EICHARDS. THE ELIMINATION OF THERMOMETRY LAG. 



11 



series in which the temperature of the environment was changed simul- 

 taneously with that of the calorimeter itself. The accomplishment of 

 this program and the comparison of the results is recorded below. 



The reaction chosen to be measured was that of sodium hydroxide on 

 sulphuric acid. This reaction has the advantage of easy repetition, as 

 well as the advantage of a less considerable change of heat evolution with 

 temperature than is the case in many reactions. In order to exclude all 

 error from this cause, the maximum temperature was about the same 

 in all cases. A slight excess of the alkali 

 was used to avoid error from decomposition 

 of carbonate. 



In a preliminary series of experiments 

 the divided beaker calorimeter used by 

 Richards and Lamb * was at first em- 

 ployed ; but because with this apparatus 

 the speed of the reaction is not easily 

 regulated, another form depending upon 

 the same principle was employed. This 

 form is shown in section in Figure 2. 



The sodic hydroxide was contained in a 

 large test-tube provided with two holes, 

 one on the side above the liquid level, 

 and the other in the middle of the bottom. 

 The latter was closed until the moment of 

 the reaction by a rubber stopper upon a 

 rod running down through the axis of the 

 tube. Before this moment arrived the test- 

 tube was immersed in the calorimeter ves- 

 sel, full of dilute acid, to the level of the 

 alkali within. When it was desired to start 



the reaction, the stopper was displaced and the test-tube still further 

 immersed, so that both holes were open under the liquid level. Screw- 

 propeller vanes on the stopper-rod made it possible to circulate the liquid 

 through these two holes, so that the mixing could be accomplished as 

 quickly or as slowly as was desired. Another screw-stirrer in the calo- 

 rimeter vessel itself assisted the mixing. The heat developed by the 

 friction of the stirring was found to be barely perceptible ; it was moreover 

 identical in each case, and may therefore be wholly neglected. 



a 



co 



w 



c 



K 



A 



Figure 2. 



* These Proceedings, 40, 675 (1905). 



