1^25.] Seleniurets of the Eastern Harz, sxA^^ 291 



1 chose, for a quantitative analysis, small ciitic morsels, 

 whose specific gravity was, by one experiment, 7-876 ; by 

 another 7*804. I analysed them, like the rest, by chlorine, but 

 *l was obliged to vary the process, in consequence of the chloride 

 ©f mercury subliming with the chloride of selenium. Corrosive 

 s'ublimate was always formed in these analyses, but never any 

 9a}omel, and consequently the product was always wholly dis- 

 silved by the water in the receiver. Corrosive sublimate has 

 some resemblance to perchloride of selenium, but is less volatile., 

 Kiid forms long brilliant needles, which are never found in ,cJiJ5)-: 

 i^ide of selenium. ' "V 



"''I made several unsuccessful attempts to separate the oxide of 

 tnercury from the selenic acid contained in the liquid in which 

 those two substances were dissolved. M. Berzelius has already 

 observed that the caustic alkalies or their carbonates only 

 imperfectly separate selenic acid from oxide of mercury, and in 

 f^Ct cannot be wholly precipitated from its solution in other acids 

 by the alkalies. I endeavoured to obtain the mercury of the 

 mineral by mixing the latter in powder with dry carbonate of 

 soda, or carbonate of lime, and heating the mixture ; but it was 

 not easy to obtain the whole of the mercury by this method. 



Hydrosulphuret of ammonia, however, throws down the 

 whole of the mercury from its alkaline solutions, and, according 

 to my experiments, even a great excess of the hydrosulphuret 

 does not redissolve the sulphuret of mercury, at least in the cold, 

 i did not expect this result, because the preparation of cinnabar, 

 in the moist way, depends on the solubihty of sulphuret of 

 mercury in hot hydrosulphuret of potash. 1-656 gramme 

 (24 grains) of the mineral gave 1*168 gramme (17-6 grains) of 

 chloride of lead which contain 0*87 gramme (13*5 grains) of lead. 

 The whole of the chloride dissolved perfectly in the water. 



The liquid in which the volatile chlorides were dissolved was 

 mixed with caustic ammonia, and then hydrosulphuret of ammo- 

 nia added in excess. Sulphuret of mercury fell down which,, 

 when collected on a weighed filter, and carefully dried, weighed 

 0-306 gramme (4*8 grains). I did not analyze this sulphuret, 

 but as the hydrosulphuret of ammonia employed had been 

 recently prepared it could not contain any free sulphpr. It^ 

 contained, therefore, 0-264 gramme (4 grains) of mercury. The . 

 liquid from which the mercury had been separated was acidulatedj 

 by muriatic acid, and heated to expel the sulphuretted hydrogen. ' 

 The sulphuret of selenium was oxidated by aqua regia, and the 

 solution added to the liquor from which the sulphuret of sele- 

 nium {mercury!) had been precipitated. The selenium was 

 reduced by sulphite of ammonia after the nitric acid of the aqua 

 regia had been decomposed as far as possible by muriatic acid. 

 The quantity of selenium obtained was 0-389 gramme (6 grains.) 

 The result of the analysis, therefore, per cent, is, 



u 2 



