SULPHURETS. 303 



unite and precipitate, while the hydrogen and oxygen, 

 previously combined with them, form water. 

 Mention the 763. The sulphuret of zinc is white ; 

 colors of some tnat o f arsen i c yellow ; and that of anti- 



of the sulphu- ' J 



rets. mony, orange. The remainder of the in- 



soluble sulphurets are black. Solutions of 

 white vitriol, arsenious acid, and tartar emetic 

 may be used, as above directed, to produce sul- 

 phurets of zinc, arsenic and antimony. If 

 the zinc precipitate should be colored, it is 

 owing to the presence of iron in the salt, as 

 impurity. Blue vitriol may be employed to produce 

 black sulphuret of copper. 



764. The sulphurets of ammonium, po- 



What is said 



of the sulphu- tassmm and sodium, cannot be precipitated 

 r aika/iel h ? e b y this P rocess - Being soluble, they re- 

 main in the liquid. Solutions of the caus- 

 tic alkalies are to be used in preparing them. The so- 

 lutions of these sulphurets are useful, as they may, in 

 many cases, be substituted with advantage for hydro- 

 sulphuric acid, in precipitating sulphurets from solutions 

 of other metals. Certain other sulphurets are soluble, 

 and do not precipitate, as will be seen from the table 

 in the Appendix. 



765. LIVER OF SULPHUR. There are a 



What is liver f . f 



of sulphur? number of sulphurets of potassium, con- 

 jj u pre " taining each a different proportion of sul- 

 phur. That which contains five atoms of 

 sulphur, to one of metal, is called, from its peculiar 

 color, liver of sulphur. It is prepared by boiling flowers 

 of sulphur in a strong solution of potash. It may also 



