on various Objects. 409 



potassium, and T find that instead of proving that potassium 

 IS a compound of potash and hydrogen, they confirm the 

 idea of its being as yet like other metals undecompounded. 



When tellurium is made the positive surface in water, 

 oxygen is given off; when it is made the negative surface, 

 the Voltaic power being from a battery composed of a 

 number of plates exceeding 300, a purple fluid is seen to 

 separate fioin it, and diffuse itself through the water; the 

 water gradually becomes opake and turbid, and at last de- 

 posits a brown poXvder, The purple fluid is, I find, a so- 

 Kuiou of a <:omp()und of tellurium and hydrogen in water; 

 which, in being diffused, is acted upon by the oxygen of 

 the common air, dissolved in the water, and gradually loses 

 a part of its hydrogen, and becomes a solid hydruret of 

 tellurium. The compound of hydrogen and tellurium pro- 

 <luced at the negative pole when uncombincd is gaseous at ' 

 connnon temperatures, and when muriatic acid or sul- 

 phuric acid are present in the water, it is not dissolved, but 

 IS given off, and may be collected and examined. 



1 acted upon potash by means of a surface of tellurium, 

 negatively electrified, by a part of the large Voltaic appa- 

 ratus latelv constructed on a new plan in the laboratory of 

 the Royal Institution, an account of which, with figures, 

 will be found annexed to this paper. 1000 double plates 

 were used. The potash was in the common state, as to 

 dryness. There was a most violent action, and a solution 

 of the tellurium, w^ith much heat, and a metallic mass, 

 not unlike nickel in colour, was formed ; which when 

 touched by water, did not inflame nor effervesce, but ren- 

 dered the water of a beautiful purple colour, and when 

 thrown into water entirely dissolved, making a bright pur- 

 ple tincture. It immediately occurred to me, that the 

 whole of the hydrogen, which in common cases would 

 have been furnished from the decomposition of the water, 

 had in this instance combined with the tellurium, and that 

 the telluretted hydrogen (if the name may be used) had 

 formed with the oxidated potassium, i.e. the potash, a 

 peculiar compound, soluble in water ; and this I found to 

 be the case ; for on pouring a little diluted muriatic acid 

 into the mixture, it effervesced violentlv, and gave a smell 

 very like that of sulphuretted hydrogen; metallic tellurium 

 was formed where it came in contact with the air, and 

 muriate of potash was found dissolved in the mixture. • 



It seemed evident from this fact, that in 'the action of 

 tdlurium negatively electrified upon potash, potassium was 



produced 



