86 



PROCEEDINGS OF THE AMERICAN ACADEMY 



cure the necessary control of the temperature of that part of tb.e 

 corahustion tube which should contain this substance. 



For this purpose was constructed a sheet-iron air-bath or chamber, 

 A, Fig. 1, provided with two holes — one in each side — to receive 



Fig. 1. 



the combustion tube, and a tubulure in the top for a thermometer. One 

 end of the air-bath is made to rest on the combustion furnace, and the 

 other, which projects a few inches from the front of the furnace to 

 make room for a lamp, is supported by a leg resting upon the table. 

 The bulb of the thermometer is placed in a central position, in the in- 

 terior of the bath, close by the side of the combustion tube. 



The temperature of the air-bath, and consequently of the substance 

 contained in the combustion tube within, is easily regulated by means 

 of a Bunsen's burner placed under the front end of the bath, as shown 

 in Fig. 1. With the exception of the air-bath, the apparatus employed 

 is the same as that used in the analysis of substances containing sul- 

 phur, a full description of which is given in the papers above referred 

 to. 



The substance that I have found best adapted to absorb the chlorine, 

 for substances easily combustible, is brown oxide of copper, prepared 

 by precipitation with potassa and ignition over a gas flame. 



Difficultly combustible substances, like chloroform, are not complete- 

 ly burnt in oxygen in contact with asbestos alone, but require the pres- 

 ence of a body having affinity for chlorine ; otherwise there is formed 

 a liquid body, difficultly volatile, — probably a chloride of carbon, 

 — which condenses in the vacant part of the tube, from b to c, Fig. 2, 



