Oct. 1, 1919 Notes on the Composition of the Sorghum Plant 1 9 



water for 1 5 minutes, filtered from the insoluble portion, and the soluble 

 portion precipitated by alcohol. The results were as follows: 



Total alcohol precipitate from 500 cc. juice 4.30 gm. 



Percentage of juice o-399- 



Composition of precipitate : 



Proteins (NX6.25) 12.00 per cent. 



Ash 22.22 per cent. 



Gums (by difference) 65.28 per cent. 



Solubility of precipitate: 



Insoluble in boiling water 23. 87 per cent. 



Soluble in boiling water, precipitated by alcohol 26.40 per cent. 



Soluble in boiling water, not precipitated by alcohol 49-73 per cent. 



No doubt most of the portion that does not redissolve in hot water con- 

 sists of protein that was coagulated by the alcohol and of fine particles of 

 pith and fiber that were suspended in the original juice. The high ash 

 content is probably due to the bases that are always associated with the 

 true gums. There is a possibility that calcium citrate constitutes a por- 

 tion of it, since this salt is rather insoluble in alcohol. 



That portion of the alcoholic precipitate which redissolved in 

 water was hydrolyzed for 15 hours Avith iV/5 sulphuric acid. The acid 

 was removed with barium hydrate and the filtrate tested for xylose, 

 arabinose, and galactose. The osazones were formed and compared with 

 those from the pure sugars. The mucic acid test was employed for galac- 

 tose, and the Bertrand reaction (j, p. loi) for xylose. The results are as 

 follows : 



Bertrand test for xylose — 



Mucic acid test for galactose -{- 



Osazone for galactose + 



Osazone for arabinose — 



These results indicate the presence of galactan in the gums. It was 

 surprising to find no pentoses in this solution, since they should be 

 present whether the alcoholic precipitate consists of true gums or pectic 

 substances. In the belief that the failure to find pentoses was due to the 

 osazone method of detection and not to their absence from the solution, 

 they were sought for by the phloroglucid method. No more sorghum 

 juice being available, some sorghum sirup was diluted with water, the 

 gums precipitated and reprecipitated with alcohol, dried, weighed, and 

 analyzed, with the following results: 



Ash 1909 per cent. 



Pentosan 376 per cent. 



The nitrogenous constituents were studied in the juice preserved by 

 freezing. The writers know of no previous work on this subject. Some 

 rather careful work has been done with sugar-cane juice, and that is the 

 only basis for comparison in the present instance. 



