42 



L. F. Nilson, 



in nitric acid, the excess of solvents expelled, and hydrochloric acid and 

 sulphurous acid were added, without causing any selenium to be precipita- 

 ted. It was not before long continued boiling that the solution showed a 

 slight opalization in red; no doubt, a small quantity of selenide of lead 

 had been formed by reducing gases under the heating. This circumstance 

 and the loss observed, too high by 6 pr. ct., induced me to repeat the ex- 

 periment of heating in an atmosphere of oxygen, which proved with full 

 evidence, that selenite of lead, at a red heat, is decomposed into subliming 

 selenious acid and remaining oxide of lead. 



1.278 gr. selenite of lead lost thus, after about an hour's heating in 

 the flame of a Bunsens gas-burner 0.427 gr. or 33.41 pr. ct, the cal- 

 culated loss being 33.23 pr. ct. 



Berzelius' statement, that the salt on heating to whiteness yields a 

 residue of basic salt, was consequently not confirmed. 



2. Diselenite : Pb.0 2 .SeO + SeO 2 . 



As Berzelius has already remarked, selenious acid does not seem 

 to dissolve the neutral salt of lead. By treating the salt with 1 and 3 mol. 

 of acid, evaporating the acid solution to dryness and allowing it to act in 

 a concentrated state, there was in both cases obtained an anhydrous salt 

 of the above-mentioned composition, in form of microscopic, four-sided, 

 rifled prisms. 



Analyses: 



1) 0.4428 gr. salt, fumed with sulphuric acid, gave 0.31 gr. sulphate of 

 lead or 0.2281 gr. oxide of lead. 



2) 0.546 gr. salt gave likewise 0.3632 gr. sulphate or 0.2673 gr. oxide 

 of lead. 



Calculated on 100 parts: 



found calculated 



Oxide of lead 51.51 48.96 PbO 223 50.11 



Selenious acid (loss). . . : _48.49 51.04 2Se0 2 222 49.89 



100.00 100.00 445 100.00 



As the salt, when tested, was not found to contain any water, sele- 

 nious acid was determined only as a loss; the analysis 1) refers to a material, 

 prepared without excess of acid, 2) on the contrary to a specimen, pro- 

 cured by adding 3 mol. selenious acid to the neutral salt, by which the 



