233 



BOTANICAL GAZETTE [april 



here. Most of the solutions used were made up from the same stock 

 solutions and all were upon the same basis of molecular weight. The 

 lipase used was taken from the same sample. Professor Gies has 

 been my counselor in this work as in the other, and the same acknowl- 

 edgments are due the New York Botanical Garden for the exception- 

 ally favorable facilities afforded. 



METHOD 



When ethyl acetate is decomposed by the action of lipase, the prod- 

 ucts are supposed to be the same as in any case of its saponification, 

 namely, acetic acid and ethyl alcohol. The amount of acid liberated 

 from initially neutral acetate under given conditions is an index of the 

 amount of enzyme activity under those conditions, and can be expressed 

 in cubic centimeters of KOH solution required for neutraHzation. 

 Since boiHng destroys the activity of the enzyme, and since the acetate 

 does not become appreciably acid in such a boiled solution of the 

 enzyme during an incubation of 5 hours at 40° C, a boiled solution of 

 the enzyme can be used as a control. The difference then in acidity 

 of a boiled and of an unboiled solution of the enzyme of equal con- 

 centration, to which the same amount of ester has been added, 

 expresses the amount of enzyme activity under the conditions imposed. 

 Six vials were used for each concentration of the toxic salt. To each 

 vial were added 2'''' of the toxic salt solution of a certain concentration, 

 say w/32. Then to each of three of the vials were added 2'''' of the 

 unboiled, filtered enzyme solution having a given concentration, say 

 o. 10 per cent. To each of the other three vials were then added 2'='= 

 of a portion of the same enzyme solution which had been boiled. Then 

 to each of the six vials was added o. 10'''' of neutral ethyl acetate free 

 from alcohol. The stoppered vials were placed in an incubator for 

 5 hours at 40°C. After incubation each vial was titrated with w/40 

 KOH, using phenolphthalein as an indicator. The difference between 

 the boiled and unboiled solutions showed the amount of enzyme 

 activity for w/64 of the salt used with a concentration of the enzyme 

 of about o . 05 per cent. Filtering the enzyme solution makes the exact 

 concentration uncertain. All of the salts used were nitrates except 

 that of mercury, which was the bichlorid. 



Since the acetate has the lower boiling-point and decomposes 

 more rapidly in the presence of water, one would expect that it would 



