Potassium Ferricyanide Potassium Iodide
also when absorbed through the skin, or by any cut or abrasion. The addition of an acid immediately causes the evolution of hydrocyanic or prussic acid, which is extremely poisonous, and when inhaled, even in small quantities, produces vertigo and headache.
Potassium Ferricyanide (Ger,, Rothes Blutlaugensalz, Kaliumeisencyanid; Fr., Ferricyanure de potassium, Cyanoferride de potassium, Prussiate rouge de potassium ; Ital., Cianuro rosso di potassio e di ferro, Prussiato rosso di potassio. K3Fe(CN)6 = 567. Synonyms : Ferridcyanide of Potash, Red Prussiate of Potash. Made by the action of chlorine gas on ferrocyanide of potash. Solubility: 36 per cent, in cold, 77*6 per cent, in hot water; insoluble in absolute alcohol; more soluble in dilute alcohol. It is met with as deep red crystals, that become covered with a yellowish powder, which should be removed by rinsing with water before use. It is used for reducing, and in some printing processes, also for toning bromide prints.
Potassium Ferrocyanide (Ger., Gelbes Blutlaugensalz, Kaliumeisencyaniir; Fr., Ferrocyanure de potassium, Prussiate iaune, Cyanoferrure de potassium ; Ital., Ci-anuro giallo di potassio e di ferro, Prussiato giallo di polassio). K4Fe(CN)6, 3H20 = 426. Synonym : Yellow Prussiate of Potash. Is prepared by heating nitrogenous matter, such as hoofs, horns, hide clippings, etc., with pearlash and iron filings in an iron pot. The resulting mass is dissolved in water and evaporated, and the large yellow plates or crystals of the salt obtained. Solubility : 26 per cent, in cold, 50 per cent, in hot water; insoluble in alcohol. The salt is non-poisonous of itself; but as a deadly poison can be easily formed from it, care should be exercised in its use. It has been recom-mended as an addition to developers, and is said to give pluck and brilliancy to the negatives.
Potassium Iodide (Ger., Iodkalium, Kaliumiodid; Yx.,Iodure de potassium; Ital., Ioduro di potassio). KI = 166. Prepared by dissolving iodine in hot solution of caustic potash, evaporating and fusing the crystalline mass with charcoal, and subsequent lixiviation. Solubility: 138 per cent, in cold, 220 per cent, in hot water; 1*5 per cent, in alcohol, 0-12 per cent, in ether; 08 per cent, in alcohol and ether; 40 per cent, in glycerine.