Cast Iron, Steel, and Malleable Iron. 299 



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 o^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. reoiain 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 ^Hhe Jinal action of chemical 

 foy'ces" — endeavour to demonstrate, that in fact 7io chemical 

 combiiiations of fwo bodies takes place without the catalytic 

 presence of a third, or in fact, that all chemical combinatioTis 

 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- 



