1902 29 18 137 18 448 4417 1903 28 21 151 24 470 4578 1904 44 23 181 35 596 4677 1905 50 18 223 40 612 4789 Average 0·8% 0·5% 3·7% 0·6% 11·5% 4615 ILLNESS AMONG CALCINERS Lead Colic Year. and Kidney Gastric Anæmia. Rheumatism. No. Lead Paralysis. Disease. Catarrh. Employed. 1902 — — 5 1 78 1149 1903 — — 9 — 112 1087 1904 2 — 68 1 136 1140 1905 1 2 47 2 134 1159 Average 0·08% 0·05% 2·6% 0·1% 10·2% 1134 In thirty-two spelter works in the district of Oppeln in the year 1905, among 4789 spelter workers proper, there were 50 cases of colic, 18 of kidney disease, 223 of gastric and intestinal catarrh, 40 of anæmia, and 612 of rheumatism, and among 1159 calciners 1 case of colic, 2 of kidney disease, 47 of gastric catarrh, 2 of anæmia, and 134 of rheumatism. Cases are much more numerous in spelter works where Swedish blende containing lead is worked. It is remarkable, however, that in large spelter works in Upper Silesia, where for years no cases of lead poisoning were reported, medical examination showed that 20·5 per cent. had signs of lead absorption. White Lead and Lead Colours MANUFACTURE.—The primitive Dutch process consisted in placing lead grids in earthenware pots containing dilute acetic acid and covering them with tan bark. Fermentation ensued with evolution of carbonic acid gas and increase in temperature. The acetic acid vapour forms, with aid of atmospheric oxygen, first basic lead acetate, which, by the action of the carbonic acid gas, becomes converted into white lead and neutral lead acetate. The product is crushed, sieved, and dried. In the German or Austrian process thin sheets of metallic lead are hung saddle-wise in chambers. Acetic acid vapour and carbonic acid gas (produced by burning coke) are led in from below. The chamber is then sealed and kept so for a considerable time. When the chamber is ‘ripe’ the white lead that has formed is taken out, freed from uncorroded lead by spraying, dried, finely ground, and packed. White lead comes on the market either as a powder or incorporated with oil. Of the remaining lead colours, red lead (Pb₃O₄) is much used. It is produced by heating lead oxide in reverberatory furnaces with access of air and stirring. Lead Poisoning in the Manufacture of White Lead and Lead Colours The manufacture by the German process may be divided into three categories according to the degree of risk run: