Characters. - In colourless rhomboidal crystalline plates, with a cool saline taste.

Preparation. - By passing chlorine through a mixture of potassium carbonate and slaked lime. If potassium carbonate alone were used part of it would be converted into KC1 and lost. 3K2CO3 + 3C12 = 5KC1 + KC1O3 + 3CO2. To save this, lime is used, which is much cheaper. After the mixture has been saturated with chlorine it is boiled, filtered, evaporated, and the chlorate crystallised out. K2CO3 + 6CaH2O2 + 6C12 = 2KC1O3 + 5CaCl2 + CaCO3 + 6H2O.

Solubility and Reactions. - Sparingly soluble in cold water. It explodes when triturated with sulphur. When heated it fuses, gives off oxygen gas, and leaves a white residue, which dissolves in water and gives the reactions of potassium and of a chloride.

Impurities. - Chloride and calcium. Test. - Its solution is not affected by nitrate of silver (no chloride) nor oxalate of ammonium (no calcium).

Dose. - 10 to 30 grains.

Officinal Preparations

B.P. and u.s.p.

Dose.

Trochisci Potassii Chloratis ..........................

5 grains in each lozenge. - 1 to 6.

Used also in preparing Potassii Permanganas.

Action. - Chlorate of potassium, when injected into the circulation, has not the same action as other salts of potassium. Small doses generally at first depress, and afterwards raise the blood-pressure and accelerate the pulse. Large doses cause sudden stoppage of respiration, and sinking of the blood-pressure down to zero, while the exposed heart continues to beat at nearly its normal rate, or a little over it, for half or three-quarters of an hour.

Large doses administered medicinally have caused poisoning, especially in children. The symptoms are due to the haemoglobin of the blood being converted into methaemoglobiri by the action of the chlorate. They consist in haematuria with blood-casts and diminished secretion of urine, many of the renal tubules being filled with plugs of blood. The skin becomes discoloured or jaundiced, and death occurs with coma or convulsions.

Uses. - Chlorate of potassium is chiefly used as a local application to the mouth, to bring about a more healthy condition of the mucous membrane, and to cause ulceration present there to heal up. It is used in stomatitis occurring during nursing, whatever it may depend upon; in aphthae, in cancrum oris. As a gargle it is used in follicular pharyngitis; and has been employed internally and as a local application in cases of croup, diphtheria, and spasm of the larynx. It may be used internally as a lotion to relieve the dryness of the throat after diphtheria and scarlatina. When taken early, it is said to lessen or arrest catarrhal conditions of the nose, throat, and larynx. It has been recommended in chronic mucous diarrhoea with whitish or mucilaginous-looking stools. It has also been used as an enema in cases of dysentery. After absorption into the blood it has been supposed to give off its oxygen, and thus to have a disinfectant action in cases of blood-poisoning and malignant fevers. A great part of it is excreted unchanged by the kidneys, but in large doses it decomposes the blood and converts it into methaemo-globin. It has been employed in acute and chronic bronchitis, in order to thin the secretion and promote expectoration, and as a diuretic in cases of dropsy. It was recommended by the late Sir James Simpson in 20-grain doses three times a day, to-pregnant women where abortion was liable to occur from fatty degeneration of the placenta.