SLOW FIXATION OF NITKOGEN. 



231 



place the gases in the annular space separating two concentric 

 glass tubes fused together at the top. 



The apparatus is shown on the preceding page. The inner 

 tube is open and filled with dilute sulphuric acid ; the outer one 

 is closed at the blowpipe, and plunged into a test-glass contain- 

 ing the same acid. The gases and other bodies are introduced 

 beforehand into the annular space, by means of small tubes, 

 which are then closed at the blowpipe. 1 The positive pole of 

 the battery is put in communication with the acid liquid of the 

 inner tube, which acts as armature ; and the negative pole with 

 the acid liquid of the test-tube, which acts as a second arma- 

 ture, separated from the first by a dielectric formed of two 

 thicknesses of glass and the gaseous stratum between. The 

 gases are thus contained in a space completely closed by fusion 

 of the glass without any metallic contact. 



3. The following results were observed under these conditions : 

 the formation of ozone, into which it is not necessary to enter 

 here; the absorption of the free nitrogen by the paper and 

 by the dextrine ; and the formation of special nitrogenous com- 

 pounds, exactly as in the experiments on p. 229. 



4. Some of the experiments were made under quantitative 

 conditions, so as to measure the 



weight of nitrogen absorbed in a 

 given time. For this purpose over 

 half the outer surface of a large 

 cylinder of thin glass, A, termi- 

 nated by a spherical cap, a sheet 

 of Swedish paper, weighed before- 

 hand and damped with pure water, 

 was laid. The other half of the 

 same outer surface was coated with 

 a syrupy solution of dextrine tested 

 and weighed under conditions that 

 enabled us to know exactly the 

 weight of dry dextrine employed. 

 The inner surface of the cylinder 

 had been covered beforehand with 

 a sheet of tinfoil (internal armature). This cylinder was placed 

 upon a glass plate, and then covered over with a concentric 

 cylinder of thin glass, B, as closely as possible, the inner surface 

 of this cylinder being left uncovered, and the outer surface 

 covered with a sheet of tinfoil (external armature). 



The system of two cylinders was covered with a bell-glass, C, 

 to keep out dust, and placed upon a glass plate, arranged so as 

 to keep the apparatus airtight. 



The internal armature was put in communication with the 

 positive pole of a battery formed of five Leclanche cells, arranged 

 1 " Annales de Chimie et de Physique," 5 e se>ie, torn. xii. p. 463. 





Fig. 39. Slow fixation of the 

 nitrogen. 



