[ ul ] 
II. 
NOTE ON THE ACTION OF PHOSPHINE ON SELENIUM 
DIOXIDE. By SIR CHARLES A. CAMERON, M.D. 
[Read Novemser 16; Received for publication Novemper 18, 1892; Published 
March 25, 1893. ] 
A current of dry phosphine gas was conducted into a solution of 
- selenium dioxide. Instantly a rich yellow precipitate began to 
form, but in about a minute it commenced to darken, and soon 
acquired a reddish hue from presence of precipitated selenium. I 
thought it possible, though far from probable, that a compound 
analogous to ammonium selenosomate (NH,Se0,(NH.)) might be 
formed. It was clear that some body was formed by the action of 
the phosphine, first because of the deep yellow precipitate, and 
secondly because I found that an alcoholic solution of selenium 
dioxide could be made to completely absorb and retain a large 
quantity of phosphine. Owing, however, to the instability of the 
yellow compound, its composition could not be satisfactorily deter- 
mined. Exposing it to low temperatures, and rigorously excluding 
atmospheric air from the solution in which it was formed, had no 
appreciable effect in retarding its decomposition. 
The altered yellow substance when dried in vacuo became of a 
dull red colour, and its odour was very offensive, even for a sele- 
nium compound. It became black on being heated, and in part 
~ volatilized. On being boiled with nitric acid it was converted into 
a mixture of phosphoric and selenious acids, the latter slightly pre- 
ponderating. 
Phosphine does not precipitate all or even the greater portion 
of the selenium from the alcoholic solution of selenium dioxide. 
Generally the greater part of the selenium remains in solution. 
When phosphine ceases to act on the selenium oxide, and when the 
precipitated matter is filtered off, the filtrate is found to have a 
yellow colour. Evaporated in vacuo, a yellow oily body remains 
which is ethyl selenide (C,H;),Se. A portion of the selenium which 
separates from the compound formed by the action of phosphine 
on selenium oxide exercises a reducing action on the alcohol, and 
produces ethyl selenide. 
