THE VOLATILE PART OF PLANTS. 67 
albuminoid substances, the fats, the sugar, and dextrin, are brought 
into such a condition that simple washing with alcohol or water suf- 
fices to remove them completely. The chief part of the phosphoric 
and silicie acids is likewise rendered soluble. The starel-grains 
are not affected, neither does the cellulose undergo alteration, cither 
qualitatively or quantitatively. In fact, this treatment serves excellently 
to isolate starch-grains for microscopic investigations. Besides starch 
and cellulose nothing resists the action of alcoholic potash save portions 
of cuticle, gum, and some earthy salts. 
When the digestion is finished, it is advisable, especially in case the 
substance is rich in fut, to bring the contents of the tube upon a filter 
while still hot, as otherwise potash-salts of the futty acids may crystallize 
‘out. It is also well to wash immediately, first, with hot absolute alcohol, 
then, with cold alcohol of ordinary strength, and finally, with cold wa- 
ter until these several solvents remove nothing more. In the analysis 
of matters which contain much mucilage, as flaxseed, the washing 
must be completed with alcohol of 8 to 10 per cent, to prevent the 
swelling up of the residue. 
The filter should be of good ordinary (not Swedish) paper, should be 
washed with chlorhydric acid and water, dried at 212°, and weighed. 
When the substance is completely washed, the filter and its contents 
are dried, first at 120°, and finally at 212°. The loss consists of albumi- 
noids, fat, sugar, and a part of the salts of the substance, and when the 
last three are separately estimated, it may serve to control the estima- 
* tion, by elementary analysis, of the albuminoids, 
The filter, with its contents, is now reduced to powder or shreds, and 
the whole is heated with water containing 5 per cent of chlorhydric 
acid until a drop of the liquid no longer reacts blue with iodine. The 
treatment with potash leaves the starch-grains in such a state of purity 
from incrusting matters, that their conversion into dextrin proceeds 
with great promptness, and is accomplished before the cellulose begins 
to be perceptibly acted upon. By weighing the residue that remains 
from the action of chlorhydric acid, after washing and drying, the 
amount of cellulose, cork, lignin, gum, and insoluble fixed matters is 
found. By subtracting these from the weight of the substance after 
exhaustion with potash, the quantity of starch is learned with great ac- 
curacy. The only error introduced by this method lies in the solution 
of some saline matters by the acid. The quantity is, however, so small 
as rarely to be appreciable. If needful, it can be taken into account by 
evaporating the acid solution to dryness, incinerating and weighing the 
residue: By warming with concentrated malt-extract at 132°, the starch 
alone is taken into solution, and no correction is needed for saline mat- 
ters. If it is wished to determine the sugar produced by the transfor- 
mation of thestarch, a weaker acid must of course be employed. Incase 
of mucilaginous substances, the starch must be extracted by digestion 
with a strong solution of chloride of sodium, with which the requisite 
quantity of chlorhydric acid has been mixed, and the residue should be 
