Lawrence Scientific School. 349 
_ Jron—A. solution of peroxyd of iron becomes of a deep vi 
let color upon the addition of hyposulphite of soda; after a 
short time the color disappears and the iron is reduced to prot- 
oxyd. According to Fordos’ and Gélis, the reaction which 
takes place in this case is represented by the equation 
Fe,Cl, + 2NaO.S,0, = NaCl + 2Fe0!+ Na, 8,0,. 
omy to the air, and is not sensibly dissolved by strong chlor- 
y 
The boiling must be continued until the whole of the sulphurous 
acid is expelled. Chancel applies this reaction to the quantita- 
tive Separation of alumina from iron, but I have always found 
that the complete precipitation of the alumina is, to say the . 
extremely difficult. This may be due to the formation of a sul- 
Phite which is not decomposed by boiling. When a solution of 
alum is heated to 120° C, with a strong solution of hyposulphite 
f soda the whole of.the alumina is precipitated after a short 
time, as a hydrate mixed with sulphur. The precipitate is white 
and of a peculiar semi-gelatinous charactér; it 1s more easil 
Washed than the ordinary hydrate thrown down by ammonia, It 
® Ann. de Chimie et de Physique, viii, 351. 
