CHLORATES, the metallic salts of chloric acid ; they are all solids, soluble in water, the least soluble being the potassium salt. They may be prepared by dissolving or suspending a metallic oxide or hydroxide in water, saturating the hot solution with chlorine; by double decomposition; or by neutralizing a solution of chloric acid by a metallic oxide, hydroxide or carbonate. They are all decom posed on heating, with evolution of oxygen; and in contact with concentrated sulphuric acid with liberation of chlorine peroxide. The most important is potassium chlorate, which was obtained in 1786 by C. L. Berthollet by the action of chlorine on caustic potash, and this method was at first used for its manu facture. The modern process consists in the electrolysis of a hot solution of potassium chloride, or, preferably, the formation of sodium chlorate by the electrolytic method and its subsequent decomposition by potassium chloride. (See ALKALI MANUFAC TURE.) Potassium chlorate crystallizes in large white tablets, of a bright lustre. It melts without decomposition, and begins to give off oxygen at about 37o°C. By very careful regulation this decom position can be made to yield the perchlorate, KC104. The de composition is rendered more easy and regular by mixing the salt with powdered manganese dioxide. The salt finds application in the preparation of oxygen as an oxidizing agent in the laboratory, with concentrated hydrochloric acid in the laboratory production of chlorine, in the manufacture of matches, for pyrotechnic pur poses, and in medicine. If crystals of potassium chlorate are rubbed together in the dark, they become faintly luminous; this phenomenon is known as "triboluminescence." Sodium chlorate, is prepared by the electrolytic process; by pass ing chlorine into milk of lime and decomposing the calcium chlo rate formed by sodium sulphate; or by the action of chlorine on sodium carbonate at low temperature (not above 35°C.). It is much more soluble in water than the potassium salt. Its crystal structure resembles that of calcite; sodium atoms occur at alter nate corners of a rhombohedron, and the other corners are occu pied by chlorine atoms each surrounded by three co-planar oxy gen atoms.
Potassium chlorate is very valuable in medicine. Given in large doses it causes rapid and characteristic poisoning, with alterations in the blood and rapid degeneration of nearly all the internal or gans; but in small doses-5 to 15 grains—it partly undergoes re duction in the blood and tissues, the chloride being formed and oxygen being supplied to the body cells in nascent form. Its spe cial uses are in ulceration of the mouth or tongue (ulcerative sto matitis), tonsillitis and pharyngitis. For these conditions it is ad ministered in the form of a lozenge, but may also be swallowed in solution, as it is excreted by the saliva and so reaches the diseased surface. Its remarkable efficacy in healing ulcers of the mouth— f or which it is the specific—has been ascribed to the production of chloric acid, which, being an extremely powerful antiseptic, kills the bacteria to which the ulcers are due.