteristic of lead poisoning, is spoken of as Saturnine cachexia. This becomes very pronounced, so that it is easy to recognize lead workers by sight. A few weeks' work will transform a 1 Dangerous Trades, pages 301, 303. 150 THE LEAD AND ZINC PIGMENTS. healthy-looking, florid young woman or man into a pallid and listless individual. During the time that the pallor is developing, the individual often complains of a disagree- able metallic taste in the mouth, especially on rising in the morning, and of a distaste for food." 193. " The reason why colic is such a common and early symptom of saturnine poisoning is because the alimentary canal is one of the principal channels by which lead enters the system, and lead is known to have a special affinity for muscular fiber and nerve tissue, and to induce spasms. Colic is often attended by vomiting and by obstinate con- stipation. The pain is of varying degrees of severity. Sometimes it is so mild that the individual is able to follow his occupation, but in discomfort. At other times it is so severe that he rolls about in agony, and is with difficulty kept in bed. After recovery most of those who have been ill return too early to employment. One attack of plumb- ism unfortunately predisposes to another. On examining the mouth of a lead worker there is usually to be seen a bluish line along the margin of the gums close to the teeth. The gums are ulcerated, and in the case of an old lead worker they are retracted, and thus expose a considerable length of the fang." 194. Effect on Nervous System. It is upon the nervous system that the worst effects of lead are seen. Usually after having experienced one or more attacks of colic, but sometimes without these, a lead worker suddenly or grad- ually loses power in his hands and fingers. His hands become paralyzed, hang powerless by his side, and the patient is said to be suffering from " wrist drop." In " wrist drop" the extensor muscles of the fingers and wrists rapidly waste. As a rule, the affection is painless, but in some instances the loss of power is preceded by muscular tenderness. The muscles of the shoulders and LEAD POISONING. 151 upper arm, too, may be affected, or the weakness affects the muscles of the foot, and causes " ankle drop." 195. Chronic Lead Poisoning. There still remains the chronic type of lead poisoning " in which the individual, after having been exposed for a lengthened period to the influence of lead, and having experienced one or more attacks of colic, indicating that his system is becoming impregnated with lead, is never well; he is profoundly anaemic, is the subject of frequent headache, imperfect vision, and incomplete wrist drop. Albumen is present in the urine, and there is a slight'degree of dropsy of the face, hands, and feet, physical signs that point with these just mentioned to structural alterations having occurred in the kidneys, liver, heart, and blood-vessels, retina and nervous system. Life drags on from day to day, only to end in a lingering illness, or it is brought to a sudden close either by urmic convulsions, or in consequence of rupture of a blood-vessel in the brain." 196. Absorption Through the Skin. Many authorities consider that the inhalation of lead dust or its intro- duction into the system through the mouth is far more dangerous than ordinary contact with the skin, as, for example, the hands and arms. The author, however, believes that the danger of absorption through the skin has been much underestimated. In one corroding plant with which the author was intimately acquainted, over twenty- five per cent of its workmen in one year received medical treatment for lead poisoning, the large majority of whom never came in contact with any perceptible amount of lead dust; and as they were required to wash thoroughly before eating, the amount introduced through the mouth was very slight. The liberal use of heavy paraffine oil on the hands and arms did much to alleviate the absorption, and immediate improvement was noticed. CHAPTER XIV. MANUFACTURE OF ZINC OXIDE. 197. Ancient History. This pigment which occupies such a prominent position in the paint world to-day was practi- cally an unknown paint material sixty years ago. Yet, while its rise into favor has been so rapid and recent, it has been known to scientists for many hundred of years. In fact, its history extends as far back as that of white lead, for Pliny mentions it under the name of cadmia when describing the sublimate of impure zinc oxide found in the chimneys of the brass foundry furnaces. Discorides also states that in the manufacture of brass " pomphlox is formed like tufts of wool." The later alchemists spoke of this characteristic formation of zinc oxide as lana philosophica. The similarity between the oxide of zinc, obtained by the combustion of metallic zinc, and snow led the alchemists to name it nix alba. 198. Production on a Commercial Scale. Unlike white lead, zinc oxide was of little or no practical use to the ancients, and the industry remained undeveloped. One of the first suggestions as to its adaptability as a paint pigment was made in 1781 by a French chemist, who discovered the process of converting zinc into oxide on a commercial scale, and advised its use instead of white lead, but with no especial results. And it was not until the time of LeClaire the famous French contractor and painter in 1847 that zinc oxide came into commercial use as a pigment. 199. Work of LeClaire. LeClaire, wiser than the major- 152 MANUFACTURE OF ZINC OXIDE. 153 ity of reformers, turned public prejudice against itself. His contracts called for the use of pure white lead, and while he believed in the superiority of zinc oxide he recog- nized the futility of attempting to convince the public by any ordinary means. He therefore interpreted his con- tracts rather liberally, and used zinc oxide instead of white lead. " The superior beauty and durability of his work rapidly increased his trade, and when he felt his position sufficiently strong, he turned the prejudice of his patrons against themselves by painting here and there in each new building a certain section with pure lead. At the end of a short period the lead naturally began to change color and to ' chalk off/ and the inferiority of these portions promptly attacked criticism. When LeClaire was ready, he proclaimed the facts, with the final result that to-day zinc holds an absolutely unassailable position in France. LeClaire received honors and medals in profusion, and the government conferred upon him the order of the Legion of Honor." 200. LeClaire 's Process. The LeClaire process of manu- facturing zinc oxide consisted of volatilizing the metallic zinc in a retort, the resulting zinc vapors being mingled with currents of air and burned, the zinc converted into the oxide which was collected as a white powder in a series of flues and chambers; his process being the precursor of the present " French Process/' The factory of LeClaire is still in operation. The high cost of the product prevented its coming into general use until after the elaborate investi- gations of the French Government which resulted in its being required in all government work. 201. Present French Process. The Societe Anonyme de la Vielle Montagne is the largest producer of zinc oxide by the French process in Europe, producing in the neighbor- hood of 8000 metric tons yearly, equivalent to 8820 154 THE LEAD AND ZINC PIGMENTS. English tons. The metallic zinc or spelter is volatilized in a special form of retort; the vapor issuing from the retort is oxidized in the presence of a current of air, and after passing through a series of pipes is collected in long settling cham- bers provided with hopper bottoms through which the collected oxide may be removed. The purity of the oxide, especially as regards whiteness, depends much upon the distance it is carried in the settling chambers before deposi- tion, and the product is graded accordingly; the two lead- ing brands being Vielle Montagne Green Seal and Red Seal, the former being the better quality and commanding the higher price. 202. Composition. The composition of the Vielle Mon- tagne zinc oxides varies according to Ingalls as follows : Zinc oxide 99.695 to 99.995 per cent Lead oxide 0.200 to .002 per cent Cadmium oxide . 100 to . 000 per cent Ferric oxide . 005 to . 003 per cent The manufacture of zinc oxide from the metal is also an important industry in Silesia, the production being in the neighborhood of about one thousand metric tons. As the Silesian zinc always contains lead which converted into oxide gives a yellowish color to the zinc oxide, carbon dioxide from burning coke is introduced into the distilling retort which converts the lead into carbonate, according to Ingalls. The zinc oxide is collected in large upright bags similar to the American practice. The largest works in Silesia is the Antionenhiitte. 203. The cost of production of zinc oxide from the metal is considerably higher than that of zinc oxide produced direct from the ore, as is the common practice in this coun- try, but it insures the absence of certain objectionable impurities like cadmium, which is considerably more vola- MANUFACTURE OF ZINC OXIDE. 155 tile than zinc, and produces a brown oxide which would cause a discoloration of the finished product if it were not removed in the process of the manufacture of the metal. As the majority of European ores contain cadmium, a direct process similar to that used in this country is out of the question. 204. Processes in Use in the United States. In the United States the larger part of the zinc oxide produced is derived from the ore. The Florence, Pennsylvania, plant of the New Jersey Zinc Company, however, manufactures zinc oxide from the metal by what' is substantially the French process, the metallic zinc being heated in retorts, volatilized, and the vapors burned to the oxide which is drawn into collecting chambers by the draught from a high chimney. The material so collected is treated to further purify it and improve its color. The greatest care must be exercised in the selection of the metal used and in all of the subsequent steps of the process, but when properly operated this pro- cess produces the purest white pigment known. The product is graded in a manner similar to the Vielle Montagne, and is known under the name of Florence Green Seal and Florence Red Seal. 205. The Work of Jones and Wetherill. The invention of the American process for the manufacture of zinc oxide is ascribed to Samuel T. Jones, who constructed a furnace for this purpose in 1850. The process was materially improved and placed on a commercial scale by Col. Samuel Wetherill in 1855, who worked with the Franklinite ores of New Jersey. The growth of the industry was somewhat slow at first, but after 1880 it developed rapidly and con- stitutes to-day one of the largest of the metallurgical indus- tries. Unlike the manufacture of the white lead pigments, the zinc oxide industry has shown comparatively few improvements in the process of manufacture during the last 156 THE LEAD AND ZINC PIGMENTS. thirty years. While the principles of the process have remained unchanged, there has been a marked improve- ment in the character of the ore sent to the oxide furnaces, which is now first given a roasting to drive off the large amount of the sulphur, because when the oxidation of the sulphides and the volatilization of the zinc is accomplished in one process in the same furnace, the collected oxide is contaminated with appreciable amounts of zinc sulphates and a considerable amount of sulphur dioxide remains occluded in the oxide particles, which is a serious considera- tion from the paint manufacturer's point of view. 206. Zinc Oxide Plants in the United States. At the present time there are four plants engaged in the manufac- ture of commercially pure zinc oxide, and they are located in the States of New Jersey and Pennsylvania. These plants are operated by the New Jersey Zinc Company. Another plant is located at Mineral Point, Wisconsin, and operated by the Mineral Point Zinc Company, which is affiliated with the New Jersey Zinc Company. The zinc oxide produced at this plant, however, contains varying quantities of lead sulphate, and is graded accordingly. Other zinc oxide plants are located near Joplin, Missouri; Coffeyville, Kansas; and at Canon City, Colorado; but as the pigments produced at these plants contain a large per- centage of lead sulphate, the procedure in these plants will be considered separately. 207. Development of the New Jersey Zinc Mines. The development of the New Jersey zinc mines constitutes a very interesting chapter in the development of our mineral resources. The mines at Sterling and Franklin were discov- ered in the latter part of the eighteenth century, it is said, by a party of Swedish miners who were traveling overland from Baltimore to New York. Some ore is supposed to have been sent to England about this time, but we find no MANUFACTURE OF ZINC OXIDE 157 S u 35 J ^ P^ N W 158 THE LEAD AND ZINC PIGMENTS. record of its having been received or treated. In any case, the mines were known to exist as early as 1824, when Messrs. Van Uxen and Keating described some of the minerals. The first mining done at Franklin was when the United States Government made the standard weights and measures. They imported some workmen from Belgium, built a spelter furnace at Washington, and made the zinc partly of ore from Franklin and from scattered boulders of ore found in Sparta Valley, and partly from ore from Perkiomen, Pennsylvania. The old pit from which this ore was taken was known as the " Weights and Measures Opening," and was in existence until about 1900, whe,n the mining operations caused its disappearance. No further mining was done until 1848, when the mines at Sterling Hill were opened. Mining did not begin at Franklin until a couple of years later. 208. At first an attempt was made to manufacture spelter from the ore, but this was not successful, and the manufacture of oxide of zinc was started at Newark. At first the ore was worked in reverberatory furnaces, and the product was of a rather poor quality, and the cost extremely high. Later the ore was treated in muffles by a process said to have been discovered by Mr. Farrington, the Super- intendent of the works, but which was identical with one patented by Atkinson in England, April 2, 1796. Still later the present method of manufacturing oxide of zinc direct from ore was discovered and patented by Col. Samuel Wetherill. 209. Controversy regarding the Ownership of the Deposits. At the time that mining operations were first started in Franklin, the mineral rights had been sold to two different companies by Col. Samuel Fowler, who owned the Mine-Hill farm, on which the principal deposit is located. In the first deed he conveyed all the gold, silver, copper, MANUFACTURE OF ZINC OXIDE. 159 lead, zinc and other ores and minerals containing gold, silver, copper, lead and zinc, except the metal, mineral, or ore known as Franklinite when it exists separate and apart from the zinc, and in the second deed he conveyed all the mineral rights that had been reserved in the first deed. The ambiguous nature of these conveyances led to litiga- tion, which lasted almost continuously from 1854 to 1897, and was only concluded when the present New Jersey Zinc Company acquired the title to all mineral rights in the Mill-Hill farm. The reason that the deeds were made in this way was that at that time it was believed that there were two separate veins, one consisting almost entirely of Franklinite, and the other of other zinc minerals. Sub- sequent work has proved that this was not the case, and the point to be decided by litigation was whether the vein, which is a mixture essentially of the minerals Franklinite, willemite, zincite and calcite, was " Franklinite separate and apart from the zinc," or " zinc." 210. Composition of Franklinite Ore. The Franklin ore l of New Jersey, from which the larger portion of our zinc oxide is produced, is a complex ore composed of Franklinite, willemite, and calcite in varying proportions, together with occasional quantities of zincite, tephroite, garnet, fowlerite, and a few other minerals. As it comes from the mines the ore varies widely in composition, but the following will serve as an example: Per cent. Iron sesquioxide 32 .06 Manganese protoxide 1 1 . 06 Zinc oxide 29.35 Calcium carbonate 12 . 67 Silica and insoluble matter . . 14 . 86 100.00 Mineral Industry, 1893, page 673. 160 THE LEAD AND ZINC PIGMENTS. 211. These figures may be calculated to the following mineral composition: Per sweat f :r 24 hours between chasings; 92 pounds lead, 8 pounds ril; c nsi ten-y medi--m soft. No. 2 same pro- portions of lead and oil, but put through ordinary mixer and ground in 30-inch mill ; consistency stiff. 358. New Jersey Zinc Oxide " XX.' First coat. Second coat. Third coat. Zinc oxide 100 Ibs. 100 Ibs. 100 Ibs Raw linseed oil 10 gal. 5* gal. 6 eral Turpentine i gal. 1 gal. Drier i eal 359. Covering Tests. Each of these paints was applied over hard pine boards, soft pine boards, cedar clapboard siding, and white pine clapboard siding, the surface cov- ered being approximately six and one-half square feet with each wood. The weights of paint applied were care- fully determined and the following tables of figures were obtained by calculating back to the paste form, i.e., the form in which the goods were received in the original package, and in the case of white leads this represented the packages as found on the market. These calculations 1 Bulletin No. 81, North Dakota Experiment Station. 242 THE LEAD AND ZINC PIGMENTS. PRACTICAL TESTS. 243 were prepared from the tables in Bulletin 81, North Dakota Experiment Station, and the author believes them to be measurably accurate. The Mild process tests were made at a later date, Mr. Campbell not being present. The con- ditions, however, were entirely similar, and the figures are from the official figures recorded at that time. The results are calculated in grams per 100 square feet. Not enough Matheson white lead was available for full sized tests and the amounts applied were not noted. 360. Hard Pine Boards, 100 Square Feet. First coat. Second coat. Third coat. Total. Red seal Grams. 1330 Grams. 863 Grams. 725 Grams. 2918 Eagle 1182 678 714 2574 Carter 1221 677 559 2457 Sublimed 1131 672 635 2438 Mild process No. 1 (double chased) Mild process No. 2 (mixed and ground) 1295 1146 661 688 603 668 2459 2502 Zinc-lead white Zinc oxide 1105 702 432 531 555 432 2092 1665 361. Soft Pine Boards, 100 Square Feet. First coat. Second coat. Third coat. Total. Red seal Grams. 884 Grams. 731 Grams. 757 Grams. 2372 Eagle 1084 610 573 2267 Carter 1038 645 767 2450 Sublimed 975 676 654 2305 Mild process No. 1 (double chased) 931 598 520 2049 Mild process No. 2 (mixed and ground) 918 621 619 2158 Zinc-lead white 1027 595 601 2223 Zinc oxide 662 474 391 1527 244 THE LEAD AND ZINC PIGMENTS. 