301 
Cast Iron, Steel, and Malleable Iron. 
feet liberty of its molecules, combines with other bodies or takes 
a new form of very different quality, under which all precipi- 
tates, separated from the solvent liquid, exist. 
In my theory of “ The Jinal action of chemical forces ’’ I 
shall endeavour to show, that one of the first principles of 
the formation of the productions of animated life is in fact only 
an action of the before-mentioned chemical forces under differ^ 
ent circumstances, which may be expressed in the short sen- 
tence: extremely fne division (molecular separation), during 
an uninterrupted motion. 
When very gray cast iron is treated by hydrochloric acid, 
the residuum is a white substance, mixed with black scales of 
graphite, which Karsten considers as being mechanically 
mixed with the mass of the iron before solution, and contrasts 
it with the black precipitate which separates from white cast 
iron, which has a dull earthy appearance ; but when this so- 
called dull and earthy powder of white cast iron is produced 
by a tolerably diluted acid, and viewed, while still in suspen- 
sion in the liquid, under a certain angle of vision, all the 
small particles appear to consist likewise of scales, as we shall 
hereafter perceive, which reflect the light with the same power 
as the scales of graphite, their only difference from them con- 
sisting in a different chemical composition. They are there- 
fore more easily decomposed, and apt from their softer nature 
to adhere rather closer to each other, in which state their 
scaly or foliaceous nature is not so easily to be discovered. 
To ascertain the relative combinations of the elementary 
constituents of the different sorts of iron of commerce, the 
treatment by means of acids is indispensable, and I prefer 
the hydrochloric and nitric acids to all others. 
The quantity and in part the quality of the different com- 
binations obtained by treatment of the iron with hydrochloric 
acid, depends a great deal on the density of the bodies brought 
into chemical contact, or, in other words, on their specific gra- 
vity. 
If irons of different specific gravity are dissolved in hydro- 
chloric acid of the same specific gravity, the residuums will 
have a different appearance. 
If filings of Swedish iron, for example, double bullet iron 
of the specific gravity 7*810, is dissolved in hydrochloric acid 
of the specific gravity of T169 in comparison with English 
iron of the specific gravity 7*60, the residuum of Swedish 
iron will appear in distinct heavy grayish scales, that of 
English iron in brown flocculent rags, partly remaining on 
the bottom of the phial and partly suspended in the liquid. 
But if the specific gravity of the acid is increased, the resi- 
