G. F. Barker—Physiological Chemistry. 261 
dissolves ; and on dropping the solution into 100 times its 
weight of boiling water, saturating by chalk, filtering and 
evaporating, a syrupy liquid, browned on heating with potassic 
hydrate, reducing the copper-tests, and fermenting with yeast, 
is obiained. Chitin when treated by the same process, also 
yields glucose. 
(46.) Some experiments on the accurate determination of 
sugar by the fermentation process in an improved apparatus, 
Were communicated by PortssEvILLE to the Academy on the 
6th of December.* The copper-test often fails to give a pre- 
cipitate in liquids containing sugar ; and the saccharimeter is 
useless when the liquid to be tested is colored. The fermen- 
tation test then is the only one left; and this is accurate only 
en certain precautions are employed. The special apparatus 
vised by Poisseuille consists of a graduated tube open at 
acid gas is disengaged and. forces the liquid up the central 
tube; it. falls on ys however, on lowering the rubber tube. 
When the experiment is concluded, the gas is easily measured, 
. lated, If the contained gas be a 
_ Potash introduced through the funnel tube, the amount of 
carbonic acid evolved may be more accurately estimated by 
Sorption 
(47.) Ina subsequent not 
ea that the liquids used in 
son 
= 
he 
; 
_ *Ftature, and the gas 
; contained carbonates, 
Si after gas ceases to escape, 