362. Cedar Clapboards, 100 Square Feet. First coat. Second coat. Third coat. Total. Red seal Grams. 1361 Grams. 974 Grams. 815 Grams. 3150 Eagle 1472 1027 808 3307 Carter 1152 777 750 2679 Sublimed 1208 852 644 2704 Mild process No. 1 (double chased) 907 547 548 2002 Mild process No. 2 (mixed and ground) Zinc-lead white 1005 1185 601 432 636 538 2242 2155 Zinc oxide 924 481 462 1867 363. White Pine Clapboards, 100 Square Feet. First coat. Second coat. Third coat. Total. Red seal Grams. 1288 Grams. 594 Grams. 577 Grams. 2459 Bade 1215 933 639 2787 Carter 1191 1045 719 2955 Sublimed 1275 750 704 2729 Mild process No. 1 (double chased) 1301 763 782 2846 Mild process No. 2 (mixed and ground) 1265 752 796 2813 Zinc-lead white 1168 641 449 2258 Zinc oxide 794 547 480 1811 364. Conclusion. In the opinion of those who con- ducted the tests there was no choice in the hiding power of any of the white leads after the third coat had been applied and dry enough to warrant inspection. The author leaves all conclusions to the reader, who if he may care to do so can easily calculate the area covered per 100 pounds, which is the more usual form of expression, or similarly calculate the total area covered per 100 pounds irre- spective of the varieties of wood over which applied. It PRACTICAL TESTS. 245 is not the purpose of the author to advertise any particular brand or process, and the above figures are here given to show the variations in amounts applied, even with an exceedingly experienced and careful brush hand and under as like conditions as possible, and to act as a suggestion that it is unwise to state definite empirical figures from a single test. CHAPTER XXIV. THE ART OF GRINDING WHITE LEAD, PASTES, AND PAINTS. 365. Importance of Careful Grinding. This is essen- tially an age of competition, a fact which has become especially noticeable in the paint industry. Paint manu- facturers have been accustomed to large profits, which are, however, rapidly becoming a thing of the past, and the manufacturer must accustom himself to a moderate return on his invested capital, and pay closer attention to the details of his business. The grinding of cheap combina- tion white leads and selling them as pure white leads is not the profitable business it was formerly; the consum- ing public is getting wiser and more discriminating. Manu- facturers whose specialty is cheap " dope " paints, or who in order to retain the odor of sanctity manufacture and sell them through a subsidiary corporation or company, are finding it harder and harder with each succeeding year to dispose of their wares. This means that paint manufacturers in order to hold their trade will have to use better materials. Many manufacturers have come to realize this and are so doing. Good materials, however, do not make good paint unless these materials are prop- erly ground and incorporated. This requires time in the mixing and grinding, which involves a considerable item of expense in keeping the mills properly dressed. 366. Careless Grinding. Many manufacturers are very slow to recognize the importance of careful and fine grind- ing. The writer while a member of the staff of the North Dakota Experiment Station examined 54 paints consist- 246 GRINDING WHITE LEAD, PASTES, AND PAINTS. 247 ing of whites, colonial yellows, and grays which were sup- posed to have been prepared with especial care by the manufacturers, as they were used to demonstrate the wearing values of various pigments and formulas. After having stood under average conditions for 8 months they were examined in the can as to condition. Twelve, or 22 per cent, were coarse, giving evidence of very careless grinding; 15, or 28 per cent, gave evidence of hardening, also presumably due to lack of care in preparation or of observing suitable precautions in grinding. Fifty per cent only were in first- class condition. Yet these 54 paints came from the largest and most progressive houses, whose aggregate yearly sales would undoubtedly more than equal the combined sales of the remaining paint houses in the country. 367. Conditions to be Observed. The white lead or paint manufacturer, therefore, should give careful heed to the condition of his mills and the conditions under which they are operated. Cheap stones, careless or infrequent dressing, loose adjustment, hasty or careless mixing, will produce poor paint, no matter how good may be the material used. The heating of mills and the use of water- cooled mills have already been discussed in several places in this book and need not be taken up again in this con- nection. 368. Mixing and Chasing. Before being delivered to the grinding mills the pigments and linseed oil or other vehicles are incorporated either in a mixer or by means of a chaser and mixer. Chasing the pigments and oil first, then plac- ing in a mixer, is undoubtedly far superior to mixing alone, although the writer is sorry to say that the latter practice is the one most commonly followed. Chasing brings the pigment particles in very close contact with each other and with the oil, and will effect a more thorough distribu- 248 THE LEAD AND ZINC PIGMENTS. tion of the different pigments present than is accom- plished in an ordinary mixer. It is a well-known fact that a paint properly chased, mixed, and ground will occupy considerably less volume than a paint simply mixed and ground. In many instances when there is a rush of orders the mixing is done hastily and the " mix " let down into the mill before all of the pigment particles have come in con- tact with the oil and become thoroughly saturated; this increases the difficulty of grinding and increases the wear on the stones, as well as lessening the wearing value of the paint. 369. Proper Selection of Stones. Every practical paint grinder should be able to judge the different stones neces- sary for the grinding of various materials, as, for in- stance, ores, which are sometimes ground into very fine particles in order to make the different paints, pastes, or pigments, and furthermore learn to know the various reliable houses furnishing such stones. The author desires at this point to express his appreciation for the valuable information and drawings furnished in this connection by Paul Oehmig & Co., who have had a wide experience in the construction of mills. 370. Every millstone must feel sharp to the touch and possess a natural cut. Successful milling depends almost entirely upon proper judgment in selecting these stones, as only such stones as possess a natural cut can be successfully dressed, which is, of course, necessary for grinding the various materials. 371. Source of Millstones. The most valuable stone material is the so-called " Fresh Water Quartz," which is imbedded in the chalk deposits, particularly in France, and these are commonly called " Old Stock French Buhrs," and are adapted for all milling processes. Others of a denser grain are found near the mouths of former hot springs, and GRINDING WHITE LEAD, PASTES, AND PAINTS. 249 still others are found in low marshy ground, which con- tained much vegetable matter at the time of their formation. The scientific name for the former is " Hydro-Quartcite," and for the latter " Limno-quartcite." The two latter kinds vary in structure and are usually called " New Stock French Buhrs." These are particularly fitted for the grinding of very hard minerals, and are generally used for this purpose, particularly in the preparation of paints, although the greater majority of these stones were, and are, imported from France, yet within the past twenty years there has been found on the American continent a consid- erable quantity of such stones which take the place of the imported ones, many of which, although not porous, are admirably suited for various milling purposes, and are sometimes preferable to the imported stones. 372. Domestic Stones. The domestic stones are com- posed of various sizes of quartz crystals and pebbles firmly united by a natural cement, and their hardness and natural " cut " suits the purpose, especially for grinding colors in oil, paste, paints, etc. The common name for these stones is " Esopus," or " Pebble Grit." The domestic stones on account of the proximity of the pebbles to each other often become glazed in grinding pastes and thereby lose their natural cut and in this respect are inferior to the imported French buhrs. However, for dry grinding, especially of medium-tempered minerals, the domestic varieties are con- sidered preferable. 373. Stone Dressing. From the grooved mortars used by the ancient Egyptians 4000 years B.C., there developed the hand mills, which, as may be observed from old illustra- tions and excavated originals, consisted of a stone surface upon which the material was ground with a pestle, hollow stones or with wooden blocks. These later were developed into large circular stone mills, in which other than human 250 THE LEAD AND ZINC PIGMENTS. power was used, as early as 200 years B.C., as mentioned in various historical accounts, and in later years similar mills of various types formed a very important part of the equipment of the Roman Legions, particularly those of Caesar, and their remains were found centuries afterwards on the Roman highways. Naturally the surfaces of these mills became worn smooth, and it was necessary to invent an artificial way of renewing the cutting surface, and there- fore arose the system of grooving the stones, and thus improving and renewing the grinding surface. This dress- ing soon took on a definite character, and is found on many stones which are exhibited in museums, as, for instance, at Field's Museum at Chicago, Illinois. They were, however, less particular in their choice of material, choosing the most convenient, such as granite, sandstone, or lava. 374. In more recent times it has become necessary to use well constructed grinding mills in order to overcome the difficulties of grinding various minerals and paints. And to-day it is required that the mills must be easily adjustable and so constructed as to admit of easy access to the grinding stones. 375. Types of Mills. Under running mills, which by their greater pressure are more effective, are generally preferable to the over running mills. If the under stone is fixed, and the upper stone rotates, the material will very slowly be carried over the grinding surface of the bed stone until at length it reaches the circumference and falls out. On the other hand, if theunderstone is to be one that rotates, all particles lying on it will be hastened along by centrifugal force, the grinding surface of the upper stone asserting a pulverizing action on the larger particles, hindering their passage outward. Correctly arranged furrows further the movement of the material and it therefore follows that under runners are better forwarders and deliverers than GRINDING WHITE LEAD, PASTES, AND PAINTS. 251 over runners, and there is less chance for accumulation and over heating. 376. Best Method of Dressing Stones. No definite system can be outlined which will be safe to follow in all cases. In the grinding of paints it is not so much a question of cutting surface as of pressure with which to reduce the material to the desired fineness. The grinding of cereals, on the other hand, necessitates a very fine, sharp and systematic dressing. The stones, in both cases, must possess a number of furrows, which bring the material from the center of the stones to the actual grinding surfaces where the material is actually ground. These furrows are necessary in order to avoid undue heating of the material, and in order to avoid over- loading the grinding surface. In under running mills, these furrows should never be too deep on the running stone, but on the stationary stone they should 'be deeper. It is also necessary that the surface of the stones be a little concave, or tapered down to the eye, which adds to the efficiency of the grinding surface. By following out the above sug- gestions it will be found that the mill will always run cool and that it will be impossible to overload the grinding surface. 377. Adjustment of Grooves. Dressing was originally done in circular and radial grooves, but this was found not to be practical for every purpose, for the reason that when two corresponding grooves of the two stones come together, they should cross in such a way as to make a scissor-like movement, and never cross in two angles. Figures 78 and 79 designate the kinds of dressings which are most easily kept in order, and which are best for various purposes. These two dressings can only be recommended for dry grinding. 378. Grinding Pastes. A portion of Fig. 79 is designed to show the actual working of the two grinding surfaces, as 252 THE LEAD AND ZINC PIGMENTS. FIG. 78. DRESSING FOR PAINT MILL. FIG. 79. ADAPTION OF GRINDING SURFACES. GRINDING WHITE LEAD, PASTES, AND PAINTS. 253 they should be, and at which angle and direction the two sets of grooves cross each other and what relation their direction has to the direction of the movement. The rela- tion of the furrows is shown on Fig. 80. For the grinding of colors the following kinds of dressings should be used. Fig. 81 is an illustration of a French buhrstone of about thirty inches in diameter, which is practically efficient for grinding heavy pastes, colors, etc., which contain a large percentage of silicates. The furrows are quite wide and deep. The stones should be dressed three-eighths of an FIG. 80. ADJUSTMENT OF FURROWS. inch apart and the grinding face should not be over 7J to 8 inches. In order to facilitate the introduction of the material to be ground, it is preferable to deepen the fur- rows somewhat toward the center, as well as deepen the grinding surface toward the eye of the stone. For the grinding of oil colors and enamels a 20-inch mill with 4-inch face is generally used (see Fig. 82). 379. Use of Mill Picks. In dressing the stones, care should always be taken that the mill picks are not too heavy and are in proper shape on the jutting edge to avoid splintering and smashing the grinding surface of the stones. The furrows of the grinding stones should be cut 254 THE LEAD AND ZINC PIGMENTS. as smooth as possible, also it is preferable to have the furrows wide rather than cutting them in a ditchy-like appearance, as the furrows are the actual transmitters of the material to the grinding surface. If this style of dressing is followed the life of the millstone will be longer and a great deal of trouble and annoyance prevented. It will be noted that Fig. 81 does not show the furrows cut to the edge of the stone, but it is the opinion of FIG. 81. DRESSING FOB HEAVY GRINDING. several stone manufacturers that it is best to cut these furrows to a feather edge up to the rim of the stone, but this should be the shop practice. 380. Pneumatic Dressing. The majority of the larger paint manufacturers now dress their mills with a pneu- matic chisel, thereby saving considerable time and labor, but the writer has noticed that where the pneumatic tool is used there is a tendency toward careless dressing. This is probably due more than anything else to inefficient GRINDING WHITE LEAD, PASTES, AND PAINTS. 255 workmen, as formerly mill dressing was a recognized trade, commanding good wages, and from long experience the men came to understand all of the fine points and require- ments of the trade, but with the advent of the pneumatic tool the mills have been intrusted to the care of cheaper and less experienced workmen who have made little or no study of paint grinding. 381. Frequency of Dressing. The frequency with which mills should be dressed is a much debated question and FIG. 82. DRESSING FOU 20 INCH MILL. depends to a large extent on the nature of the material to be ground and the tightness of the tension used. One of the leading manufacturers, whose lead and paste mills are in almost continuous operation, takes down his mills for dressing about once a year, varying as occasion may demand between six and eighteen months. The inevita- ble consequence was that the stones had, long before the time of dressing, worn smooth, the grooves having entirely disappeared, and in order to secure the customary output the tension had been released to such an extent that the stones exerted little if any grinding or crushing force on 256 THE LEAD AND ZINC PIGMENTS. the pigment particles. It is needless to add that his prod- ucts plainly showed lack of grinding. 382. Paint grinders who have given the matter careful study dress their paste, semi-paste and lead mills every hundred to two hundred grinding hours, varying somewhat as occasion may require. Strictly pure leads which are of very fine texture are not as hard on the mill and con- sequently it may go for a considerably longer period. Much of course depends on the hardness and nature of the stones themselves. The above figures are based on an average grade of domestic stones. The various lead and zinc pigments are easy to grind as compared with ochres, metallics, e.g., Princes, and the various greens, etc. 383. Types of Dressing. As the dressing of mills is essentially the development of a scissor-like movement between the surfaces, the dressing of mills for the grind- ing of various paint products resolves itself into a fine dressing for oil color and coach color mills, which are usu- ally about twenty inches in diameter, having a medium face and furrows of medium draft, while large mills for heavy pastes require a much heavier, deeper and sharper edged dressing with sufficient draft to move the product swiftly between the grinding faces to the edge. With a freshly dressed mill there is always a strong tendency of heating, which by expansion tightens the tension, increas- ing the friction and thus making the heating more rapid. Especial attention should be given a freshly dressed mill and the tension released as the mill begins to warm up. It is almost unnecessary to state that all mills should be as efficiently water cooled as possible. 384. Speed of Mills. As in the above instance no definite rules can be laid down. Some factories are running their mills at a rate of from 55 to 60 r.p.m. with very satisfactory results, while others do not run over 35 to 40 r.p.m., as it GRINDING WHITE LEAD, PASTES, AND PAINTS. 257 largely depends upon how the product to be ground is treated before it is given to the mill, also upon the nature of the product, and upon the construction of the mills used for grinding same. Mills grinding very heavy pastes should run slower, 35 to 40 r.p.m., while mills grinding an easy-to-finish or liquid paint, can run faster, 50 to 60 r.p.m. CHAPTER XXV. ANALYSIS OF COMMERCIALLY PURE WHITE LEADS. 385. Sulphur Dioxide. In the manufacture of quick process white leads, where the carbon dioxide is obtained from fuel gases, it is liable to contain sulphur compounds which will remain in the white lead combined in the form of sulphite of lead. 386. The sulphur dioxide may be estimated by treating 10 grams of the pigment with 50 c.c. of water and 25 c.c. of hydrochloric acid. Allow to stand 5 minutes and titrate with hundredth normal iodine solution as described under the estimation of sulphur dioxide in zinc pigments. The same objections apply to its presence in white lead as in zinc oxides. 