EXPERIMENTS WITH POTATOES. 
17 
CHEMICAL. SECTION. 
The following method (Sachsse’s) was used for de¬ 
termining the starch in potatoes : 
Ten grams of potatoes, cut from a section through 
the center, were grated fine and pulverized in a mortar, 
and 200 cubic centimeters of water added, 20 cubic centi¬ 
meters of hydrochloric acid (sp. gr. 1.125), and the 
flask heated 100° C. on a water bath for three hours. 
The flask is provided with a glass tube, three feet long 
and one-fourth inch in diameter, fastened in the cork, to 
act as a condenser. After cooling, enough sodium hy¬ 
droxide is added to nearly neutralize the acid, and the 
liquid made up to 500 cubic centimeters. An alkaline 
copper solution, made as follows : Solution No. 1 con¬ 
tains 173 grams of Rochelle salts and 125 grams of caus¬ 
tic potash, dissolved in 500 cubic centimeters of water. 
Solution No. 2 contains 34.69 grams crystalized copper 
sulphate, dissolved in 500 cubic centimeters of water. 
Five cubic centimeters of No. 1 and five cubic centime¬ 
ters of No. 2 are mixed in a casserole and heated to boil¬ 
ing, the boiling being continued while the solution of 
dextrose is being added from a burette, until all the cop¬ 
per is precipitated as a sub-oxide. The end reaction be¬ 
ing tested for copper by acetic acid and ferrocyanide of 
potassium. The amount of dextrose multiplied by 9-10 
gives the weight of starch, according to the formula 
0 6 H 10 O 5. The analyses were completed about 
the 1st of January, 1889. 
COMPARATIVE METHODS. 
A number of methods of determining starch 
were tried, for the purpose of comparison of re¬ 
sults. It has long been claimed by some chemists 
that the direct heating of agricultural products, as pota¬ 
toes, grain, etc., with acids, changes the cellulose into 
dextrose, and may render some of the ash ingredients 
soluble, and that in that condition they might afterward 
precipitate the copper solution. In order to test the ac¬ 
curacy and also the convenience of the many methods pro- 
