acid, with constant stirring. The precipitate was washed with hot water; boiled with water; washed with alcohol, and ether; and dried over phosphorous pentoxide. If stannous chloride be used, the precipitate always contains a chloride. If the stannous sulphate soln. be poured into the hydrophosphate soln., a yellow basic salt is formed owing to hydrolysis. Stannous orthophosphate is a white amorphous solid with a sp. gr. 3-823 at 17.4°/4°. It is stable in air; insoluble in water, but soluble in dil. mineral acids and alkali-lyes. By dissolving 5 grms. of tin in 22 c.c. of warm phosphoric acid of sp. gr. 1-23, and adding water from time to time so that the soln. is not too viscid, and slowly cooling the resulting liquid, there are deposited six-sided plates of stannous hydrophosphate, SnHPO4, of sp. gr. 3.476 at 15.5°/4°. If 13 grms. of tin be dissolved in 35 c.c. of warm phosphoric acid, and 15 c.c. of hot water be added to the hot soln., the hydrophosphate is precipitated in narrow, pointed crystals. If 10 grms. of the hydrophosphate be dissolved in 10 grms. of phosphoric acid of sp. gr. 1.7, heated to 140°, and the liquid cooled slowly in a desiccator with phosphorous pentoxide, rhombic crystals of stannous dihydrophosphate, Sn(H2PO4)2, are formed. Their sp. gr. is 3.167 at 22.8°/4°. By heating the hydrophosphate to 350°-400°, in an atm. of carbon dioxide, stannous pyrophosphate, Sn2P2O7, is formed as an amorphous powder, of sp. gr. 4·009 at 16-4°/4°. If the dihydrophosphate be similarly heated, stannous metaphosphate, Sn(PO3)2, is formed as an amorphous, glassy mass of sp. gr. 3-380 at 22-8°/4°. These phosphates resemble those of lead except that lead orthophosphate is not altered by dil. phosphoric acid, while stannous orthophosphate forms the hydrophosphate; that lead hydrophosphate in boiling water easily forms the orthophosphate but not so with the tin salt; and that lead dihydrophosphate is fairly stable in air, but not so with the tin salt. The stannous salts are more readily hydrolyzed than the lead salts.

According to E. Haeffely, when stannic oxide is treated with phosphoric acid. stannic oxydiphosphate, Sn2O(PO4)2.10H2O, or 2SnO2.P2O5.10H2O, is formed; P. Hautefeuille and J. Margottet found that orthophosphoric acid, at a temp. below that at which water is given off, dissolves stannic hydroxide, and on cooling furnishes octahedral crystals of the anhydrous salt Sn2O(PO4)2; and H. Kopp melted stannic oxide with microcosmic salt, and obtained two kinds of crystals, viz., pyramidal crystals of the oxydiphosphate, and cubic crystals of stannic pyrophosphate, SnP207. L. Ouvrard obtained the pyrophosphate but not the oxydiphosphate by fusing stannic oxide with sodium metaphosphate. G. Bornemann obtained a precipitate of variable composition: 22-21-29-53 per cent. P2O5 and 70-47-77-8 per cent. SnO2, by adding an excess of sodium phosphate to a soln. of a sodium stannate; and W. T. Casselmann obtained a gelatinous mass of stannic phosphate by the decomposition of 2SnCl4.PCl5 with an excess of water. The very sparing solubility of stannic phosphate in dil. nitric acid was utilized by A. Reynoso, W. Reissig, and A. Girard for the determination of phosphoric acid in nitric acid soln. free from chlorine. U. Antony and G. H. Mondolfo examined the insoluble compound obtained by adding a phosphate to a metastannic acid. P. Heermann, and H. Silbermann used stannic phosphate as a filling for silk.

L. Ouvrard fused stannic oxide with a large excess of potassium metaphosphate, and obtained potassium triphosphatostannate, K20.4SnO2.3P2O5, or KSn(PO4)3, isomorphous with the corresponding titanium salt; no cassiterite was formed. If potassium pyro-or ortho-phosphate be employed, potassium oxyphosphatostannate, K2O.2SnO2.P2O5, or KSnOPO4, analogous with the corresponding titanium compound, is formed. According to G. Wunder, when a mixture of stannic oxide, microcosmic salt, and borax or sodium pyroborate is fused in a crucible; the clear molten liquid poured into another crucible and slowly cooled; the product washed with dil. hydrochloric acid; and the residue separated by elutriation, the tetragonal prisms, resembling anatase, which are obtained have the composition Na2Sn(PO4)2, or sodium diphosphatostannate; and the rhombohedral crystals, almost cubic, have the composition NaSną(PO4)2, or Na(SnPO4)2, sodium diphosphatodistannate.

