S36 Upon the Existence of Plat'ina 



at a difierent point from the former one,) I recognised in a 

 variety of thtse mines tlTfe presence of a considerable quan- 

 tity of platina. This species of ore is gray, and has a strong 

 resemblance to that with which we are acquainted under the 

 name of gray silver, the fuhleriz of the Germans ; it con- 

 tains copper, lead, antimony, iron, sulphur, silver, and 

 soi"netimes arsenic. Its matrix is generally formed of car- 

 bonate of lime, to which sulphate of barytes and quartz are 

 united. I communicated this discovery to M. Fourcroy in 

 October last: this learned coadjutor, whose genius and 

 friendship have been of great service to me for twenty years 

 past, urged me to verify the fact, which he thought very 

 important, by muhijjlied and varied experiments, in order 

 to put it beyond all doubt. I took his advice, and the fol- 

 lowing are the results I obtained ; they leave no doubt in 

 my own mind, although I have been able as yet to operate 

 upon very small quantities of ores only. 



The plalina seems to exist in varied proportions in, the 

 silver ores of Guadalcanal ; some specimens furnished me 

 in the proportion of 10 of platina in the 100 of silver, while 

 others yielded almost imperceptible traces only: this shows 

 that this metal does not form an essential or truly consti- 

 tuent part of these ores, and that it is only mixed with them 

 in unequal quantities in various parts of the vein. The silver 

 seems to be in the same case ; it varies much in its pro- 

 portions also : I have found it in the gray silver mines of 

 Guadalcanal from 2 up to 7 hundredth parts of the total 

 weight. 



The process I used, after several comparative trials, in 

 order to extract the platina from these ores, consists in the 

 followino operations : — 1. After having reduced the mineral 

 into fine powder I roasted it by a gentle heat, stirring it con- 

 tinually. 2. I melted the matter with an equal quantity of 

 common potash, by which means I obtained a metallic but- 

 ton composed of ]ilatina, silver, lead, copper, and sometimes 

 a little antimony ; iron and a part of the lead remained in 

 the scoriae. 3. I afterwards separated the copper, lead, and 

 antimony, bycupellation ; nothing except silver and platina 

 then remained. 4. I freed this last metal from the silver by 



means 



