150 Scientific Notices — Chemistry. [Aug. 



more, than that quantity. Even in the hands of the late Mr. 

 Cavendish, it seems to have given capricious results, sometimes 

 producing a diminution, in a mixture of 125 nitrous gas and 100 

 air, of 115 parts, and at others of 121*2 parts.* By Gay-Lus- 

 sac's method of applying the test, however, the results are con- 

 stant. It consists, as is well known, in introducing a known 

 bulk of air into a wide vessel over water, and afterwards adding 

 an equal bulk of nitrous gas ; after standing one minute, the 

 residuum is transferred to a graduated tube, and the diminution 

 of volume noted. This divided by 4, gives the quantity of 

 oxygen. 



Mr. Dana remarks, that the true theory of the effect thus pro- 

 duced has never been explained, and he offers the following 

 ingenious solution : 



" It is perfectly well established, that 



Vols, oxygen. Vols, nitrous gas. 



100 unite with 400*00 and form hyponitrous acid 

 100 200-00 nitrous acid, and 



100 133-33 nitric acid. 



" When we mix, therefore, 100 parts of atmospheric air with 

 100 parts of nitrous gas, the diminution in volume, if nitric acid 

 only be formed, should be 49 parts ; if nitrous acid only, 63 

 parts ; if hyponitrous acid only, 105 parts. But experiment 

 teaches us that the diminution of volume is actually 84 parts, 

 and that all the oxygen disappears ; now this degree of diminu- 

 tion can be produced only by the formation and absorption of 

 hyponitrous acid and of nitrous acid ; and the oxygen present is 

 equally divided between them, viz. 



Vols, oxygen. Vols, nitrous gas. 



50 unite with 200 and form hyponitrous acid 

 50 100 nitrous acid 



100 300 



" Or, as in the analysis of the air, which contains 21 per cent, 

 of oxygen, and the diminution amounts to 84 parts when 100 

 each of air and nitrous gas are employed, 



Vols. 



One-half its oxygen, equal 10-5 



Unites, to form hyponitrous acid, with nitrous gas .... 42-0 



The remainder of the oxygen 10-5 



To form nitrous acid, unites with nitrous gas 21*0 



All of which are condensed, equal 84-0 



• u 



The greatest diminution was 1 10, the least 106-8; the mean 108-4." Thomson's 

 Chemistry, vol. iii. p. 166. 



