Note 50 — A CYCLOPÆDIA OF PRACTICAL RECEIPTS, PROCESSES, AND COLLATERAL INFORMATION (continued 7)

That employed in England is chiefly obtained, as already mentioned, from the manufacturers of bone-black or animal charcoal; but, on the Continent, the liquor obtained by a like destructive distillation of various animal offals (blood, flesh, horn, hoofs, woollen rags and waste, hair, scrapings of hides, leather cuttings, &c.) is employed for the same purpose. The preparatory process by which this liquor is obtained is essentially the same in each case; except that with animal offal the temperature should not exceed a red-brown heat, in order that the resulting charcoal may afterwards serve to make ferrocyanide of potassium and Prussian blue. These liquors have usually a density ranging between 8° and 9° Baumé (Ure; = sp. gr. 1·056 to 1·063).