372 DISOXIDATION OF IRON RY IIIDROGEN CAS. 



. thollet to employ hidrogen gas in his experiments, which 

 I repeated as follows. 

 Two specimens I took 5 gram. [77*23 grs.] of oxidulatcd iron of Cogne, 



of native oxide ^^ J ^ gjjjjjj^j. quantity of oligist iron of Klba, and placed 

 of iron exposed ^ j o 7 r 



to the action of them in a semicircular tube with two compartments, intend. 

 hidrogen gas. ^^ g^^h to hold one of the oxides. This tube, furnished 

 -with a long stem curved at one end, was placed in a gun- 

 barrel open at both ends, previously cleaned, and coated 

 externally with loam, to preserve it from oxidation. At 

 the curved end of the stem, which answered to one of the 

 ends of the gunbarrel, a curved tube was luted, terminat- 

 ing underwater, and intended to afford a passage to the super- 

 fluous hidrogen gas and the vapours of the apparatus, which 

 were collected in bottles filled with water, and resting on a 

 perforated test, underneath which the tube opened. The 

 gunbarrel was placed 4 inches from the grate in a furnace, 

 the opening of which was 8 in. [85 Eng.] wide, and 12 

 '[12'8] high from the grate, which rested immediately on 

 the nozzle of a pair of forge bellows. To the other end of 

 the guijbarrel was fitted a tube, curved likewise, commu- 

 nicating with a cock placed under a jar completely im- 

 mersed in a tub of water, the pressure of which was in- 

 tended to force out the hidrogen gas, with which the jar 

 was kept constantly filled. 



All the parts of the apparatus being securely fixed and 

 luted, it was found to be air tight, by passing a measured 

 portion of air from the jar into the receivers at the other 

 extremity. 



Hidrogen gas was then prepared from iron filings and 

 diluted sulphuric acid; the furnace was filled with charcoal; 

 the fire was kindled, and blown gently. When the gun- 

 barrel was redhot, which might easily be seen through the 

 glass tubes at its two extremities, the cock was closed, and 

 the jar filled with hidrogen gas. This gas was then passed 

 through the apparatus, by opening the cock a little. Part 

 of the gas was absorbed; and the remainder, which was re- 

 <Jeived in the bottles with theaqueous vapour that condensed 

 in them, was returned into the jar. In this process the 

 oxidule and oligist iron at this temperature, presenting to 

 the gas a porous mass, which it could easily traverse, each 



particle 



