Cast Iron, Steel, and Malleable Iron. 301 



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 final action of chemical forces " I 

 shall endeavour to show, that one o/' the first jpi'inciples 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 fine division (molecular separation), during 

 an iminterrupted 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 ]*169 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- 



