34 On Selenic Acid and other Selenium Compounds. [May 2, 



antimony with selenic acid until it dissolved, and then continuing the 

 heating until the excess of acid was driven off. It forms a white 

 crystalline mass, which under the microscope is seen to consist of 

 minute prisms. It is not very soluble in acids, but on boiling with 

 selenic acid for some time it dissolves slightly, but apparently without 

 formation of an acid salt, as the crystals deposited on evaporating 

 the solution have the same shape and size as the original salt. It is 

 not decomposed on boiling with water, nor is it soluble ; if, however, 

 the excess of selenic acid has not been expelled in its preparation, a 

 little of it dissolves in the weak acid formed, and crystallises out 

 again on cooling. 



Bismuthous Selenate. — This was prepared by boiling bismuthous 

 carbonate with selenic acid, and continuing the heating until the 

 excess of acid was expelled. It crystallises in minute white prisms. 

 It is insoluble in water, and is not decomposed by it on boiling, but 

 if selenic acid is present it dissolves. It is also soluble in sulphuric 

 acid on boiling, and readily in hydrochloric and nitric acid. Potash 

 and soda decompose it, uniting with the selenic acid. 



Platinic Selenate. — This was prepared by heating platinic chloride 

 with selenic acid until the hydrochloric and excess of selenic acid 

 were expelled. It is a dark-brown body, which dissolves slightly in 

 water on boiling, forming a yellowish-brown solution. It is insoluble 

 iu alcohol. It dissolves readily in hydrochloric acid, and leaves 

 metallic platinum on ignition. 



The Action of Phosphoric Anhydride upon Selenic Acid. 



When sulphuric acid is heated strongly with phosphoric anhydride 

 sulphuric anhydride is evolved ; on the other hand, the effect of heating 

 a mixture of anhydrous selenic acid and phosphoric anhydride to a 

 high temperature is, that selenious anhydride is given off, and not 

 selenic. In order to see if a different reaction occurs between the 

 latter two bodies at a lower temperature, some anhydrous acid was 

 mixed with phosphoric anhydride in a flask, which was then tightly 

 closed and placed in the water-oven. After heating for some time a 

 clear solution was obtained, and the flask was then removed and 

 allowed to stand in the cold. Crystals were slowly deposited, which 

 under the microscope were seen to be transparent cubes. The acid 

 liquid was drained off, and the crystals examined. So far as an 

 analysis could be carried out the result agrees with the view that the 

 body thus obtained is selenic anhydride, Se0 3 , but the quantity of 

 material at our disposal at the time was too small to admit of its 

 satisfactory separation and examination. We are, however, at present 

 engaged in operating upon larger quantities, and hope, at no distant 

 date, to submit our results to the Royal Society. 



