586 Dr, Schafhaeutl on the Different Species of 
35 grains of this steel dissolved in hydro-chloric acid of 
sp. gr. = 1*104, deposited on the vault of the retort, soon 
after the acid began to act upon the iron, a dark ring of car- 
bonaceous matter twice the diameter of the space occupied 
by the steel filings at the bottom of the retort. The inside of 
this ring was gradually filled up by the black residuum, 
whilst at the same time it collected in rays around the filings 
at the bottom of the retort, which filings in the same ratio 
disappeared, till the space formerly occupied by them was 
filled up entirely by the black powder, gradually increasing 
towards the centre, each grain of this black powder retaining 
the form of the particle of steel filing from which it had its 
origin. The action of the acid and the evolution of gas had 
not ceased in three weeks. The residuum, of a dark brown 
greenish colour, was equal to T995 grains. Heated in a pla- 
tinum crucible, a single bright spark appeared towards the 
centre, which immediately disappeared. Long after this the 
mass ignited within the crucible, and had increased in weight 
= 0*959. After being treated by hydrochloric acid, 0*381 
of silica remained, contaminated with a little iron. The 
greatest quantity of arsenic was found to be contained in the 
acid from the retort. 
Arsenic, sulphur, silicon, and azote are constituent parts 
of all the best English steel which I have analysed, made 
from the Dannemora iron, called Hoop L. and double 
Bullet. Their relative proportions in all specimens are 
nearly the same. In some specimens of very hard steel 
I found the carbon increased to 1*69 per cent. It is 
scarcely necessary to add, that the arsenic, antimony, and tin 
were precipitated together by a current of sulphuretted hy- 
drogen, and sometimes by means of hydro-sulphuret of am- 
monia. The precipitate was divided into two equal parts ; 
one part dissolved in aqua regia, the diluted solution mixed 
with tartaric acid and the quantity of sulphuric acid ascer- 
tained in the usual way. The other portion of the precipi- 
tate obtained by sulphuretted hydrogen was heated carefully 
in a glass capsule in a current of dry hydrogen, till the arse- 
nic was driven off. The antimony and tin were of course 
left behind. I endeavoured to separate both these, as pro- 
posed by Gay Lussac, by dissolving the residuum in aqua re- 
gia, and precipitating one half of the solution by means of 
metallic zinc ; the other by metallic tin, which only separates 
the antimony. But to gain an exact result, a larger quantity 
of the material for analysis is necessary than can be conve- 
niently obtained by analysing iron. 
If a current of sulphuretted hydrogen is driven through an 
