1819.] Lead and Arsenic. 97 



Some bits of this compound sulphuret heated in a tube over a 

 candle, melted, and a red sublimate rose, which became yellow 

 on cooling, and looked like brpiment. 



Some of this ore, being fused with nitre, deflagrated, and 

 became a white oxide. The solution of this nitre afforded a 

 white precipitate with muriate of barytes ; and with nitrate ok 

 silver, a brick-red precipitate of arseniate of silver. 



The white precipitate by muriate of bary tes was only partially 

 soluble in nitric acid. The insoluble part of this precipitate, of 

 which the quantity was so minute that no balance would have 

 been sensible to it, was carefully collected on to a very small 

 bit of charcoal fixed to a pin. It was then strongly heated at 

 the blow-pipe. This bit of charcoal now put into a drop of 

 water, placed on a silver coin, immediately made a black stain of 

 sulphuret of silver on the coin. This is the nicest test 1 am 

 acquainted with of the presence of sulphur, or sulphuric acid, in 

 bodies. 



The quantity I possessed of this mineral for experiment was 

 very small. The above trials were made with particles little 

 more than visible ; however, the results, I think, sufficiently 

 establish the nature of the constituent parts. Their respective 

 proportions must remain for inquiries on another scale. 



Article III. 



Researches on a new Mineral Body found in the Sulphur extracted 

 from Pyrites at Fahlun. By J. Beczelius. 



{Continued from vol. xiii. p. 412.) 



_ Composition of Selenic Acid. — I have found it almost impos- 

 sible to determine exactly the composition of selenic acid 

 directly. Among the methods to which I have had recourse, 

 none has appeared to me better than the analysis of the double 

 acid of which I have just given aa account. 



To make this analysis, 1 took a piece of barometer tube, and 

 blew two hollow spheres in the middle of it at the distance of 

 two inches from each other. Into one of these balls I put a 

 piece of selenium, after determining its weight with accuracy. 

 I then drew out the two ends of the barometrical tube into tubes 

 almost capillary. The object of the second ball was to receive 

 the vapours of the double acid which might be volatilized by the 

 heat evolved in the ball containing the selenium. The apparatus 

 thus prepared was accurately weighed. I then introduced into 

 it chlorine gas, which had passed through a tube 21 inches in 

 length, and filled with dry muriate of lime. The gas was intro- 

 duced by the tube till it came in contact with the selenium, and 



Vol. XIV. N° II. G 



