56 Scientific Proceedings, Royal Dublin Society. 



material referred to later on. The iron barrel, of a diameter of 1 J inch, con- 

 sisted of two six-inch leugtlis connected in the middle by a T piece, which 

 allowed the insertion of a thermometer or pyrometer, the bulb of which could 

 be placed in the exact centre of the iron barrel. This iron gauze or other 

 material (peat, &c.) was arranged in equal quantities on either side of the 

 thermometer bulb. The thermometer was held in position in the T piece by 

 a special preparation of asbestos fibre and plaster-of-Paris, which had also 

 been carefully tested, and proved to contain no nitrogen compounds. 



The iron barrel was provided at both ends with reducing pieces to \ inch, 

 allowing a short length of j-ineh iron tube to be screwed into the end 

 admitting the air from the flask 



The gases were passed through a Liebig condenser, and through dilute 

 sulphuric acid in a special absorption apparatus. 



All results were duplicated for comparison and determined by distillation 

 with sodium carbonate, absorption in — V n- HCl, and titration with j^-g- 

 n. Na^COa. 



To determine the most favourable temperature a series of experiments 

 was made under the following conditions : — 



A li-inch iron barrel was filled with freshly reduced iron wire gauze, and 

 air saturated with steam at 80° C. was passed over it at a uniform rate and 

 under identical conditions, except for variations in temperature. 



The duration of each experiment was 4| hours ; and the amount of air 

 passed was 4| cubic feet, the contact material being reduced after each test 

 for several hours by means of carbon monoxide. The yields in milligrams at 

 the different temperatures were as follows : — 



250-300° . . 80-3 mg. 400-450° . . 73-4 mg. 



300-350° . . 204-0 mg. 450-550° . . 41-7 mg. 



350-400° . . 119-0 mg. 550-650° . . 23-6 mg. 



By comparing the results of this series of experiments, it was found that 



under the various tested conditions the most favourable temperature was 



between 300 and 350° C. 



To exclude ammonia, which might be obtained from the decomposition of 

 iron nitride, the iron tubes used in these experiments were treated for several 

 days with steam and carbon monoxide alternately, until the quantity of 

 ammonia formed per hour did not exceed 0-01 mg. 



Experiments were then made to determine whether it would be possible to 

 lengthen the zone of contact; and an iron barrel 6 feet long and li inches 

 in diameter was filled with wire gauze, and placed in a lead bath at a 

 temperature of 350° C, air and steam being passed through it under the 

 same conditions as in the former series. 



