1819.] M. Labillardiere on a new Acid. 265 



Seleniate of soda was employed by me to determine the degree 

 of saturation of the acid in the alkaline seleniates, and to com- 

 pare it with what takes place in the earthy and metalline 

 seleniates. The analysis of these salts, however, is not so 

 simple as it appears at first sight. 



1 attempted to precipitate the solution of the seleniate rendered 

 acid by the muriatic acid necessary to saturate the soda by 

 passing through it a current of sulphuretted hydrogen gas as 

 long as any precipitate fell. But the precipitation was not 

 complete ; for on evaporating the liquid, sulphuret of selenium 

 still continued to fall. The muriate of soda, when heated to 

 redness, gave out a strong odour of selenium, and the crucible 

 was attacked. The best mode of performing the analysis is to 

 heat the neutral seleniate of soda with twice its weight of sal- 

 ammoniac. By this means the selenium is driven off, and 

 nothing remains but muriate of soda. 



One hundred parts of seleniate of soda that had been strongly 

 heated and then reduced to powder produced, by such an opera- 

 tion, 66|- parts of muriate of soda, equivalent to 35-5 parts of 

 soda. Therefore 100 parts of selenic acid had been combined 

 with 55 parts of soda, containing 14T1 of oxygen; or very 

 nearly half the oxygen contained in the acid. 



One hundred parts of the biseleniate, which had been fused 

 under a gentle heat, to drive off the water of combination (but 

 it was impossible to prevent traces of the acid from appearing in 

 the last portions of the water), produced by the same analytical 

 method, 41f parts of muriate of soda, equivalent to 22-17 parts 

 of soda: 100 parts of the acid, therefore, were combined with 

 28-48 parts of soda, containing 7-5 parts of oxygen; which 

 exceeds a little half the quantity found by experiment in the 

 neutral salt. I ought to mention that it is veiy difficult to obtain 

 these salts at their true point of saturation, when we want them 

 dry, since, in the biseleniate, we cannot separate all the water 

 without, at the same time, driving off a small portion of acid. 

 On the other hand, when we endeavour to obtain the neutral 

 seleniate by heating a seleniate containing a small excess of 

 acid, this excess is not driven off, except by a long exposure to 

 the action of the fire. 



(To be continued.) 



Article V. 



Memoir on a new Acid produced during the Calcination of 

 Muck Acid* By M. Houton Labillardiere. 



While treating sugar of milk with nitric acid, Scheele disco- 

 vered a peculiar acid, to which he gave the name of saclactic 



* Translated from the Annates de Cliimie et dc Physique, ix. 365. 



