ON COLLOID CHEMISTRY AND ITS INDUSTRIAL APPLICATIONS. 81 
( Centr. Bakt.’ Par. II. 698-703) also discovered a bacterium—Bacterium 
acacie—in the gum of plum, cedar, peach, almond, and date trees. B. 
persice, found on peach and almond trees and Cedrela Australis, also pro- 
bably influences the formation of gum. Ina medium containing sucrose 
it forms a mucus or gummy matter which yields galactose and arabinose 
on hydrolysis. The gum of the fruit of Sterculia diversiola contains arabin 
and par-arabin (insoluble gum); these are stated to be produced by 
two organisms, B. acacie and B. par-arabiniwn respectively. Several 
varieties of the latter have been isolated and they produce par-arabin 
(v.e., insoluble mucus) when grown under suitable conditions. 
In the manufacture of sugar the juice sometimes becomes extremely 
viscous and very difficult to filter. This has been found to be due to an 
organism, Bacillus levaniformis, which forms a viscous or gummy product 
known as levan ; this yields only levulose on hydrolysis (Greig Smith and 
Thomas Steel,‘ Jour. Soc. Chem. Ind.’ 1902, 1381, 1904, 105). The product 
differs from that formed during the ‘ gummosis’ disease or ‘gumming’ 
which takes place within the sugar-cane, the fibro-vascular bundles becom- 
ing filled with a viscous gum to which the name ‘ vasculin’ has been 
applied by Cobb (‘ Agric. Gaz. N.S.W.’ 1893, 777). Levan dissolves 
in cold water, but on dilution the sol becomes turbid and opaque, although 
no separation takes place either on standing or on centrifuging. It is 
not precipitated by basic lead acetate, but it forms an adsorption product 
with BaO containing 19-85 per cent. of the latter, similarly to starch. 
Gum appears, however, to be present normally in unripe cane-juice, 
as this after evaporation thickens with acetic acid and on cooling sets 
to a solid mass. The amount of gum in the molasses was found to be 
8 per cent. (Hazewinkel, ‘ Archiv Suikerind. Nederl. Ind.’ 1910, 18, 4445). 
Beet-juice sometimes becomes mucilaginous owing to a peculiar fer- 
mentation which is induced by an organism, Leucostoccus mesenteroides, 
resulting in the conversion of the sugar into a carbohydrate known as 
dextran or fermentation gum. Two varieties of this carbohydrate appear 
to be formed, one of which is soluble, the other insoluble in water. Bacillus 
gummosis also develops in sugar solution, forming a gum having the com- 
position represented by the formula C,;H;,0; (Happ). It is remarkable 
that in both these cases at a certain period in the growth of the organism 
it swells up enormously, diffusing itself through the liquid, thus forming 
a mucilaginous fluid. 
Ropiness also occurs in beer, milk, wine, infusions of Tpecacuanha, 
Radix Althea, Senegw, Folia Farfare, Folia Digitalis, &c., from time 
to time ; in all cases the cause has been traced to the action of micro- 
organisms. (For further information on this subject see Lafar, ‘ Micro- 
organisms and Fermentation,’ pp. 270-278.) 
Hemicelluloses. 
The hemicelluloses constitute a group of closely related substances 
contained in the seeds, roots, &c., of various plants, the cellular tissues of 
certain plants consisting largely of these products intimately associated 
with cellulose, to which they are also allied. 
On heating with water, some of the hemicelluloses swell up enormously 
and pass into the state of colloidal sols, which are extremely viscous and 
which revert to non-rigid gels after keeping for a few days. 
1917. G 
