Feb. i 5> 1921 Amylase of Rhizopus tntici 773 



The results show that the amount of reducing sugars steadily increased 

 for the first 7 days but remained practically stationary thereafter. At 

 the end of 18 days a small amount of starch yet remained nonhydrolyzed. 



To determine whether the addition of a small amount of starch would 

 stimulate further hydrolysis, 100 cc. of the solution described on page 772 

 were mixed with 100 cc. of an approximately 0.5 per cent starch paste 

 solution. A small amount (20 cc.) was drawn off, and the actual amount 

 of starch was determined. The remainder was hydrolyzed at 45 ° C. 



After acid hydrolysis reducing sugars to the amount of 1,568 mgm. 

 were found in 200 cc. of the original solution. Of this amount 1,088.89 

 mgm. of reducing sugars and 27.33 mgm. of nonhydrolyzed starch 

 (equivalent to 29.38 mgm. reducing sugars) were brought over to the 

 solution when the dilution was made, making a total of 1,118.27 mgm. 

 reducing sugars. Deducting this amount from the amount originally 

 found (1,568 less 1,118.27 mgm.), the result gives the amount of reducing 

 sugars added in the form of starch, or 449.73 mgm. This is calculated 

 to be equivalent to 418.2489 mgm. of starch. To this amount should 

 be added 27.33 mgm., the quantity of nonhydrolyzed starch present 

 before the solutions were mixed, making a total of 445.58 mgm. starch 

 present in 200 cc. of the solution when hydrolysis was started. After 

 hydrolysis had gone on for 24 hours a sample was taken, and the reducing 

 sugars were determined, which gave in 200 cc. a total of iJ5i6.6 mgm. 

 There was no starch left in the solution according to the iodin test. 

 Since in the original solution there were 1,568 mgm. of reducing sugars 

 present, 51.4 mgm. (equivalent to 47.8 mgm. starch) remain unaccounted 

 for, except as intermediate products between starch and reducing sugars. 



Parallel experiments, which will not be given in detail, gave similar 

 results. 



The evidence brought out shows that an equilibrium is established 

 in the solution before quite all the starch is hydrolyzed. Also that if 

 more starch is added and the solution is diluted the starch finally dis- 

 appears so far as its presence is indicated by the iodin test. 



So far as these and many other results go, an end point is reached if 

 the disappearance of the starch alone is considered. Viewed from the 

 standpoint of reducing sugars found, an end point is not reached. Many 

 experiments not designed primarily to demonstrate this point have 

 shown that no starch, as indicated by iodin, remains in the solution after 

 a definite length of time. On the other hand, starch is shown to be 

 present in some solutions by the same test after a considerable time. 

 It was also shown by experiments that if an end point was not reached 

 at a certain temperature, namely 45 ° C, the starch would completely 

 disappear in 24 hours by shifting the solution to a temperature of 35 . 



Perhaps an explanation of some of these facts may be found in the 

 results of other investigations. The results of the above experiments 

 show that all the starch was not accounted for as reducing sugars, 



