274 



EXPERIMENTAL INVESTIGATIONS. 



voltaic current* I should perhaps except olefiant gas, which 

 appears to give rise to a continuous though extremely feeble 

 current ; and the vapours of bromine and iodine, were they 

 less soluble, would probably also be found efficient as electro- 

 negative gases. 



It now occurred to me that as several of these gases (take 

 as an instance nitrogen) were absolutely without effect in the 

 gas battery, this would form a valuable instrument for the 

 analysis of atmospheric air or other mixed gases. I therefore 

 procured, 



Experiment 24, Two narrow cubic inch tubes of seven 

 inches long, carefully graduated into 100 parts. These were 

 immersed in separate vessels of dilute sulphuric acid, and filled 

 with atmospheric air exactly to the extreme graduation ; the 

 water-mark within the tube was examined when exactly at 

 the same level as the exterior surface of the liquid ; folds of 

 paper were used to protect them from the warmth of the 

 hands, and thus prevent expansion ; the barometer and ther- 

 mometer were examined, and every precaution taken for 

 accurate admeasurement. One of these tubes was left empty, 

 in order to ascertain, and eliminate from the result, the effect 

 of solubility. Into the other was placed a strip of platinised 

 platinum foil, one quarter of an inch wide. This strip of foil 

 was connected by a platinum wire with another strip placed 

 * n a tu ^ e f hydrogen and inserted in the same 

 vessel. The apparatus is shown in fig. 1 2. After 

 the circuit had been closed for two days, the 

 liquid was found to have risen in the tube a 

 twenty-two parts out of the 100; in the tube 

 placed by its side it had risen one division. The 

 tubes were allowed to remain several days 

 longer, but no farther alteration took place. This 

 analysis gives, therefore, twenty-one parts in 100 

 as the amount of oxygen in a given portion of air. 

 Experiment 25. The tube a (fig. 12) was 

 charged with nitrogen to a given mark, and 0*5 

 cubic inch of pure hydrogen added ; the tube h was then 

 charged with oxygen, and the circuit closed. Examined 

 after twenty-four hours, the water had risen in the tube a 



* See Postscript. 



Fig 12 