These salts were also obtained by H. Knop in an analogous manner. L. Ouvrard prepared sodium diphosphatostannate, and sodium triphosphatostannate, Na20.4SnO2.3P205, or NaSn(PO4)3. W. Prandtl and O. Rosenthal mixed sodium phosphate and stannate in alkaline soln., or dissolved stannic phosphate in sodium hydroxide and obtained complex salts or mixed crystals with the composition Na SnO3.4Na3PO4.48H2O; Na2SnO3.5Na3PO4.60H2O; NagSnO3.6Na3PO4.72H2O; and Na2SnO3.4Nag(P,V)04.48H2O. H. Zocher showed that the alleged complex phosphatostannates are not chemical individuals because they form a continuous series whose composition depends on the stannate conc. of the mother liquid. G. Saring also reported potassium calcium phosphatostannate, Ca3(PO4)2(CaO)2(K2O)2SnO2, analogous with the corresponding phosphato-silicate, titanate, zirconate, cerate, thorate, and plumbate.

REFERENCES.

1 E. Lenssen, Liebig's Ann., 114. 113, 1860; H. Kopp, ib., 159. 39, 1871; W. Reissig, ib., 98. 339, 1856; W. T. Casselmann, ib., 83. 257, 1852; H. Silbermann, Färber Ztg., 8. 34, 51, 68, 1897; P. Heermann, ib., 16. 353, 1905; Zeit, angew. Chem., 20. 416, 485, 1907; G. Bornemann, ib., 12. 635, 1899; A. Reynoso, Journ. prakt. Chem., (1), 54. 261, 1851; G. Wunder, ib., (2), 2. 206, 1870; (2), 4. 339, 1871; A. Girard, Chem. News, 5. 281, 1862; 6. 99, 1862; Bull. Soc. Chim., (1), 4. 20, 1862; Compt. Rend., 54. 468, 1862; P. Hautefeuille and J. Margottet, ib., 102. 1017, 1886; L. Ouvrard, ib., 111. 177, 1890; E Haeffely, Phil. Mag., (4), 10. 290, 1855; U. Antony and G. H. Mondolfo, Gazz. Chim. Ital., 28. ii, 142, 1898; W. Prandtl and O. Rosenthal, Ber., 40. 2125, 1907; W. Prandtl, Verbindungen höherer Ordnung zwischen den Oxyden RO2 und R203 Ein Beitrag zur Systematik anorganischer Verbindungen, München, 1906; G. Saring, Versuche über von Aufschluss von Phosphaten durch Kieselsäure bei hohen Temperaturen, Dresden, 1906; H. Zocher, Zeit. anorg. Chem., 112. 1, 1920; E. Jablczynsky and W. Wieckowsky, ib., 152. 207, 1926.

