8 



filtered off, washed with alcohol, then with ether, and dried over 

 sulphuric acid in a desiccator. The mass, which resembled horn in 

 superficial appearance, was dissolved in 50 cc of water, and its 

 inverting activity was found to be 78 per cent of that of the original 

 sample. The second method of precipitation, at low temperature 

 (0C.), gave a small recovery and is not to be recommended. 



In order to test the protective action of cane sugar, 25 grams of it 

 were dissolved in 50 cc of dialyzed invertase and 95 per cent alcohol 

 added until the strength of the mixture became 70 per cent alcohol. 

 The precipitate was filtered off, washed with ether, and dried in a 

 desiccator. On redissolving, it showed 94 per cent of the original 

 activity and a second experiment gave a recovery of 96 per cent. 

 These experiments demonstrate that it is possible to precipitate 

 invertase with alcohol without any important loss of activity pro- 

 vided the enzym is protected by cane sugar. Other sugars may 

 have this protective action also, but this point has not yet been 

 investigated. ' 



SUMMARY. 



O'Sullivan and Tompson's observation that alcohol reduces the 

 activity of invertase is confirmed, and the relation between alcoholic 

 strength and inactivation is shown to be graphically a rounded curve 

 (fig. 1). Alcohol is found to destroy invertase, and the relation 

 between alcoholic strength and rate of destruction is very peculiar, 

 as it shows a high maximum at about 50 per cent alcohol. The 

 destruction follows the course of unimolecular reactions; it is not 

 noticeable below 20 per cent alcohol at 30 C., is almost instantaneous 

 at 50 per cent, and decreases to nearly zero at 80 per cent (fig. 2). 

 If the alcohol contains cane sugar, the destruction is much slower; 

 thus, 6 per cent cane sugar reduces the rate of destruction in 50 per 

 cent alcohol from 0.850 to 0.009, or to about 1 per cent of its original 

 value. A mathematical theory of the progress of the inversion of 

 cane sugar by invertase in alcoholic solutions of sufficient strength to 

 slowly destroy the enzym has been worked out and its conclusions 

 found to agree with the results of the experiments. In this way it 

 has been possible to measure the activity of invertase in 50 and 70 

 per cent alcohol, where the destruction plays an important r61e. 

 Invertase can be precipitated by alcohol without much destruction, 

 provided the strength of alcohol in the final solution is high, approxi- 

 mately 90 per cent. By this method of precipitation, working at 

 room temperature, a solid preparation was obtained which had 78 

 per cent of the activity of the original solution. If cane sugar is 

 present, invertase can be precipitated with no important destruction 

 by even 70 per cent alcohol; this method of precipitation gave a 

 recovery of 94 and 96 per cent of the original activity. 



[Cir. 58] 



O 



