Citric acid is tribasic. It forms with silver a white insoluble salt, containing 3 atoms of oxide of silver to 1 atom of citric acid. If the citrate of silver be heated in a current of hydrogen gas, a part of the acid is liberated and the salt is reduced to a citrate of suboxide of silver; which is of a red color. The action of white light in reddening citrate of silver is shown by the author to be of a similar nature.
Cyanide of Potassium.
Symbol, K, C{2}N, or KCy. Atomic weight, 66.
This salt is a compound of cyanogen gas with the metal potassium. Cyanogen is not an elementary body, like chlorine or iodine, but consists of carbon and nitrogen united in a peculiar manner. Although a compound substance, it reacts in the manner of an element, and is therefore (like ammonium, previously described) an exception to the usual laws of chemistry. Many other bodies of a similar character are known.
Ether.
Symbol, C{4}H{5}O. Atomic weight, 37.
Ether is obtained by distilling a mixture of sulphuric acid and alcohol. If the formula of alcohol (C{4}H{6}O{2}) be compared with that of ether, it will be seen to differ from it in the possession of an additional atom of hydrogen and of oxygen: in the reaction, the sulphuric acid removes these elements in the form of water, and by so doing converts one atom of alcohol into an atom of ether. The term sulphuric applied to the commercial ether has reference only to the manner of its formation.
Properties of Ether.—It is neither acid nor alkaline to test-paper. Specific gravity, at 60°, about ·720. Boils at 98° Fahrenheit. The vapor is exceedingly dense, and may be seen passing off from the liquid and falling to the ground: hence the danger of pouring ether from one bottle to another if a flame be near at hand.
Ether does not mix with water in all proportions; if the two are shaken together, after a short time the former rises and floats upon the surface. In this way a mixture of ether and alcohol may be purified to some extent, as in the common process of washing ether. The water employed however always retains a certain portion of ether (about a tenth part of its bulk), and acquires a strong ethereal odor; washed ether also contains water in small quantity.
Bromine and iodine are both soluble in ether, and gradually react upon and decompose it.