OF ARTS AND SCIENCES : JANUARY 31, 1866. 



87 



and which cannot be entirely burnt off and save the analysis. In 

 such cases the absorbing substance is mixed with the asbestos occupy- 

 ing the back part of the tube, where the combustion takes place. It is 

 evident that oxide of copper would not answer for this purpose, as at so 

 high a temperature dichloride of copper would be formed, which, being 

 insoluble in dilute acids, would interfere with the determination of the 

 chlorine. Oxide of zinc has been found to give good results with such 

 substances. 



The preparation of the combustion tube, and the arrangement of the 

 mixture of asbestos and the absorbing substance, is the same — except 

 in the case last mentioned — as in the analysis of substances containing 

 sulphur, as shown in Fig. 2, viz. the space between a and b, about 

 10 inches in length, is Fig. 2. 



packed with pure asbes- 

 tos ; between b and c, — a 

 space of about two inches, 



— being left vacant, a plug ^aaHBBBB " MM 



of asbestos is placed at c; 



the space between c and d, 4 to 5 inches in length, is filled with an 

 intimate mixture of asbestos and brown oxide of copper ; and, finally, a 

 plug of asbestos is placed at d. 



After the combustion, the chloride, together 

 with the excess of oxide, is extracted from the 

 asbestos by means of dilute nitric acid. 



To facilitate the removal of what may ad- 

 here to the sides of the tube, the apparatus 

 shown in Fig. 3 will be found serviceable, as 

 in the analysis of sulphur compounds. 



I. Experiments with Oxide of Lead and with 

 Oxide of Copper, placed in the anterior 

 end of the combustion tube, as absorbents 

 of Chlorine in the analysis of substances 

 difficultly combustible. 

 The substance selected for analysis, as a test 

 of the process for that class of bodies which 

 are difficultly combustible, containing but a small 

 percentage of hydrogen, was commercial chloro- 

 form. The preparation employed was first subjected to redistillation. 



Fig- s. 



