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to an acid rapacious of that principle. The marine acid has the greatest affinity to its earth, which however it cannot attack till the phlogiston has been detached from it. This last office is performed by the nitrous acid in the aqua regia, which evidently acquires phlogiston in the process ; and the marine acid is thus left at liberty to dissolve the earth. But the Author having discovered a method, not here indicated, of dephlogislicating marine acid (by means, we believe, of manganese), found that the marine acid, thus deprived of its own phlogiston, was capable, singly, of dissolving gold in its metallic state; in consequence of the avidity which, by its own dephlor gistication, it had acquired for phlogifton. A solution of gold, thus effected, being distilled in a retort with a strong heat, the gold is reduced without addition: for it recovers back again the very phlogiston which, during its solution, it had before parted with to the marine acid; and the acid accordingly passes over into the receiver in its prior dephlogisticated state. Gold, thus dissolved by the dephlogisticated marine acid alone, is actually precipitated, on the addition of a volatile alcali, in the form of fulminating gold. From this process it appears clearly that the peculiar qualities of this powder are not to be accounted for from the presence of any nitrous acid supposed to be contained in it. That the earth of gold + attracts a volatile alcali more strongly than the latter is attracted even by the vitriolic acid, the Author shews by digesting this calx in a solution of Glauber’s sal animoniac. In this case, this neutral solution of volatile alcaii and vitriolic acid became acidulous; in consequence of its parting with a portion of its volatile alcali, which had left the vitriolic acid, and united itself with the earth of gold; constituting with it a true aurum fulminans, which, from these and other experiments, appears evidently to be nothing more than a combination of the earth of gold and volatile alcali ;-particularly from the foliowing: The Author dissolved fulminating gold in marine acid, and put several pieces of copper into the solution. The gold was precipitated, on recovering its phlogiston from the copper; and the volatile alcali which had beeh a constituent part of the fulminating gold, and which had been expelled from it on its redućtion, and had entered into the solution, was readily recognised, on adding some fixed alcali to expel it from the solution previously evaporated to dryness. The Author's analysis of fulminating gold, particularly with

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* There are some peculiarities respecting heat, in the Author’s mode of explication, which differ somewhat from this account : but they cannot be here easily explained, as they are founded on his particular theory of fire; and the subject is certainly rendered clearer by

the omission of thein. low,

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the form of vapours t, coagulate into siliceous earth; and acid of

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ART. IV. An Examination of Dr. Crawford's Theory of Heat and Combustion : By William Morgan. Svo. 1 s. 6d. Cadell. 1781.

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* See M. Review, Vol. lxi. November 1779, pag. 378; and Mr. Magellan's explanation of Dr. Crawford's theory of fire, in the

4Aendix to our 63d volume [1789] Pag. 499. - That

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