»

[ 610 ]

is therefore a perfect metal, of the fame class with gold andsilver, and perhaps more perfect, or less alterable, thanthey : — which, with the colour of silver, possesses thespecific weight, and several other of the reputedly mostdiscriminative properties of gold ; resisting, equally withgold, many agents, which discolour, corrode, dissolve, orscorify silver and the base metals, as air and sulphureousexhalations,-the nitrous, marine, and vitriolic acids bothin their liquid state and when resolved by fire into fume,and sulphur and antimony in fusion : — with these valua-ble properties of gold, it adds some to gold itself, makingit both less soft and less fusible, which no other alloy-does: hence a due proportion of it bids fair to removethose ineonveniencies, which the enamellers complain of,when they work upon plates either of sine gold or of alloyedgold.

2. Though platina undoubtedly belongs to the famegenus of bodies with gold and silver, of which genus nomore than these three species have hitherto been discover-ed ; and though it agrees with gold in many properties■which have been universally supposed distinctive ef thespecies : yet there are other important characters in whichit remarkably differs from gold. Its white colour; itswant of fusibility; the singular alterations which it pro-duces in some of the ether metals, and in gold itself; itsbeing difficultly and sparingly acted on by hepar sulphuris,by which gold is plentifully dissolved ; its solution in aqua<regis giving no stain to the substances which by solutionsof gold are tinged red or purple ; its being in part precipi-tated from its solution by sal ammoniac, which does notin the least precipitate gold; its being precipitated onlypartially by vegetable fixt alcaldes and by volatile alcalies,and not in the least by the mineral alcali or by solution ofgreen .vitriol, by all which gold is precipitated entirely ;

its