[ 205 ] ,-.^ 



XXIX. On the Composition of the Gold from California. 

 ^,S; By T. H. Henry, Esq., F.R.S* 



/^OLD as found in nature is never chemically pure, being 

 ^^ combined with variable proportions of silver and traces 

 of iron and copper, and occasionally it occurs with palladium 

 and also with tellurium. ' 



The amount of silver was found by Boussingault in a series 

 of analyses of the native gold of Columbia to vary between 2 

 and 35 per cent., from which he drew the conclusion that the 

 gold and silver were combined in atomic proportions, 1 atom 

 of silver being constantly combined with more than 1 atom of 

 gold. 'J.'he specimen containing 35 per cent, of silver he con- 

 sidered to be a compound of 1 atom of silver and 2 atoms of 

 gold, Ag Au^, and that containing 2 per cent, of silver 1 atom 

 of silver and 12 gold, Ag Au^^. 



This view of Boussingault was controverted by Gustav 

 Rose on his return from his celebrated journey to' the Ural 

 Mountains theoretically, on the ground that gold and silver 

 were isomorphous bodies, and such substances are not gene- 

 rally met with combined in atomic proportion. " It would be 

 as remarkable as if antimony, arsenic and tellurium were found 

 combined in atomic proportion," he remarks f ; " but as iso- 

 morphous substances do sometimes occur combined in atomic 

 proportion, as in bitterspar, diopside, &c., the only remarkable 

 result of the analyses of Boussingault is, that the gold and 

 silver should be constantly so combined ; " and experimentally 

 by the analyses of several specimens of native gold from the 

 Ural Mountains, in the greater number of which no such defi- 

 nite composition existed. 



The purest specimen analysed by Rose contained 98*96 per" 

 cent, of gold and 0*16 per cent, of silver; the others contained 

 from 60 to 94< per cent, of gold. 



The gold from California, a small quantity of which I ob-^ 

 tained from Mr. Tennant of the Strand, was taken from a 

 quantity of about 60 lbs. weight, and was considered a fair 

 average sample of the whole : the greater part of it was in the 

 form of flattened grains or spangles, varying from j\jth of a 

 grain to 2 or 3 grains in weight ; one piece however weighed 

 upwards of 30 grains : the surface was rough and irregular, 

 with minute portions of siliceous matter imbedded in it. The 

 specific gravity of a number of the smaller grains taken toge- 

 ther by the bottle was 15*96; an analysis was made of these 



• Communicated by the Author. 



t PoggendorfTs Annalen, vol. xxiii. p, 164. 



