198 ANNUAL OF SCIENTIFIC DISCOVERT. 



plained, until some very interesting experiments established its 

 scientific rationale. We believe that this scientific discovery is 

 due to Mr. Crace Calvert, of Mancliester, who some 3'ear3 l)ack 

 carried out a series of very interesting experiments on this point. 

 Mr. Calvert immersed cast-iron cubes, made of Staffordshire cold 

 blast iron, and cast 1 centimetre in dimension, into acidulated 

 water. Each cube was placed by itself in a corked bottle with 

 80 cubic centimetres of a very diluted acid. Amongst the 

 acids tried were sulphuric, hydrochloric, and acetic acid ; their 

 action upon the iron was very slow, and it required a long time 

 to show any change whatever. After 3 months of contact, Mr, 

 Calvert found that, although the external appearance of the cubes 

 was not changed in any way, some of the cubes, and particularly 

 that in contact with acetic acid, had become so soft externally that 

 a knife-blade could penetrate 3 or 4 millimetres deep into the 

 cube. The solutions were then removed and replaced by fresh 

 acid of the same kind iu each bottle, this removal being continued 

 every month for 2 years. After this period, changes had been 

 effected in almost all the cubes, only the penetration was more or 

 less*complete according to the nature of the acid. Acetic acid 

 had acted most energetically of all ; next came hydrochloric and 

 sulphuric acid. Phosphoric acid showed no similar action. The 

 result of the action of the acid was a complete change of the na- 

 ture of the metal, without any alteration of its bulk or of the 

 appearance of its surface. The cubes of gray cast iron, which 

 originallv weighed 15.324 grammes each, weighed onlv about 3^ 

 grammes at the end of 2 years, and their specific gravity was 

 reduced from 7.858 to 2.751. The iron had been gradually dis- 

 solved or extracted from the mass, and in its place remained a 

 carbon compound of less specific weight, and very small cohesive 

 force, which occupied the same bulk as the original cast iron. 

 The composition of the cast iron and of the carbon compound 

 which remained in its place after 2 j'ears of contact with acetic 

 acid was found by Mr. Calvert as follows : — 



Original Cubes. Carboaaceous Substance. 



Iron, 95.413 79.960 



Carbon, . 2.900 li.070 



Nitrogen, 0.790 2.590 



Silicium, 0.478 6.070 



Phosphorus, 0.132 0.059 



Sulphur, 0.179 0.096 



Loss, 0.108 0.205 



Acids, like hydrochloric, sulphuric, and acetic acid, are to be 

 found in water under a great variety of circumstances. Sea-water 

 contains these, or at least the elements from which they can be 

 formed by decomposition of the organic or inorganic matter con- 

 tained in them ; they appear in the air, and are carried by the rain 

 or snow down to the surface, particularly in the vicinity of manu- 

 facturing localities. The gradual deterioration of cast iron when 

 exposed to actions of that kind — a change which is all the more 

 dangerous, as it is not immediately apparent to the e3-e — may 

 therefore be considered as a possibility, and in the presence of 



