ON THE CI{EMICAL NATURE OF CAST IRON. 343 
hydrochloric acid, and precipitating the solution by ammonia, washing the 
oxide, and reducing it. The iron thus prepared contained sulphur. The 
next experiments were made by dissolving the crystalline oxide in hydro- 
ehloric acid, digesting with chloride of barium for several days, decanting 
and filtering through paper (previously digested with dilute nitric acid), pre- 
cipitating by ammonia (distilled from ammonia to which chloride of barium 
had been added), washing, and reducing the oxide. The iron thus prepared 
still contained sulphur. 
The third series of experiments were made with sublimed proto- or sesqui- 
chloride of iron by dissolving it in water, precipitating with pure ammonia, 
washing, and reducing in hydrogen. All the specimens thus prepared 
contained sulphur. The sublimed chloride was obtained sometimes from the 
red oxide prepared by heating the oxalate of iron, obtained as above described, 
or from the crystalline oxide by dissolving it in hydrochloric acid, digesting 
with chloride of barium, evaporating to dryness, and subliming either in 
platinum vessels or in porcelain tubes, or in clay retorts, either alone or in a 
eurrent of chlorine or of hydrochloric-acid gas. 
In the fourth series of ewperiments the metal produced by either of the 
aboye methods was submitted in the platinum-tube, whilst red-hot, alterna- 
tively to the influence of hydrogen and oxygen, or hydrogen and steam, or of 
yapours of nitric acid and hydrogen, or of ammonia yapours, oxygen, and 
hydrogen. In all the cases the operation was repeated several times, and 
although sulphuretted hydrogen was given off during these operations, yet 
the iron always contained sulphur. 
Further experiments were made by dissolving the purest iron in dilute 
acetic acid, evaporating to dryness and heating. The metal obtained still 
contained sulphur. 
Also the iron obtained from ferrocyanide of potassium* was found to contain 
sulphur. 
In fact we have never made or found a specimen of iron which did not 
contain sulphur. Even electrotype iron, said to be prepared from chloride of 
iron, eyolyed, by dissolving in dilute hydrochloric acid, a very appreciable 
quantity of sulphuretted hydrogen. 
On the whole we have made upwards of seventy series of experiments. 
From the above it will be seen that we have not yet obtained a method of 
preparing iron free from sulphur. In fact one great difficulty is to obtain 
vessels which will not give up sulphur to the iron in some form or another. 
For instance, the platinum-tube had to be polished and boiled out with acid 
eyery time before use. It may be mentioned that the hydrogen employed 
was led through the platinum-tube before reducing the oxide of iron for a 
quarter of an hour or more, and yielded no sulphuretted hydrogen. 
Although no positive results have been obtained, we have in no ways lost 
hope of preparing iron free from sulphur. No doubt, on a very small scale, 
this might be done without much trouble; but we must bear in mind that 
our method must be such a one as to allow the preparation of pure iron on 
at least the ounce-scale. 
November 1868.—The amount of sulphur contained in some specimens 
prepared since the Meeting of the Association amounted to only 0-001 to 
0-005 per cent., the presence of the former quantity being easily detected 
both by the smell as well by the lead paper. 
*® Crystallized from a solution containing chloride of barium. 
