852 Mr. D. Forbes's Researches in 



portion of the iron, and the greater part of the copper, zinc, and 

 lead in the form of chlorides. 



B, a solution containing all the antimony, along with part of 

 the iron and a little zinc, copper, and lead, all in the form of 

 chlorides, as well as all the sulphur contained in the mineral, 

 which, however, in order to simplify the analysis, was neglected 

 and determined separately upon another portion of the mineral. 



This solution was now heated to boiling, and after being fil- 

 tered from the floating flakes of sulphur, was precipitated by a 

 current of sulphuretted hydrogen gas passed through it, by 

 which the whole of the antimony, along with traces of copper 

 and lead and some free sulphur, were thrown down. This pre- 

 cipitate was washed off the filter into a stoppered bottle and 

 treated with excess of hydrosulphide of ammonium, which, by 

 dissolving out the sulphide of antimony and free sulphur, left a 

 minute quantity of the sulphides of copper and lead behind, 

 which were added to the same sulphides obtained in the treat- 

 ment of the solid residue A. 



The filtrate, containing the antimony, was now supersaturated 

 with sulphuric acid ; and after the precipitated sulphide of anti- 

 mony along with free sulphur had been collected on a filter pre- 

 viously dried at 212° F. and tared, they were dried at 212° and 

 the weights determined. 



A weighed portion of this was now fused with a mixture of 

 four parts of nitrate of soda along with two parts of carbonate 

 of soda in a platinum crucible, digested with water, the anti- 

 moniate of soda collected upon a filter, washed with dilute alco- 

 hol, and determined, the amount of antimony being then cal- 

 culated from this result. 



The filtrate from which the antimony had been precipitated 

 by sulphuretted hydrogen, and which now contained the iron 

 with a little zinc, was added to the similar product obtained in 

 the treatment of the solid residue A. 



The solid residue A was treated as follows : — Water acidulated 

 with a little hydrochloric acid being added, all the copper, iron, 

 zinc, and some of the lead dissolved, leaving the silver (as chlo- 

 ride), insoluble quartz, and a trace of chloride of lead behind; 

 these were filtered off, well washed with water to dissolve out the 

 trace of chloride of lead, and the chloride of silver, along with the 

 insoluble quartz, then determined ; and afterwards the former 

 was dissolved out by ammonia, leaving the quartz behind, which 

 was estimated. 



The copper and lead in this solution were now precipitated by 

 sulphuretted hydrogen, and the sulphides, added to those previ- 

 ously obtained (solution B), were converted into anhydrous sul- 

 phates, weighed conjointly ; and the sulphate of copper being 



