4192. Hydrate of Potassa

4192.    Hydrate of Potassa. This is also known under the name of caustic potash. Liquor of potassa, 1 gallon; evaporate in a clean iron vessel over the fire until the ebullition being finished, the hydrate of potassa liquefies; pour this into proper moulds. A pale greyish or bluish solid, very soluble in water and alcohol.. It should be totally soluble in alcohol. Its solution should be scarcely affected by the nitrates of baryta and silver. It is chiefly used as a caustic, and in chemistry. ( Cooley.)

4193. Potassa with Lime

4193.     Potassa with Lime. Rub together, in a warm mortar, 1 ounce each of hydrate of potassa and quicklime, and keep the powder from the air in a well-stopped bottle. This is a caustic, but less manageable than either nitrate of silver (lunar caustic) or hydrate of potassa (caustic potash.)

4194. Nitrate of Potassa

4194.    Nitrate of Potassa. Called also nitre and saltpetre. This salt is spontaneously generated in the soil, owing to the action of the atmosphere, and crystallizes upon its surface in various parts of the world, especially in the Bast Indies. It is also produced artificially by exposing a mixture of calcareous soil and animal matter to the atmosphere, when nitrate of lime is slowly formed, and is extracted by lixiviation. The liquid is then decomposed by adding carbonate of potash, by which carbonate of lime is precipitated and nitrate of potash remains in solution.

4195. To Purify Nitre

4195.    To Purify Nitre. Nitre or saltpetre is purified for medicinal use in the fol-lowing manner: Dissolve 4 pounds commercial nitre in 1 quart boiling distilled water; withdraw the heat, and stir constantly as it cools. The minute crystals, thus obtained, are to be drained, and washed in a glass or earthenware percolator, with cold distilled water, until the washings cease to give a precipitate with a solution of nitrate of silver. The contents of the percolator are then to be withdrawn and dried in an oven. (Cooley.)

4196. Tartrate of Potassa

4196.    Tartrate of Potassa. Dissolve 8 ounces carbonate of potash in 2 quarts distilled water; whilst boiling hot, add gradually 1 pound, more or less, of bitartrate of potassa (cream of tartar) in fine powder, until the solution is neutralized, or ceases to change the color of either blue or reddened litmus paper. Filter through muslin, and evaporate until a pellicle forms on the surface; then set it aside to crystallize. After 12 hours, collect the crystals, dry them on bibulous paper, and keep preserved from the air.

4197. Bitartrate of Potassa

4197.     Bitartrate of Potassa. This is well known under the name of cream of tartar, and is found deposited as a crust on the sides of the casks and vats used for the fermentation of grape juice. The deposit from white wine is white tartar; that from red wine is red tartar, or argol. It is purified by boiling it in water, and crystallizing; it is then again dissolved in boiling water, and decolorized with charcoal (see No. 1729 (Properties of Charcoal)), and aluminous clay; the resulting clear liquid is allowed to cool slowly, forming crystals of the cream of tartar of commerce.