HISTORY or COLD, 245 . .. 



A solution of mercury is first to be prepared by dissolving Pro<;flBS. 

 some red oxide in nitric acid. This is to be diluted with eight 

 or ten times its bulk of pure water, and solution of gold is af- 

 terward to be added at different intervals. A yellow precipi- 

 tate will thus be produced, in colour much resembling fulmi- 

 nating gold. Leave this to subside, draw off the liquid, wasH 

 the precipitate several times with boiling water, and dry it in a 

 capsule. 



If we go on to exhaust the solution of mercury by continu- 

 ing to add that of gold, we shall arrive at a point when the 

 latter will render it turbid no longer. The reason of this is 

 obvious : the nitrate of mercury is at length entirely converted 

 into corrosive subhmate ; and sublimate, the oxide of which 

 is saturated with oxigen, cannot decompose the muriate of 

 gold. 



If the nitrate of mercury employed in this experiment be 

 not completely at the maximum, it is easy to perceive that 

 we should be liable to produce mercurius dulcis, which would 

 then unite with the oxide of gold. 



This precipitate is not, as I at first hoped, a pure oxide. It 

 remains mixed or combined with a portion of corrosive subli- 

 piate, from which it could not be freed by repeated washings. 



A hundred parts of this dry precipitate, heated in a retort, Component 



afforded, P"^^' °[ *'!f 



' precipitate. 



Water 8, 



Corrosive sublimate mixed with mercurius dulcis l6. 



Gold 70, 



Total 94. 



The oxigen fixed in the gold, therefore, amounted to 6 ; 100 p, of gold 

 consequently a hundred parts of gold require S'57 of oxigen to ^f oxja-eii! 

 become an oxide. But as these results did not yet afford me 

 any thin^ satisfactory, I thought it necessary to proceed to a Process repeat- 

 fresh precipitation. The precipitation took place with the ^ 

 same appearances, but the washing was carried much farther 

 than before. The last washings, however, were still rendered 

 turbid by the test of muriate of tin at a minimum ; but the 

 products of the distillation, though the same, exhibited them- 

 selves very differently. 



I put 



