Page:Proceedings of the Royal Society of London Vol 1.djvu/296

Rh and by Pliny, as well as by Pococke, Volney, and other modern travellers, who all concur with respect to the intense saltness of the water, which is such as to prevent either animals or vegetables from living in it,—a peculiarity from which it has derived its name.

The only analysis which Dr. Marcet has been able to ﬁnd recorded, is that of Macquer, Lavoisier, and Sage, in the Mém. de l’Académie for 1778. But these chemists had not attained that accuracy of which modern analysis is susceptible, and appear not to have bestowed upon the subject that attention which is requisite in minute analytical experiments.

The quantity of the water of the Dead Sea, which was the subject of Dr. Marcet’s experiments, amounted onlyto about 1% ounce; but it was in a phial, carefully corked, and appeared to be in a state of perfect preservation. The smallness of the quantity, and difﬁculty of obtaining a further supply, occasioned Dr. Marcet to be anxious that none might be wasted in previous trials. He accordingly began by a variety of comparative experiments on artiﬁcial solutions, in order to ascertain the accuracy of various modes of operating; and as he knew by the analysis of Lavoisier and his associates, that the principal ingredients which he might expect to ﬁnd were the mu- riates of soda, of magnesia, and of lime; and as the general effect of reagents tended to conﬁrm their results, excepting that they indicated the presence of a small quantity of selenite that had been overlooked, the solutions on which Dr. Marcet’s experiments were conducted were made to consist of the same ingredients, and in proportions which he previously ascertained with great precision.

The ﬁrst step, which appeared indispensable, was to determine the proportions of acid and base in each of the three muriates.

The composition of muriate of lime was ascertained by pouring a quantity of muriatic acid on a piece of marble of known weight, and larger than was necessary to saturate the acid: after saturation and evaporation of the solution, the residuum was heated to redness, and careth weighed. From the weight of this residuum, after subtracting the quantity of lime contained in a given weight of marble, which, by a number of experiments performed jointly with Mr. Tennant. was found to be 56'] per cent., it appeared that 100 parts of muriate of lime consist of 50'77 lime, and 49-23 muriatic acid.

To discover the proportional parts of muriate of magnesia required a synthetic process somewhat different. To a known weight of magnesia previously calcined, was added such a quantity of muriatic acid as would dissolve a known weight of marble; and after the whole of the magnesia had been dissolved, the excess of acid was saturated with marble, by which the redundant quantity was ascertained. Hence the quantity of acid combined with the given weight of magnesia was deduced, and the component parts of muriate of magnesia determined to be 43'99 magnesia, and 56'01 acid.

The proportion of acid and alkali in muriate of soda, was found, by various methods, to be 46 acid, and 54 soda. The best method appeared to be that of precipitation by nitrate of silver; the quan-