387. Sandy Lead. 1 " A certain degree of density is always desired in white lead, since both the corroder and the grinder know that the smaller the amount of oil required to bring a given lead to paste form, the cheaper it is for him, since the average price per pound of linseed oil is greater than that of dry lead, while the same pigment is equally sought after by the consumer, since he, too, desires density and opacity in this pigment. However, efforts in this direction are not infrequently carried too far, with the result of a crystalline overcorroded lead, which settles and hardens badly. Such lead causes loss and trouble both to the grinder and the consumer. 388. Determination. " Based upon the undesirable fea- ture of settling, a comparative separation is easily made. 1 Hooker, Treatise on White Lead, page 24. 258 ANALYSIS OF COMMERCIALLY PURE WHITE LEADS. 259 A fairly large sample, say 100 grams, is taken. This if in paste form is thinned with benzine and run through a fine bolting cloth. Any paint skins are retained, but all of the lead should, when sufficiently thinned, wash through a fine bolting cloth. The very thin paint is now thor- oughly stirred and allowed to settle for a short time only. Nearly all of the benzine is now poured off and then the washing of the sediment with benzine repeated until the benzine comes off nearly clear, leaving the ' sand ' alone as a residue." While present in all commercial lead, the amount should be small, scarcely exceeding 2.5 per cent; objectionable samples will frequently show much more, at times over 10 per cent. 389. Tan-bark. The determination of tan-bark and other organic matter is seldom required. It may, however, be made by dissolving 50 grams of the sample in 75 c.c. of nitric acid diluted with 250 c.c. of water. Filter through a weighed Gooch crucible, provided with a disk of filter paper on the top of the asbestos felt, wash thoroughly dry and weigh. The amount present should not exceed one- tenth of one per cent, according to Hooker. 390. Sulphate of lead, which may be present in some of the quick-process leads, would largely remain undissolved in the nitric acid solution and unless removed would be weighed up as tan-bark, etc. When present it may be dissolved by placing the Gooch crucible and contents in a small beaker containing acid ammonium acetate for a few minutes, after which the crucible is placed in the holder, washed with a further quantity of acetate solution, then with a little warm water, and dried as before. 391. Metallic Lead. Like the previous determination it is seldom made. Occasionally in poorly prepared white leads a sufficient amount may be present to warrant a determination; in which case it is best made in conjunction 260 THE LEAD AND ZINC PIGMENTS. with the determination of " sandy lead/' which, after being weighed up, is carefully dissolved in dilute nitric acid, the operation being checked the moment the sandy white lead has dissolved by dilution with a large quantity of water. The particles of metallic lead are but very slightly acted upon by acid and may be filtered off on to a weighed Gooch crucible, washed thoroughly, dried and weighed. The amount found should- not exceed one- tenth of one per cent. 392. Lead Sulphate. This impurity may be present in small quantities in white leads prepared by the newer processes and sometimes in old Dutch process lead in the settling tanks and wash water tanks. When present in quantities less than one-half of one per cent it should not be considered as seriously objectionable. 393. Determination. Dissolve 1 gram in water 25 c.c., ammonia 10 c.c., hydrochloric acid in slight excess. Dilute to 200 c.c., and add a piece of aluminum foil which should about cover the bottom of the beaker. It is important that this be held at the bottom by a glass rod. Boil gently until the lead is precipitated. Completion of this is shown by the lead ceasing to coat or cling to the aluminum. Decant through a filter, pressing the lead sponge into a cake to free it from solution. Add to filtrate a little sulphur-free bromine water, boil until the bromine is expelled, add 15 c.c. of barium chloride, boil 10 minutes, fifter, wash with hot water, ignite and weigh as barium sulphate. Calculate to lead sulphate by multiplying by 1.3 as a factor. 394. Volumetric Estimation of Lead, Method I. 1 Dissolve 1 gram in 15 c.c. nitric acid, specific gravity 1 .20, neutralize the solution with ammonia in excess, and then make strongly acid with acetic acid. It is then boiled and 1 Wainwright, J., Am. Chem. Soc. ; vol. 19, page 389. ANALYSIS OF COMMERCIALLY PURE WHITE LEADS. 261 standard potassium bichromate solution in sufficient quantity to precipitate nearly all the lead is run in from a burette. The liquid is boiled until the precipitate be- comes orange colored. The titration is continued, one- half c.c. or so at a time, the solution being well stirred after each addition of bichromate until the reaction is almost complete, which can be observed by the sudden clearing up of the solution, the lead chromate settling promptly to the bottom of the beaker; this will usually occur within 1 c.c. of the end of the reaction. The titra- tion is then finished, the end point being indicated by the use of a silver nitrate as an outside indicator, on a white plate. The solution of the lead salt should be as concentrated as possible before titration and decidedly acid with acetic acid. The titration should be performed in a solution kept at all times as near the boiling point as possible. 395. Potassium Bichromate Solution. This should be of such strength that 1 c.c. equals approximately 0.01 gram of metallic lead, and should be standardized against a weighed amount of pure metallic lead as described above. 396. Silver Nitrate Solution. Dissolve 2.5 grams of silver nitrate in 100 c.c. of water. NOTE. This method is applicable for determination of lead in red lead, the solution being effected with nitric acid, boiling, and adding dilute oxalic acid drop by drop until the lead oxide formed is completely dissolved. 397. Volumetric Estimation of Lead, Method II. 1 Dis- solve 0.5 to 1 gram of the pigment in acetic acid if white lead, if lead sulphide, dissolve in nitric acid, dilute with 25 c.c. cold water, add strong ammonia until just alkaline to litmus paper, then make distinctly acid with strong acetic acid. 1 Alexander's Method, Ore Analysis, Low, page 113. 262 THE LEAD AND ZINC PIGMENTS. 398. Heat to boiling, dilute to about 200 c.c. with boiling hot water, and titrate with standard ammonium molybdate solution. Reserve about 10 c.c. of the hot solution in a small beaker, run in molybdate solution into the large beaker from a burette, with constant stirring, until a drop placed in contact with a drop of tannic acid solution on a white plate gives a brown or yellow tinge. Add the 10 c.c. reserved and finish the titration carefully at the rate of two drops addition at a time. When the final yellow tinge is obtained, it is probable that some of the im- mediately preceding test drops may have developed a tinge also. If such is the case deduct the volume of two drops from each test showing a color from the final burette reading. 399. Molybdate Solution. Prepare a solution of ammo- nium molybdate 1 c.c. of which is equal to approximately .01 gram of lead. Standardize against a weighed amount of chemically pure lead, dissolving in nitric acid and treating as described above. 400. Tannic Acid Solution. Dissolve 0.5 gram of tannic acid in 100 c.c. water. 401. Carbon Dioxide. The amount of carbon dioxide in white lead can be most accurately estimated by means of Knorr's apparatus. This apparatus employs only ground-glass joints, and may be quickly made ready for use or taken to pieces and packed away. 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 con- taining acid; C, soda-lime tube; D, condenser; E, cal- cium chloride tube; F, U-tube filled with pumice stone moistened with sulphuric 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 con- nected with an aspirator at L. ANALYSIS OF COMMERCIALLY PURE WHITE LEADS. 263 The calcium chloride and soda lime employed should be finely granulated and freed from dust with a sieve. 402. 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 hydroxide and the other for sulphuric acid, to absorb the moisture given up by the potassium hydroxide solution, it FIG. 83. KNORR'S APPARATUS. 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 bulb 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. 264 THE LEAD AND ZINC PIGMENTS. 403. After the acid has all been introduced, the aspira- tion is continued, when the contents of the flask are gradu- ally heated to boiling, the valve 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 opera- tion. 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 appa- ratus allowed to cool with continued aspiration. The ab- sorption tubes are then removed and weighed, the increase in weight being due to carbon dioxide. 404. Where extreme accuracy is desired the carbon diox- ide after passing through the condenser should pass through a U-tube filled with calcium chloride, a (J-tube filled with lumps of dehydrated copper sulphate moistened with sul- phuric acid (sp. gr. 1.84), and then through a U-tube filled with pumice stone moistened with sulphuric acid before being absorbed by soda-lime. The air used for aspi- rating should also pass through a large U-tube filled with soda lime before passing through the small soda-lime tube C. In order to make the apparatus compact the soda-lime tubes may be laid side by side on a small rack constructed for the purpose, the soda-lime tubes being connected with each other by small U-shaped glass tubing connections. 405. Acetic Acid in White Lead. 1 " In the manufacture of white lead by any process involving the use of acetic acid, a certain portion of the acetic acid seems to be bound firmly so that it cannot be washed out in any ordinary process of manufacture. The amount of the acetic acid which is fixed by the white lead depends largely upon the quantity used in the process of manufacture. The Navy Yard specifications demand a white lead which shall not 1 G. W. Thompson, J. Soc. Chem. Ind., vol. xxiv, No. 9. ANALYSIS OF COMMERCIALLY PURE WHITE LEADS. 265 contain ' acetate in excess of fifteen one-hundredths of 1 per cent of glacial acetic acid.' It seems reasonable, fur- thermore, that whether the acetic acid is objectionable or not, the intelligent purchaser of white lead should be en- abled, as far as possible, to know what he is buying, and perhaps trace back results to some definite cause. 406. " Ordinary lead acetate solution will take up vary- ing amounts of lead oxide to form basic lead acetate. The more concentrated the lead acetate solution is, the less basic will be the formed acetate; for instance, the ordinary pharmacopoeia solution ' Liquor Plumbi Subacetatis ' contains two equivalents of lead to one of acetic acid, and, while this solution may be made more basic than this by adding an excess of litharge, the amount of litharge which it will take into solution in excess of that required to form the pharmacopoeia solution is comparatively small." 407. " Working with dilute solutions of lead acetate, however, solutions can be obtained containing as much as ten equivalents of lead to one of acetic acid. These very basic dilute solutions may, however, be regarded by some as supersaturated solutions, for the reason that the basic lead tends to separate out on slight provocation, carrying with it some acetic acid. If this very basic lead acetate, which separates out, is washed with distilled water, it appears to form a colloidal solution, from which the basic lead is readily precipitated in the presence of suspended inert material, and especially in the presence of electro- lytes. Ordinary water is usually used for washing white lead, and, as this water contains more or less saline sub- stances, any of this extremely basic acetate that is present will be precipitated with the white lead, and go into the finished product." 408. " Determination. 18 grams of the dry white lead are placed in a 500-c.c. flask, this flask being arranged for con- 266 THE LEAD AND ZINC PIGMENTS. nection with a steam supply, and also with an ordinary Liebig condenser. To this white lead is added 40 c.c. of syrupy phosphoric acid, 18 grams of zinc dust, and about 50 c.c. of water. The flask containing the material is heated directly and distilled down to a small bulk. Then the steam is passed into the flask until it becomes about half full of condensed water, when the steam is shut off and the original flask heated directly and distilled down to the same small bulk, this operation being conducted twice. The dis- tillate is then transferred to a special flask and 1 c.c. of syrupy phosphoric acid added to insure a slightly acid condition." 409. "The flask is then heated and distilled down to a small bulk say, 20 c.c. Steam is then passed through the flask until it contains about 200 c.c. of condensed water, when the steam is shut off and the flask heated directly. These operations of direct distillation and steam distillation are conducted until 10 c.c. of the distillate require but a drop of N/10 alkali to produce a change in the presence of phenolphthalein. Then the bulk of the distillate is titrated with N/10 sodium hydroxide, and the acetic acid calculated. It will be found very convenient in this titration, which amounts in some cases to 600 to 700 c.c., to titrate the dis- tillate when it reaches 200 c.c., and so continue titrating every 200 c.c. as it distills over." 410. " Conclusions. The details in this described method, as regards the supply of steam from an outside flask, its condensation and subsequent evaporation, are not essential to the process, but can, of course, be modified so as to con- form to the ordinary method of distilling acetic acid from acetate of lime. If the white lead contains appreciable amounts of chlorine, it is well to add some silver phosphate to the second distillation flask, and not to carry the dis- tillation from this flask too far at any time. If the dry ANALYSIS OF COMMERCIALLY PURE WHITE LEADS 267 white lead under examination has been obtained by extrac- tion as a residue from white lead paste, it is well that this extraction should be exceedingly thorough, as otherwise fatty acids may be held and distilled with the acetic acid. Even then they will not interfere with the final titration, as they may be filtered from the distillate before titration, should that be desired." CHAPTER XXVI. ANALYSIS OF THE ZINC PIGMENTS. 411. Moisture. Two grams of the pigment are weighed out on to a watch glass, provided with a cover glass and clip, dried for two hours in a steam oven, the cover glass placed in position and held by the clip, the glasses cooled in the desiccator and weighed. Loss in weight represents the amount of moisture in the pigment. 412. Silica. Weigh one gram of pigment into a 250-c.c. covered beaker, add 25 c.c. of concentrated hydrochloric acid, heat gently for five minutes, or until the pigment has dissolved (if lead sulphate is present in considerable quan- tity, this may take quite a few minutes), add 50 c.c. hot water, and continue the heating for about five minutes longer. Filter boiling hot with the aid of suction, washing thoroughly with boiling water so as to thoroughly remove all the lead and zinc salts from the filter-paper. The filter- paper and any residue of silica is burned, ignited and weighed in the usual manner. Any weighable residue is reported as silica. 413. This treatment may give results that are slightly low, owing to the slight solubility of silica in strong hydro- chloric acid, but for commercial purposes this slight error may be neglected. In carefully prepared zinc pigments the amount of silica present will be unweighable ; even with careless processing the amount will seldom exceed a very few hundredths of one per cent. 414. Sulphur Dioxide. Weigh 3 grams of the pigment into a 250-c.c. beaker; add 100 c.c. of distilled water, that has been recently boiled and cooled. Add 5 c.c. of concen- 268 ANALYSIS OF THE ZINC PIGMENTS. 269 t rated sulphuric acid, stir thoroughly and allow to stand 15 minutes. Titrate with standard hundredth normal iodine solution, using starch paste as an indicator. 1 c.c. hundreth normal iodine = 0.00032 gram sulphur dioxide. 415. Preparation of Reagents Iodine Solution. Dis- solve 1.268 grams of pure iodine and 1.8 grams of potassium iodide in about 150 c.c. of water in a graduated liter flask. After solution, fill to the mark with water that has been freshly boiled. 416. Sodium Thiosulphate. Dissolve 2.5 grams in recently boiled distilled water and make up to one liter. Preserve in a brown glass bottle or one that has received a liberal coat of asphaltum. 417. Starch Paste. One gram of starch is boiled in 200 c.c. of distilled water. 418. Standardizing the Sodium Thiosulphate Solution. Pipette 20 c.c. of standard potassium dichrornate solution in a 250-c.c. beaker; add 10 c.c. of a 15-per cent solution of potassium iodide. Add to this 5 c.c. of strong hydro- chloric acid. Allow the solution of thiosulphate to run in slowly from a burette until the yellow color has almost disappeared. Add a few drops of starch paste and continue the addition of thiosulphate with constant stirring until the blue color just disappears. The burette reading is then made and the value of the thiosulphate calculated. 419. Standard of Acceptance. A good grade of zinc oxide should contain only a trace of sulphur dioxide. Many paint chemists reject oxides containing more than six hun- dred ths of one per cent. The reason for this is that the sulphur dioxide affects the character of the linseed oil very strongly, causing the paint to thicken and ultimately " liver " in the package. This may be shown in an ex- perimental way by dividing a sample of zinc oxide into 270 THE LEAD AND ZINC PIGMENTS. two parts, exposing one part to an atmosphere of sulphur dioxide, then spreading equal amounts of both samples on a glass plate and mixing to a paste with the same number of drops of oil in exactly the same manner. It will be found that the sample containing the sulphur dioxide will be thicker and stiffer than the other, showing the effect of the sulphur dioxide on the oil. 420. Reaction with Rosin Products. In the presence of rosin products of any kind, such as are often used in the driers of mixed paints, sulphur dioxide acts as a contact agent of great strength, causing changes all out of propor- tion to the amount present, often resulting in hardening, " washing " of the paint film, " livering " in the package, etc. These results will be influenced to a considerable degree by the acidity, moisture, and temperature of the paint, and hence no hard and fast deductions can be made as to what may .be expected of any particular paint con- taining sulphur dioxide in excess of the prescribed amount. 