HEMICELLULOSES i8i 



cellulose to which they assign the formula sCgHioOs + 2H2O 

 (see also p. 154). 



MANNAN. 

 Mannan occurs in salep mucilage, and has been extracted 

 by Ritthausen * and Effront f and others from wheat and 

 barley. Mannans are also found in Penicillium glaiiciim, 

 ergot, in the roots of several plants such as asparagus, chicory 

 Helianthus and Taraxacum ; also in the wood and leaves of 

 many trees, such as lime, chestnut, apple, mulberry, certain 

 Oleaceae and conifers ; the so-called reserve celluloses and 

 hemicelluloses contained in seeds of Palmaceae, LiHacese, 

 elder, cedar, and larch, and many other plants, are also very 

 rich in mannans. Evidence for the occurrence of a manno- 

 galactan in the American white oak has been furnished by 

 O'Dwyer.J 



The mannan of the vegetable ivory, the endosperm of the 

 seeds of Phytelephas macrocarpa, may be prepared in 8-10 per 

 cent yield by treating the ground ivory meal with five times 

 its weight of 10 per cent caustic soda for half an hour ; § the 

 black alkaline liquid is filtered through copper gauze, and the 

 residue after washing with water is boiled for half an hour 

 with five times its weight of 20 per cent caustic soda ; the 

 solution is then precipitated by the addition of one-third of 

 its volume of rectified alcohol spirits and the precipitate 

 after washing with the same precipitant is dissolved in hot 

 water ; after adding sufficient acetic acid to render just acid, 

 the solution is boiled for a few minutes when the mannan is 

 precipitated as a white powder. 



The mannan of vegetable ivory was shown by Baker and 

 Pope II to be contaminated with laevulo-mannan and galacto- 

 mannan. 



It was shown by Pringsheim ]f that ivory nut shavings were 



* Ritthausen : " J. prakt. Chem.," 1867, 102, 321 ; and " Chem. 

 Zeit.," 1897, 21, 717. 



t Effront : " Compt. rend.," 1897, 125, 38, 116. 



I O'Dwyer : " Biochem. Journ.," 1923, 17, 501. 



§ Patterson : " J. Chem. Soc," 1923, 123, 1139 ; Schmidt and Grau- 

 mann : " Ber. deut. chem. Gesells.," 1921, 521, 1867. 



II Baker and Pope : " J. Chem. Soc," 1900, 77, 696. 



t Pringsheim : " Zeit. physiol. Chem.." 191 2, 80, 376. 



