Page:On the various forces of nature and their relations to each other.djvu/203

Rh be rubbed together in a pestle and mortar without fear. One part of chlorate of potash and three parts of sugar will answer. The mixture need only be touched with a glass rod dipped in oil of vitriol.

($19$) Page 107. Two Salts Dissolved in Water.—Sulphate of soda and chloride of calcium. The solutions must be saturated for the experiment to succeed well.

($20$) Page 111. Lead Pyrophorous.—This is a tartrate of lead which has been heated in a glass tube to dull redness as long as vapours are emitted. As soon as they cease to be evolved, the end of the tube is sealed, and it is allowed to cool.

($21$) Page 115. Gun-Cotton is made by immersing cotton-wool in a mixture of sulphuric acid and the strongest nitric acid, or of sulphuric acid and nitrate of potash.

($22$) Page 115. Paper Prepared like Gun-Cotton.—It should be bibulous paper, and must be soaked for ten minutes in a mixture of ten parts by measure of oil of vitriol with five parts of strong fuming nitric acid. The paper must afterwards be thoroughly washed with warm distilled water, and then carefully dried at a gentle heat. The paper is then saturated with chlorate of strontia, or chlorate of baryta, or nitrate of copper, by immersion in a warm solution of these salts. (See Chemical News, Vol. I., page 36.)