§ 103. Pharmaceutical Preparations.—Potassium hydrate, as well as the solution of potash, is officinal in all pharmacopœias. The liquor potassæ, or solution of potash, of the British Pharmacopœia, is a strongly alkaline, caustic liquid, of 1·058 specific gravity, and containing 5·84 per cent. by weight of KHO. It should, theoretically, not effervesce, when treated with an acid, but its affinity for CO2 is so great that all solutions of potash, which have been in any way exposed to air, contain a little carbonate. Caustic sticks of potash and lime used to be officinal in the British Pharmacopœia. Filho’s caustic is still in commerce, and is made by melting together two parts of potassium hydrate and one part of lime in an iron ladle or vessel; the melted mass is now moulded by pouring it into leaden moulds. Vienna paste is composed of equal weights of potash and lime made into a paste with rectified spirit or glycerin.
§ 104. Carbonate of Potash (K2CO3 + 11⁄2H2O), when pure, is in the form of small white crystalline grains, alkaline in taste and reaction, and rapidly deliquescing when exposed to moist air; it gives all the chemical reactions of potassium oxide, and carbon dioxide. Carbonate of potash, under the name of salt of tartar, or potashes, is sold by oilmen for cleansing purposes. They supply it either in a fairly pure state, or as a darkish moist mass containing many impurities.
§ 105. Bicarbonate of Potash (KHCO3) is in the form of large transparent rhombic prisms, and is not deliquescent. The effervescing solution of potash (liquor potassæ effervescens) consists of 30 grains of KHCO3 in a pint of water (3·45 grms. per litre), and as much CO2 as the water will take up under a pressure of seven atmospheres.
§ 106. Caustic Soda—Sodium Hydrate (NaHO).—This substance is a white solid, very similar in appearance to potassium hydrate; it absorbs moisture from the air, and afterwards carbon dioxide, becoming solid again, for the carbonate is not deliquescent. In this respect, then, there is a great difference between potash and soda, for the former is deliquescent both as hydrate and carbonate; a stick of potash in a semi-liquid state, by exposure to the air, continues liquid, although saturated with carbon dioxide. Pure sodium hydrate has a specific gravity of 2·0; it dissolves in water with evolution of heat, and the solution gives all the reactions of sodium hydrate, and absorbs carbon dioxide as readily as the corresponding solution of potash. The liquor sodæ of the B.P. should contain 4·1 per cent. of NaHO.
§ 107. Sodæ Carbonas—Carbonate of Soda—(Na2CO310H2O).—The pure carbonate of soda for medicinal use is in colourless and transparent rhombic octahedrons; when exposed to air, the crystals effloresce and crumble. The sodæ carbonas exsiccata, or dried carbonate of soda, is simply the ordinary carbonate, deprived of its water of crystallisation, which amounts to 62·93 per cent.
§ 108. Bicarbonate of Soda (NaHCO3) occurs in the form of minute crystals, or, more commonly, as a white powder. The liquor sodæ effervescens of the B.P. is a solution of the bicarbonate, 30 grains of the salt in 20 ozs. of water (3·45 grms. per litre), the water being charged with as much carbonic acid as it will hold under a pressure of seven atmospheres. The bicarbonate of soda lozenges (trochisci sodæ bicarbonatis) contain in each lozenge 5 grains (327 mgrms.) of the bicarbonate. The carbonate of soda sold for household purposes is of two kinds—the one, “seconds,” of a dirty white colour and somewhat impure; the other, “best,” is a white mass of much greater purity. Javelle water (Eau de Javelle) is a solution of hypochlorite of soda; its action is poisonous, more from the caustic alkali than from the chlorine, and may, therefore, be here included.
§ 109. Statistics.—Poisoning by the fixed alkalies is not so frequent as poisoning by ammonia. Falck has collected, from medical literature, 27 cases, 2 of which were the criminal administering of Eau de Javelle, and 5 were suicidal; 22, or 81·5 per cent., died—in 1 of the cases after twenty-four hours; in the others, life was prolonged for days, weeks, or months—in 1 case for twenty-seven months. In the ten years 1883-1892, in England and Wales, there were 27 deaths from poisoning by the fixed alkalies; 2 were suicidal (1 from potash, the other from soda); the remaining 25 were due to accident; of these, 7 (3 males and 4 females) were from caustic soda, and 18 (8 males and 10 females) from caustic potash.
§ 110. Effects on Animal and Vegetable Life.—The fixed alkalies destroy all vegetable life, if applied in strong solution or in substance, by dehydrating and dissolving the tissues. The effects on animal tissues are, in part, due also to the affinity of the alkalies for water. They extract water from the tissues with which they come in contact, and also attack the albuminous constituents, forming alkali-albuminate, which swells on the addition of water, and, in a large quantity, even dissolves. Cartilaginous and horny tissues are also acted upon, and strong alkalies will dissolve hair, silk, &c. The action of the alkali is by no means restricted to the part first touched, but has a remarkable faculty of spreading in all directions.
§ 111. Local Effects.—The effects of strong alkali applied to the epidermis are similar to, but not identical with, those produced by strong acids. S. Samuel[122] has studied this experimentally on the ear of the rabbit; a drop of a strong solution of caustic alkali, placed on the ear of a white rabbit, caused stasis in the arteries and veins, with first a greenish, then a black colour of the blood; the epidermis was bleached, the hair loosened, and there quickly followed a greenish coloration on the back of the ear, opposite to the place of application. Around the burned spot appeared a circle of anastomising vessels, a blister rose, and a slough separated in a few days. The whole thickness of the ear was coloured yellowish-green, and, later, the spot became of a rusty brown.