299 
Cast Iron^ Steely and Malleable Iron, 
a mass of iron with a mass of acid, and allows only a separated 
molecular contact between the iron and the acid. 
When the liquid contains a great deal of free acid, after the 
evolution of hydrogen has ceased, and the air has free access 
to it, the residuum, after the following invisible action has 
ceased, will be more or less plastic. If the liquid contains 
very little free acid and the air is excluded, a basic proto- 
chloride of iron is formed by the liquid attacking only the 
carburets of iron, leaving the sulphurets of iron, the carburets 
of silicon, and the higher carburets of iron, as a skeleton be- 
hind; a similar effect takes place when the solutions contain 
only chlorides of magnesium and sodium. When the air has 
access, the metal becomes oxidized by the air contained in the 
liquid, and forms invariably basic salts with the chlorides in 
solution, which, when washed away (as is the case when iron 
is immersed in the sea), the skeleton of carburets of iron, sili- 
con, &c. remain behind, which, from its highly spongy na- 
ture, condenses and compresses in its pores, when exposed to 
the atmosphere, atmospheric air in great quantity ; part of 
the iron is oxidized, and when the iron is in very large masses, 
the temperature is generally increased to the boiling point. 
The action of oxygen, by the presence of acid and water, 
on a solution of chlorides, presents one of the cases of chemi- 
cal decomposition by which two or more chemical bodies enter 
into a new combination by the sole presence of another che- 
mical body, which during the whole decomposition remains 
entirely unchanged. Berzelius explained this by a reference 
to a new force, which he called catalytic force, I shall, in 
another place — in my theory of ^^tJie fnal action of chemical 
forcesf — endeavour to demonstrate, that in fact no chemical 
combinations of tw bodies takes place without the catalytic 
presence of a third, or in fact, that all chemical combinatio7is 
and decompositions are produced by catalytic force. 
All cast iron, when dissolved in acids, provided the frag- 
ments retain their form after the action has ceased, show, after 
being washed on a filter, the same property of condensing air 
in their pores, and of increasing the temperature by the oxida- 
tion of the iron left in a lower state of carburation. If the li- 
quid contained very little free acid, very soon a basic salt is 
formed; and where the access of air is prevented during the 
progress of the solution, the remainder, when placed on a filter, 
oxidates extremely rapidly, and a hydrate of oxide of iron goes 
with the water through the filter, even after a week’s incessant 
washing. Similar and often highly-interesting results are ob- 
tained by a peculiar sort of chemical action, where one body 
slowly separates from others, by combining with a third, with- 
