A text-book of inorganic chemistry / by Dr. A.F. Holleman ... Issued in English in coöperation with Hermon Charles Cooper.

  • Arnold F. Holleman
Date:
1912
Catalogue details

Licence: In copyright

Credit: A text-book of inorganic chemistry / by Dr. A.F. Holleman ... Issued in English in coöperation with Hermon Charles Cooper. Source: Wellcome Collection.

    27/556 (page 7)
    8.] THE ELEMENTS. Sublimation.—Certain solids, e.g, camphor, when heated (at ordinary pressure), turn to vapor without melting. If this vapor comes in contact with a cold surface, the substance is deposited in the solid, crystallized state. It is evident that we have here another method of separating some substances. THE ELEMENTS. 8. When a substance (§6) is subjected to various influences, such as heat, electricity, or light, or is brought in contact witli other substances, it is very often split up into two or more dis- similar components. As an example let us take gunjjowder. Water is added and the whole is stirred well and gently warmed; after a while it is filtered, and that which remains on the filter is found to be no longer gunpowder, for it is unexplosive. On evapo- rating the filtrate a white crystalline substance, saltpetre, remains. The undissolved part is dried and then shaken with another sol- vent, carbon disulphide. After a time the mixture is filtered, as before, and there is left on the filter a black mass, consisting of charcoal powder. The carbon disulphide of the filtrate evaporates and leaves yellow crystals of sulphur. Thus we see that, l)y suc- cessive treatment with water and carbon disulphide, gunpowder can be separated into three substances, viz. carbon, sulphur and saltpetre. The two former are incapable, even when subjected to all the agencies at our command, of division into different com- ponents. Not so with saltpetre, for when the latter is heated strongly a gas is given off in which a glowing wooden splinter is at once ignited. When the evolution of gas ceases, a suljstance remains which gives off red fumes on treatment with sulphuric acid, something that saltpetre does not do. Saltpetre can evidently be broken up still farther by heating. If we subject all sorts of substances to a successive treatment with reagents of the most different kinds, we finally discover cer- tain ones that cannot be resolved into simpler substances by our present means. Such substances are called elements. Although the number of substances, according to § 6, may be considered as infiniteh/ great, experience has taught that the number of elements is small. There are about eighty. As our methods of examination improve, it may quite possibly