1889.] On Selenic Acid and other Selenium Compounds. 33 



In order to examine if selenic anhydride is produced in the manner 

 just described, the following experiments were made : — 



Some platinum sponge was introduced into a combustion tube, and 

 a quantity of selenious anhydride placed behind it. The platinum 

 sponge was kept at a red heat, and the selenious anhydride was also 

 heated until it sublimed. Oxygen, which was first dried by passing- 

 through a series of tubes containing calcium chloride and sulphuric 

 acid, was led through the platinum sponge, carrying the vapour of 

 the selenious anhydride with it. A white deposit formed in front of 

 the platinum sponge, which, on examination, was found to consist 

 solely of selenious anhydride. 



The experiment was repeated, substituting selenium for selenious 

 anhydride. The vapour of the selenium, on passing through the 

 platinum sponge, was oxidised to selenious anhydride, but no selenic 

 anhydride was formed. 



The next experiment was similar to the first, but platinum black 

 was substituted for platinum sponge. As before, only selenious 

 anhydride was deposited. 



In the next experiment selenious anhydride was mixed with 

 platinum sponge, and placed within a tube arranged in such a way 

 that it could be placed in an oil-bath. The temperature was then 

 raised gradually to 250°, oxygen being led through continuously. 

 At the temperature mentioned a sublimate formed, and this, as well 

 as the platinum sponge, was treated with water and tested, but no 

 selenic acid was found. 



The next experiment was similar to the last, except that the sele- 

 nious anhydride was mixed with platinum black instead of platinum 

 sponge, but, as before, nothing but selenious anhydride was obtained. 



As may be seen from the above experiments, we have been unable 

 to confirm the observation made by von Gerichten. 



We have found that oxygen in the active condition is unable to 

 oxidise selenious anhydride. Oxygen, which was first passed through 

 a series of drying tubes, was ozonised by means of a Houzeau's 

 ozoniser, and then led slowly through a tube containing selenious 

 anhydride for three hours and a half. At the end of that time the 

 tube was disconnected, the ozone displaced by a current of dried air, 

 and the contents of the tube dissolved in water and tested for selenic 

 acid, but no trace of it was detected. 



The Selenates of Antimony, Bismuth, and Platinum. 



In the examination of the action of heat upon selenates, the three 

 above mentioned were included. We have been unable to find any 

 published account of these, and accordingly give here a short descrip- 

 tion of them. 



Antimonious Selenate. — This body was formed by heating metallic 



VOL. XLVI. d 



