906 Transactions of the American Institute. 



placed by itself iu a corked bottle, filled with eighty centiineters 

 of very diluted .acid. Amoiig the acids tried were sulphuric, 

 hj'-drochloric and acetic; their action; upon the iron was very slow, 

 and it required a long time to show any change whatever. After 

 three months of contact, it was found that some of the, cubes, and 

 particularly that immersed in acetic acid, had become so soft. exter- 

 nally that a knif^-blade could penetrate three or four millimeters 

 deep. The solutions were then removed, and rephiced by fresh 

 ^acid of the same kind in each bottle — this removal being continued 

 every month for two years. After this length of time, changes had 

 been elfected in almost all the cubes, the penetration being more 

 or less complete according to the nature of the acid. Next to acetic 

 acid, in energy, came hydrochloric, then sulphuric acid. Phosphoric 

 acid showed no similar action. The result of the action of other 

 acids was a complete change in the nature of the metal, without 

 any alteration of its bulk or appearance of its surface. The specific 

 gravity of gray cast-iron cubes was reduced from 7.858 to 2.751. 

 On analyzing the cube which had been exposed for j'^ears to acetic 

 acid, and compai'ing its ingredients with those of gray cast-iron of 

 the same quality as that composing the original cube, Mr, Calvert 

 found that the quantity of pure iron had decreased from 95.413 

 to 79.960; of phosphorous, from 0.132 to 0.059; of sulphur, from 

 0.179 to 0.096; while the amount of carbon had increased from 2.90 

 to 11.07; of nitrogen, from .0.79 to 2.59; of silicon, from 0.478 to 

 6,07. Seawater contains the elements from which the destructive 

 acids mentioned may be formed, by the decomposition of organic 

 or inorganic matter present in such water. The gradual deteriora- 

 tion of certain kinds of cast-iron, w^hen exposed to seawater, may be 

 considered as established. This action is of course extremel}' slow, 

 yet it should be taken into account in all engineering structures, 

 relying for their safety upon cast-iron in contact with the seawater 

 ,or any w\ater w^hich is the receptacle of acids. The experiments by 

 Calvert confirm those made several years before by Mallet, who 

 found that the corrosion of cast-iron depended upon a want of its 

 homogeneousness of surface, density or hardness, or the imperfect 

 combination of the carbon with the iron. The Institution of 

 Civil Engineers in London, recently discussed this question at 

 great length, and cited numerous cases where cast-iron, which had 

 been immersed from thirty to forty years in seawater, was found 

 ■wholly unaffected. Mr. Simpson, the president, stated that " the 

 square angles of the Iron were as sharp ..as when they left the 



