THE 



PHILOSOPHICAL MAGAZINE. 



I. Experiments which prove Plativa, token combined with 

 Gold and Siluer, to be soluble in Nitric Acid. By Mr. 

 Pekcival Johnson. 



To Mr. Tilloch. 



Sir, JL/uring the practice of a profession where much 

 depends on depriving gold of its alloys, h;iving lieard U 

 siiagesied that platina mioht he used as an advantageous 

 one, under the idea of us being but slightlv afltcttd by 

 the nitric acid, I oeterniined on a closer inspection of its 

 action on that metal than had hitherto been described. 

 The insertion of the following reniaiks on niv experuneiits 

 will oblige me. 



I find, although platina when in a pure state is not acted 

 upon by the nitric acid, ihat when allovcd with gold and 

 silver it is [-perfectly soluble, and with sdver alone partially 



BO. 



From 1 to 13 per cent, of platina to the ijold was entirely 

 diss.)lved, leaving the gold a good colour and perfectly pure, 

 having previf)iisly nnxed the gold with three times its 

 weight of silver h)r quanalion. 



Twenty per cent, lost -rV'hs, leaving the cornet flaked 

 and black inside; 30 per cent, lost ^ths with the same ap- 

 pearances. 



The buttons have an indented crystalline and red appear- 

 ance alter ciipellation, nioie so in proportion lo the qu.uiliiy 

 of platina, and \\\ the two latter proportions are roiuuleil at 

 the edges. 



By mixing double the qnantiiy of silver the gold was 

 freed ot upwards of 20 per cent, of platma, and more ;ic- 



Vol.40. No. 171. Juti/ 1812. A 2 toiding 