421. Zinc Sulphate. Ten grams of the pigment are weighed into a 250-c.c. Erlenmeyer flask, 100 c.c. of boil- ing water added. The contents of the flask are then shaken thoroughly for several minutes and filtered and the residue on the filter paper washed with several por- tions of boiling water. The soluble zinc in the filtrate is then titrated as described under the Estimation of Zinc by titration with ferrocyanide, and calculated to zinc sulphate. 422. It is not advisable to boil the zinc oxide pigment with the water, as interaction may occur between the zinc oxide and any lead sulphate present, resulting in the for- mation of more zinc sulphate. Neither is it wise to esti- mate the soluble combined sulphuric acid in the hot aqueous filtrate and calculate to zinc sulphate, as there often seems to be an excess over what is required to form ANALYSIS OF THE ZINC PIGMENTS. 271 the normal sulphate of zinc and hence the results are apt to be too high. 423. Effect. Zinc sulphate is not considered by many paint chemists to be as objectionable in zinc pigments as sulphur dioxide, and is often permitted in amounts under one per cent. In amounts above one per cent it seems to act as an astringent on the oil when used in the prepara- tion of mixed paints, tending to prevent the proper pene- tration of the wood, especially if the paint has been ground for some length of time. A prominent paint chemist dis- cusses its effect as follows: " The action of zinc sulphate is two-fold : first, as an astringent upon the oil and tending to cause a distinct demarcation between two coats; and second, that of a contact agent, facilitating reaction be- tween the different pigments. The visible results of its presence are peeling and ' washing.' Apparently, rather more than the normal amount of moisture must be present to cause its activity, and if the paint coat has set under dry or normal conditions, the zinc sulphate produces no apparent effect." In the exposure tests conducted by the author, the worst cases of " washing " have occurred with zinc pigments in which the sulphur dioxide was less than one one-hundredth of a per cent and the zinc sulphate between one and one and one-half per cent. 424. Lead. The lead present in zinc pigments is usually in the form of sulphate and may be estimated by either of the following methods. 425. Method I. The filtrate from the silica, which need not exceed 100 c.c. in volume if the washing has been judiciously conducted by suction or the hydrochloric acid solution, if silica is absent, is evaporated very nearly to dry ness in an uncovered beaker on the hot plate, avoiding actual boiling, 10 c.c. of warm water added and evapo- rated again nearly to dryness in order to expel the hydro- 272 THE LEAD AND ZINC PIGMENTS. chloric acid. Cool, add 30 c.c. dilute sulphuric acid, heat to boiling for five minutes in covered beaker, cool, add 50 c.c. of alcohol and allow to stand one-half hour or until all of the lead sulphate is precipitated from solution. Filter through a weighed Gooch crucible, washing thoroughly with 50 per cent alcohol, until the precipitate is entirely freed from zinc sulphate. Dry on hot plate, heat gently over a Bunsen burner, cool in desiccator, and weigh as lead sulphate. If heated over the flame before drying, a portion of the lead is liable to be reduced to lead oxide by the alcohol, and the weight will be low. 426. Method II. The lead may be separated from the zinc in a solution barely acid with hydrochloric acid, by hydrogen sulphide, the precipitated lead sulphide dis- solved in nitric acid and titrated with standard molybdate or bichromate solution as described in Chapter XXX, Analysis of Combination White Leads, and White Paints. 427. Method III. The amount of lead sulphate may be rapidly estimated by dissolving a weighed amount of the pigment in dilute acetic acid, filtering on to a weighed Gooch crucible, washing with warm water, heating gently, and weighing the lead sulphate direct. Lead sulphate being slightly soluble in acetic acid the results will be somewhat low and can only be considered as roughly approximate. 428. Total Zinc. The zinc can be rapidly and accu- rately estimated volumetrically by the following methods. 429. I. Potassium Ferrocyanide Method. Preparation of reagents. 430. Standard Zinc Solution. Dissolve 10 grams; of chemically pure zinc in hydrochloric acid in a graduated liter flask, add 50 grams of ammonium chloride and "make up to one liter. ' r : 1 c.c. = 0.01 gram zinc or 0.01245 gram zinc oxide; : ^ ANALYSIS OF THE ZINC PIGMENTS. 273 431. Standard Potassium Ferrocyanide Solution. Dis- solve 46 to 48 grams of crystallized potassium ferrocyanide in water, make up to 1000 c.c. 432. Uranium Nitrate Solution. Dissolve 15 grams of uranium nitrate in 100 c.c. of water. 433. Standardizing the Ferrocyanide Solution. To deter- mine the value of the potassium-ferrocyanide solution, pipette 25 c.c. of the zinc solution into a 400 c.c., beaker. Dilute somewhat and make faintly alkaline with ammonia, bring to a faintly acid condition with hydrochloric acid and then add 3 c.c. excess of the concentrated acid, dilute to a total volume of about 250 c.c., heat to 80 C. and titrate as follows: Pour off about 10 c.c. of the zinc solu- tion into a small beaker and set aside, run the ferrocya- nide into the remainder from a burette, a few c.c. at a time, until the solution takes on a slight ash gray color, or until a drop of the solution placed in contact with a drop of the uranium nitrate solution on a porcelain plate turns to a distinct brownish color. 434. Often the end point has been passed by quite a little. The 10 c.c. of zinc solution that has been reserved is now added and the titration continued, drop by drop, testing a drop of the solution carefully on the porcelain plate after each addition of ferrocyanide solution. Some little time is required for the test drop to change color, so that the end point may have been passed slightly; this may be corrected for by making a memorandum of the burette readings, having the test drops arranged in regular order and taking as the proper reading the one first show- ing a distinct brownish tinge. Having noted the number of cubic centimeters ferrocyanide required for the titration of the standard zinc solution, the value of 1 c.c. may be readily calculated. 274 THE LEAD AND ZINC PIGMENTS. 435. Titration of Sample. One-half gram of the sample if high in zinc, or 1 gram if the zinc content is fairly low, is dissolved in a covered beaker in 10 c.c. of hydrochloric acid and 10 c.c. of water, the solution diluted somewhat, neutralized with ammonia and treated exactly as de- scribed above for the standard zinc solution, care being taken to titrate to exactly the same depth of color on the porcelain test plate. If the method is carefully carried out, the procedure being uniformly the same in each deter- mination, the results will be found satisfactorily accurate. 436. II. Precipitation of Zinc as Carbonate. The alco- holic filtrate from the lead sulphate method of estimating lead is heated gently until practically all of the alcohol has been driven off. The remaining liquid is transferred to a porcelain dish provided with a beaker cover, and sodium carbonate added cautiously until the liquid is alkaline, care being taken that no loss occurs due to the efferves- cence. The zinc is precipitated as a basic carbonate, and the solution should be boiled gently for a few minutes in order to insure complete precipitation. As stated above this operation should be conducted in a porcelain dish, as the boiling akaline solution attacks glass to a consider- able extent. Allow the precipitate to subside, decant through a filter, and boil the precipitate three times with water, decanting each time, wash thoroughly with boiling water, dry and remove the precipitate as completely as possible from the filter paper. Saturate the paper with a strong solution of ammonium nitrate, dry again and ignite the paper. The ammonium nitrate serves to oxidize any of the zinc that is reduced to the metallic state by the carbon of the filter paper and which would otherwise be lost by volatilization. The precipitate is then intro- duced into the crucible and converted by ignition into the oxide and weighed as such. ANALYSIS OF THE ZINC PIGMENTS. 275 437. III. Precipitation of the Zinc as Phosphate. The alcoholic filtrate from the lead sulphate after the removal of the alcohol as described above is diluted somewhat if necessary, about 20 to 30 grams of dry ammonium chloride added and made alkaline with ammonia, then just barely acid with acetic acid and 10 c.c. of a cold saturated solu- tion of microcosmic salt added. The solution is diluted to a bulk of about 200 c.c., heated nearly to boiling with vigorous stirring, in order to make the precipitate crystal- line. Cool, make exactly neutral with amrnonia, allow to stand until the precipitation is complete, filter on to a weighed Gooch crucible, washing with ammonium nitrate solution, ignite, and weigh as zinc pyrophosphate. 438. Combined Sulphuric Acid. Dissolve 0.5 gram to 1 gram of the pigment, according to the amount of sul- phates present, in Water, 25 c.c. Ammonia, 10 c.c. Hydrochloric acid, a slight excess. 439. Dilute to 200 c.c. and add a disk of aluminum foil, which should about cover the bottom of the beaker. Boil gently until the lead is precipitated, holding the disk if necessary to the bottom of the beaker with a glass rod. The completion of precipitation is shown by the lead ceasing to coat or cling to the aluminum. Decant through a filter, pressing the lead sponge into a cake and washing thoroughly to free from solution. 440. Add to the filtrate a few drops of bromine water, boil and precipitate with barium chloride in the usual manner for sulphates. In order to avoid a possible reduc- tion of a portion of the barium sulphate in the pores of the filter paper during its incineration, the precipitate may be filtered directly on to a Gooch crucible, which after being 276 THE LEAD AND ZINC PIGMENTS. weighed has a disk of ashless filter paper placed on top of the customary asbestos felt. This will effectually prevent any of the precipitate from burrowing through the filter. The ignition of the precipitate in the presence of the small disk of filter paper will cause no appreciable reduction to sulphide. 441. Calculations. The amount of zinc present as sul- phate of zinc is deducted from the total zinc and the remainder calculated to zinc oxide. The sulphuric acid combined with the zinc is deducted from the total combined sulphuric acid and the remainder calculated to lead sul- phate. Any excess of lead over that required to combine with the sulphuric acid is calculated to lead oxide. Unless sublimed lead is present there will be little or no lead oxide. 442. Estimation of Arsenic and Antimony in Zinc Leads. Weigh 2 grams of the sample into a 200-c.c. digestion flask. Add 7 grams of potassium bisulphate, 0.5 gram of tartaric acid, and 10 c.c. of concentrated sulphuric acid. Digest carefully at first, but finally with the full power of a Bunsen burner until a clear mass remains, containing but little free sulphuric acid. Cool, spreading the melt around on the sides of the flask. And 50 c.c. of water, 10 c.c. of strong hydrochloric acid, and digest for about twenty minutes without boiling. 443. Cool thoroughly under the tap, and filter off the separated lead sulphate. Dilute the filtrate to about 300 c.c. with hot water, maintain the liquid warm, and pass in hydrogen sulphide for about fifteen minutes or until precipitation is complete. Filter, washing with hydrogen sulphide water. Digest filter and contents in a rather small amount of yellow ammonium sulphide. Filter on suction cone, washing with as small a quantity of water as possible. ANALYSIS OF THE ZINC PIGMENTS. 277 444. Digest the filtrate with 3 grams of potassium bisulphate and 10 c.c. of strong sulphuric acid over a free flame until all of the free sulphur and the larger portion of free acid are expelled. Cool, spreading the melt around on the sides of the flask as before. Add 25 c.c. of water and 10 c.c. of strong hydrochloric acid, and warm to effect complete solution. Cool under the tap, add 40 c.c. of strong hydrochloric acid, and pass in hydrogen sulphide until complete precipitation of the arsenic takes place, 15 to 30 minutes. The antimony remains in solution. 445. Filter off the precipitated arsenious sulphide on to a weighed Gooch crucible, washing with a mixture pf two volumes of hydrochloric arid and one of water. The filtrate is reserved at this point for the estimation of anti- mony. The precipitate is next washed with alcohol, the crucible and contents placed in a small beaker, the cruci- ble nearly filled with carbon bisulphide, and the contents allowed to digest at ordinary temperature for about twenty minutes in order to dissolve the free sulphur. The carbon bisulphide is removed by suction, the crucible dried in the steam oven, cooled, and the precipitate weighed as arsenious sulphide and calculated to arsenious oxide. Weight arsenious sulphide X 0.8043 = weight arsenious oxide. 446. Instead of weighing as the sulphide, the arsenic may be estimated volumetrically as follows: Wash out the hydrochloric acid from the sulphide precipitate with hydro- gen sulphide water. Digest filter and contents in a little warm ammonium sulphide, filter on a suction cone, wash- ing with a little dilutea mmonium sulphide solution. Place the filtrate in digestion flask, add 2 to 3 grams of potassium bisulphate and 5 c.c. of strong sulphuric acid. Evaporate, boiling to a small bulk, and then manipulate 278 THE LEAD AND ZINC PIGMENTS. the flask over a free flame until the sulphur is entirely expelled and most of the free acid also. Take up, after cooling, by warming with 50 c.c. of water, and then boil sufficiently to expel any possible sulphur dioxide. Now drop in a bit of litmus paper as an indicator, and then add ammonia until the solution is slightly alkaline. Again slightly acidify with hydrochloric acid and cool to room temperature. Finally, add 3 to 4 grams of sodium acid carbonate and a little starch liquor and titrate with standard iodine solution. Pay no attention to a slight discoloration toward the end, but proceed slowly until a single drop of the iodine produces a strong permanent blue color. 447. Preparation of Iodine Solution. The iodine solu- tion may be prepared by dissolving about 11 grams of iodine in a little water with the addition of about 20 grams of potassium iodide and diluting to 1 liter. Stand- ardize with arsenious oxide. Dissolve about 0.150 gram in 5 c.c. of strong hydrochloric acid by warming very gently, dilute and neutralize as described above, and finally titrate with the iodine solution. One c.c of the latter will equal about 0.003 gram of arsenic. 448. Antimony. Very nearly neutralize the filtrate reserved for the antimony estimation with hydrochloric acid, dilute with double its volume of hot water, and pass in hydrogen sulphide until all of the antimony is precipi- tated. Filter, washing with hydrogen sulphide water. Digest filter and contents in a little ammonium sulphide, filter on suction cone and wash with dilute ammonium sulphide. Place the filtrate in the digestion flask and add about 3 to 4 grams of (pure) potassium bisulphate and 10 c.c. of strong sulphuric acid. Boil as previously de- scribed to expel first the water, then all the free sulphur, and finally most of the free acid. ANALYSIS OF THE ZINC PIGMENTS. 279 449. Cool, add 50 c.c. of water and 10 c.c. of strong hydrochloric acid. Heat to effect solution, and then boil for a few minutes to expel any possible sulphur dioxide. Finally, add 10 c.c. more of strong hydrochloric acid, cool under the tap, dilute to about 200 c.c. with cold water and titrate with a standard solution of potassium perman- ganate. The solution ordinarily used for iron titrations will answer. The oxalic acid value of the permanganate multiplied by 0.9532 will give the antimony value. 450. Methods of Determining Small Amounts of Arsenic and Antimony in Use at Canon City, Colorado. 451. Method I. Take two or three grams of pigment and dissolve in 10 c.c. nitric acid and 10 c.c. sulphuric *ac id. Heat to expel the nitric acid and evaporate to sulphuric fumes. The advantage of the nitric acid is to oxidize the arsenic present and thereby avoid any loss of arsenious acid by volatilization. Allow to cool and dilute with cold water, add about 50 per cent of the volume of alcohol to insure complete precipitation of all lead as lead sulphate. Filter and wash, boil filtrate to expel alcohol, and add about ten to fifteen cubic centimeters hydrochloric acid. Precipitate the warm solution with hydrogen sulphide. Filter and wash with dilute hydrogen sulphide water. All arsenic, antimony, and copper are on the filter as sulphides. Test filtrate with hydrogen sulphide as a check on precipitation. 452. Dissolve the sulphides in caustic potash solution, then bring to a boil and pass hydrogen sulphide into warm solution as before. Filter and test filtrate. Wash with dilute ammonium sulphide solution. All arsenic and anti- mony are in filtrate and any copper present is on the filter. If any copper is present, dissolve and titrate by the iodide method. 453. Make filtrate acid with hydrochloric acid and add about 10 c.c. excess and pass in hydrogen sulphide gas as 280 THE LEAD AND ZINC PIGMENTS. before. Filter off the sulphides of arsenic and antimony and wash with hydrogen sulphide water. Dissolve these sulphides in about 10 c.c. aqua-regia, then dilute with water and make alkaline with ammonia, adding about 25 c.c. excess. Then add from one to two grams tartaric acid and 10 to 15 c.c. magnesia mixture. Allow to stand over night. All the arsenic is precipitated as ammonium mag- nesium arsenate. Antimony remains in solution, being held there by the tartaric acid present. Filter off the ammonium magnesium arsenate, washing with cold water containing a little ammonia, then dry, ignite, and weigh as magnesium pyroarsenate. 454. Acidify the filtrate with hydrochloric acid and pre- cipitate the antimony with hydrogen sulphide as before; filter and wash with hydrogen sulphide water. Separate the antimony sulphide from the filter paper and dissolve the adhering particles with ammonium sulphide, trans- ferring to a beaker. Wash with ammonia and evaporate to dry ness on water bath. Carefully add a few drops of nitric acid and then 1 to 2 c.c. of fuming nitric acid to oxi- dize the antimony. Then evaporate to small bulk for crucible, and heat to dryness on water bath, then ignite at low red heat to constant weight. Weigh as lead sulphate. 