346 Dr. Vest on Vestium. _ [May, 
diligence to prevent the barytes from forming a powder. 
Instantly a great quantity of orpiment falls to the bottom. 
This process I repeat till the whole of the arsenic is thrown 
down. After the separation of the orpiment, I try the clear 
liquid with water saturated with sulphuretted hydrogen gas. If 
it betrays arsenic, I repeat the preceding process till the sulphur- 
etted hydrogen water ceases to mdicate the presence of that 
metal. The liquid during the whole of this process should con- 
tain an excess of acid in order to prevent any other metal from 
being thrown down; though indeed a small loss of the other 
metals is scarcely to be avoided. 
When the arsenic is thus removed and the liquid still acid, a 
small additional quantity of dry sulphuret of barytes may be put 
into it, by means of which the existence of sulphuretted hydrogen 
gas in the liquid may be continued for some time ; but the whole 
must be frequently and carefully agitated to prevent the sulphate 
of barytes from cohering together in lumps. After some time, 
the clear liquid must be drawn off and the residue filtered, and 
the whole must be put into a wide vessel in a warm place and 
freely exposed to the air. The excess of sulphuretted hydrogen 
partly flies off, and is partly decomposed. We know that the 
process is completed when, some drops of the liquid being let 
fall into a potash solution, no black-coloured precipitate falls. 
I now neutralize the solution with carbonate of potash, and 
digest it for some time ina warm place. This has.a tendency to 
separate oxide of iron. This oxide and the sulphur are then 
separated from the liquid by the filter. 
Method of freeing Vestium from Nickel. 
I concentrate the clear solution obtained by the process above 
described till I bring it to a considerable consistence. A salt is 
formed and swims in the liquid in fine needles, like flakes of 
snow. I separate it by the filter, wash it with cold water, and 
evaporate the liquid a little further, in order to obtain an addi- 
tional. portion of the salt. I have obtamed the same salt from 
some purified solutions of cobalt pyrites from the same mine, It 
is a salt of vestzum. 
I now dilute the green-coloured liquid with water, decompose 
it by potash, collect the precipitate upon a filter, wash it, and 
dissolve it in diluted sulphuric acid. In case there has been 
added an excess of acid, | saturate it with potash, then I add 
the requisite quantity of sulphate of potash, and evaporate the 
whole till it is reduced to the point of crystallizing. 
The crust of salt obtained after the liquid has become cold I 
wash off with the requisite quantity of cold water, and separate 
the green-coloured and difficultly soluble nickel crystals from the 
white flocks lying on them, by agitation in a glass, and by gently 
rubbing them between the fingers, and 1 wash them very care- 
