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per ton of sulphuric acid of sp. gr. 1"840. From 1856 to 1862, the chamber acid contained nitrous acid, and 2'52 grins, of platinum were dissolved per ton of acid at 1"840. From 1862 to 1866, sulphurous acid was present, and the amount of platinum dissolved was 1'05 grms. per ton of acid of the same strength.
The chemical works at Hautmont (Department Nord) procured in 1865 a platinum apparatus holding 150 litres and weighing 28,548 grms. In 1870 the apparatus was repaired in Paris, when 7891 grins, of platinum were used, but 6275 grins, of old platinumwere allowed for, and the weight of the apparatus, by the addition of 1616 grins., was increased to 30,164 grms. At the end of 1873 the apparatus weighed 28,452 grins., showing a loss of 1712 grms. During nine years' working, 6796 tons of sulphuric acid of 1"840 sp. gr. had been prepared in the'apparatus. The loss of platinum was, therefore, 0"252 grm. per ton of sulphuric acid. The apparatus cost 30,588"40 francs, at 1050 francs per kilo. The repairs in 1870 cost 8439"95 francs ; together, 34,028"35 francs. The worn-out apparatus was sold at 810 francs per kilo. ~---23,046"12 francs. The expenditure was, therefore, 34,028"35 --23,046"12 ~ 10,982'23 francs, or per 1000 kilos, sulphuric acid at sp. gr. 1"800, 1"616 francs, or about