482 PROCEEDINGS OF THE AMERICAN ACADEMY. 



filling the burette, the inflow cock (O) was closed. When the acid was 

 to be drawn from the burette, the cock (E) connecting with the outside 

 air through the wash bottle (D) was opened and the pressure thus 

 equalized. As the wash bottle was filled with acid of the same con- 

 centration as that in the reservoir, the tension of aqueous vapor of the 

 air introduced was the same as that obtaining in the system. The 

 flask was always shaken before anything was drawn from it. By this 

 means an acid was secured of unvarying composition, as shown by 

 numerous experiments. In a similar way, with the addition of a soda- 

 lime tower for the removal of carbon dioxide, the alkaline solution was 

 maintained at constant strength. 



It is needless to say that the thennometers were compared with 

 Sevres standards with the greatest care, especially that designated 

 31. Successive standardizations at different times were gratifyingly 

 concordant. 



Conduct of an Experiment* 



The calorimeter proper ( W, Figure 1) was partly filled with about 0.47 

 litre of the desired liquid, ^ either pure water to serve as a standard, 

 or a solution to be studied. It was then brought to the temperature 

 selected for the experiment, accurately weighed, and placed inside the 

 jacket (E, Figure 1). This latter contained its charge of dilute crude 

 alkaline solution, and was also near the selected initial temperature. 

 About 0.1 litre of pure acid (1.34 normal) was then run into the plati- 

 num bottle (X, Figure 1), weighed carefully, and placed in a thermostat 

 to bring it to the desired temperature. The innermost short burette 

 (Z) was filled to the mark with about 0.02 litre of pure alkaline solu- 

 tion and brought near the reciuired temperature. The whole apparatus 

 was then rapidly assembled in the form already described. A few 

 minutes after the stirrers were put in operation, the whole system was 

 in thermal equilibrium, as was shown by the constant readings of the 

 various thermometers. The temperatures of the calorimeter and the 

 pure alkaline solution, indicated by the thermometers 31 and K re- 

 spectively, were then carefully recorded, the stirrer in the bottle was 

 disconnected, and the pure alkali discharged into the bottle as rapidly 

 as possible. The immediate temperature rise, as the heavy alkali sank 

 through the acid, was paralleled outside by running acid into jacket 

 and cover. The bottle-stirrer (J) was then agitated by hand, this 

 permitting excellent control of the mixing of pure acid and alkali and 

 the resulting rise in temperature. When the mixing was almost com- 

 plete, as shown by the rise of the thermometer 31, the stirrer was 

 reconnected with the motor and the final mixing done mechanically. 

 The changes in the calorimeter throughout the experiment were care- 