455. Method II. Treat ten grams pigment in No. 3-A casserole with about ten grams potassium bisulphate, 10 c.c. nitric acid, 15 c.c. sulphuric acid, and about 0.5 gram tartaric acid. Run to strong fumes; continue heating until all the carbon is destroyed and the solution is clear. Cool, dilute, and boil until soluble sulphates are in solution. Cool, filter, and wash thoroughly. Add tartaric acid and pass hydrogen sulphide gas. Filter off arsenic and antimony sulphides. Dissolve precipitate in potassium hydroxide solution and filter. Pour filtrate into solution of hydro- chloric acid (2 to 1). Pass hydrogen sulphide gas and ANALYSIS OF THE ZINC PIGMENTS. 281 filter off As 2 S 3 on a weighed Gooch crucible. Wash with alcohol and carbon bisulphide to remove sulphur. 456. Neturalize filtrate until Sb 2 S 3 begins to precipitate. Dilute with equal volume of water, pass hydrogen sulphide gas, and filter off precipitate, Sb 2 S 3 , on a weighed Gooch crucible. Wash with alcohol and carbon bisulphide to remove sulphur. Dry and weigh. CHAPTER XXVII. ANALYSIS OF WHITE LEAD AND PAINTS IN OIL. 457. Securing a Fair Sample. There are probably more disagreements and differences between chemists engaged in paint analysis in the resulting analyses obtained than in any other field requiring the services of trained analytical chemists. The writer has seen the results obtained by taking a gallon of a mixed paint of one of the leading brands on the market and dividing it into quarts and send- ing the four cans to different chemists who made a specialty of paint analysis. The four analyses bore very little observable connection with the formula by which the paint was made or, in fact, with each other. These differences could have arisen from only the following causes : 1. The paint not being compounded strictly according to formula. 2. Chemical changes and loss of some of the volatile constituents in mixing and grinding. 3. Not securing a fair sample for analysis. 4. Inaccurate methods of analysis. 458. Variations from Formula. Where paints are made in large quantities, each mix representing 100 gallons or more, it is a very easy matter for the man who does the weighing or measuring to make a mistake. This is especially true of the liquid constituents, part of which are added before the mix is run through the mill and the remainder in the thinning tank. The keeping in mind the number of gallons of linseed oil, volatile oil, water, etc., added as the workman goes back and forth from the faucets to the mixer 282 ANALYSIS OF WHITE LEAD AND PAINTS IN OIL. 283 or thinning tanks, is not as easy as it may seem at first glance, especially if the batch is a large one. 459. Chemical Changes in Grinding. The chemical reactions that may occur between different pigments when subjected to the combined action of heat and pressure have not been given the consideration they should by the majority of paint chemists. The day of water-cooled paint mills is here, but there are many paint manufacturers who are yet grinding their various pigments in mills that are not water-cooled, and most of them have but little idea how hot the paste will get toward the close of a day's run ; 280 and even 300 F. are not unusual temperatures/ The effect of high-temperature grinding on white lead and lin- seed oil has already been spoken of under the discussion of properties of white lead. 460. The effect of pressure is well illustrated by the following experiment. Using considerable pressure, grind intimately 1 gram of lead sulphate with 3 grams of sodium carbonate for some minutes in an agate mortar, and it will be found that practically all of the lead sulphate has been converted into carbonate and the sodium carbonate into sodium sulphate. Bleached oil carrying traces of sulphuric acid and zinc oxide containing zinc sulphate will certainly react with white lead when ground under pressure at a comparatively high temperature. In this connection the catalytic action of sulphur dioxide, which occurs in greater or less quantities in zinc oxides and especially in leaded zincs, should not be overlooked, especially when these pig- ments are used in the manufacture of mixed paints. 461. In paint factories where the different operations are under the guidance of a capable chemist, losses arising from evaporation of the volatile thinners in the mixing tanks, etc., should not occur, but there is many a mixed paint that when sealed in the can does not contain the 284 THE LEAD AND ZINC PIGMENTS. same percentage of volatile thinners as was originally added. 462. Obtaining an Average Sample. The reason, how- ever, for the majority of the disagreements between paint chemists lies in not securing an average sample for analy- sis, i.e., the sample taken does not represent the average composition of the paint in the package to be analyzed. This is especially true of mixed paints. The can of paint submitted to the chemist may have been on a store shelf for some months, until the pigments have settled hard in the bottom of the can and the task of breaking them up and recombining them with the oil portion is by no means an easy one. Whenever a sample is received in which the pigments have settled out, the oil portion should be poured off as completely as possible, the remaining paste entirely removed from the can into the mixing can, which should have at least twice the capacity of the sample can. Using a very stiff spatula, break up the paste thoroughly and gradually work the oil portion back into the paste. The first addition of oil should be small and the paste worked thoroughly after each addition. When the oil is all in, the paint should run off from the spatula smoothly without showing any evidence of lumps. 463. Having reduced the paint to uniform consistency, it should be kept tightly covered to prevent loss of the volatile thinners until all the samples necessary for analy- sis have been taken out, and especial care should be taken to stir the paint thoroughly each time before taking the samples, as the heavier pigments tend to settle more rapidly than those having a lighter specific gravity. 464. Inaccurate Methods of Analysis. Inaccurate meth- ods in making the analysis have doubtless had consid- erable to do with the disagreements above mentioned. However, much progress has been made in improving ANALYSIS OF WHITE LEAD AND PAINTS IN OIL. 285 methods during the last few years, so that this considera- tion does not apply as seriously as formerly. 465. Extraction of the Vehicle. The pigment may be freed from oil in the following type of ap- paratus, although the Soxhlet extractor may be used if desired. A folded filter paper is inserted in a suitable sized S. & S. thimble, dried in the oven for a few min- utes, cooled in the desiccator, and weighed. A weighed amount of the sample re- duced to a uniform consistency is intro- duced into the thimble; 12 to 18 grams will furnish an ample amount of pigment for analysis. Ether can be used to advan- tage as the volatile solvent when the paint contains little or no water, but for paints containing a considerable amount of water, acetone will be found superior to ether as a solvent. In order to secure as complete a removal of the vehicle as pos- sible, the extraction should continue for 24 hours. In order to reduce the danger from fire, the extractor can be heated with advantage by means of an electrically heated water-bath. After the extraction is complete, the thimble and contents are dried for two to three hours in the steam oven, cooled in the dessicator, and weighed. The loss in weight suffered by the paint represents the amount of vehicle. The pigment is reduced to a uniformly fine powder and placed in a small tightly stoppered sample bottle until required for analysis. 466. Removal of Vehicle for Examination. A conven- FIG. 84. EXTRACTION APPARATUS. 286 THE LEAD AND ZINC PIGMENTS. lent method of obtaining sufficient vehicle from a paint for the determination of the volatile oils, the quality of the linseed oil, etc., is to fill a tall cylinder with such of the sample as is not needed for the water estimation (100 to 150 grams) and for obtaining the free pigment, corking it tightly and placing it in a tall copper can filled with water heated to about 70 C. By reducing the viscosity of the oil in this manner the pigment will settle quite rapidly, and in 24 hours, if the temperature is maintained at 70 C., sufficient oil may be siphoned off with the aid of the suction pump. For the removal of volatile oils by distillation with steam at 130 C. and an examination of the linseed oil remaining behind, as well as for the identi- fication and separation of the volatile oils from each other, the reader is referred to the " Analysis of Mixed Paints, Color Pigments, and Varnishes/' published by the writer. 467. Use of Centrifuge. By far the most convenient method of obtaining sufficient vehicle for examination is by centrifuging the paint. In the average laboratory an electric centrifuge is the most convenient type. The cyl- inders used may be of glass, but preferably of aluminum, as the pressure on the ends will often exceed 50 pounds per square inch when the centrifuge is in motion. The bottoms of the cylinders should be removable, being screwed on to the cylinder. This permits of the easy removal of the precipitated paint and the rapid cleaning of the cylinders. 468. It is necessary that the cylinders opposite each other be evenly balanced, and it is always advisable to balance up the cylinders on the scales before placing them in the centrifuge. The cylinders should be tightly corked to prevent loss by evaporation of the volatile thinners, and live steam admitted into the centrifuge chamber suffi- cient to heat the contents of the tubes to about 70 C. ANALYSIS OF WHITE LEAD AND PAINTS IN OIL. 287 In the majority of cases the pigment will be thrown out rapidly and cleanly and, by using a number of cylinders, an ample amount of the oils may be easily obtained. 469. In the factory laboratory, where steam pressure is always available, an ordinary steam centrifuge such as is used for the ordinary Babcock butter-fat test is more convenient than the electric machine, as the steam leak- age into the upper chambers is sufficient to keep the tubes warm enough to insure the rapid precipitation of the pigment. 470. Use of Volatile Petroleum Thinners. A word may be said in connection with the increased use of -volatile petroleum products as paint thinners. In discussing this subject a prominent paint chemist states the problem as follows : " The rapid depletion of our turpentine forests and the rapid advance in the price of turpentine has brought prominently before every paint and varnish manufac- turer the absolute necessity for some volatile solvent capable of replacing entirely or in part the turpentine he used." The answer to this problem has been, naturally, the flooding of the market with an innumerable number of substitutes of uncertain merit. Some of the smaller paint companies, and especially those making paint for " a price," have adopted some of these substitutes without a careful investigation of their merits. On the other hand, some of the larger and more completely equipped com- panies have devoted considerable study to the question of turpentine substitutes, first endeavoring to ascertain the exact function of the turpentine in the paint and then seeking to prepare an article that would have the same essential properties and at the same time be free from objectionable characteristics. 471. According to the views of leading chemists, the 288 THE LEAD AND ZINC PIGMENTS. purpose of the turpentine in the paint is to increase the penetration of the oil and pigments into the wood and under coats of paints; to produce a " flat " or " semi-flat " surface, permitting a closer union with the succeeding coat, or for appearance as in the case of paints intended for inside use; to render the paint more fluid without the use of an excessive amount of oil; to increase the speed of the drying of the paint both by evaporation and by oxidation; and finally, to act as a bleaching agent on the oil, rendering the paint whiter; this, however, is not as essential as the other functions of the turpentine. Naturally chemists turned to the various petroleum products in their search for the desired substitute, and as a result of their studies a number of companies are using a product which does not behave like any of the petroleum distillates with which the chemist is ordinarily familiar. 472. Characteristics. This product is used under various trade names and differs slightly in composition according to the petroleum or petroleums from which it is derived, i.e., whether of Texas, Russian, or of some other origin. It is prepared so that it has a flash point slightly above that of turpentine, and hence as a fire risk it is as safe as turpentine, which is in marked contradistinction to benzine. It evaporates cleanly, and at a rate about or slightly slower than ordinary turpentine. In securing penetration of the paint it is fully equal to turpentine and is free from objectionable odors. In order to overcome the deficiency of not assisting the paint in drying by oxidation and the lack of bleaching action on the linseed oil, several paint manufacturers add a sufficient percentage of spirits of turpentine to supply these desired qualities. 473 . Reporting Results. The chemist in making an analysis of paints should be very careful in stating the composition of the volatile oils used in the vehicle, and not confound ANALYSIS OF WHITE LEAD AND PAINTS IN OIL. 289 these turpentine substitutes with ordinary benzine, which costs considerably less than half as much and is danger- ous to use on account of the fire risk and is too volatile to be accepted as a proper turpentine substitute. The analysis of these substitutes when once incorporated into the paint is somewhat difficult, but with care may be obtained by distillation as above mentioned. Having secured the volatile distillate and having freed it from all traces of water it may be redistilled, using a small distilling flask and carefully noting the temperatures at which the product passes over. The substitutes of recognized merit distil usually between 150 and 200 C. Any benzine present will pass over below 150 C., and kerosene mostly above 200 C. If the latter is present, however, a large portion will not be volatile in the steam distillation and will remain in the linseed oil, being readily detected in the latter by pouring six drops in a few cubic centimeters of an alcoholic solution of potash, boiling gently for two minutes and pouring into a little distilled water, a decided cloudiness indicating the presence of unsaponifiable petro- leum oils. CHAPTER XXVIII. ESTIMATION OF WATER IN WHITE LEADS AND PAINTS. 474. Occurrence. A fraction of 1 per cent of water may occur normally in the vehicle. A small percentage, 1 to 3 per cent, may be incorporated into the paint by the manufacturer under the belief that it secures better pene- tration 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 sepa- rated vehicle 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 sub- stance such as sublimed lead, as the water remains with the pigment. 475. 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 gelatirie may be immersed in the paint for several hours. If water is present the gelatine will soften and increase in weight, the adhering paint being removed by the use of petroleum ether and drying for a 290 WATER IN WHITE LEADS AND PAINTS. 291 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. 476. Estimation. Quantitatively, the water may be esti- mated by distillation, using a retort, the neck of which FIG. 85. ESTIMATION OP WATER. 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 292 THE LEAD AND ZINC PIGMENTS. 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- meters. 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. 477. 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 indicator 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. 478. It is impossible to remove the water by this method, without decomposing part of the lead hydrox- ide of the white lead, as it begins to lose the combined water at 105 to 120 C., the total 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 degrees results in the loss of all the water and a slight amount of carbon dioxide; at 200 degrees 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. 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 WATER IN WHITE LEADS AND PAINTS. 293 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 illuminating gas and the lead oxide present, if the temperature is raised .too high. 479. Estimation of Water with Amyl Reagent. This method, worked out by the author in his laboratory, has given excellent results, not only in mixed paints but also in paste and semi-paste goods. The determination re- quires only a few minutes and as the combined water of the white lead is not driven off, there is no correction to be applied. 480. Preparation of Amyl Reagent. The components of the amyl reagent amyl acetate and amyl valerianate should be as pure as possible, and unless of specified purity an inferior grade is apt to be obtained. Fritsche Bros., New York City, have furnished the most satisfactory article the author has been able to secure. The amyl acetate and valerianate should be washed, before mixing, with at least two changes of pure distilled water at room temperature. This can readily be accomplished in a large separatory funnel. Washing with water will remove prac- tically all of the impurities and such as may remain will be saturated at that temperature. The reagent is pre- pared by mixing 5 parts of amyl acetate with 1 part of amyl valerianate. 481. Determination. About 100 grams of the thoroughly stirred sample of paint are weighed into a flat-bottomed, 200-250-c.c., side-necked distilling flask. Add 75 c.c. of the amyl reagent and with a gentle rotary motion secure a thorough mixing of the contents of the flask. Connect with an upright condenser and distill over about 60 c.c. of the reagent into a cylinder graduated into tenths of cubic centimeters. When the larger portion of water has passed 294 THE LEAD AND ZINC PIGMENTS. over, the upper portion of the flask should be warmed gently with the naked flame, in order to expel the small portion of moisture that will have collected on the sides of the flask. The distillation should then be continued until the requisite amount of reagent has distilled over. The percentage of water can then be easily read off from the graduated cylinder and the contents of the distilling flask will be sufficiently liquid to insure easy removal. With paints high in volatile oils the volume of the dis- tillate should be increased to at least 75 c.c. 482. Practical Example. The following determination with a paint of known water content indicates the satis- factory nature and accuracy of this method. White lead 115 grams Linseed oil 40 grams Turpentine 10 grams Water 6 grams were thoroughly mixed, introduced into a side-necked dis- tilling flask, 75 c.c. of the prepared amyl reagent added and the mixture agitated until of uniform consistency. The following distillation figures were obtained: Temperature. Water. Amyl reagent and turpentine. 