ANTIMONY AND LEAD. 81 



and afterwards with an excess of yellow sulphide of 

 ammonium, with which it is digested for some time 

 until the precipitate is perfectly black. The solution 

 is then diluted with water, the sulphide of lead col- 

 lected upon a dried and weighed filter, thoroughly 

 washed with dilute sulphide of ammonium, and after- 

 wards with water, dried at 150, and weighed. (See 

 No. 39.) 



The sulphide of antimony is precipitated from the 

 solution by dilute sulphuric acid, and the liquid ex- 

 posed to the air until most of the sulphuretted hydro- 

 gen has been dissipated. The precipitate is then 

 thrown upon a dried and weighed filter, well washed, 

 and dried at 100 till its weight is constant. 



Since the quantitative composition of this precipitate 

 is not accurately known, and since, moreover, it con- 

 tains some free sulphur, it must now be analyzed, and 

 either the sulphur or the antimony in it determined. 



To determine the amount of sulphur which it con- 

 tains, a weighed quantity is detached from the filter 

 and oxidized, very gradually and cautiously, in a flask, 

 with concentrated nitric acid. Concentrated hydro- 

 chloric acid is afterwards added, and the mixture di- 

 gested until all the antimony and all the sulphur are 

 dissolved. As soon as this is the case, so much tartaric 

 acid is added, that the solution may be diluted with 

 water without any precipitation taking place. If any 

 sulphur should have been separated in an unoxidized 

 state, it must be collected upon a weighed filter. The 

 sulphuric acid is then precipitated from the diluted 

 solution by chloride of barium, and the precipitate 

 washed with hot water. The quantity of sulphur, and, 

 in consequence, that of the antimony, are calculated 

 for the total weight of the precipitated sulphide of 

 antimony. 



For the direct estimation of the antimony, a weighed 

 portion of the original precipitate is introduced into a 



