174 PROCEEDINGS OF THE AMERICAN ACADEMY. 



brought into the system, this feature introduced uncertainty, espe- 

 cially as the liquid might undergo slight Ijut undetermined changes 

 in temperature during the act of transference. This point was recog- 

 nized l)y the authors at the time of the initial publication and at that 

 time a method for its elimination was suggested. A description of the 

 improved apparatus and some of the results yielded by it are embodied 

 in the present communication. 



Method and Apparatus. 



As in the earlier form, the neutralization of sulphuric acid with 

 sodium hydroxide was selected as the source of heat. The stability 

 of solutions made from this acid renders it especially suitable for such 

 purposes. In carrying out the neutralization a concentrated solution 

 of caustic soda was placed in a small stoppered platinum can, which 

 was suspended within a platinum bottle containing the acid to be 

 neutralized. At the appointed moment, the two liquids were allowed 

 to mix. This bottle, closed with a platinum stopper, had previously 

 been submerged in the liquid to be studied, which was itself held in a 

 large platinum calorimeter. The whole was provided with an environ- 

 ment so arranged as to vary in temperature at the same rate as the 

 calorimeter, and this eliminated the troublesome and inexact cooling 

 correction. 



It is perhaps worth while to describe the affair in detail because 

 much time was spent in working out the most advantageous arrange- 

 ment. The accompanying diagram will assist in the explanation. 

 (Figure 1.) 



The platinum bottle (D) used to contain the weighed amount of 

 acid was provided with a very wide mouth, in order that the receptacle 

 for the alkali could be introduced within it. The mouth was narrowed 

 by a hollow platinum stopper or cap (E) of peculiar shape, the joint 

 being made tight by a thin smooth rubber band or collar between the 

 stopper and bottle. The upper end of the open stopper was fastened 

 by stout platinum wires to a hollow tube of hard rubber which passed 

 through an opening in the jacket above, and held the bottle in suspen- 

 sion. 



The receptacle for the alkali also was unusual in its form, consisting 

 of a very small platinum can (F) (of a diameter slightly less than that 

 of the mouth of the bottle) with a hole in the bottom closed by a 

 small rubber stopper (r). This can was open at the top and was sus- 



