338 PLANT AND ORGANIC CHEMISTRY 
sidered by him an isomer of grape sugar; but it was shown 
by Kiliani to possess the formula C 5 H 10 O 5 . Although the 
natural arabinose turns the plane of polarized light to the right, 
on account of its relation to /-glucose, it should be considered 
as a left compound. Artificially, the right-turning arabinose 
may be made from glucose by a building-down process, as it 
were, discovered by Wohl. This process consists in passing 
from a sugar richer in carbon atoms to one containing fewer 
carbon atoms. 
On boiling bran, wood, jute, straw and like substances, 
with acids, pentosan compounds are obtained. In some cases 
they may be isolated, or their presence may be proved by the 
furfurol reaction. This is a well-known test for their identi¬ 
fication. If compounds belonging to the hexose groups be 
heated with acids, they yield kevulinic acid (CH 3 COCH 2 CH 2 
C 0 2 H). On the contrary, pentose compounds, by distillation 
with strong acids, yield furfurol compounds, which easily 
pass over with steam. 
The portions of the coffee berry insoluble in water, when 
distilled with dilute hydrochloric acid, yield furfurol alde¬ 
hyde, which demonstrates the presence in the coffee of a com¬ 
pound belonging to the pentosans. 
By warming with phloroglucin and hydrochloric acid, the 
pentosans, as also all compounds which, by decomposition, 
yield sugar compounds containing 5 carbon atoms, give a 
cherry-red color reaction. 
Ribose, a colorless syrup, and xylose, wood sugar, are 
isomeric with arabinose. 
Rhamnose, formerly erroneously called “ isodulcite, ” is 
a methylpentose. It is obtained from datiscin by hydrolytic 
reaction, and by the same method from different glucosides. 
Fucose, obtained from the sea-tangle or grass wrack, is 
isomeric with rhamnose, also chinovose, which is derived from 
chinovite. The alcohols, xylite and adonite, belonging to the 
sugars xylose and ribose, correspond to arabite, the alcohol of 
the sugar arabinose, and are inactive. 
The remaining series of compounds, which chemically 
belong to the same class as the sugars, are designated as 
