Dixon and Ball — Heat produced during Inversion of Sucrose. 161 



noticed that the temperature rises steadily from the moment mixing takes 

 place, and after the correction is made for radiation losses the curve is very 

 nearly a straight line throughout the course of tlie experiment. This is 

 probably due to tlie fact that the sucrose is largely in excess of the enzyme, 

 so that the rate of the reaction is not sensibly diminished even after about 

 40 per cent, of the sucrose has been hydrolysed. 



In calculating the results, a correction is applied for the difference in the 

 specific heat of the sucrose solution used from that of water, and also a 

 correction for the very slight reducing power of the sucrose and invertase 

 rsolutions. 



The results of our two final experiments are shown below. The tempera- 

 ture of the solution during both these experiments was about 10° C. The 

 values obtained in earlier experiments are not given, as, owing to the metliod 

 ■of stirring adopted, the radiation error was very large and uncertain, and 

 therefore the results were unreliable. 



Tlie radiation correction in Expt. 6 is slightly smaller than in Expt. 7, 

 although in the former ease the rise in temperature was greater than in the 

 latter. This is due to the fact that, at the commencement of the experiments, 

 the experimental flask was slightly cooler than the control in Expt. 6, and 

 slightly warmer in Expt. 7. 



The values, ll-:20 and 11-27, obtained in our experiments agree well with 

 ■the values, 11-28 and 1113, given in Brown and Pickering's paper, and the 

 mean of all these, 11-22, may be regarded as a reasonably accurate estimate 

 ■of the number of calories evolved per gram of sucrose when inverted in 

 solution by means of invertase. This is equal to 3-83 calories per gram 

 molecule. 



Since these experiments have been concluded, the results obtained by 

 Barry (7 and 8) on the heat of inversion of sucrose by hydrochloric acid have 

 been published. In this case a value of + 10-4 eal. per gram inverted at 20" C. 

 was obtained. It seems possibh; that the discrepancy between this value and 

 that obtained in our experiments is due to the fact that the energy-changes 



SCIENT. PKOC. r..D.S., VOL. XVI., NO. XIV. Z 