92-110C. 110-125C. 125-140 C. 140-145 C. 5.5 c.c. 0.9 c.c. 0.0 c.c. 0.0 c.c. 16 c.c. 13 c.c. 18 c.c. 14 c.c. 6.4 c.c. 61 c.c. The same mixture without the addition of water gave 0.3 c.c. of water when run as a blank. Theoretical percentage of added water 3 . 51 Percentage of water obtained (corrected ) . . . 3 . 56 CHAPTER XXIX. QUALITATIVE ANALYSIS OF COMBINATION WHITE LEADS AND PASTES. 483. Classification. The various pigments to be found in " combination leads," base whites and the various mixed paints may be divided into two classes, the so-called active pigments and the inert pigments. The active pigments comprise White lead. Sublimed white lead. Zinc oxide. Zinc lead white. Leaded zincs and Lithopone. The inert pigments comprise Barium sulphate (Barytes, Blanc fixe). Barium carbonate. Calcium carbonate (Whiting, Paris white, White mineral primer). Calcium sulphate (Gypsum, Terra alba). China clay (Kaolin). Asbestine (Magnesium silicate). Silica (Silex). The properties of the various active pigments have been discussed under their methods of manufacture and need not be taken up here. 484. Inert Pigments. The inert pigments have widely different properties not only from a chemical standpoint but from a physical standpoint as well, and while two pigments may have the same chemical composition they 295 296 THE LEAD AND ZINC PIGMENTS. may differ greatly in physical properties, producing entirely different results when used in paints. Hence it is practi- cally impossible to judge service values of paints contain- ing inert pigments from the chemical analysis. Chemical analysis, however, in conjunction with a careful micro- scopic examination, especially if a polarizing microscope be used, may give some idea of what the service value should be. 485. Barium Sulphate (Barytes, Blanc Fixe). Barytes is perhaps the most extensively used of the inert pigments. It more nearly approximates white lead in specific gravity and oil-taking capacity than any of the others. It is absolutely unaffected by acids, alkalies or atmospheric influences of any kind. Its hiding power or opacity when ground in oil is very low, and hence when used in any considerable percentage in a mixed paint or com- bination lead its presence is indicated by the reduced opacity of the paint film. The requisites of a high grade of barytes are whiteness and fineness. The cheaper grades of barytes have a yellowish gray color and are often treated with sulphuric acid to improve the color by removing the iron. A considerable portion of the barytes on the market is " blued/' either by precipitating the iron sulphate obtained by the treatment with the sul- phuric acid as Prussian blue, or adding the Prussian or ultramarine blue separately. The majority of paint manu- facturers, however, prefer to blue their goods them- selves, if necessary, during the process of manufacture. The fineness with which barytes has been ground can be easily determined by examination under the microscope after the acid soluble pigments have been dissolved out. 486. Blanc fixe is a precipitated barium sulphate. Owing to its more amorphous character it has a much greater hiding power than barytes. Its oil-taking capacity QUALITATIVE ANALYSIS OF LEADS AND PASTES. 297 is greater; it does not settle in a paint as badly as barytes and is much whiter; its cost, however, is about twice as great. It is largely used as an inert base for organic lakes. 487. Barium Carbonate. This pigment is used compar- atively little in the United States a* a paint pigment. In physical and chemical properties it much resembles white mineral primer, a form of calcium carbonate, although it does not require as much oil in grinding. Its specific gravity is about that of barytes. It dissolves readily in acetic, nitric and hydrochloric acids; sulphuric acid con- verts it slowly into insoluble barium sulphate. In the hundreds of mixed paints examined by the writer barium carbonate was found to be present in only one paint, although its presence in certain organic lakes is not uncommon in a precipitated form. 488. Calcium Carbonate, Paris White, Whiting, Alba Whiting, White Mineral Primer. Under the heading of calcium carbonate we have three distinct classes of pigments. Those obtained from 1. English cliffstone or similar chalk formations such as Paris white, gilders' whiting and commercial whiting. 2. Marble or a crystalline calcium carbonate such as marble dust, white mineral primer, etc. 3. Precipitated calcium carbonate such as alba whiting. 489. The English cliffstone pigments are usually put on the market in about three grades. The first grade is the whitest and most finely ground and bolted and is usually sold under some such name as Paris white, and finds its use largely in first quality mixed paints and combination leads. The second grade is slightly coarser and has a slightly grayish tint and is usually sold under some such name as gilders' whiting. It is also usually bolted, and is used in second and third grade paints. The third grade 298 THE LEAD AND ZINC PIGMENTS. is inferior in color and fineness to the other two grades. It finds its chief use in kalsomine; although it is used in some of the very inferior paints, it never should be, owing to the fact that it is not bolted, and therefore contains some relatively large particles. It is usually sold as com- mercial whiting. 490. The various forms of white mineral primer are of an entirely different nature physically from the cliffstone products, being fragments of small crystals. They have very little body in oil, being nearly transparent. They are usually whiter than Paris white and possess much greater tooth, but are not much used in mixed paints owing to the fact that they settle badly in the can and have very little opacity. They find their chief use in primers and in putty for making it work shorter. Being of a crystalline nature it is natural that they require less oil in grinding than Paris white. Alba whiting and other precipitated calcium carbonate pigments are very white, but being very light and fluffy require an enormous amount of oil in grinding. While it is not an easy matter to distinguish these different products in a paint, yet the microscope is of much value in determining the fineness of grinding. 491. Calcium Sulphate (Gypsum, Terra Alba). This pig- ment is found in combination white leads and exterior white paints only to a limited extent. Its chief use seems to be in certain lines of railroad paints and in dipping or implement paints. It is also used to some extent as a base for striking certain organic lakes upon, notably the para reds. The writer, despite the favorable opinions of many eminent paint authorities, does not believe that calcium sulphate, or gypsum, as it is more commonly known, is adapted for use in exterior paints owing to its solubility in water, it being soluble about one part in five QUALITATIVE ANALYSIS OF LEADS AND PASTES. 299 hundred. A linseed oil paint film is by no means impervious to moisture and the continued action of rains and storms cannot be otherwise than unfavorable, as the solvent action of the water in removing a portion of the gypsum .renders the paint film more porous and its disintegration more rapid. 492. Venetian reds often contain fifty to eighty per cent of calcium sulphate. The better class of Venetian reds are composed of fifty per cent of ferric oxide and fifty per cent of calcium sulphate. This calcium sulphate should not be confounded with the forms above discussed, as it has been subjected to the action of a high heat and is, therefore, insoluble in water, and is regarded as a proper constituent of Venetian reds. 493. Aluminum Silicate (China clay, Kaolin, Tolanite). This pigment also finds but little use in combination white leads owing to its low specific gravity. It is, however, used extensively in mixed paints, implement paints, and as an inert base for striking para and other organic reds upon, especially for colors which are used in dipping paints. Its functions and properties are very similar to those of mag- nesium silicate, it being essentially a suspender for prevent- ing settling in paints. It is very inert in its action with acids and alkalies. Strong hydrochloric acid with con- tinued boiling will dissolve a very slight fraction of one per cent, hence traces of aluminum may be found in a hydro- chloric acid solution of a paint containing aluminum sili- cate. Some of the silicates much in favor with the paint trade contain a considerable percentage of what is appar- ently uncombined silica. In mixed paints it is often used with magnesium silicate. Hence a microscopic examina- tion is usually required to determine whether the latter is present or not. It yields to treatment by fusion with sodium carbonate more readily than magnesium silicate. 300 THE LEAD AND ZINC PIGMENTS. When subjected to a high temperature it loses eleven to thirteen per cent of water of hydration. 494. Magnesium Silicate (Asbestine pulp, Talcose). This pigment is sold under the various names of white silicate, asbestine, asbestine pulp, etc. Large amounts are obtained from natural deposits in and around Gouverneur, N. Y. It has a very low specific gravity, and is much used in lead and zinc paints to prevent those pigments from settling hard in the bottom of the package. Chemically it is very inert, being unacted upon by any of the ordinary acids. It is, however, decomposable with hydrofluoric acid in a plati- num dish and by fusion with sodium carbonate. Fusion with potassium bisulphate decomposes it only partially. Continued heating at a bright red heat will cause a loss of three to five per cent in weight, due to loss of water of hydration. It is easily recognized under the microscope by the fibrous or rod-like structure of the particles. 495. Silica (Silex). There are two distinct kinds of silica to be found on the market, that obtained from crushed quartz, which is a very pure form of silica, and an impure form found in natural deposits especially in Illinois. The former possesses a very pronounced " tooth;" under the microscope the particles are very sharp and jagged, and it is quite transparent in oil. The second form is composed of rounded particles of a complex chemical nature; besides free silica there are usually found associated with it cal- cium carbonate, aluminum silicate and magnesium silicate, besides a small amount of magnesium carbonate. This product requires more oil in grinding, and has much more body, but considerably less tooth. 496. In the majority of cases a complete qualitative analysis of the pigments present is hardly worth the time it requires, as there is but little time lost in following the regu- lar quantitative scheme. If, however, a qualitative analy- QUALITATIVE ANALYSIS OF LEADS AND PASTES. 301 sis is desired, the following outline will be found sufficient in most instances, the removal of the vehicle previous to these tests being understood. 497. Carbonates. Effervescence with concentrated hydro- chloric acid indicates carbonates, or hydrogen sulphide if zinc sulphide be present, the latter being distinguished by its odor and by the fumes blackening a piece of filter paper moistened with lead acetate. 498. Barytes, Silica, Clay, or other Silicates. Boil above mixtures five minutes, dilute with boiling water, filter. An insoluble residue may be barytes, silica, clay, or other sili- cates. Test for barytes with flame test, using a platinum wire. A characteristic green color indicates barium. 499. Sulphates. Test a small portion of the acid filtrate for combined sulphuric acid with a few drops of barium chloride. 500. Lead. Test another small portion of the acid fil- trate with sulphuric acid. A white precipitate at once or on standing indicates lead. 501. Zinc. Take another small portion of the acid fil- trate and add a few drops of potassium ferrocyanide. A white precipitate with a bluish tinge indicates zinc. 502. Calcium. The remaining portion of the acid filtrate is made alkaline with ammonia and hydrogen sulphide passed in for five minutes. Filter and test filtrate for calcium with ammonium oxalate, setting aside in a warm place. 503. Magnesium. After completely precipitating the calcium, add a few drops of hydrogen sodium phosphate. A precipitate on standing indicates the presence of mag- nesium compounds. The identification of the forms in which the lead may occur can only be determined by the quantitative scheme if both sulphates and carbonates are present. CHAPTER XXX. QUANTITATIVE ANALYSIS OF COMBINATION WHITE LEADS AND PAINTS. 504. Total Lead. Weigh 1 gram of the dry pigment into a 250-c.c. beaker. Add 30 c.c. of strong hydrochloric acid, boil 5 minutes, add 50 c.c. of hot water, heat 15 minutes longer, settle, filter while hot, and wash thoroughly with boiling water. The washing should be begun the instant the solution has filtered through, in order to avoid any crystallization of lead chloride in the pores of the filter paper. Once formed the crystals can only be dissolved with difficulty and with the use of an excess of wash water, which, as stated, must be at boiling temperature. This operation is best conducted by the aid of suction. Casein and other products of a similar nature are occasionally used in the manufacture of mixed paints in considerable quantities, and the analyst should always be on the lookout for the possible presence of these substances. 505. The solution is made just alkaline with ammonia, then just acid to litmus with hydrochloric acid. It is very necessary that the solution be only barely acid, as a comparatively small quantity of free acid will keep consid- erable lead from precipitating. Having been made barely alkaline, which is indicated by the precipitation of the lead, the solution is brought to a faintly acid condition by using dilute hydrochloric acid (1 to 10). Dilute to about 350 c.c. Cool, pass in hydrogen sulphide gas, noting the color of the precipitate; if gray, some zinc is being thrown down; if reddish black, the solution is too acid; add a few drops of dilute acid or ammonia as the case requires. Settle, filter, and wash with cold water. 302 QUANTITATIVE ANALYSIS OF LEADS AND PAINTS. 303 506. Place filter and precipitate in 25 c.c. of nitric acid and 25 c.c. of water, heat gently until the lead has all dissolved as shown by the residual sulphur having a yellow to whitish color. Do not boil hard enough to thoroughly disintegrate the filter paper. If difficulty is experienced in dissolving the lead contained in the sulphur particles, it is better to collect them into a ball with the aid of a stirring rod and remove to a small beaker and treat with a few cubic centimeters of concentrated nitric acid, and heat until dissolved, then pour back into the larger beaker. 507. Pour solution and filter paper on to a suction funnel provided with a platinum cone. If any fine part ides pass through, pour the filtrate back again. This procedure permits the washing of the filter mass with a very small amount of water, thus saving considerable time in the subsequent evaporation. Add 5 c.c. of dilute sulphuric acid to filtrate, and evaporate until sulphur trioxide fumes appear. Cool, add 25 c.c. of water, 25 c.c. of alcohol; allow to stand one-half hour with occasional stirring; filter, using Gooch crucible, wash with dilute alcohol, dry, heat gently over ordinary lamp, and weigh as lead sulphate. 508. Calcium. The filtrate containing the zinc, calcium, and possibly magnesium is made slightly alkaline with ammonia, a few drops of a mercuric chloride solution (1 to 10) added, and a stream of hydrogen sulphide gas passed into the solution for about ten minutes. The addition of the mercuric chloride renders the precipitate granular and very easy to filter, and entirely obviates the difficulty of filtering a slimy zinc sulphide precipitate. In the analysis of tints where the zinc can- not be titrated until it has been freed from iron, the addi- tion of the mercuric chloride will not cause any trouble, 304 THE LEAD AND ZINC PIGMENTS. as treatment with hydrochloric acid results in the solution of the zinc only, the mercuric sulphide being insoluble in hydrochloric acid. Settle, decant, filter, and wash. 509. Evaporate the filtrate from abave precipitate to about 150 c.c., make alkaline with ammonia, add ammo- nium oxalate (50 c.c. for 1 gram of lime), usually 20 c.c. is sufficient, and set in a warm place for two or three hcurs. Filter, wash, ignite, and weigh as calcium oxide, or titrate precipitate with permanganate by placing filter and pre- cipitate in a 400-c.c. beaker, adding 200 c.c. of boiling water and 25 c.c. of dilute sulphuric acid, and titrate with standard tenth-normal potassium permanganate. 1 c.c. tenth-normal permanganate = 0.0028 gram CaO. 1 c.c. tenth-normal permanganate = . 0050 gram CaC0 3 . Barium carbonate is still to be found in certain mixed paints, and it is advisable to test for the presence of solu- ble barium before precipitating the calcium. 510. Magnesium. The filtrate from the calcium oxalate should be tested for magnesium, by treating with hydro- gen sodium phosphate. Allow to stand one-half hour, add 25 c.c. of ammonia, allow to stand one hour, then filter on to a Gooch crucible, wash with dilute ammonia, ignite, and weigh. Weight precipitate X 0.7575 = weight magnesium car- bonate. 511. Zinc Oxide. Reagents. Standard Zinc Solution. Dissolve 10 grams of chemically pure zinc in hydrochloric acid in a graduated liter flask, add 50 grams of ammonium chloride and make Up to one liter. 1 c.c. =0.01 gram zinc or 0.01245 gram zinc oxide. 512. Standard Potassium Ferrocyanide Solution. Dis- solve 46 to 48 grams of crystallized potassium ferrocyanide in water, make to 1000 c.c. QUANTITATIVE / NALYSIS OF LEADS AND PAINTS. 305 513. Uranium Nitrate Solution. Dissolve 15 grams of uranium nitrate in 100 c.c. of water. 514. Standardizing the Ferrocyanide Solution. To deter- mine the value of the potassium ferrocyanide solution, pipette 25 c.c. of the zinc solution into a 400 c.c. beaker. Dilute somewhat and make faintly alkaline with ammonia, bring to a faintly acid condition with hydrochloric acid, and then add 3 c.c. excess of the concentrated acid, dilute to a total volume of about 250 c.c., heat to 80 C. and titrate as follows: Pour off about 10 c.c. of the zinc solution into a small beaker and set aside, run the ferrocyanide into the remainder from a burette, a few cubic centimeters at a time, until the solution takes on a slight ash gray color, or until a drop of the solution placed in contact with a drop of the uranium nitrate solution on a porcelain plate turns to a distinct brownish color. Often the end point has been passed by quite a little. 