Nitrate of Silver

See Argenti Nitras. P. F. It may be prepared from impure silver by the following process: - Dissolve the silver in nitric acid, add common salt till no more silver remains in solution. Wash the precipitate thoroughly; then add water and a very little hydrochloric acid, and introduce some pieces of zinc; let them remain together 24 hours, stirring frequently. Remove the zinc, and wash the reduced silver thoroughly. Again dissolve it in nitric acid, diluted with 2 or 3 parts of water; filter and evaporate, that it may crystallize.

Nitrate of Strontian

This may be obtained from the native carbonate of strontian, or more cheaply from the native sulphate, by the processes employed for Nitrate of Baryta.

Nitric and Nitro-hydrochloric Acids

See Acids.

Nitrite of Potash

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, nitrate crystallizes, and the liquid separates into two layers; the upper is alcoholic solution of acetate of potash, the lower is solution of nitrite of potash, which may be evaporated to dryness or kept in solution. Used as a test for iodine, with starch paste and hydrochloric acid. Corenwinder passes nitrous acid gas, formed by acting on 1 part of starch with 10 of nitric acid, through a solution of caustic potash, sp. gr. 1.38, until it becomes acid; then adds a little caustic potash, so as to render it distinctly alkaline.

Nitro-prusside of Sodium

To 213 parts of powdered ferro-prussiate of potash, in a porcelain basin, add 450 parts of nitric acid of 1.42 density (or 337 1/2 parts at 1.50), adding all the acid at once. When dissolved, transfer to a bolt-head, and digest in a water-bath, until the solution precipitates salts of protoxide of iron of a slate colour. Neutralize, when cold, with a cold solution of carbonate of soda; then boil, and separate the precipitate, by filtration. Evaporate the liquid again, filter, and allow the nitrates of potash and soda to crystallize out. Evaporate the liquid again, and remove the prismatic crystals of nitro-prusside as they form. They may be dissolved in water and recrystallized by cooling.

Novargent

This is said to consist of a solution of freshly precipitated chloride of silver in hyposulphite of soda (or, according to the Pharmaceutical Journal, of oxide of silver in cyanide of potassium), mixed with prepared chalk.

Oxygen Gas

See Gases.

Copying Paper

Mix lard with black lead or lamp-black, into a stiff paste, rub it over writing paper with a flannel, and wipe off the superfluous quantity with a soft rag. These sheets alternated with writing paper and written on with a solid pen, produce 2 or 3 copies of a letter at once. Lithographic Paper. Give the paper 3 coats of thin size, 1 of starch, and 1 of solution of gamboge. Each to be applied with a sponge, and allowed to dry before the next is applied.