CHAPTER XLVII

LEAD

§ 1. The History of Lead

THE metal lead is one of the seven metals known to man from the earliest times. The Egyptians must have been familiar with the metal at the time of Rameses III. (1200 B.C.), since lead plates and small statues, chiefly of Osiris and Anubis, have been found in the tombs of that period. M. Berthelot 1 showed that lead was used by the Egyptians in making jewellery, mirrors, etc.; and R. Lepsius reported that lead is mentioned in Egyptian hieroglyphics, 1515–1461 B.C. The British Museum has a lead figure found in the temple of Osiris at Abydos, and which probably dates from 3000 B.C. Old Egyptian pottery has also been found covered with plumbiferous glazes (6. 40, 36). According to Numbers (31. 32), lead was included in the spoil taken from the Midianites by the Israelites. The opheret of the Hebrews, Phoenicians, and Egyptians was rendered μóλußdos, molybdos, in the earliest Greek translations of the Old Testament, and as lead in the English version; while bedil was generally translated kaooíTepos, and later tin (q.v.). F. Hoefer's suggestion that the term opheret should be rendered copper is not generally accepted. According to Ezekiel (27. 12), the Carthaginians traded in silver, iron, tin, and lead. The Israelites do not appear to have made a clear distinction between lead and tin, and their bedil is sometimes translated tin, and sometimes lead. Lead is mentioned by Homer. As indicated in connection with tin, Pliny, in his Historia naturalis of the first century, distinguished the two metals by calling tin plumbum candidum, and lead plumbum nigrum. The use of lead among the ancients was discussed by Theophrastus, in his Пepi Ai0wv (2. 8, 56) in the third century B.C.; by Pliny, Historia naturalis (34. 173), Dioscorides, De materia medica (5. 100), and Vitruvius, De architectura (7. 12), all in the first century of our era; Strabo, Geographica (3. 148), in the first century B.C.; and Gahlen, De simplicium medicamentorum temperamentis (9. 22; 12: 230), in the second century; and by the later writers: K. B. Hofmann, H. Blümmer, A. Gobantz, C. G. Fiedler, H. Faure, E. O. von Lippmann, A. Rössing, B. Neumann, A. F. von Pauly and G. Wissowa, J. A. Overbeck, A. Baumeister, H. Droysen, G. Bapst, H. Faure, L. Guillaume, and F. X. M. Zippe. Lead was used for sling-bolts, tipping arrows, coffins, tablets, toys, vases, tokens, weights, net-sinkers, plummets, scals, water-pipes, backing glass mirrors, and Pliny (33. 19) referred to the use of lead discs for drawing lines on parchment. Several of the literary men-Catullus, Herodotus, Thucydides, and Cicero-made allusions to lead. Cicero, for instance, humorously emphasized the feeble character of a man by saying that he could be slain with a plumbo gladio, or leaden sword; and stupid people were called plumbei.

Lead was mined in considerable quantities by the Greeks and Romans. Polybius, in his Historia, in the second century B.C., said that the mines at Carthagena employed 40,000 men; Xenophon, in his treatise on the revenues of Athens-Ilópo пερì проσódшv-written in the fourth century B.C., stated that the mines at Laurium were worked in ancient times, and he advocated the better

