100 PHILOSOPHICAL TRANSACTIONS. [aNNO 1750. 



in a sand-heat for 12 hours: the platina, when taken out of the aqua fortis, was 

 found of the same weight as when put into it ; being in nowise dissolved or cor- 

 roded by that menstruum. 



It had been reported, that this semi-metal was specifically heavier than gold ; * 

 but having weighed several pieces of it hydrostatically in a nice assay-balance, he 

 found one of these pieces was to that of water exactly as 1 5 to 1 . Another piece, 

 that seemed to be cast very open and porous, he found in gravity to water only 

 as 13.91 to 1 : though this last-mentioned piece, could it have endured the ham- 

 mer as well as gold, might probably have been reduced to a considerably greater 

 degree of solidity than that of the first-mentioned specimen. For the purest gold 

 is seldom found, after fusion, to come up to its true specific weight, till it has 

 been brought up to its greatest degree of solidity under the hammer. 



He also weighed an equal mixture of gold and platina, which he found nearly 

 as ponderous as gold itself; the specific weight of this mixture being to that of 

 water as 1 9 to 1 . 



It had been reported, that the Spaniards had sometimes been tempted to adul- 

 terate gold with platina, as the mixture could not be distinguished from true 

 gold by all the ordinary trials : but the gold thus adulterated was, on a nicer 

 examination, found hard and brittle, and could not be separated from the platina, 

 and rendered ductile and pure, either by cementation, or by the more ordinary 

 operations with lead and antimony. In order therefore to prevent this fraud, the 

 king of Spain commanded that the mines of platina should be stopped up ; so 

 that this semi-metal is now much scarcer than formerly. 



From the foregoing account it appears, that no known body approaches nearer 

 to the nature of gold, in its most essential properties of fixedness and solidity, 

 than the semi-metal here treated of; and that it also bears a great resemblance 

 to gold in other particulars. Some alchemists have thought that gold differed 

 from other metals in nothing so much as in its specific gravity ; and that, if 

 they could obtain a body that had the specific weight of gold, they could easily 

 give it all the other qualities of that metal. Let them try their art on this body; 

 which, if it can be made as ductile as gold, will not easily be distinguished from 

 gold itself. 



On the whole, this semi-metal seems a very singular body, that merits an 

 exacter inquiry into its nature than has yet been made; since it is not altogether 

 improbable that, like the magnet, iron, antimony, mercury, and other metallic 

 substances, it may be endowed with some peculiar qualities, that may render it 

 of singular use and importance to mankind. 



♦When thoroughly purified, it is specifically heavier than gold, weighing 23.000 j whereas the 

 specific gravity of gold is only 19.3. . , 



