" Take of carbonate of soda, a pound; distilled water, forty-eight fluid ounces; chloride of sodium, four ounces; binoxide of manganese, three ounces; sulphuric acid, four ounces. Dissolve the carbonate of soda in two pints of the water, then put the chloride of sodium and the binoxide of manganese, rubbed into powder, into a retort; and add to them the sulphuric acid mixed with three fluid ounces of water and cooled. Heat the mixture, and transmit the chlorine thus evolved, first through five ounces of water, and then the above prescribed solution of the carbonate of soda."

1 Gehlen, Journ. iv. 210. Thomson's Chymistry, 4th edit. iii. 96.

2 Hence its appellations of Sal de Seignette, Sal Ruppellensis.

In this process the chlorine is extricated by the oxygen furnished from the binoxide of manganese combining with the sodium to form soda, which unites with the sulphuric acid, and constitutes a sulphate, the chlorine escaping in the form of gas. The object of passing the liberated chlorine through water, before it enters the alkaline solution, is to free it from any hydrochloric acid which may be formed by a partial decomposition of the water of the mixed materials. The mixture formed with the alkaline solution and the chlorine closely resembles that which is known as La-barraque's disinfecting soda liquid; and is supposed to be a solution of the carbonate of soda, merely holding chlorine in such a manner that it admits of being crystallized with the carbonate.

Qualities. -The solution, whether recent, or of the crystals redissolved, is of a pale yellow colour, with a sharp, brackish, acerb taste. It first browns and then bleaches turmeric paper: the browning depends on the carbonate of soda; the bleaching on the chlorine. It slowly evolves the chlorine when it is exposed to the air, and crystals of carbonate of soda form as the fluid evaporates.

Medical properties and uses. - This solution is astringent, and, if any thing can strictly be so termed, antiseptic. I have administered it, largely diluted, in typhus and other low fevers, to counteract the sedative influence of the sul-phureted hydrogen which accumulates in the intestines, in these fevers. I have found it, also, most valuable as an injection into the nostrils, for correcting the acrid, offensive discharge which takes place from the nostrils in malignant scarlatina. Its chief use, however, is as a disinfecting agent. No satisfactory theory of its action has been advanced; but I am disposed to think that the benefit arises from the decomposition of the pernicious effluvia, which seems to consist of sulphureted hydrogen, holding in solution an ammoniacal oil. Now, when chlorine comes in contact with sulphureted hydrogen, the hydrogen combines with the chlorine and forms hydrochloric acid, whilst the sulphur is precipitated, and along with it the ammoniacal oil.