0_^2 JirSTORY OF GOLD. 



uncJer water, because in this state it is proper for experiments' 

 that require an easy and prompt solution of this metal. 

 Gives a deep This gold applied on porcelain gives a deep purple. We 



celaii'T ^"^ ^'''' ^^^^^^ ^^^""^ ^^ ^^^^ ^^^^'^ °^*^^*^ S°^^' '" ^^^^ colour. 



Partly soluble Marine acid of 12°' boiled on this powder of gold, very eVi- 



111 marine acK . ^j^j^|.|y dissolves some of it, and" acquires a yellow colour. A 



Gold capable slip of tin put into it produces the purple in an instant. Gold, 



water °™^'^^^"° therefore, assisted by the affinities that favour iron, zinc, &c., 



is capable of decomposing water. Thus the marine acid, 



contrary to the received opinion, is capable of attacking gold 



and silver, as it does so many other metals. 



This precipitate Nitric acid of 40° boiled on this gold dissolves some of it 



partly soluble jike^^ise, and becomes coloured. 



in strong nitric _ 



acid; An acid of 36° dissolves some too, but so little, that it is 



— but not by scarcely to be detected by means of tin. With an acid of 32°. 

 partin^^*^ "^ ^'^^ ^^^^ employed in parting, it may be doubted whether any 

 gold can he taken up ; particularl3- as the cornet js far from 

 exposing so many points to the attack of the acid as the pow- 

 der in question. 

 Solution of gold Hydrophosphorated water precipitates the solution of gold, 

 precipitated by rpj^g^j. jj^ xvhich phosphorus is kept does the same, but the etfecfe 

 phosphorus . , • i , ^ , i i • i i 



gas, but not by 's Owing exclusively to the gas, for the phosphorus acid has 



phosphorus j^g action on this solution in less than ten or twelve hours. 



acid. 



Precipitation by Alkalis. 



Precipitated by . Potash purified by alcohol precipitates from the muriate of 



P° ^* ■ gold a powder, that is at first yellow, and then violet, if we 



operate with a large quantity of water, but which appears 



An uncertain black when it has been washed and dried. Nothing is so ca- 



prepaiatiou. pncious as this preparation. An excess of alkali, saturatioDy 



a boiling heat, are insufficient to render us masters of it. The 



liquors always remain more or less impregnated with gold. 



It frequently happens, that the precipitation goes on till the 

 next day: but instead of adding to the black powder, it covers 

 it with a metallic pellicle, or even gilds the vessel in a very 

 brilliant manner. I iTave kept one in this state as an object 

 of curiosity. 

 A mixture of Jf tlie black powder have been washed and dried with the 

 dueed gold. gentlest heat, what we should expect to be a pure oxide,^is 

 nothing but a mixture of oxide and reduced gold. This is what 



mihtates 