515. The 10 c.c. of zinc solution that has been reserved is now added and the titration continued, drop by drop, testing a drop 6f the solution carefully on the porcelain plate after each addition of ferrocyanide solution. Some little time is required for the test drop to change color, so that the end point may have been passed slightly. This may be corrected for by making a memorandum of the burette readings, having the test drops arranged in regu- lar order and taking as the proper reading the one first showing a distinct brownish tinge. Having noted the number of cubic centimeters of ferrocyanide required for the titration of the standard zinc solution, the value of 1 c.c. may be readily calculated. 516. Titration of Sample. One-half gram of the sample, if high in zinc, or 1 gram, if the zinc content is fairly low, is dissolved in a covered beaker in 10 c.c. of hydrochloric acid and 10 c.c. of water, the solution diluted and treated 306 THE LEAD AND ZINC PIGMENTS. exactly as described above for the standard zinc solution, care being taken to titrate to exactly the same depth of color on the porcelain test plate. If the method is care- fully carried out, the procedure being uniformly the same in each determination, the results will be found satisfac- torily accurate. 517. Lead Sulphate. Dissolve 0.5 gram in water, 25 c.c. hydrochloric acid in light excess. Dilute to 200 c.c. and add a piece of aluminum foil which about covers the bottom of the beaker. It is important that this be held at the bottom by a glass rod. Boil gently until the lead is precipitated. Completion of this is shown by the lead ceasing to coat or cling to the aluminum. Decant through a filter, pressing the lead sponge into a cake to free it from solution. Add to filtrate a little sulphur-free bromine water, ignite, and weigh as barium sulphate. Calculate to lead sulphate by multiplying by 1.3 as a factor, unless calcium sulphate is present, in which case it is advisable to make use of Thompson's separation. 518. In the absence of barium sulphate, the combined sulphuric acid may be estimated by H. Mannhardt's method : Grind 1 gram of pigment with 1 gram of sodium carbonate, very intimately in an agate mortar. Boil gently for ten minutes, the combined sulphuric acid, and in the case of colors containing chromates, the chromic acid will pass into solution and may be estimated in the filtrate in the usual manner. If necessary collect the insoluble portion on a filter, dry, detach and triturate a second time. 519. Basic Carbonate of Lead (White lead). After deducting the amount of lead present in the pigment as sulphate of lead, calculate the rest of the lead as white lead by multiplying the remaining sulphate by 0.852, unless sublimed lead is suspected to be present, in which case the combined lead oxide must be taken into consideration. QUANTITATIVE ANALYSIS OF LEADS AND PAINTS 307 520. Insoluble Residue. The insoluble residue from the original hydrochloric acid treatment may contain barytes, magnesium silicate, silica and clay. Ignite, filter paper and residue until white, weigh as total insoluble matter; grind in agate mortar with about 10 times its weight of sodium carbonate, fuse for 1 hour in a platinum crucible, and dissolve out in hot water. 521. Barium Sulphate. The solution from the fusion is filtered. The residue coasists of barium carbonate, mag- nesium carbonate, etc., and is washed with hot water. The filtrate and washings are saved. Pierce filter paper and wash precipitate into clean beaker with hot dilute hydrochloric acid; finish washing with hot water, 4ieat to boiling, add 10 c.c. of dilute sulphuric acid to precipitate barium, filter, ignite, and weigh as barium sulphate. 522. Silica. The filtrate from the barium sulphate is added with care to the filtrate reserved in the preceding paragraph, making distinctly acid; evaporate to complete dryness, cool, add 15 c.c. of hydrochloric acid, heat to boiling, cool, settle, filter, ignite, and weigh as silica. 523. Alumina. The filtrate from the silica will contain all of the alumina except that which was dissolved in the original treatment with hydrochloric acid. This is quite constant, varying from .004 to .005 gram per gram of clay. The acid filtrates are made slightly alkaline with ammonia, and boil until odor disappears. Settle, filter, wash, ignite, and weigh as alumina. Weight alumina X 2.5372 = weight clay. Weight clay X .4667 = weight of silica in clay. Any difference greater than 5 per cent may be considered as free or added silica, according to Scott. 524. Calcium and Magnesium Oxides. If qualitative test shows presence of ' magnesium in insoluble residue 308 THE LEAD AND ZINC PIGMENTS. from the first hydrochloric acid treatment it was present probably as magnesium silicate. Treat filtrate from the aluminum hydroxide for calcium and magnesium oxides. Magnesium silicate contains 3-5 per cent combined water. 525. Hydrofluoric Acid Treatment. Instead of resorting to fusion with sodium carbonate, the insoluble residue, which should be weighed up in a clean platinum crucible, may be treated with several drops of pure concentrated hydrofluoric acid and of sulphuric acid and heated gently on a sand bath under the hood, using only sufficient heat to slowly volatilize the silica and sulphuric acid. Dissolve out in water acidulated with hydrochloric acid. The residue, which is barium sulphate, is filtered off and estimated as such. The filtrate will contain any aluminum, calcium and magnesium present and which may be estimated and calculated as oxides as above described. The combined weight of the barium sulphate, alumina, calcium and mag- nesium oxides subtracted from the weight of the insolu- ble residue used gives the weight of silica. This operation is much shorter than resorting to a fusion. 526. Mixed Carbonates and Sulphates. Occasionally paints are met with which contain calcium sulphate, calcium carbonate, sulphate of lead and white lead (basic carbonate of lead), in which case it is necessary to make a separation of the calcium compounds, which may be effected by Thompson's method as follows : 527. To 1 gram of the sample are added 20 c.c. of a mixture of nine parts alcohol (95 per cent) and one part of concentrated nitric acid. Stir, and allow to stand 20 minutes. Decant on a filter and repeat the treatment with the acid-alcohol mixture four times, allowing it to stand each time before decanting. The calcium carbonate will go into solution, while the calcium sulphate or gypsum remains undissolved. Add filter and contents to the QUANTITATIVE ANALYSIS OF LEADS AND PAINTS. 309 residue remaining in the beaker ; dissolve in hydrochloric acid with sufficient water to insure the solution of the calcium. Make alkaline with ammonia, pass in hydrogen sulphide for 10 minutes, boil, settle, filter. The filtrate and washings are concentrated to about 150 c.c. and the calcium precipitated with ammonium oxalate in the usual manner. The ignited precipitate is calculated to hydrated calcium sulphate. 528. Calculations. The ignited precipitate of calcium oxide obtained from the portion insoluble in the acid- alcohol mixture is subtracted from the total calcium weighed as oxide; the remaining calcium oxide is calcu- lated to calcium carbonate. The total carbon dioxide is determined in a portion of the sample, the portion due to the calcium carbonate is deducted from the total amount, and the remainder calculated to basic carbonate of lead. The combined sulphuric acid due to the sulphate of lime is deducted from the total combined sulphuric acid, and the remainder calculated to sulphate of lead. Wt. calcium oxide X 3.0715 = hydrated calcium sulphate. Wt. calcium oxide X 1.784 = calcium carbonate. Wt. calcium carbonate X 0.440 = carbon dioxide. Wt. carbon dioxide X 8.8068 = basic carbonate of lead. Wt. of hydrated sulphate of lime X 0.4561 = combined sulphuric acid. Wt. of combined sulphuric acid X 3.788 = sulphate of lead. CHAPTER XXXI. LABORATORY EQUIPMENT AND MANIPULATION. 529. The two essential requisites required of a paint chemist are accuracy and rapidity. Often a pigment or combination of pigments in oil or other thinners is brought into the laboratory and a complete analysis desired on the same day. Unless the laboratory is equipped with all possible labor and time-saving devices this will prove generally impossible. To the experienced paint chemist many of these devices naturally suggest themselves, but to the young chemist who is just beginning his paint work the following points, which have been of assistance to the author in his laboratory work, may be of interest. 530. Weight per Gallon. The use of the " cubic inch " with counterpoise weight will serve for this determina- tion excellently. 531. Specific Gravities. Special hydrometers reading 0.850 to 0.900 and 0.900 to 0.950 can be secured which will afford the desired accuracy with ordinary paint vehi- cles. For other determinations the Westphal balance should bs used. 532. Rapid Extraction of Pigment. The pigment can be rapidly freed from the vehicle by the use of a steam- heated high-speed centrifuge. The cylinders should be of aluminum provided with screw bottoms, rendering the removal of the pigment easy. The use of several of these cylinders, tightly corked, will afford sufficient vehicle for estimation of the amount and nature of volatile oils present. The centrifuge should be strongly constructed, as the pres- sure on the containing cups due to centrifugal force may 310 LABORATORY EQUIPMENT AND MANIPULATION. 311 reach 100 pounds to the square inch. If only the pigment is desired, thinning the sample with benzine before centri- fuging will materially hasten the operation. On removal from the tubes the pigment should be washed slightly with benzine or acetone on a suction filter. 533. Estimation of Water in Paints. This estimation may be accurately performed in a very few minutes by use of the amyl reagent as described in Chapter XXVIII. 534. Estimation of Volatile Oils. This determination can be made very rapidly by distilling with steam at 130 C. as described in " Analysis of Mixed Paints, Color Pigments and Varnishes," Holley and Ladd, page 39. The apparatus for this determination should have an*allotted place in the laboratory and be kept set up ready for use. 535. Rapid Drying. A double wall copper drying oven, to which is attached a Soxhlet ball condenser, a soldered connection being preferable, possesses obvious advantages over the more ordinary type of water oven, especially if a suitable mixture of toluene and xylene, boiling at 115C., be used instead of water. This w r ill assure a very rapid drying of any material in the oven and the top of the oven will serve as an excellent substitute for a hot plate for evaporations. The oven should be set in a small lead pan so as to avoid danger of fire in case of a leakage. 536. Filtering by Suction. Much time is saved by using the filter pump whenever possible. It also reduces the amount of wash water required so that the resulting fil- trates will not be too bulky for convenient handling or require concentration before undergoing further treat- ment. Instead of the ordinary filter-bottle or flask, a 500 to 1000-c.c. separatory funnel of the conical type can be used to advantage, it being supported by a clamp at- tached to the neck. The advantage consists in the fact that the filtrate can easily be drawn off from the bottom 312 THE LEAD AND ZINC PIGMENTS. without disturbing the funnel containing the precipitate, which is advantageous in the treatment of precipitates which tend to pass through the filter-paper, especially when subjected to washing, as for example chromium hydroxide, or when it is desired to examine a portion of the filtrate before completing the filtration. 537. Use of Gooch Crucible. The Gooch crucible affords the most rapid method for obtaining precipitates in the most desirable form for drying or ignition. Many precipi- tates which pass through an ordinary Gooch crucible, as for example barium sulphate, can be easily retained by inserting a disk of ashless filter paper on the layer of asbestos after the weighing of the crucible if it is to be subsequently ignited. This disk should be cut slightly larger than the crucible so that when moistened and fitted down tightly, it will be rimmed up slightly all around the edge. In collecting gelatinous precipitates the Gooch should not be allowed to suck dry until the filtering opera- tion is completed. 538. The preparation of the asbestos for use in the Gooch crucible is a most important item. The short-fiber asbes- tos sold for this purpose by the chemical supply houses should be shaken up in a large bottle of water, the heavy fibers allowed to settle for two or three seconds, the con- tents tjien poured into another bottle, leaving the heavy fibers behind, then allowed to settle until all but the finest particles have been deposited, which are then poured off, leaving a medium-fiber asbestos which when treated by boiling with hydrochloric acid to remove iron and any other impurities soluble in acid is excellently adapted for rapid filtering. 539. Bottles for Standard Solutions. Many of the stand- ard solutions used in paint analysis, such as potassium ferrocyanide, permanganate, sodium thiosulphate, etc., LABORATORY EQUIPMENT AND MANIPULATION. 313 have to be frequently restandardized on account of the effect of light upon them unless kept in a dark closet, which is not always easy to manage. By giving the bot- tles two coats of an opaque, quick-drying black paint, the solutions will keep their strength for considerable inter- vals of time, even in a strong light. APPENDIX. 316 THE LEAD AND ZINC PIGMENTS. 540. Table I. Atomic Weights. 1 Name. Symbol. O = 16. H= 1. Aluminium Al Antimony Sb Argon A Arsenic As Barium Ba Bismuth Bi Boron B Bromine Br Cadmium Cd Caesium Cs Calcium Ca Carbon C Cerium Ce Chlorine Cl Chromium Cr Cobalt Co Columbium Cb Copper Cu Erbium E Fluorine F Gadolinium Gd Gallium Ga Germanium Ge Glucinum Gl Gold Au Helium He Hydrogen H Indium In Iodine I Iridium Ir Iron Fe Krypton Kr Lanthanum La Lead Pb Lithium Li Magnesium Mg Manganese Mn Mercury Hg Molybdenum Mo 27.1 120.2 39.9 75.0 137.4 208.5 11.0 79.96 112.4 132.9 40.1 12.0 140.25 35.45 52.1 59.0 ' 94.0 63.6 166 19.0 156.0 70.0 72.5 9.1 197.2 4.0 1.008 114.0 126.85 193.0 55.9 81.8 138.9 206.9 7.03 24.36 55.0 200.0 96.0 26.9 119.3 39.6 74.4 136.4 206.9 10.9 79.36 111.6 131.9 39.8 11.91 139.2 35.18 51.7 58.56 93.3 63.1 164.8 18.9 155.0 69.5 71.9 9.03 195.7 4.0 1.0 113.1 125.9 191.5 55.5 81.2 137.9 205.35 6.98 24.18 54.6 198.5 95.3 J. Am. Chem. Soc., xxvi, 3. APPENDIX. 317 Table I (Continued) . Name. Symbol. O = 16. H= 1. Neodymium Nd 143 6 142 5 Neon Ne 20 19 9 Nickel Ni 58 7 58 3 Nitrogen Osmium N Os 14.04 191 13.93 189 6 Oxvffen O 16 15 88 Palladium Pd 106 5 105 7 Phosphorus P 31 30 77 Platinum Pt 194 8 193 3 Potassium K 39 15 38 86 Praseodymium Pr 140 5 139 4 Radium Ra 225 223 3 Rhodium Rh 103 102 2 Rubidium Rb 85 4 84 8 Ruthenium Samarium Ru Sm 101.7 150 100.9 148 9 Scandium Sc 44 1 43 8 Selenium Se 79 2 78 6 Silicon Si 28 4 28 2 Silver Ac 107 93 107 12 Sodium Na 23 05 22 88 Strontium Sr 87 6 86 94 Sulphur s 32 06 31 83 Tantalum Tellurium . . . Ta Te 183.0 127 6 181.6 126 6 Terbium Tb 160 158 8 Thallium Tl 204 1 202 6 Thorium Th 232 5 230 8 Thulium Tm 171 169 7 Tin Sn 119 118 1 Titanium Tungsten Ti W 48.1 184 47.7 182 6 Uranium u 238 5 236 7 Vanadium V 51 2 50 8 Xenon X 128.0 127 Ytterbium Yb 173 171 7 Yttrium Yt 89 88 3 Zinc Zn 65 4 64 9 Zirconium Zr 90 6 89 9 318 THE LEAD AND ZINC PIGMENTS. 541. Table II. Formulas and Molecular Weights. Name. Formula. Mol. Wt. Acid, acetic HC 2 H 3 O 2 60 Acid, arsenious H 3 ASO 3 125 9 Acid, boric H 3 BO 3 62 Acid citric H,C fi H,O 7 + H 9 O 210 Acid hydrochloric HC1 36 4 Acid, hydrosulphuric Acid nitric H 2 S HNO 3 34 63 Acid nitrous HNO 2 47 Acid oleic HC, 8 H 33 O 2 282 Acid, oxalic Acid sulphuric H 2 C 2 O 4 + 2H 2 O H 2 SO 4 126 98 Acid sulphurous H 2 SO, 82 Acid tannic C 14 H 1( iO 322 Acid, tartaric Amyl acetate Antimony chloride Antimony oxide HAHA C,H n C 2 H 3 O 2 SbCl, SbjO. 150 130 226.2 288 Antimony sulphide Sb 2 S, 336 Arsenious oxide AsoO, 309 8 Arsenious sulphide As 2 S 3 245 8 Barium carbonate BaCO 3 196 8 Barium chloride BaCl 2 + 2H 2 O 243 6 Barium nitrate Barium sulphate Ba(N0 3 ) 2 BaSO. 260.8 232 8 Benzole C 6 H 6 78 Calcium carbonate Calcium hydroxide Calcium sulphate Calcium sulphate, crystallized. Carbon dioxide Carbon disulphide CaCO 3 Ca(OH) 2 CaSO 4 CaSO 4 + 2H 2 O CO 2 CS 2 100 74 136 172 44 76 APPENDIX. 319 Table II (Continued). Name. Formula. Mol. Wt. Chromium trioxide CrO 100 4 Copper sulphate CuSO 4- 5H,O 249 2 Cuprous oxide Cu 2 O 142 4 Glycerin C,H,(OH) 92 Lead acetate. Pb(C 2 H O 2 ) 2 4- 3H 2 O 378 5 Lead acetate, basic Lead carbonate, basic Lead carbonate, normal Lead chromate Lead dioxide ... Pb.O(C 2 HA) 2 2PbCO 3 .Pb(OH) 2 PbCO, PbCrO 4 PbO 2 547 773.5 * 266.5 323.0 238 5 Lead nitrate Pb(NO,) 9 330 5 Lead oxide Lead, red oxide of PbO Pb-A, 222.5 683 5 Lead sulphate Potassium bichromate piM K 2 Cr 2 O 7 302.5 294 8 Potassium carbonate K 2 CO 3 + 3H,O 330 Potassium chromate K 2 CrO. 194 4 Potassium ferrocyanide Potassium hydroxide K^e5N). + 3H,0 421.9 56 Potassium iodide KI 165 6 Potassium permanganate Silver nitrate KMnO 4 AgNO 157 169 7 Sodium acetate . NaC 2 H O 2 + 3H O 136 Sodium arseniate NaoHAsO ~\- 7H 2 O 312 Sodium borate Na.jB O -I- 10H 2 O 382 Sodium carbonate, dry Sodium carbonate, crystallized Sodium nitrate Na,jCO 3 NaaCO, + 10H 2 O NaNO 3 106 286 85 Zinc oxide ZnO 80 9 Zinc sulphate ZnSCX + 7H,O 286 9 Zinc sulphide ZnS 96 9 320 THE LEAD AND ZINC PIGMENTS. 542. Table III. Factors for Gravimetric Analysis. Determined as Required. Factor. ALO 3 Al 5303 AsJS, As 6093 AsoO, 8043 Mg 2 As 2 O 7 As 2 O 3 6372 Ba 5885 BaSO 4 . . PbSO 4 1 3004 BaSO 4 . . CaSO 4 5837 BaSO 4 . . . CaSO 4 2H 2 O 7382 BaSO 4 SO, 3433 BaSO 4 so! 2747 CaO Ca 7143 CaO CaCO 3 1 784 CaCO 3 CO 2 440 CaO CaSO 2H 2 O 3 0715 CaSO 4 2H 2 O SO 4561 CO 9 2PbCO 3 Pb(OH) 2 8 8068 Cr 2 O s PbCrO 4 4 2288 Cr,O, CrO 3 1 3137 Cr,O, PbCrO PbO 7 1438 FeA Fe 7000 K 2 SO 4 K 4491 K 2 PtCL K 1612 K 2 PtCL K 9 O 1941 MffoP 2 O 7 Mg 2188 Mg 2 PA. MgO 3624 Mg,PA MgCO, 7575 Na2SO 4 ^o 3 Na 3243 Na^CX Na,O 4368 PbSO 4 Pb 6832 PbSO 4 PbO 7359 PbSO 4 . . . Pb,O 4 0.7536 PbSO 4 . . 2PbCO 3 Pb(OH) 2 0.8526 PbSO 4 PbCrO 4 1 0676 Mg 2 P 2 O 7 PoO, 6376 SO 3 . PbSO 4 3 788 Zn ZnSO 4 2 478 Zn ZnO 1 2452 ZnSO 4 . ... ZnO 503 APPENDIX. 321 543. Table IV. Specific Gravities Corresponding to Degrees Baume for Liquids Lighter than Water. Degrees Baume. Specific gravity. Degrees Baume. Specific gravity. 10 1.000 37 0.843 11 0.993 38 0.838 12 0.986 39 0.833 13 0.979 40 0.829 14 0.973 41 0.824 15 0.967 42 0.819 16 0.960 43 0.815 17 0.954 44 (T.810 18 0.948 45 0.806 19 0.942 46 0.801 20 0.935 47 0.797 21 0.929 48 0.792 22 0.924 49 0.788 23 0.918 50 0.784 24 0.912 51 0.781 25 0.906 52 0.776 26 0.901 53 0.771 27 0.895 54 0.769 28 0.889 55 0.763 29 0.884 56 0.759 30 0.879 57 0.755 31 0.873 58 0.751 32 0.868 59 0.748 33 0.863 60 0.744 34 0.858 61 0.740 35 0.853 62 0.736 36 0.848 322 THE LEAD AND ZINC PIGMENTS. 544. Table V. Specific Gravities Corresponding to Degrees Baume for Liquids Heavier than Water. Degrees Baume. Specific gravity. Degrees Baume. Specific gravity. 