Experimculs on Platlnj. 4^ 



blow in diflerent direftion?^ the platina may be rendered fo 

 pure that, when examined with a magnifying glal's, a grain 

 of i'and will not be found in a pound oTit. 



III. Of the Gold. 



All the gold contained in crude platina is fcldom difco- 

 vered, even with the help of a magnifying glafs; and as 

 mercury is the means employed to leparate them, it is evi- 

 dent that, if a few grains of sold remain, ihev muft retain 

 tlieir portion of the mercury. Hence the gold acquires a 

 white hue, which aliimilates it to the colour of the platiua, 

 and prevents it from beine; perceived. 



I do not know whether the workmen at the platina mines 

 arc acquainted with any certain method of afcertaiiiing whe- 

 ther the feparation be complete. A very fimple proceis is, to 

 heat the platina in an iron fpoon or crucible. The mercurv 

 becomes volatilized, the gold refumes its colour, and the 

 platina acquires that of calcined iron. The gold then, on 

 account of its colour, may be very eafily dilUnguiflied from 

 the platina. 



In this manner I feparated 7 ounces of gold grains, or 

 fcales, from 100 ounces of Tome kinds of crude platina, and 

 73 from others. The mean produft is 10 per cent., as I 

 announced at the time to government. 



Thefe fcales are of different colours: fome have the yel- 

 low colour of gold, others are of a pale or a green yellow. 

 -he lafl^, tried with the blowpipe and borax, tine themfelves, 

 ttWcing the borax green, as iron would doj which llious that 

 It is-i green native gold, like that of the jewellers. 



^_b- nitric acid alio, digelted cold over theie kinds of crude 

 P''^^'"''>feparates the mercury from the gold, but not fo com- 

 pletely a. heat. 



Crude jlatina of a black colour, finer than the white, is 

 very comniinly brought from America. It ftains the fino-ers, 

 probably on ucount of the fupcrabundance of graphite or 

 plombago whic. it contains, I never found gold iirifiis kind, 

 and I have not b^.^ able to obtain any information refped- 

 Ing its origin. 



IV. Of Sulphite as the Mineralizer of Plalina. 

 When crude platina i-. expofed to the heat of the blow- 

 pipe on charcoal, a ftrongfniell of fulphur is exhaled, ac- 

 companied with fumes whic'a do not whiten cold, and which 

 are_ not produced but by a -legree of hcat'fuperior to that 

 which volatilizes mercury. Black plalina sirains give more 

 lumes than the white. 



3 L'irgc 



