OF ARTS AND SCIENCES : JANUARY 31, 1866. 85 



to that which I have already described for substances containing sul- 

 phur.* 



As in that process, so also in this, the substance is burnt in a stream 

 of oxygen gas, in the manner described in my first paper, on Organic 

 Elementary Analysis.! 



Similarly, also, as in the analysis of sulphur compounds, the chlo- 

 rine is absorbed and retained during the combustion, by a suitable sub- 

 stance placed in the anterior end of the combustion tube ; this substance 

 being subsequently removed, and the chlorine determined therefrom in 

 the usual manner. The carbon and hydrogen, in either process, are 

 determined from the same portion of the substance as the sulphur or 

 chlorine, in a manner similar in other respects to that described for 

 simple hydrocarbons. + 



In pursuing this research some difficulty was experienced, as was 

 anticipated, in finding a substance which would absorb and retain the 

 whole of the chlorine, under conditions that would at the same time 

 insure that every trace of the carbonic acid and water should pass 

 through unabsorbed. 



The search for this substance was confined to the oxides of the heavy 

 metals, as these alone, from their strong affinity for chlorine, and weak 

 affinity for carbonic acid, seemed to give encouragement of success. 



The difficulty, however, in finding such a substance was chiefly due 

 to the circumstance that most of the chlorides of these metals are either 

 too volatile, or begin to suffer decomposition at too low a temperature ; 

 it being requisite that the absorbing substance, and the newly formed 

 chloride of the same, should bear to be heated sufficiently to prevent 

 both condensation of water and absorption of carbonic acid, and at the 

 same time avoid a temperature high enough to occasion any apprecia- 

 ble decomposition of the chlorid. 



This question of temperature became, therefore, a prominent one in 

 the investigation, as evidently the success of the process must depend, 

 in a great degree, on the proper management of the temperature of 

 the absorbing substance, within such limits as might be found to give 

 satisfactory results. Hence, my first step was to devise means to se- 



* Proceedings of the American Academy, March, 1865; American Journal of 

 Science and Arts, 1866, XLI. 40. 



t Proceedings of the American Academy, 1864, p. 251 ; American Journal of 

 Science and Arts, 1864, XXXVIII. 387. 



t Lo<\ cit. 



