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 [alcohol, C2H5O HO; ether, (C2H5)2O]. Distilling spirit of wine and sulphuric acid together, it seemed obvious that the sulphuric acid should possess itself of the H2O, and leave the ether. But on this theory it was not possible to explain the invariable formation of sulphovinic acid (a sulphate of ethyl) in the process, nor the simultaneous distillation of water with the ether. Williamson proved that the acid first combined with the alcohol molecule, setting the water free, and that then an excess of alcohol decomposed the sulphovinic acid thus formed into free sulphuric acid and ether, this circuit proceeding continuously.

This popular medicine has been traced back to Raymond Lully in the thirteenth century, and to Basil Valentine. But the doctor who brought it into general use was Sylvius (de la Boe) of Leyden, for whom it was sold as a lithontryptic at a very high price. It first appeared in the P.L., 1746, as Spiritus Nitri dulcis. In English this was for a long time called "dulcified spirit of nitre," and in the form of sweet spirit of nitre still remains on our labels. In the P.L., 1788, the title was changed to Spiritus Ætheris nitrosi, and in that of 1809 to Spiritus Ætheris nitrici. The process ordered in the first official formula was to distil 6 oz. (apoth. weight) of nitric acid of 1·5 specific gravity, with 32 fluid oz. of rectified spirit. Successive reductions were made in the proportion and strength of the acid in the pharmacopœias of 1809, 1824, and 1851, to 3-1/2 fluid ounces of nitric acid, sp. gr. 1·42, with 40 fluid ounces of rectified spirit, and a product of 28 fluid ounces. The object of these several modifications was to avoid the violent reaction which affected the nature of the product.