management of the mines as a means of improving the revenue. For three hundred years these mines were a source of revenue to Athens. The mines at Linares were worked in turn by the Phoenicians, Carthaginians, and Romans. Some old shafts in the neighbourhood are still known as Los Pozos de Anibal-Hannibal's Wells. According to Pliny, Historia naturalis (34. 138, 164), and Strabo, Geographica (3. 148), the Romans obtained large amounts of lead from South-Eastern Spain. These mines were opened in the twelfth century B.C. The mines in Crete were described by A. Mosso. The early Spanish mines were described by K. B. Hofmann, H. Blümmer, etc., and they form the main lead district in Spain to-day. The Phoenicians bartered earthenware, salt, and copper with Britain in exchange for lead, tin, and hides-vide history of tin. Cicero, in his Epistolæ ad Atticum, said that there was no silver in Britain;. but he must have been misinformed, because Strabo, Pliny, and others mention it. This shows that cupellation must have been in operation, because the only source of the silver was the lead ore. According to Pliny, the Romans also carried on mining operations in various parts of Britain (Somersetshire, Shropshire, Yorkshire, Derbyshire, Durham, Cumberland, Northumberland, and Scotland), and the British mines have been described by G. Chalmers, H. Blümmer, R. I. Murchison, J. Childrey, J. C. Bruce, and K. B. Hofmann. The lead industry in Scotland dates from a very early period. According to G. V. Wilson and J. Š. Flett, there is no evidence that the Romans worked lead in Scotland, although J. R. S. Hunter reported the finding of bronze and stone implements in some old surface workings at Leadhills and Wanlockhead, and D. Wilson, the finding of some pigs of Roman lead. According to T. Pennant, the mines of Islay were worked by the Norwegian invaders when they occupied the country. G. V. Irving, R. W. C. Patrick, J. Leslie, and S. Atkinson have referred to the mining of lead during the Middle Ages in Scotland. J. A. Phillips has suggested that the great wall of Hadrian (A.D. 117–138) was built partly with a view of enclosing and protecting the lead mines of Northumberland and Cumberland. There are ingots in existence to-day with the inscription: Britannicus ad Verum. A. Way has given a list of known ingots, and they range from the time of Claudius (A.D. 44-48) to the reign of Hadrian (A.D. 117-138). Many examples are in the British Museum. Lead mining in England may have been restricted, but there is nothing to show that it stopped after the Roman withdrawal. Lead coffins of Saxon age are known. There is a reference in the Doomsday Book of the eleventh century to a lead mine at Crice, and there are records of grants to miners dating from the thirteenth century. The furnaces, etc., were described by J. Glanvil, G. Plattes, T. Houghton, R. Watson, J. Martyn, J. Farey, W. Wallace, and P. A. Dufrénoy. The mining in the Mendip Hills probably dates from pre-Roman times, and has been described by R. Hunt, J. McMurtrie, and T. Morgan. The Roman mines in Gaul, along the Rhine from Bâle to Cologne, have been described by A. Daubrée, and H. Blümmer. Blocks of lead have been found with inscriptions: Nero, Hadrian, and Septimus Severus. The Roman mines in Germany have been described by H. Blümner, A. Frantz, T. Haupt, A. Daubrée, and K. B. Hofmann. The mines of Saxony, Silesia, and the Harz Mountains, as well as the Austrian mines, were discovered about A.D. 1000. The history of the German mines has been discussed by G. Agricola, P. Bech, P. Albinus, H. Ermisch, C. Blömeke, etc. Lead was smelted in the United States at the beginning of the seventeenth century, and this subject has been discussed by H. R. Schoolcraft, C. L. Henning, H. Garlichs, W. H. Pulsifer, etc. According to W. Gowland, although galena is common in Japan, the early Japanese rarely used the metal, copper being usually employed where Europeans use lead. In the ninth and tenth centuries, lead or pewter coins were employed. According to W. H. Adolph, in China, lead was used as a substitute for tin from very early times. The Chinese and Japanese bronzes were discussed by H. Morin, P. Christofle and H. Bouilhet, and S. Kalischer.

