772 



Journal of Agricultural Research 



Vol. XX, No. 10 



Table IX. — Volume of 0.5 per cent starch paste solution used, total reducing sugars, and 



reducing sugars per 10 cc. 



IS AN END POINT IN HYDROLYSIS REACHED? 



Theoretically an end point should not be reached without shifting the 

 point of equilibrium of the solution. As a matter of fact, to settle the 

 question is difficult by any method, since there may be intermediate 

 products between starch and reducing sugars which are not revealed 

 by the iodin test and do not reduce copper. The experiments were made 

 with extracts of the mycelium. The mycelium (1.5 gm.) after powdering 

 was extracted in a pyrex flask for 24 hours at 9 C. in 300 cc. of distilled 

 water. The extract was then filtered. Two hundred fifty cc. of the 

 extract were then diluted with 250 cc. of a 2 per cent starch paste solu- 

 tion. After thorough mixing 20 cc. were drawn off, 2.5 cc. concentrated 

 hydrochloric acid were added and the mixture was hydrolyzed by boiling 

 for 2.5 hours. The solution was neutralized with sodium hydroxid 

 made up to 200 cc. with water, and the starch present was determined 

 as reducing sugars. A preliminary test showed that no reducing sugars 

 were present in the original starch paste solution. After hydrolysis 

 reducing sugars equivalent to 104 mgm. of starch per 10 cc. were found. 



The solutions were mixed on May 22 and hydrolysis carried out at 

 45 C. Reducing sugars were determined approximately 24 hours apart 

 for several days thereafter with the results shown in the Table X. 



Table X. — Amount of reducing sugars at different dates and equivalent in starch 

 [Expressed in milligrams per 10 cc] 



Reducing 

 sugars. 



Equivalent 

 in starch. 



May 23 



24, 9.30 a. m 

 24, 3.30 p. m 

 26 



27 



28 



29 



3° 



31 



June 9 



56- 516 



79. 236 



84. 518 



99. 968 



103. 092 



105. 364 



108. 866 



108. 866 



108. 866 



108. 889 



52 



73 



78, 



92. 



95 



97 



101 



101 



101 



101 



560 



689 



602 



970 



87s 



988 

 245 

 245 

 245 



267 



