08 Berzelius on a new Mineral Body, [Aug. 



the operation was continued for five hours ; or till the selenium 

 was entirely saturated with the gas. The double acid thus 

 obtained had some yellow spots which 1 was unable to make 

 disappear. The chlorine remaining in the apparatus was now 

 expelled by common air, which was made likewise to pass 

 through the muriate of lime. The apparatus was now weighed. 

 Its weight had increased 1*79 gramme, the original weight of 

 the selenium being one gramme ; consequently the weight of 

 the double acid was 2-79 grammes. If, according to the result 

 of experiments stated elsewhere,* 100 of chlorine gas supposes 

 22*59 of oxygen, it follows from this experiment that 100 of 

 selenium have combined with 40-436 oxygen. 



But as it might be supposed that, notwithstanding the pre- 

 cautions which I had taken, the gas absorbed retained water, I 

 endeavoured to determine the point in the following way : I 

 dissolved the double acid in water, taking care that nothing was 

 lost, and precipitated the liquid by nitrate of silver. The preci- 

 pitate, which was a mixture of muriate and seleniate of silver, 

 was washed with boiling water, acidulated with nitric acid, as 

 long as it continued to carry off any portions of seleniate of 

 silver. The muriate of silver, washed, dried, and melted, 

 weighed 7-2285 grammes = 1-38 gr. of anhydrous muriatic acid, 

 and = 40-274 of oxygen combined with 100 of selenium. If we 

 admit that this analysis was made without loss, the chlorine 

 must have contained 0*0073 gr. of humidity ; but as it is scarcely 

 possible to avoid some loss, we may presume that the true quan- 

 tity of oxygen is between 40*274 and 40*436. I, therefore, 

 assume 40*33 for 100 of selenium. 



In another experiment, in which I was able to procure only 

 0*937 gramme of double acid, I obtained 2*43 gr. of fused muriate 

 of silver. This amounts to 40* 1 of oxygen to the 100 of sele- 

 nium ; but I consider the result of the first experiment, which 

 was on a larger scale, as more entitled to confidence ; especially 

 because the other served to enable me to study this method of 

 analysis. 



It follows then that selenic acid is a compound of 



Selenium 71*261 100*00 



Oxygen 28*739 40*33 ■ 



100*000 



From experiments, of which I shall give an account below, it 

 appears very probable that selenic acid contains two atoms of 

 oxygen for one atom of the radical. On this supposition, an 

 atom of selenium will weigh 495*91, an atom of oxygen being 

 considered as weighing" 100. 



1 made an experiment to saturate the double acid with sele- 

 nium till it ceased to dissolve it even when assisted by heat, and 



• Afhandlingar i FjMk Kemi ocb Mioeralogi, v. 381, 



