4 Scientific Proceedings, Roi/al Dublin Society. 



per 100 gm. of water) was weighed, and into the control tube a similar 

 amount of distilled water. From a previously calibrated capillary tube 

 0''i^2 gm. of invertase solution was introduced into each test tube. (In Obs. 2 

 only 0'24 gm. was used), and then a drop of toluene on a glass rod, with 

 wliich the mixtures were briskly stirred. 



The test tubes were then tightly corked and stored at 28" in a thermostat; 

 on withdrawal of tlie first six on the following day (approximately 24 hrs.) 

 the deflections produced by the freezing-point depressions of the sucrose- 

 iuvertase solutions and the controls (invertase solutions) were independently 

 determined against distilled water. The solutions used in the subsequent 

 five observations were left in the thermostat for another day, and then 

 examined in a similar way. 



It is more direct, and has been found more satisfactory, to add a measured 

 quantity of the invertase-toluene mixture to the weighed sucrose solution, 

 keeping both at a low temperature to prevent premature inversion. Then, 

 without allowing the temperature to rise, a determination of the freezing- 

 point is made. The second freezing-point determination is made after 

 incubation, and the diiference of the two depressions found is a measure of 

 the sucrose inverted. 



For example, in Obs. 1, Table II, the deflection produced by the solution 

 before the addition of the invertase was 33 mm., so that 31'0 (viz. 64'0 — the 

 corrected deflection for the sugar-invertase mixture — less 33), represents the 

 mcrease in deflection due to inversion ; 304'] mm. with this thermo-couple 

 represents 1°. Hence, the increase representing a difference in depression of 

 freezing-point of only 0101° (0'210' - 0'109°), it is evident that the inversion 

 was not complete. Complete inversion of the sucrose present would have 

 produced an increase in the depression of freezing-point of O'lOS"'. This 

 stage has been reached, and is recorded in the observations made after 

 48 hours. The results afford an index as to the agreement that may be 

 expected when sucrose is inverted under these conditions. 



As the invertase solution employed had a needlessly low depression of 

 freezing-point, and was not of great activity, being prepared two years 

 previously, a new preparation was made, wliich v/as used in subsequent 

 observations. 



In Table III are shown the results obtained on inverting a sucrose solution 

 containing 4 gm. of sucrose in 100 gm. of water under the conditions described 

 iu the last experhnent. The weight of invertase solution employed was 

 approximately 0-38 gm. per 5 gm. sucrose solution. That inversion was 

 complete in this experiment is evident from the figures presented in the 

 last column 



