EXPERIMENTS WITH POTATOES. 
19 
This shows that for three hours the starch was practi¬ 
cally what was obtained before (17.75 ), and that for 
longer time there was diminution in the per cent, of 
starch. 
Second —In regard to heating the potatoes under pres¬ 
sure, all the other conditions being alike : 
Strong glass beer bottles were used, and the cork 
securely fastened so as to admit of no escape of vapor; 
they were placed in water bath and heated as before de¬ 
scribed. 
Time of heating. Per cent, ot starch. 
3 hours_17.80 
6 hours_18.40 
9 hours_18.00 
This shows that putting the potato under pressure 
while heating increased the per cent, of starch, or possi¬ 
bly it renders other matters soluble, that assist in re¬ 
ducing the copper solution. 
Third —Potato starch was made by grating the pota¬ 
toes and pulverizing them in a mortar, and washing out 
the starch upon a fine linen filter; the starch was dried 
at 100° C. Three-tenths of a gram was taken and treated 
as in Sachsse’s method for starch. 
Time of heating. Per cent, of starch. 
3 hours_.309 grams 
8 hours_.306 grams 
12 hours_.304 grams 
Theoretically there should be only 3-10 gram, and the 
small error may be due to the starch not being absolutely 
pure. 
Fourth —The potatoes were washed clean, dried with 
a towel and placed in a solution of common salt, in which 
some would sink and others float. The specific gravity 
of the solution ascertained with a hydrometer, which 
would give the specific gravity of potatoes. The tables 
giving the specific gravity and the corresponding per cent, 
of dry matter, and also of starch, varied so much that no 
