404 
Cast Steel, 
In all the varieties of iron and steel, the principal ingre- 
dient is metallic iron, and as this metal in the reguline 
state alone, has the property of giving out hydrogen gas 
while dissolving in dilute sulphuric or muriatic acids, 
the amount of inflammable gas thus produced has been 
adopted by Bergman, by Berthollet, and Pearson, as upon 
the whole the most satisfactory and compendious expo- 
nent of the quantity of reguline iron contained in any of 
the known varieties and forms of this metal. Thus a 
mixture of equal parts of reguline and oxydized iron by 
treatment with dilute sulphuric acid, will produce only 
half the quantity of hydrogen gas that an equal weight of 
pure iron would. But this can be admitted to be a per- 
fectly accurate mode of proceeding, only where the mix- 
ture thus analyzed, contains nothing that is soluble in 
hydrogen gas at the temperature, and in the other circum- 
stances under which the experiment is performed. None 
of the kinds of manufactured iron is entirely free from car- 
bon, and this according to Berthollet is taken up by the 
nascent hydrogen as the metal dissolves in the acid, w hence 
originates a material source of error, the quantity of gas 
produced depending not merely on the proportion of iron, 
but also of carbon in the mixture. It appears from Ber- 
thollet’s experiments that when cast iron or steel is treat- - 
ed by dilute sulphuric acid, at a boiling temperature, in 
proportion as the metal dissolves, a black spungy matter 
is observed floating in the solution : the quantity of this 
increases till the process is about half over, then it begins 
to diminish, and will be found to have entirely disappear- 
ed by the time that the last portions of iron have dissolved^ 
This black matter is carbon, which being insoluble in sul- 
phuric acid or sulphat of iron, must necessarily have been 
taken up by the hydrogen. This accordingly is found to 
be the case, for the gas produced requires a greater pro- 
portion of oxygen for its combustion, and the result of 
