Researches on the Salts of Selenious Acid. 



69 



The mixture of mercuric sulphide with sulphur and selenium thus precipi- 

 tated was treated with a warm solution of cyanide of potassium by means 

 of which selenium and sulphur were dissolved out and the mercuric sul- 

 phide remained. This was weighed, after washing- and drying at 100°, 

 and from the filtrate selenium was precipitated with hydrochloric acid. In 

 this manner, in which all the mercurous selenites have been analyzed, 



1) 0.514 gr. salt gave, immediately with hydrochloric acid, 0.0375 gr. se- 

 lenium = 0.0527 gr. selenious acid and from the filtrate 0.457 gv. mer- 

 curic sulphide = 0.4097 gr. mercurous oxide and 0.0173 gr. selenium or 

 0.0243 gr. selenious acid. 



2) 0.6495 gr. salt, treated with hydrochloric acid, immediately gave 0.0495 

 gr. selenium or 0.0695 gr. selenious acid and from the filtrate 0.58 gr. 

 mercuric sulphide = 0.52 gr. mercurous oxide and 0.022 gr. selenium 

 or 0.0309 gr. selenious acid. 



3) 0.7795 gr. salt heated to 100°, very slowly lost 0.0155 gr. water. 



Represented in 100 parts: 



experiment theory 



1. 2. 3. 



Mercurous oxide . 79.71 80.06 — 3Hg 2 1248 80.00 



Selenious acid . . 14.98 15.47 — 2Se0 2 222 14.23 



Water (loss) ... 5.31 4.47 1-99 5H 2 90 5/T7 



100.00 100.00 1560 100.00 



That the salt had this composition, may also be inferred from the 

 quantity of selenium first precipitated with hydrochloric acid, as compared 

 with that subsequently obtained from the solution. Their relation is namely 

 very nearly as 2 to 1. The following equation illustrates this transposition: 



2(Hg 6 .0\2SeO) + 24HCl = 12HgCP + 12H 2 + Se0 2 + 2Se, 

 showing that such must be the relation between these quantities of selenium. 



This result not agreeing with statements of Berzelius and Muspratt, 

 which do not, however, seem to be founded on any kind of analytical de- 

 termination, that neutral, waterfree selenite ought to be formed under the 

 circumstances under which I obtained the said basic salt, a statement, which 

 also Kohler J ), on account of a communicated analysis, asserts to be the 

 case, I repeated the preparation of mercurous selenite, employing a much 

 more concentrated solution of mercurous nitrate, than in the former case, 

 so that, on adding selenite of sodium, the salt was thrown down as a thick 

 pulpy precipitate. This was not, however, a neutral salt, but a 



') Ann. d Phys. u. Ch. LXXKIX. S. 146 (1853). 



