4198. Bromide of Potassium

4198.    Bromide of Potassium. Put 1 troy ounce iron filings into 11/2 pints distilled water; add 2 troy ounces bromine, stirring frequently during 30 minutes; heat gently until the liquid assumes a greenish color, and add gradually 21/8 troy ounces pure carbonate of potassa (previously dissolved in 11/2 pints distilled water), until it ceases to produce a precipitate; continue the heat for 30 minutes, then filter. Wash the precipitate with 1 pint boiling distilled water, and filter. Mix the filtered liquids, and crystallize by evaporation. Dry the crystals on bibulous paper and keep them in a well-stoppered bottle. ( U. S. Ph.)

4199. Chloride of Potassium

4199.    Chloride of Potassium. This is obtained from the mother liquor after making chlorate of potassa (see No. 4184 (Chlorate of Potassa)), by evaporating it to dryness, and heating it to a dull redness; it is then dissolved in water, purified by defecation and crystallized by evaporation.

4200. Ferricyanide of Potassium

4200.     Ferricyanide of Potassium. This is the red prussiate of potash, and is obtained from a solution of 1 part ferrocyanide of potassium in 16 parts cold water, by passing chlorine gas slowly through it, with constant agitation, until the liquid appears of a reddish green color, and ceases to give a blue precipitate, or even a blue tinge, to a solution of a sesquisalt of iron, an excess of chlorine being carefully avoided. The liquor is then evaporated till a pellicle forms on the surface, filtered while hot, and set aside to cool; the crystals are again dissolved and crystallized. (Cooley.)

4201. Ferrocyanide of Potassium

4201. Ferrocyanide of Potassium. This yellow prussiate of potash is the prussiate of potash of commerce. It is obtained by exposing 10 parts potash or pearlash; 10 parts coke, cinders, or coal; and 5 parts iron turnings, all in coarse powder, to a full red heat in an open crucible, stirring occasionally until small jets of purple flame are no longer seen. "When cool, the soluble matter is dissolved out of it, the solution filtered, evaporated, and crystallized. The crystals obtained are redissolved in hot water and cooled very slowly, forming largo yellow crystals of the ferrocyanide of potassium of commerce. In order to obtain a pure article, fuse effloresced commercial prussiate of potash in a glass vessel, dissolve the fused mass in water, neutralize any excess of alkali with acetic acid, and precipitate the salt with strong alcohol ; wash the precipitate with a little weak alcohol, redissolve it in water, and crystallize. (Cooley.)

4202. Cyanide (Cyanuret) of Potassium

4202. Cyanide (Cyanuret) of Potassium. Mix thoroughly 8 ounces of dry ferrocyanide of potassium and 3 ounces dry carbonate of potassa; throw the mixture into a deep red-hot earthen crucible, the heat being sustained until effervescence ceases, and the fluid portion of the mass becomes colorless; after a few minutes' rest, to allow the contents to settle, the clear portion is poured from the heavy black sediment at the bottom on a clean marble slab; and, while yet warm, broMISCELLANEOUS CHEMICALS.

ken up and placed in well-closed bottles. When pure, this salt is colorless and odorless, its crystals are cubic or octahedral, and are anhydrous. If it effervesces with acids, it contain carbonate of potassa. If it be yellow, it contains iron. (Liebig.)