on various Ohjecls* 411 



two substances is almost precisely the same*. Its aqueous 

 solution is of a claret colour; but it soon becomes brown, 

 and deposits tellurium, by exposure to air. When disen- 

 gaged from an alkaline solution by muriatic acid, it reddens 

 moistened litmus ; but after being washed in a small quan- 

 tity of water, it loses this property ; l)ut in this case like- 

 wise it is partially decomposed by the air in tlie water; so 

 that it is not easy to say, whetlier the power is inherent in 

 it, or depends upon the diffusion of a small quantity of 

 muriatic acid through it. In other respects, it resembles ~ 

 a weak acid, combining with water, and with the alkalies. 

 It precipitates most metallic solutions. It is instantly de- 

 composed by oxymuriatic acid, depositing a film, at first 

 metallic, but which is SQon converted into muriate of 

 tellurium f. 



As arsenic has an affinity for hydrogen, it occurred, ta 

 me as probable, that it would present some pheenomena 

 analogous to those offered by tellurium, in its action upon 

 potassium, and in its operation upon water, when electri- 

 fied. 



Arsenic made the negative surface, in water, by means 

 of a part of the new battery, containing 6()0 double plates, 

 became dnrk-coloured, and threw down a brown powder j 

 but it likewise gave off a considerable quantity of inflam-r 

 mable gas. 



Arsenic negatively electrified in a solution of potash, 

 likewise afforded elastic matter ; but in this case the whole 

 .solution took a deep tint of brown, and was pellucid; but 

 it became turbid, and slowly deposited a brown powder, by 

 the action of an acid. When arsenic was made the negar 



* In some experiments, made on the action of tellurium and potassium, ia 

 the laboratory of my frieiid John George Children, esq. of Tunbridge, in 

 which Mr. Children, Mr. Pepys, and Mr. Warbutton co-operated, th^ ana- 

 logy between the two substances struck us so forcibly, as for some time to 

 induce us to conceive that tellurium mi«;ht contain sulphur, not manifested 

 in any other way but by the action of Voltaic electricity, or by potassium ; 

 and some researches made upon the habitudes of difFerent metallic sul- 

 phurets,at the Voltaic negative surface, rather confirmed the suspicion ; for 

 most of the sulphurets that we tried, which were conductors of electricity, 

 absorbed hydrogen in the Voltaic circuit. Tlic great improbability, how-r 

 ever, of the circumstance that sulphuric acid, or sulphur in any state of oxy- 

 genation could exist in a metallic solution, which was not manifested by the 

 action of barytes, induced me to resist the inference ; and further researches, 

 made in the laboratory of the Royal Institution, proved that the substance 

 jn question was a new and singular combination. 



+ From the results of one experiment which I tried, it seems that tel- 

 lurium, merely by being heated strongly in drv hydrogen, enters into com- 

 bination with it. An accident prevented me from ascertaining whether the 

 fomp'ound so formed, is exactly the same as that described m the text. 



' tivp 



