August 24, 1917] 



SCIENCE 



193 



that mannite could be isolated from practically 

 every sample of normal corn silage. The alco- 

 holic extract from dried silage yielded, on 

 evaporation, considerable amounts of mannite, 

 which after one recrystallization gave the 

 characteristic crystals melting at 168-169°. 

 That the presence of mannite can not be con- 

 sidered a local phenomenon is shown by the 

 fact that silage samples obtained from a num- 

 ber of other states in the middle west all con- 

 tained mannite. The only previous reference 

 to the occurrence of mannite in silage is in 

 a paper by Manns,'- published a quarter of a 

 century ago. In his work, however, only one 

 sample of silage was examined and the ap- 

 proximate amount of mannite found was not 

 stated. 



The following table shows the amount of 

 mannite actually isolated by us from samples 

 of silage obtained from various sources : 



It vsdll be noted that the highest percentages 

 of mannite are to be found in the sunflower 

 silage, the cane silage and the experimental 

 com silage to which sucrose had been added. 

 Evidently the mother substance of the man- 

 nite is sucrose, or more specifically its fructose 

 moiety. 



The production of mannite no doubt reaches 

 1 Illinois Ag. Exp. Sta. Bulletin, No. 7, pp. 190- 

 193. 



a maximum soon after filling the silo and then 

 some loss probably occurs, owing to further 

 bacterial activities. However, the amount of 

 mannite is still considerable when the silage 

 is several months old. 



If it is desired to prepare quantities of man- 

 nite without reference to an approximately 

 quantitative yield, the method may be much 

 simplified. The silage is put in a powerful 

 press, the juice filtered, evaporated to about 

 one sixth of its volume and two or three vol- 

 umes of alcohol added. The mannite then 

 crystallizes out, and the alcohol can be recov- 

 ered in the usual way. In this manner it 

 should be possible to extract the mannite on a 

 large scale at very little cost. The pressed 

 residue and the mother liquor could be com- 

 bined and used for feeding in place of the orig- 

 inal silage, since practically nothing would be 

 removed but the mannite and the volatile acids. 



Mannite yields a nitration product very 

 similar in properties to nitroglycerin. Accord- 

 ing to Sanford,- " Nitromannite is more dan- 

 gerous than nitroglycerin, as it is more sensi- 

 tive to shock. It is intermediate in its shat- 

 tering properties between nitroglycerin and 

 fulminate of mercury. ... It is not manufac- 

 tured upon the commercial scale." 



The reason nitromannite is not made com- 

 mercially is probably the prohibitive cost of 

 mannite. Prepared by the above method from 

 silage, mannite should be even cheaper than 

 glycerin, especially if the residues are utilized 

 as cattle feed. The thousands of tons of silage 

 used every year by the farmers of this country 

 could be made to yield a valuable by-product if 

 treated by this simple process. 



Arthur "W. Dox, 



G. P. PL.\IS.iNCE 



Iowa Agricdltukal Experiment Station 



THE NORTH CAROLINA ACADEMY OF 

 SCIENCE 

 The sixteenth annual meeting of the North Caro- 

 lina Academy of Science was held at the Univer- 

 sity of North Carolina on Friday and Saturday, 

 April 27 and 28, 1917. At 2:30 P.M. the executive 



2 Nitro-Explosives, p. 110, D. Van Nostrand Co., 

 1906. 



