the quantity of invertase that is present in the solution. The great 

 changes in composition which occur during the dialysis of the solu- 

 tion involve little, if any, loss of invertase for the maximum activity 

 remains nearly constant. Invertase does not pass through dialyzing 

 parchment paper. The natural activity, however, shows a peculiar 

 change during dialysis, decreasing at first and later rising to about 

 its original value. As the invertase does not disappear this change in 

 natural activity must be ascribed to the changing acidity or alkalinity 

 of the solution, and the explanation of its peculiar course doubtless 

 lies in a rapid loss of acids through the parchment paper in the first 

 stages of the dialysis, leaving alkaline substances behind which inac- 

 tivate the invertase; as the dialysis proceeds these substances also 

 pass through the filter, and the lessened alkalinity causes an activa- 

 tion of the invertase. 



The values of the activity w r ere measured as follows: 5 cc of the 

 solution, the activity of which was to be measured, were added to 

 100 cc of a 0.2 formular solution of cane sugar, 5 cc of water, or of 

 acid in the experiments on the effect of acids, were added and the 

 mixture allowed to proceed in reaction in a thermostat at 30 C. At 

 the end of one or two hours 50 cc of the mixture were removed, made 

 alkaline with sodium carbonate to stop the action of the enzym and 

 complete the mutarotation of the invert sugar, and the rotation was 

 read on the polariscope. The velocity coefficient of the reaction, 



k^ =-r log - , was calculated and its value after multiplication 



C/ f / QD 



by 10,000 to avoid decimals, was recorded as the activity of the given 

 invertase solution. In the calculations the time (t) was expressed in 

 hours and decimal logarithms were used. The determination of the 

 rotation of the solutions after complete inversion (r) was not made 

 in each case, but instead the ratio r<x to r , usually known as the 

 Clerget factor, was measured accurately in a special investigation, 

 which gave the value 0.317 for this factor at 20 C., this being the 

 same value as that found when hydrochloric acid is used as the invert- 

 ing agent and the acid is neutralized before the polariscopic reading is 

 made. The identity of the values of the factor for the two inverting 

 agents shows that invertase accomplishes as complete a hydrolysis of 

 cane sugar as does hydrochloric acid. Visser 6 has concluded from his 

 similar experiments that invertase does not accomplish as complete 

 an inversion of cane sugar as does hydrochloric acid, because his 

 factor for invertase inversions was always smaller than that for the 

 acid ; but he overlooked the essential fact that the acid must be neu- 

 tralized before the reading is made if the results are to be compared 

 with the reading of the neutral invertase solutions. 



U. S. Dept. Agr., Bureau of Chemistry fir. No. 50, p. 2. 

 6 Zts. phyeikal. Them., 1905, 52: 275. 



[Cir. 55] 



