9S On the Composition of Sulphuret of /Inthnomj. [Aug. 



weight of an atom of antimony ; a problem of some difficulty, on 

 account of the impossibility of hitherto obtaining the oxides of that 

 metal in a pure and uncombined state, so as to determine their 

 composition with the requisite precision. 



I employed a pure specimen of the common radiated variety, which 

 I had in my cabinet, and which 1 believe was found in the south of 

 Scotland; though I am not quite certain of this. The object 

 which I had in view, was to ascertain the whole of the sulphur 

 which the specimen contained. It is obvious, that as no foreign 

 matter was present, the knowledge of this would be sufficient to 

 determine the composition of the sulphuret. 



It is well known, that when muriatic acid is boiled upon this 

 sulphuret in powder, sulphurated hydrogen gas is given out in 

 abundance, while the oxide of antimony is taken up by the acid. 

 It would appear therefore, that in this case, the ore and the acid 

 determine the decomposition of a quantity of water, the hydrogen 

 of which Combines with the sulphur, and flics off in the state of 

 gas, while the oxygen unites with the metal and converts it into an 

 oxide, which is taken up by the aeid. It occurred to me, it) con- 

 sequence of my knowledge ot-this, that in order to know correctly 

 the composition of sulphuret of antimony, it would be merely 

 necessary to decompose a determinate weight of it by means of 

 muriatic acid and hear, and receive the sulphureted hydrogen gas 

 over mercury. The knowledge of the quantity of this gas ob- 

 tained, would not only show the quantity of sulphur in the 

 ore, but enable me also to determine the quantity of oxygen which 

 had united with the metal. But upon repeating this experiment 

 two or three times, I found that the analysis of the ore in this way 

 could not be depended on. For there always sublimed into the 

 neck of the retort a quantity of golden sulphur of antimony (pro- 

 bably a hydrosulphureted autimonial oxide) which I could neither 

 collect with precision, nor allow for in a satisfactory manner. 



Disappointed in this process, I had recourse to the well known 

 action of nitro-miiriatic acid upon sulphuret of antimony. Into a 

 large phial I put 100 grains of the pure ore in the state of a fine 

 powder, and poured over it a quantity of nitro-muriatie acid. 

 When the action was over, I decanted off the liquid portion, and 

 treated the undissolved residue with fresh portions of acid, till 1 had 

 reason to be satisfied that all the metallic part of the ore was 

 taken up. The residuum being now dried had all the appearance 

 of sulphur. It weighed ten grains, and when kindled, burnt all 

 away with a blue flame, leaving no appreciable residue. 



The acid solutions being mixed I , were poured into about 



a quart of distilled water, in order to precipitate the oxide of anti- 

 mony. For greater security, I then saturated the aeid in this 

 watery solution with ammonia. The white precipitate, being sepa- 

 rated by the filter, was well washed and dried. In this state it 

 weighed 93T-5 grains; and as far as I' could judge, was a pure oxide 

 •f aritimoi . 



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