5G6 Proceedings of the Poyal Society 
8. Bismutho-hypobismuthic oxide (I tliink the oxide Bi 4 0 7 may 
he thus named) is a heavy dark grey crystalline salt ; the specific 
gravity varies, according to the method of preparation, from 7 *8 to 
8 '5 (at 20° referred to water at the same temperature, weighings 
made in benzene), which is higher than that of any other oxide of 
bismuth. This oxide suffers no loss of weight at 300° ; it gives off 
oxygen at a red heat with production of Bi 2 0 3 . It undergoes no 
change either in ordinary or in moist air, nor is it affected when 
covered with water and exposed to direct sunlight for some days. 
Strong hot nitric acid readily dissolves this oxide with formation of 
a purple-red liquid, which is slowly decomposed on evaporation. 
A solution of the salt in strong hydrochloric acid, which solution 
is also red-coloured, is more quickly decolorised on boiling ; hot con- 
centrated sulphuric acid partly dissolves this oxide, forming a brown- 
red liquid, and partly converts it into an almost colourless salt, which, 
after being washed free from acid, appeared to be (Bi0) 2 S0 4 H 2 0 
(Bi found = 75 , 0 per cent.; calculated = 74'21 per cent.). The 
sulphuric acid solution, on evaporation, yielded colourless crystals 
which, after drying on a porous tile, contained about 56 per cent, of 
bismuth (Bi 2 .3S0 4 requires 59 ‘32 per cent.). I think it very 
probable that the green oxide of bismuth described by Arppe, 
(Pogg. 64, 237) as produced by the action of boiling nitric acid on 
(so-called) bismuthic acid, consisted of Bi 4 0 7 containing a little 
undecomposed Bi 2 0 5 . 
6. Mathematical Note. By Mr. T. B. Sprague. 
7. On the manner in which Silicon, Phosphorus, Manganese, 
and other elements exert their influence upon Steel. 
By 11. Sydney Marsden, D.Sc., F.R.S.E., F.C.S., &c. 
(Abstract). 
This paper is a continuation of the author’s previous paper on 
“ Ihe state of carbon in iron and steel, a new hypothesis of the 
hardening of steel” (read on the 19th December 1881, see p. 368), 
and is an attempt to give an explanation in accordance with the 
