Dixon and Hai.l — Heat produced during Inversion of Sucrose. 159 



where A is the initial temperature, T the final temperature, T^ the 

 temperature of the surrounding air, and t tlie time in hours during which 

 the temperature falls from A to T. It was found that the rate of cooling 

 of one flask was slightly greater than that of the other, but, as Hill (4) has 

 pointed out, compensation can be made for this by adjusting the amounts of 

 liquid in the two flasks. By putting 315 c.c. of water in the experimental 

 ilask, and 287 c.c. in the control flask, it was found that the rate of cooling 

 was approximately the same in both. 



A more accurate determination of the value of li was made in the following 

 manner. The apparatus was set up with the thermocouple in the flasks, the 

 water in the experimental flask being about 1° C. warmer than that in the 

 control flask, and the amounts of liquid in the flasks adjusted so as to make 

 their conductivity constants approximately ecpial, i.e. 315 c.c. in experimental 

 flask and 287 c.c. in the control. The rate of cooling was determined by 

 noting the decrease in the galvanometer deflections during different periods 

 of more than one hour while stirring was carried on, and the constant h was 

 calculated from the formula. In this case the rate of cooling at any instant 

 is proportional to the deflection of the galvanometer, and therefore A and T 

 are equal to the initial and final deflections respectively, and T,, is equal to 0. 

 The value of 0'05 for It was obtained as the mean of a number of concordant 

 observations. This means that at any temperature the rate of cooling per 

 hour was 5 per cent, of that temperature. The smallness of the correction 

 for radiation losses clearly demonstrates the value of this apparatus for the 

 determination of the amount of heat produced during a cliemical reaction, 

 when the time of the reaction is necessarily prolonged. 



Determination of the Heat Produced dtiring the Inversion of Sucrose. 



The sucrose solution which was used contained 100 gm. per litre of solution. 

 Both experimental and control flasks were charged with 300 c.c. of this 

 solution. As the temperature during the experiment could be kept constant, 

 the same quantity of liquid was used in each flask. The solution of invertase 

 was prepared according to Davis' (6) method. In one capsule was put 15 c.c. 

 of the enzyme solution, and in the other 15 c.c. of the same solution which 

 had been previously heated to 100° C. After the capsules had been sealed, the 

 thermocouple was inserted into the flasks, which were then corked with the 

 split corks. The silk threads passed out tlirough grooves between the two 

 halves of the corks. If the corks and threads are well greased, no leakage 

 from the flasks occurs. 



The diagram (8g. 1) shows the arrangement of the thermocouple and flaskg 

 when assembled. 



