WATER. H0=9. Water may be considered as the protoxide of hydrogen, being composed of one atom of oxygen and one of hydrogen ; or, which is the same thing, of two volumes of hydrogen and one of oxygen.
Water in its ordinary state exists either as rain, or river, or spring water.
Rain-water always contains carbonic acid, ammonia, organic matters, and sometimes nitric acid. It becomes putrid when kept. If collected in leaden vessels oxide of lead is readily formed and a small quantity dissolved by it. Rain-water is not suitable for the nitrate bath or developer, although perhaps better than spring water since it does not contain salts which form precipitates with nitrate of silver.
River and spring waters contain various salts and organic impuri ties ; the principal salts being chloride of sodium, sulphate of lime, and carbonate of lime dissolved in carbonic acid ; these produce pre cipitates or turbidity in the water when nitrate of silver is added to it. Carbonate of lime may be thrown down by boiling the water, which expels the carbonic acid which keeps it in solution. Water is said to be " hard " when it contains salts of lime.
Water may be purified by distillation and condensation of the steam, provided it does not contain volatile oil or empyreumatic matter, which impurities are generally present in the distilled water obtained by condensing the steam from steam boilers. Perfectly pure distilled water for delicate chemical operations is obtained by the redistillation of ordinary distilled water in silver vessels at a low temperature. It is then perfectly neutral to test paper, and a cubic inch of it at weighs grains.
Water is very slightly compressible, and when submitted to sudden and violent compression becomes luminous. It freezes at 32°, and boils at In freezing, or crystallizing, it expands in bulk, therefore ice floats. Water, in freezing, rejects impurities, or salts held in solution, therefore melted ice is very pure water. The
combustion of 2 volumes of hydrogen and 1 of oxygen produces 2 volumes of steam. At a mean atmospheric pressure, and tempera ture the bulk of steam is 1689 times that of water.
Wax. This substance is supposed to be produced by the bee from the honey which it collects. Its composition is stated by Lowig as 02 ; but it varies, although in every case but one there are as many equivalents of carbon as of hydrogen.
Bees' wax in its ordinary state is yellow, but is bleached by being exposed in thin ribands to the joint action of air, light, and moisture. Sometimes, however, it is bleached more expeditiously by mixing with it nitrate of soda and dilute sulphuric acid, and then traces of sulphate of soda and nitric acid are generally retained. Wax melts at 150°, and is almost entirely soluble in boiling alcohol, and ether; but on cooling the alcohol only retains a small quantity, and the ether none. When caustic potass is added to melted wax, a soapy gela tinous substance is formed which is soluble in a large quantity of water. On adding an acid an oily liquid forms, which solidifies on cooling and is soluble in hot alcohol; it is probably the " Ceraine" of Ettling. Succinic acid is obtained by digesting wax for some days with nitric acid.
Many vegetables secrete wax from their leaves and stems. In stances of this occur as myrtle-wax, palm-wax, Japan-wax, Ocuba wax, sugar-cane-wax, cork-tree-wax, &c.
White wax is commonly sold in round flat cakes, and is frequently adulterated with tallow, stearine, &c.
Wax may be mixed in any proportions with oil of turpentine. Positive prints, or sheets of paper rubbed with this mixture, acquire a high polish on the evaporation of the turpentine. The ancient fresco paintings upon the walls of houses were varnished and pre served with wax. See " Encaustic Painting."