4188. Substitute for Bichromate of Potassa

4188.    Substitute for Bichromate of Potassa. One of the German scientific journals calls attention to the fact that for many purposes, such as for dyeing wool black, Glauber's salt and sulphuric acid can be economically substituted for bichromate of potassa. It gives the following recipe for dyeing 100 pounds of loose wool - namely, 6 pounds sulphate of soda, 2 pounds sulphuric acid, and 2 pounds sulphate of copper, which are to be boded together for an hour, and colored with 40 to 50 pounds logwood, and 1 pound sulphate of copper, and finally colored black by means of a little sulphate of iron. The black thus obtained is pronounced to be beautiful, cheap, and easily spun, remaining loose and soft.

4189. Nitrite of Potassa

4189.    Nitrite of Potassa. It is obtained mixed with a little nitre and potash by heating nitre to redness. To purify the residuum, dissolve it in boiling water, set aside for 24 hours, pour off the liquid from the deposited nitre, neutralize the free alkali with acetic acid, and add twice its volume of alcohol. In a few hours more, nitre crystallizes, and tho liquid separates into two layers; the upper is alcoholic solution of acetate of potash, the lower is solution of nitrate of potash, which may be evaporated to dryness, or kept in solution. (Beasley.)

Or, pass nitrous acid gas, formed by acting on 1 part of starch with 10 of nitric acid, through a solution of caustic potash, specific gravity 1.38, until it becomes acid; then add a little caustic potash, so as to render it distinctly alkaline. It may then be kept in the liquid form, or evaporated to dryness. ( Coren-winder.)

4190. Permanganate of Potassa

4190.      Permanganate of Potassa. This consists of slender, prismatic crystals,. of a dark-purple color, inodorous, and of a sweetish, astringent taste. It is a powerful disinfectant, and oxidizing agent, from the facility with which it parts with its oxygen. It has been found useful in medicine in various ways, and forms an excellent, though unstable hair dye. (See No. 1211 (Brown Hair Dye).) It may be obtained by mixing 8 parts of peroxide of manganese with 7 parts chlorate of potassa, both in line powder, adding 10 parts of hydrate of potassa, dissolved in a small quantity of water, evaporating to dryness, powdering, exposing the powder to a low red heat in a platinum crucible, dissolving tho mass in a largo quantity of water, decanting, evaporating, and crystallizing. These crystals are permanganate of potassa. The PERMANGANATES or basic compounds of permanganic (manga-nesic) acid are all marked by their rapid decomposition when in contact with organic matter. (Cooley.)

4191. Tests for Permanganate of Potassa

4191.      Tests for Permanganate of Potassa. A very dilute solution has a rose-color, free from green tinge, and is instantly decolorized by arsenite of potassa, with the formation of a brown precipitate. (U. S. Ph.) Dissolve 44 grains granulated sulphate of iron in 2 fluid drachms dilute sulphuric acid ; the solution should completely decolorize 5 grains of the permanganate dissolved in water. (Br. Ph.)