The alchemists of the Middle Ages represented lead by h, the symbol for

Saturn. It has been suggested that this symbolizes the scythe of Saturn-Father Time-but, according to J. Beckmann,2 the imaginary scythe has been really formed from the first two letters of his name κρóvos, which transcribers, for the sake of dispatch, made more convenient for use, but at the same time less perceptible. In the Latin work, Summa prefectionis magisterii, of Geber, probably of the twelfth century, lead is thus described:

Lead is a metal which is livid, dull, and white; it is heavy; not sonorous; extensible under the hammer; and easily fused. When exposed to the vapour of vinegar, it forms white lead, and when roasted, red lead. Although lead scarcely resembles silver, it can be easily converted into silver per nostrum artificium. It does not maintain its weight during calcination, but acquires a new weight by this operation. Lead is employed in cupellation.

REFERENCES.

1 F. Hoefer, Histoire de la chimie, Paris, 1. 47, 1842; A. Rössing, Geschichte der Metalle, Berlin, 1901; F. X. M. Zippe, Geschichte der Metalle, Wien, 1857; L. Guillaume, La métallurgie du plomb au Laurium, Paris, 1909; R. Lepsius, Sitzber. Akad. Berlin, 112, 1871; Die Metalle in den ägyptischen Inschriften, Berlin, 1872; K. B. Hofmann, Das Blei bei den Völkern des Altertums, Berlin, 1885; H. Blümmer, Technologie und Terminologie der Gewerbe und Künste bei Griechen und Römern, Leipzig, 4. 89, 290, 1887; C. G. Fiedler, Reise durch alle Theile des königreichs Griechenland in den Jahren 1834 bis 1837, Leipzig, 2. 111, 336, 557, 1841; L. Gouïn, Notice sur les mines de l'île de Sardegna, Cagliari, 1869; A. Daubrée, Rev. Archéol., (2), 17. 300, 1868; G. Bapst, ib., (3), 1. 100, 1883; A. Frantz, Esterr. Zeit. Berg. Hütt., 28. 450, 1880; A. Gobantz, ib., 42. 123, 1894; T. Haupt, Berg. Hütt. Ztg., 42. 290, 1883; C. Blömeke, ib., 48. 15, 1889; J. A. Overbeck, Pompeji in seinem Gebäuden Altertümern und Kunstwerken, Leipzig, 4. 621, 1875; A. Baumeister, Denkmäler des klassischen Altertums, München, 1884; H. Droysen, Heerwesen und Kriegsführung der Griechen, Freiburg, 20, 1888; A. F. von Pauly and G. Wissowa, Real-Encyclopädie der classischen Altertumsarrenschaft, Stuttgart, 5. 561, 1893; B. Neumann, Metalle, Geschichte, Vorkommen, und Gewinnung, Halle a. S., 1904; H. Ermisch, Das sächsische Bergrecht, Leipzig, 1887; P. Albinus, Commentarius novus de Mysnia, Wittenberg, 1580; C. A. Schlüter, Gründlicher Unterricht von Hüttenwerken, Braunschweig, 110, 1738; G. Agricola, Bermannus, sive de re metallica, Basileæ, 1546; P. Bech, (G. Agricola) Vom Bergkwerck, Basel, 1557; H. R. Schoolcraft, Narrative Journal of Travels through the North-Western Regions of the United States, Albany, 348, 1821; C. L. Henning, Die Erzlagerstätte der Vereinigten Staaten von Nordamerika, Stuttgart, 200, 1911; G. Chalmers, Caledonia, London, 1. 55, 1824; E. O. von Lippmann, Entstehung und Ausbreitung der Alchemie, Berlin, 574, 1919; W. H. Pulsifer, Notes for a History of Lead and the Manufacture of White Lead and Lead Oxides, New York, 1888; W. H. Adolph, Chem. Met. Engg., 26. 914, 1922; Scient. Monthly, 14. 441, 1922; H. Faure, Histoire de la céruse suivie d'un essai sur l'histoire du plomb, Lille, 1889; W. Gowland, The Early Metallurgy of Silver and Lead, London, 1901; Archælogia, 57. 1, 1901; Trans. Japan Soc. London, 13. 20, 1915; Journ. Ind. Metals, 4. 4, 1910; M. Berthelot, Ann. Chim. Phys., (6), 30. 285, 1893; (7), 12. 451, 1897; (7), 15. 433, 1898; Compt. Rend., 127. 259, 1898; H. Morin, ib., 78. 811, 1874; P. Christofle and H. Bouilhet, ib., 78. 1019, 1874; S. Kalischer, Ber., 7. 1114, 1874; J. A. Phillips, On the Metallurgy of Lead, London, 1859; Proc. Yorkshire Phil. Soc., 1. 77, 1848; Archæol. Journ., 16. 7, 1859; R. Watson, Chemical Essays, London, 3. 273, 1782; W. Wallace, Alston Moor, its Pastoral People, its Mines and Miners, from the Earliest Periods to Recent Times, Newcastle-on-Tyne, 1890; R. I. Murchison, The Silurian System, London, 279, 1839; J. C. Bruce, The Roman Wall, Newcastle-on-Tyne, 433, 1851; A. Way, Journ. Arch, Soc., 16. 22, 1859; 23. 277, 1866; J. Childrey, Britannia Baconia, London, 112, 1660; J. Glanvil, Phil. Trans., 2. 525, 770, 1668; J. Martyn, ib., 36. 22, 1729; J. Farey, General View of the Agriculture and Minerals of Derbyshire, London, 382, 1815; P. A. Dufrénoy, Voyage métallurgique en Angleterre, Paris, 1839; H. Garlichs, Min. Scient. Press., 115. 315, 1917; G. Plattes, A Discovery of Subterranean Treasure, London, 1679; T. Houghton, Rara avis in terris, or The Compleat Miner, London, 1681; A. Mosso, Atti Accad. Lincei, (5), 19. ii, 225, 1910; Excursioni nel Mediterraneo e gli scavi di Creta, Milano, 117, 1910; R. Hunt, British Mining, London, 31, 131, 230, 1884; J. McMurtrie, Trans. Inst. Min. Eng., 20. 528, 1902; T. Morgan, ib., 20. 478, 1902; G. V. Wilson and J. S. Flett, The Lead, Zinc, Copper and Nickel Ores of Scotland, Edinburgh, 1921; J. R. S. Hunter, Trans. Geol. Soc. Glasgow, 7. 376, 1884; D. Wilson, Prehistoric Annals of Scotland, London, 2. 64, 1863; T. Pennant, A Tour of Scotland, London, 2. 250, 1790; G. V. Irving, The Upper Ward of Lanarkshire, Glasgow, 1. 50, 1864; R. W. C. Patrick, Early Records relating to Mining in Scotland, Edinburgh, 34, 1878; J. Leslie, De origine moribus et rebus gestis Scotorum, Romæ, 1578; Amsterdam, 11, 1675; S. Atkinson, Discovery and Historie of the Gold Mynes in Scotland, Edinburgh, 47, 1825.

2 J. Beckmann, Beyträge zur Geschichte der Erfindungen, Leipzig, 3. 373, 1792; London, 2. 29, 1846.