DETERMINATION OF SUGARS IN GRAIN AND CATTLE FOODS. 3 



Alcoholic digestion was then tried. By this method duplicate 

 results were obtained on different days, and there was an agreement 

 of results whether cold or hot solvents were used, although with cold 

 extraction great difficulty was experienced at times in filtering, but 

 even under these circumstances the results of the sugar determina- 

 tion in the extract, provided evaporation was guarded against, were 

 practically the same. In a study made on the " Influence of Environ- 

 ment on the Composition of Sweet Corn/' 1 the alcohol digestion 

 method was used. 



The sugar laboratory in 1905 conducted a long series of experi- 

 ments on the various methods of extraction and the solvents to be 

 used for dissolving the sugars from grain. The results confirmed 

 those of Church and Straughn on the whole. It was found that 50 

 per cent alcohol was the best solvent and that the extraction should 

 be carried on hot. At this strength it was noted that all enzymic 

 action seemed to be stopped and the extracts were easily filtered. 

 The method was tried on many dried plants, grains, and numerous 

 other materials sent to this laboratory for examination. Slight 

 modifications have been made in the procedure of the method from 

 time to time, and its final statement is given in the following section. 



STATEMENT OF ALCOHOL DIGESTION METHOD. 



Place 12 grams of material in a 300-cc graduated flask, 2 add 150 cc 

 of 50 per cent alcohol by volume (carefully neutralized), mix thor- 

 oughly, and boil on a steam bath for one hour, using a small funnel 

 in the neck of the flask to condense the vapor. Then cool. If 

 desired, allow it to stand overnight. Make up to volume with 95 

 per cent alcohol (neutral in reaction), mix thoroughly, allow to 

 settle, transfer 200 cc to a beaker with a pipette, and evaporate on 

 steam bath to a volume of from 20 to 30 cc. The presence of a trace 

 of alcohol is not harmful. Do not evaporate the solution to dryness. 

 (By evaporating the 200 cc portion in a short-necked, balloon-shaped 

 distilling flask, connected with a condenser, 75 to 80 per cent of alcohol 

 can be recovered before the material in the flask foams violently. 

 The short neck 1 inch of these flasks makes it possible to remove 

 the residue easily. The 100 cc remaining in the digestion flask may 

 be strained through a cotton bag and the alcohol recovered from the 

 liquid as just described. This is easily accomplished and results in a 

 marked saving when a large number of samples are run.) Transfer 

 the contents of the beaker or flask, as the case may be, to a 100-cc 

 graduated flask, washing thoroughly with water. Add enough of a 

 saturated solution of neutral lead acetate to produce a flocculent pre- 



iU. S. Dept. Agr., Bureau of Chemistry Bui. 127. 



1 If the material Is acid In reaction, it would be well to add Irom 1 to 3 grams of precipitated calcium car- 

 bonate to neutralize the acidity. 



