ANNUAL REPORT, 1945-46 27 



The quantitative evaluation of this factor affords, for the first time, an ac- 

 curate measurement of the specific heat of starch suspensions and permits the 

 measurement of the heat of gelatinization. Preliminary experiments have indi- 

 cated that this may be much lower than previously reported in the literature 

 and may even be non-existent. Further experiments now in progress are ex- 

 pected to throw some light on the mechanism of starch gelatinization. 



The Chemical Investigations of Hemicelluloses. (Emmett Bennett.) During 

 the past year some of the data reported previously have been checked and cer- 

 tain difificulties encountered have been eliminated. The acetylation procedure 

 generally used in this investigation would not produce the diacetate of xylan 

 in the hemicellulose from rye straw. It was necessary to hydrate this material 

 and to dehydrate it without exposure to air just prior to acetylation. In this 

 way, the theoretical acetyl content could be obtained almost completely. 



Results obtained so far in this investigation would seem to indicate that an- 

 hydroxylose and a hexuronic acid anhydride account for approximately 85 and 

 90 percent of the hemicelluloses of maize cobs and rye straw respectively. The 

 proportions of these two constituents would correspond to a chain of anhydroxy- 

 lose units approximately 30-32 units in length and terminating in a hexuronic 

 acid group. The sugars seem to have the pyranose structure and to be connected 

 to each other through a beta-linkage. A hexose was present to a slight extent in 

 both hemicelluloses, while 1-arabinose was detected in maize cob hemicellulose 

 only.i 



Studies on the Quantitative Estimation of Hemicelluloses. (Emmett Bennett.) 

 The success of the method being tested for the quantitative deterrrtination of 

 hemicelluloses depends upon the production of a holocellulose which contains all 

 the hemicellulose. The percentage recovery of furfural and the color of the 

 holocellulose were used as an index for the preparation of a holocellulose fraction 

 which would be suitable for the quantitative extraction of hemicelluloses. A 

 procedure suitable for the determination of this fraction in non-woody plants has 

 been standardized. Furfural determinations on holocellulose from five different 

 plants indicate that from 95 to 99 percent of the furfural in the original tissue 

 can be recovered. 



Nitrogenous residues seem to be the chief contaminants of holocellulose pre- 

 pared from cereal grasses. In some cases 50 percent of the total nitrogen may be 

 retained. 



Preliminary extractions of hemicelluloses from holocellulose with 1.25 percent 

 sodium hydroxide and the aid of a Waring blendor for periods of different length, 

 yield the same results. This is believed to be indicative of a complete extraction 

 of the more loosely bound hemicelluloses, since the residual material still bears 

 compounds which will 3'ield furfural. 



Extracts were oxidized under definite conditions by means of a solution of hot 

 chromic acid. The amount of material oxidized was determined colorimetrically 

 by means of a spectrophotometer. Calibration lines were constructed from data 

 obtained by oxidizing pure solutions of glucose and xylose under definite con- 

 ditions. From such lines and the percentage transmission of an unknown solu- 

 tion, the percentage concentration can be determined as xylose or glucose. 



The Investigation of Agricultural Waste Products. — 1. The Chemical In- 

 vestigation of Lignin. (Emmett Bennett.) The results of the study of the 

 effects of large quantities of pure lignin upon the aerobic decomposition of plant 

 materials appear in the forthcoming volume of the Proceedings of the American 

 Society for Horticultural Science. 



^The results have been accepted for publication by the Journal of Agricultural Research. 



