528 Mr. T. Graham on the Absorption and 



Iron. 



The penetration of iron by hydrogen is demonstrated as clearly 

 by MM. Deville and Troost as that of platinum. A thin tube 

 of cast steel, 3 or 4 millims. in thickness, already enclosing hy- 

 drogen gas in its cavity, was surrounded by air or by nitrogen 

 gas circulating in an annular space between the steel tube men- 

 tioned and a wider external porcelain tube. In the absence of 

 any visible pores in the steel, hydrogen made its way through 

 the substance of the metal, and escaped into the annular space 

 as soon as the system of tubes was exposed to a red heat. A 

 nearly if not entirely complete vacuum was formed within the 

 iron tube*. In another modification of the experiment, carbonic 

 oxide from an uncertain source appeared within the iron tube, 

 particularly when the temperature was most elevated f. 



Wrought iron, in the form of thin wire (No. 23), about 0*4 

 miliim. in diameter/ first carefully cleaned with caustic alkali and 

 water, was heated alone in the porcelain tube exhausted of air, 

 for the purpose of eliminating any natural gases. 



1. Of the iron wire referred to, 46 grms., with a volume of 

 5*9 cub. centims., the specific gravity of the metal being taken 

 at 7*8, were heated by the open combustion-furnace. Gas came 

 off freely at a red heat, — 



(1) Id fifteen minutes, 15'6 cub. centims., containing 3*5 

 cub. centims. carbonic acid, or 22*4 per cent. 



(2) In fifteen minutes, 7*17 cub. centims., containing 052 

 cub. centim. or 7*2 per cent, of carbonic acid. The gas of this 

 and the following stages of observation now burnt with a blue 

 flame, and was principally carbonic oxide. 



(3) In thirty minutes, 104 cub. centims., of which 6*86 cub. 

 centims. were carbonic oxide. 



(4) In thirty minutes, 8 # 16 cub. centims., of which 0*12, or 

 1*4 per cent., was carbonic acid. 



(5) In thirty minutes, 5*52 cub. centims., of which 0*3 was 

 carbonic acid — that is, 0*5 per cent. 



Hence 46 grms. of wrought iron have in two hours given off 

 46*85 cub. centims. of gas, measured at about 15°*C. ; or 1 vo- 

 lume of iron has discharged 7*94 volumes of gas, of which about 

 two-thirds was carbonic oxide • and the metal does not appear to 

 be yet quite exhausted. Iron is a metal not unlikely to contain 

 small quantities of carbon and oxygen, both in chemical union 

 with iron ; and the gas extricated may partly be due to a reac- 

 tion of these elements upon each other at a red heat. 



2. In another, similar experiment upon 32 grms. of clean iron 



* Comptes Rendus, vol. lvii. p. 965 (1863). 

 t Ibid. vol. lix. p. 102(1864). 



