The rates of destruction of invertase which were found in various 

 strengths of alcohol are recorded in Table 3, the values of & 2 being 

 expressed in minutes and decimal logarithms and multiplied by 

 1,000 to avoid decimals. The results are also shown graphically in 

 figure 2. 



TABLE 3. Rates of destruction of invertase by alcohol. 



The rate of destruction changes most peculiarly with the strength 

 of the alcohol, reaching a pronounced maximum at about 50 per 

 cent. Presumably the protective action of strong alcohol is due to 

 its precipitating the invertase,, or some other substance whose pre- 

 cipitation protects the invertase, as a visible precipitation begins at 

 or near the strength of 50 per cent, at which the maximum of the curve 

 falls and the protective action begins. If the curve to the left of the 

 maximum is alone regarded as the curve of the destruction in solu- 

 tion it is noticed that it is very similar to the curve for the destruc- 

 tion of the enzym by acids and alkalis. It appears, therefore, that 

 the destruction by alcohol in homogeneous solution is due to a decom- 

 position of the invertase similar to the hydrolytic decompositions that 

 are presumably the cause of the destruction by acids and alkalis. 

 The practical application of the results on alcoholic precipitation 

 is given on page 7. 



THE ACTION OF CANE SUGAR IN PREVENTING THE DESTRUCTION 



OF INVERTASE. 



In order to learn whether cane sugar protects invertase from 

 destruction by alcohol the rate of destruction in a 0.2 normal solution 

 of cane sugar in 50 per cent alcohol was measured at 30 C. by the 

 method already described. A correction was applied for the rota- 

 tion of the sugar in the samples as they were removed to test their 

 activities. The method of preparing the mixture of cane sugar, 

 aqueous alcohol, invertase, and acetic acid is shown in the descrip- 

 tion of the experiment recorded in Table 5; the results on the rate 

 of destruction are given in Table 4. 



U. S. Dept. Agr., Bureau of Chemistry Cir. 55, p. 6. 



[Cir. 58] 



