I 1419) 

 GIFT 



Issued April 19, 1911. 



United States Department of Agriculture, 



BUREAU OF CHEMISTRY Circular No. 71. 

 H. W. WILEY, Chief of Bureau. 



EXTRACTION OF GRAINS AND CATTLE FOODS FOR THE DETER- 

 MINATION OF SUGARS: A COMPARISON OF THE ALCOHOL AND 

 THE SODIUM CARBONATE DIGESTIONS. 



By A. HUGH BRYAN, A. GIVEN, and M. N. STRAUGHN, Sugar Laboratory. 

 INTRODUCTION. 



There has been some discussion among chemists as to methods of 

 determining sugars in agricultural products, such as grains, plants, 

 both dried and fresh, and cattle foods. Figures obtained by different 

 chemists on the same sample varied many times by 1 per cent or 

 more. This wide variation in results was also noted when the same 

 chemist used different methods or made a slight modification of his 

 own in a printed method. The difficulty experienced was not so 

 much in the actual determination of the sugar as in the solvent and 

 the method of procedure used to obtain an extract on which to work. 

 Again, sometimes the results obtained on one day could not be 

 duplicated on the same sample at a later date. Often this may be 

 attributed to lack of homogeneity of the sample, a fault remedied by 

 better preparation of the material, especially by finer grinding. 

 But the chief difficulty appears to lie in the changes due to enzymic 

 action during or after extraction and also somewhat to the solvent 

 and the clarification agents used. In this class of material, sugars 

 are usually present in small quantities and the other carbohydrates, 

 such as starch, pentosans, gums, etc., in much larger amounts. It 

 is because of the latter substances that the usual water methods for 

 sugar-beet analysis can not be successfully used. 



LITERATURE ON THE SUBJECT. 



The literature contains but few definite methods for the determina- 

 tion of sugars in grains, although alcohol is often spoken of as the 

 solvent used for extracting materials, especially when sugars are to 

 be obtained. Other references are found to the determination of 



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