ACTION OF WATER ON IRON. 



267 



It is obvious that each of these must be considered, not as a 

 binary alloy, but as a ternary compound of two metals with 

 carbon, or of one metal with a carburet of iron. These tables 

 point out a wide field for experiment of great interest. 



We may from these results conclude, that the alloy of iron 

 with any metal in a negative relation to it, unless the alloy be 

 definite, will probably be attended with an increased corrosion 

 of the metal; and that its alloy with a metal positive to it, though 

 it may possibly initially protect the iron from action, will, by 

 its own removal, be likely to render its texture open and porous, 

 and hence more fitted for subsequent solution and removal. 



85. M. Vazie has recommended an alloy of brass and cast 

 iron, in other words, a quadruple compound of carbon, copper, 

 iron, and zinc, as a suitable metal for various large works where 

 capability of resisting rusting or corrosion is important. It is 

 stated that experiments made with it on a large scale, at Glei- 

 witz, in Silesia, were attended with satisfactory results. These 

 require repetition, and much may possibly yet be done in im- 

 proving the durability of cast iron by minutely alloying it. It 

 will be recollected, that a minute quantity of iridium alloyed 

 with iron confers on it the same power of being hardened by 

 rapid cooling that carbon, boron, and silicon do. 



36. The porousness of the ci'ystalline grain of cast iron is 

 frequently very remarkable, and is such as to permit many fluids 

 to enter its pores, and actually saturate the metal like a sponge. 

 A very remarkable case of this is recorded in the Quarterly 

 Journal of Science, vol. ii. p. 385. M. Clement formed a 

 large cylinder of coppei', within which he placed a turned cylin- 

 der of cast-iron, also bored out ; a space intervened between 

 the two, into which he poured melted tin. To his surprise, on 

 becoming cold, much of the tin was squeezed through the cast- 

 iron cylinder, and appeared as a fine filamentous wool, lining 