1.000 37 .337 1 1.007 38 .349 2 .014 39 .361 3 .020 40 .375 4 .028 41 .388 5 .034 42 .401 6 .041 43 .414 7 .049 44 .428 8 .057 45 .442 9 .064 46 1.456 10 .072 47 1.470 11 .080 48 1.485 12 .088 49 1.500 13 .096 50 1.515 14 .104 51 1.531 15 .113 52 .546 16 .121 53 .562 17 .130 54 .578 18 .138 55 .596 19 .147 56 .615 20 .157 57 .634 21 .166 58 .653 22 .176 59 .671 23 .185 60 .690 24 .195 61 .709 25 1.205 62 .729 26 1.215 63 .750 27 1.225 64 .771 28 1.235 65 .793 29 .245 66 .815 30 .256 67 1.839 31 .267 68 1 . 834 32 .278 69 1.885 33 .289 70 1.909 34 .300 71 1.035 35 .312 72 1.960 36 1.324 APPENDIX. 323 545. Table VI. Relation of Baume Degrees to Specific Gravity, and the Weight per United States Gallon at 15-5 C. Baurne. $ 11 02 a Pounds in gallon. I Specific gravity. a ii |i Baume. * *! 02 fe c ii P 10 1 . 0000 8.33 38 0.8333 6.94 66 0.7142 5.95 11 0.9929 8.27 39 0.8284 6.90 67 0.7106 5.92 12 0.9859 8.21 40 0.8235 6.86 68 0.7070 5.89 13 0.9790 8.16 41 0.8187 6.82 69 0.7035 5.86 14 0.9722 8.10 42 0.8139 6.78 70 0.7000 5.83 15 0.9655 8.04 43 0.8092 6.74 71 0.6965 5.80 16 0.9589 7.99 44 0.8045 6.70 72 0.6930 5.78 17 0.9523 7.93 45 0.8000 6.66 73 0.6896 5.75 18 0.9459 7.88 46 0.7954 6.63 74 0.6863 5.72 19 0.9395 7.83 47 0.7909 6.59 75 0.6829 5.69 20 0.9333 7.78 48 0.7865 6.55 76 0.6796 5.66 21 0.9271 7.72 49 0.7821 6.52 77 0.6763 5.63 22 0.9210 7.67 50 0.7777 6.48 78 0.6730 5.60 23 0.9150 7.62 51 0.7734 6.44 79 0.6698 5.58 .24 0.9090 7.57 52 0.7692 6.41 80 0.6666 5.55 25 0.9032 7.53 53 0.7650 6.37 81 0.6635 5.52 26 0.8974 7.48 54 0.7608 6.34 82 0.6604 5.50 27 0.8917 7.43 55 0.7567 6.30 83 0.6573 5.48 28 0.8860 7.38 56 0.7526 6.27 84 0.6542 5.45 29 0.8805 7.34 57 0.7486 6.24 85 0.6511 5.42 30 0.8750 7.29 58 0.7446 6.20 86 0.6481 5.40 31 0.8695 7.24 59 0.7407 6.17 87 0.6451 5.38 32 0.8641 7.20 60 0.7368 6.14 88 0.6422 5.36 33 0.8588 7.15 61 0.7329 6.11 89 0.6392 5.33 34 0.8536 7.11 62 0.7290 6.07 90 0.6363 5.30 35 0.8484 7.07 63 0.7253 6.04 95 0.6222 5.18 36 0.8433 7.03 64 0.7216 6.01 37 0.8383 6.98 65' 0.7179 5.98 324 THE LEAD AND ZINC PIGMENTS. 546. Table VII. Specific Gravity of Acetic Acid, Tem- perature 15 C. Per cent. Specific gravity. Per cent. Specific gravity. Per cent. Specific gravity. Per cent. Specific gravity. 100 1.0553 75 1.0746 50 1.0615 25 1.0350 99 .0580 74 1.0744 49 1.0607 24 1.0337 98 .0604 73 1.0742 48 1.0598 23 1.0324 97 .0625 72 1.0740 47 1.0589 22 1.0311 96 .0644 71 1.0737 46 1.0580 21 1.0298 95 .0660 70 .0733 45 1.0571 20 1.0284 94 .0674 69 .0729 44 1.0562 19 1.0270 93 .0686 68 .0725 43 1.0552 18 1.0256 92 .0696 67 .0721 42 .0543 17 1.0242 91 .0705 66 .0717 41 .0533 16 .0228 90 .0713 65 .0712 40 .0523 15 .0214 89 .0720 64 .0700 39 .0513 14 .0201 88 .0726 63 .0702 38 .0502 13 .0185 87 1.0731 62 .0697 37 .0492 12 .0171 86 1.0736 61 .0691 36 1.0481 11 .0157 85 1.0739 60 1.0685 35 1.0470 10 1.0142 84 1.0742 59 1.0679 34 1.0459 9 1.0127 83 1.0744 58 1.0673 33 1.0447 8 1.0113 82 .0746 57 1.0666 32 1.0436 7 1.0098 81 .0747 56 1.0660 31 1.0424 6 1.0083 80 .0748 55 1.0653 30 1.0412 5 1.0067 79 .0748 54 1.0646 29 1 . 0400 4 1.0052 78 .0748 53 1.0638 28 1.0388 3 1.0037 77 .0748 52 1.0631 27 1.0375 2 1.0022 76 .0747 51 1.0623 26 1.0363 1 1 . 0007 APPENDIX. 325 547. Table VIII. Specific Gravity of Nitric Acid. Speci fie gravity. De- grees B. 100 pts. contain grms. HN0 3 . Speci fie gravity. De- grees B. 100 pts. contain grms. HNO 3 . 1.007 1 1.5 .231 27 37.0 1.014 2 2.6 .242 28 38.6 .022 3 4.0 .252 29 40.2 .029 4 5.1 .261 30 41.5 .036 5 6.3 .275 31 "43.5 .044 6 7.6 .286 32 45.0 .052 7 9.0 .298 33 47.1 .060 8 10.2 .309 34 48.6 .067 9 11.4 .321 35 50.7 .075 10 12.7 .334 36 52.9 .083 11 14.0 .346 37 55.0 .091 12 15.3 .359 38 57.3 1.100 13 16.8 .372 39 59.6 1.108 14 18.0 .384 40 61.7 1.116 15 19.4 .398 41 64.5 1.125 16 20.8 .412 42 67.5 1.134 17 22.2 .426 43 70.6 1.143 18 23.6 .440 44 74.4 1.152 19 24.9 .454 45 78.4 .161 20 26.6 .470 46 83.0 .171 21 27.8 .485 47 87.1 .180 22 29.2 .501 48 92.6 .190 23 30.7 .516 49 96.0 .199 24 32.1 .524 49.5 98.0 .210 25 33.8 .530 49.9 100.0 .221 26 35.5 326 THE LEAD AND ZINC PIGMENTS. 548. Table IX. Specific Gravity of Hydrochloric Acid. Percentage by weight at 15.5C. compared with water at 4C. (Lunge & Marchlewski.) Specific gravity. Percent- tage HC1. Specific gravity. Percent- age HC1. Speci fie gravity. Percent- age HC1. 1.000 0.16 1.070 14.17 1.140 27.66 1.005 1.15 1.075 15.16 1.145 28.61 1.010 2.14 1.080 16.15 1.150 29.57 1.015 3.12 1.085 17.13 1.155 30.55 1.020 4.13 1.090 18.11 1.160 31.52 1.025 5.15 1.095 19.06 1.165 32.49 1.030 6.15 1.100 20.01 1.170 33.46 1.035 7.15 1.105 20.97 1.175 34.42 .040 8.16 .110 21.92 1.180 35.39 .045 9.16 .115 22.86 1.185 36.31 .050 10.17 .120 23.82 1.190 37.23 .055 11.18 .125 24.78 1.195 38.16 .060 12.19 .130 25.75 1.200 39.11 .065 13.19 .135 26.70 APPENDIX. 327 549. Table X. Sulphuric Acid. Percentage by weight of H,,SO 4 at 15.5C. (Lung and Isler.) Specific gravity. Percentage of H 2 SO 4 . Specific gravity. Percentage of H 2 SO 4 . Specific gravity. Percentage of H 2 S0 4 . 1.005 0.83 .200 27.32 1.395 49.59 1.010 1.57 .205 27.95 1.400 50.11 1.015 2.30 .210 28.58 1.405 50.63 1.020 3.03 .215 29.21 .410 51.15 1.025 3.76 .220 29.84 .415 51.66 1.030 4.49 .225 30.48 .420 52.15 1.035 5.23 .230 31.11 .425 52.63 1.040 5.96 .235 31.70 .430 53.11 1.045 6.67 .240 32.28 .435 53.59 1.050 7.37 .245 32.86 .440 % 54.07 1.055 8.07 .250 33.43 .445 54.55 1.060 8.77 .255 34.00 .450 55.03 1.065 9.47 .260 34.57 .455 55.50 1.070 10.19 .265 35.14 .460 55.97 1.075 10.90 .270 35.71 .465 56.43 1.080 11.60 1.275 36.29 .470 56.90 1.085 12.30 1.280 36.87 1.475 57.37 1.090 12.99 1.285 37.45 1.480 57.83 .095 13.67 1.290 38.03 1.485 58.28 .100 14.35 1.295 :vs 61 1.490 58.74 .105 15.03 1.300 39.19 1.495 59.22 .110 15.71 1.305 39.77 1.500 59.70 .115 16.36 .1.310 40.35 1.505 60.18 .120 17.01 1.315 40.93 1.510 60.65 .125 17.66 .320 41.50 .515 61.12 .130 18.31 .325 42.08 .520 61.59 .135 18.96 .330 42.66 .525 62.06 .140 19.61 .335 43.20 .530 62.53 .145 20.26 .340 43.74 .535 63.00 1.150 20.91 .345 44.28 .540 63.43 1.155 21.55 .350 44.82 .545 63.85 1.160 22.19 .355 45.35 .550 64.26 .165 22.83 1.360 45.88 .555 64.67 .170 23.47 1.365 46.41 .560 65.08 .175 24.12 1.370 46.94 .565 65.49 .180 24.76 1.375 47.47 .570 65.90 .185 25.40 1.380 48.00 .575 66.30 .190 26.04 1.385 48.53 .580 66.71 .195 26.68 1.390 49.06 .585 67.13 328 THE LEAD AND ZINC PIGMENTS Table X (Continued). Specific gravity. Percentage of H 2 SO 4 . Specific gravity. Percentage of H 2 SO 4 . Specific gravity. Percentage of H 2 SO 4 . 1.590 67.59 1.720 78.92 .825 91.00 .595 68.05 1.725 79.36 .826 91.25 .600 68.51 1.730 79.80 .827 91.50 .605 68.97 .735 80.24 .828 91.70 .610 69.43 .740 80.68 .829 91.90 .615 69.89 .745 81.12 .830 92.10 .620 70.32 .750 81.56 .831 92.30 1.625 70.74 .755 82.00 .832 92.52 1.630 71.16 .760 82.44 .833 92.75 1.635 71.57 .765 82.88 .834 93.05 1.640 71.99 .770 83.32 .835 93.43 1.645 72.40 .775 83.90 .836 93.80 1.650 72.87 .780 84.50 .837 94.20 1.655 73.23 .785 85.10 .838 94.60 1.660 73.64 .790 85.70 .839 95.00 .665 74.07 1.795 86.30 .840 95.60 .670 74.51 1.800 86.90 .8405 95.95 .675 74.97 1.805 87.60 .8410 97.00 .680 75.42 .810 88.30 .8415 97.70 .685 75.86 .815 89.05 .8410 98.20 .690 76.30 .820 90.05 .8405 98.70 .695 76.73 .821 90.20 .8400 99.20 1.700 77.17 .822 90.40 .8395 99.45 1.705 77.60 .823 90.60 .8390 99.70 1.710 78.04 .824 90.80 .8385 99.95 1.715 78.48 APPENDIX. 329 550. Measures, Weights and Temperatures. One Imperial gallon = 277.27 cubic inches. One wine gallon = 231.0 cubic inches. One wine gallon = 3.7854 liters. One wine gallon = 8.3389 pounds water at 4 C. One quart = 57.88 cubic inches. One quart .9464 liter. One liter 1.0567 quart. One cubic foot = 28,315 cubic centimeters. One cubic inch 16.38 cubic centimeters. One cubic centimeter .061 cubic inch. One pound Avoirdupois = 453.6 grams. One ounce Avoirdupois = 28.35 grams. One gram = 15.432 grains. One inch = .0254 meter. One foot = .3048 meter. One yard = .91438 meter. One meter = 39.3708 inches. INDEX. A. PAGE Acetic acid in white lead 264 conclusions 266 determination 265 Action of white lead on linseed oil 138 Adams White Lead Company 74 Adulteration of white lead 9 Ageing of white lead 134 American vermilion 222 care in grinding 224 preparation 223 Amorphous character of white lead 230 Analysis of commercially pure white leads 258 metallic lead 259 sandy lead 258 sulphur dioxide 258 tan bark 259 Analysis of zinc pigments 268 calculations 276 combined sulphuric acid 275 effect 271 lead 271 moisture 268 precipitation of zinc as carbonate '..:.'....'.. 274 precipitation of zinc as phosphate !" 275 potassium ferrocyanide method 272 reaction with rosin products 270 silica 268 standards of acceptance 269 sulphur dioxide 268 total zinc 272 zinc sulphate ' ." 270 Annual production of white lead 35 Atomic weights 317 Average sample for analysis 284 331 332 INDEX. B. PAGE Bailey process 27 Barium carbonate 297 Barium sulphate 296 Blanc fixe" 296 Brands of white lead 34 C. Calcium carbonate 297 Carter process 74 characteristics of 84 chemical composition of 82 granulating lead 78 history of 74 principles of 76 success of 84 washing and floating 80 Chalking of white lead 140 Characteristics of English White Lead 125 Chemical changes in grinding 67 and 283 Chemical composition of white lead 133 China clay 299 Color of white lead 230 Combination leads 71 Commercial classification of lead oxides 105 Comparative costs of manufacture 122 Comparison of pig lead and white lead prices 39 Comparative prices of zinc oxides 1 79 D. Determination of bulking figure 235 Determination of the specific gravity 233 Development of lead industry by the Dutch 8 Displacement of pigments in oil 235 Dutch method of white lead manufacture 11 E. Early manufacture of white lead in United States 17 Early use of white lead 14 Effect of acids on white lead 139 Effect of free fatty acids 136 Effect of the War of 1812. . 17 INDEX 333 PAGfi Effect of the Civil War 20 Effect of residual acetates 141 Effect of sulphur compounds on white lead 139 English method of grinding 69 English method of white lead manufacture 13 and 123 English regulations 122 Estimation of arsenic and antimony at Cafion City, Colorado. . . . 279 Estimation of arsenic and antimony in zinc leads 276 Estimation of carbon dioxide 262 Estimation of volatile oils 311 Estimation of water in paints 311 Extraction of vehicle 285 F. Fineness of white lead particles 136 Formulas and molecular weights 319 French process 1 30 present practice .* 131 G. German chamber process 125 corroding 128 Klagenfurth modification 125 . present methods 1 27 rapidity of corrosion 1 29 Gooch crucible 312 Gravimetric factors 320 Grinding white lead 66 and 246 careless grinding 246 conditions to be observed 247 importance of careful grinding 246 mixing and chasing 247 Gypsum 298 H. Higher carbonates of lead 134 I. Imports of litharge 206 Improvements in Dutch process 23 Inaccurate methods 285 Independent white lead companies 27 Inert pigments 296 334 INDEX. - PAGE Laboratory equipment ...................................... 310 Laboratory tests for opacity and covering power ................ 232 Lead chromates ............................................ 217 orange chrome yellow ..................................... 221 practical formulas for .............. . ...................... 221 precautions to be observed ................................ 219 precipitation of .......................................... 221 presence of lead sulphate in ................................ 218 raw materials for ......................................... 218 secret formulas ........................................... 220 sodium bichromate ........................................ 219 tinting strength of ........................................ 217 use of the calcium oxide ................................... 222 varieties of .............................................. 217 Lead suboxide ............................................. 200 Lead sulphate ............................................. 260 Leaded zincs .............................................. 182 characteristics of ......................................... 185 history of ............................................... 182 process of manufacture .................................... 183 results .................................................. 187 zinc sulphate ............................................ 187 Legislation ............ ................................... 148 Litharge ........ ........................................... 201 cupellation process ........... . ............................ 204 development of litharge industry .......................... 202 early confusion regarding nature of ......................... 202 manufacture ............................................. 204 other processes ........................................... 204 properties .............................................. 205 Lithopone ................................................. 225 comparison with white lead ................................ 228 early history ............................................. 225 grades of ................................................ 228 manufacturers of ......................................... 229 physical properties of ..................................... 227 preparation of barium sulphide ............................. 226 preparation of zinc sulphate ............................... 226 precipitating and calcining ................................ 226 production of ............................................ 229 reductions for ............................................ 227 zinc sulphide ............................................ 226 Location of lead plants in United States .......... . ............ 32 INDEX. 335 M . PAGE Magnesium silicate 300 Manufacture of white lead in the 17th century 9 Massicot 205 Matheson process 101 characteristics of product 103 development of 103 manufacture by 105 nature of 101 uses of 107 Microscopical measurements Mild process 85 advantages of 98 atomizing the lead 91 carbonating 93 control of 95 growth of process 89 oxidizing and hydrating * 91 W. H. Rowley early training of 87 use of superheated steam 87 Millstones 248 adjustment of grooves 251 domestic stones 249 frequency of dressing 255 grinding pastes 252 pneumatic dressing 254 proper selection of 248 source of 248 speed of 256. stone dressing 249 types of dressing 256 use of mill picks 253 N. National Lead Trust, formation of 23 absorption of other companies by. . 23 branches of 25 dissolution of 23 National Lead Company, formation of 24 operation of factories by 26 North Dakota paint tests 238 conclusions 244 covering tests 241 reductions used 238 336 INDEX. O. PAGE Obtaining a fair sample 282 Oil requirements and reductions 231 Old Dutch process 42 building the stack 46 casting the buckles for 44 chemical reactions 50 conditions required for successful corrosion 51 cost of production 62 disintegrating the buckles 56 drying the lead 60 economy of process 64 effect of sandy lead 62 grade of pig lead required for 44 loss of lead in washing 60 sandy lead 53 taking down the stack 53 variation in quality 66 washing the lead 56 and 58 Omaha White Lead Company 74 Opacity of white lead 231 Orange mineral 215 production and imports of 216 Oxides of lead 200 classification of 200 P. Patents issued 20 Physical properties of white lead 230 Practical paint tests 238 Processes in use in United States 42 Production of litharge in the United States 206 Production of zinc oxide 181 Protracted oxidation 141 Pulp ground lead 71 characteristics of 72 Q. Qualitative analysis of combination leads 295 and 301 Quantitative analysis of white leads 302 alumina 307 barium sulphate 307 calcium and magnesium oxides 307 INDEX. 337 PAGE Quantitative analysis of white lead, calcium 303 lead sulphate 306 magnesium 304 mixed carbonates and sulphates 308 silica : 307 total lead 302 white lead 300 zinc oxide 304 R. Rapid drying 311 Rapid extraction of pigment 310 Red lead 207 adulteration of 214 coloring 211 development of the industry * 208 dressing 211 early history of 207 early manufacture in the United States 208 early methods of preparation of 207 furnace temperature 209 modern improvements 212 present methods of manufacture 209 productions and imports of 216 properties of 213 selection for vermilions 214 the nitrate process 212 S. Sale of dry white lead 38 Short weight packages 34 Silica 300 Solubility of lead compounds 139 Specific gravities 310 Specific gravities corresponding to degrees baume 322 and 323 Specific gravity of acetic acid 325 Specific gravity of hydrochloric acid 327 Specific gravity of nitric acid 326 Specific gravity of sulphuric acid 328 Spiegeleisen 171 Stability of white lead 139 Standard solutions, bottles for 312 338 INDEX. PAGE Sublimed blue lead 120 composition of 120 properties of 120 yearly production 120 Sublimed litharge 121 Sublimed white lead 108 chalking of 118 chemical constitution of 115 condensation of fume 110 early manufacture of 108 inertness of 119 physical characteristics of 117 sublimation of the ore 110 uniformity of composition 113 uses of 118 whiteness of 119 yearly production 115 T. Table of weights and measures 330 U. United Lead Company, formation of 29 growth of 29 Use of centrifuge 286 Use of petroleum thinners 287 V. Variations from formula 282 Volumetric estimation of lead 262 W. Water in paints 290 detection of 290 estimation of 291 and 293 occurrence of 290 Weights per gallon 310 and 324 White lead in ancient times 1 White lead poisoning 143 absorption through skin 151 chronic lead poisoning 151 effect on nervous system 150 INDEX. 339 PAGE White lead poisoning, effect on women 149 English regulations 144 English statistics 146 precautions 147 symptoms of 141) White lead prices IS White lead specifications 141 White lead, uses of 1 composition of 1 early history of 2 early improvements in manufacture of 6 and 7 essential conditions for manufacture of 3 Whiting 297 Z. Zinc lead white 188 chemical composition of i 198 collection of fume 191 early manufacture of 189 physical properties of 194 production of 194 recent improvements 196 source of 188 s.tandard of composition 189 sublimation of fume 191 use in paints 196 zinc sulphate 198 Zinc oxide as a paint pigment 179 Zinc oxide 162 analysis of 176, 177, 178 collection of fume 164 composition of French oxide 153 early history of 152 furnace assays 168 furnaces 162 imported oxides 178 Mineral Point works 171 New Jersey zinc mines 156 Palmerton plant 166 plants in the United States 156 preliminary treatment of ore 160 present French process 153 processes in the United States 155 340 INDEX, PAGE Zinc oxide, properties of 175 solubility in acids 175 sulphur dioxide in 178 work of LeClaire 152 work of Jones & Wetherill 155 zinc sulphate in 178 SHORT-TITLE CATALOGUE OF THE PUBLICATIONS OF JOHN WILEY & SONS NEW YORK LONDON: CHAPMAN & HALL, LIMITED ARRANGED UNDKR SUBJECTS Descriptive circulars sent on application. 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