1820.] Specific Gravity of Gases. 173 



the volume of azotic gas present in the nitrous gas subjected to 

 experiment in my laboratory had amounted to 1*42 percent, and 

 I am persuaded it could not be less, it would fully account for the 

 specific gravity formed ; for the specific gravity of a mixture of 

 98*58 volumes of nitrous gas and 1*42 volumes of azotic gas 

 would be 1 -04096, if we suppose the specific gravity of pure 

 nitrous gas to be 1-04166, and that of azotic gas 0-97222. 



Thus the specific gravities of the gaseous compounds of oxy- 

 gen and azote correspond with theory, and serve, therefore, to 

 confirm and establish the important law of Gay-Lussac. 



2. There is a gaseous compound of oxygen and chlorine first 

 recognised as a peculiar substance by Sir H. Davy, though it 

 had been prepared, and even slightly examined, many years 

 before by Mr. Cruikshanks. It is prepared by pouring dilute 

 muriatic acid on chlorate of potash, and exposing the mixture to 

 a very gentle heat. The gas, which is of a strong yellowish- 

 green colour, comes over, and must be received over mercury. 

 Before submitting it to examination, it should be allowed to 

 stand over mercury for 24 hours in order to get rid of the chlo- 

 rine with which it is always mixed at first. The mercury gra- 

 dually absorbs and condenses the chlorine, while it does not act 

 upon the other gas. Davy gave to this gas the name of euchlo- 

 rine, but I have distinguished it by the more systematic appella- 

 tion of protoxide of chlorine. When this gas is exposed to a 

 shght heat, it is decomposed with an explosion, and, according 

 to the observations of Sir H. Davy, five volumes of it when thus 

 exploded are converted into six volumes, which consist of a mix- 

 ture of two parts by bulk of chlorine and one part of oxygen. 

 Hence it follows that this gas is a compound of four volumes of 

 chlorine and two volumes of oxygen coiidensed into five volumes ; 

 so that by uniting together these two gases undergo a diminu- 

 tion of one-sixth of their bulk. It is obvious from this that in 

 order to obtain the specific gravity of protoxide of chlorine we 

 must add together four times the specific gravity of chlorine gas 

 and twice the specific gravity of oxygen gas, and divide the sum 

 by 5. 



Specific gravity of chlorine = 2-5000 x 4 = lO'OOOO 

 oxygen =1-1111 x 2 = 2-2222 



5)12-2222 



2-4444 



Thus it appears that the specific gravity of protoxide of chlorine 

 is 2-4444. 



Two experiments were made upon the specific gravity of this 

 gas in my laboratory. The results obtained were as follows: 



By first trial 2-400 



By second trial 2-403 



