66 STUDIES ON APPLES. 
shaken, and allowed to stand over night. The solution was then filtered, the lead 
nearly all removed by dry sodium sulphate, followed by dry sodium carbonate, the 
solution again filtered, and the filtrate used in the determination of sugars by polar- 
imetric and gravimetric methods. The Clerget method was used for the polari- 
metric work, calculating by the formula as modified by Tolman, ?¢ viz: 
a=) 
- = 
= 
T 
141.85-+ .062b—> 
Soxhlet’s method was used in the determination of reducing sugar as invert before 
and after inversion. The tables of Meissl and Wein were used, and the cuprous 
oxid was filtered off on Gooch crucibles and weighed as such, as described by 
Munson. ? 
DETERMINATION OF STARCH. 
Fifty grams of pulp were weighed into a clean cloth bag, the mouth of the bag 
closed with a rubber band, and the contents squeezed with the hand or lemon 
squeezer, and then washed with portions of about 25 ce of water until the washings 
amounted to about 250 ec. The last washings were in all cases neutral to litmus 
and free from reducing sugar. The starch was settled from the washings by means 
of a centrifugal machine, repeatedly washed by stirring with fresh portions of water 
and settling, and transferred to a 300-cc flask, roughly graduated at 200 cc. The 
mare from the cloth bag, separated as completely as possible by scraping with a 
spatula, was washed into the flask, and the whole made up to 200 cc. Twenty cubic 
centimeters of approximately 25 per cent hydrochloric acid (sp. gr. 1.125) was added, 
and the whole heated for three hours in, not on, the steam bath under an air con- 
denser. The mixture was then cooled, almost neutralized by sodium hydroxid, 
cooled again, made up to 300 cc, filtered, and 25 ce portions employed for the 
determination of dextrose by Allihn’s method. ¢ 
DISCUSSION OF METHOD FOR STARCH. 
Determinations by the above method are all 0.5 to 0.8 per cent too 
high, owing to bodies not starch which remain in the mare and become 
partially hydrolyzed to reducing bodies by the acid treatment. 
The supernatant liquors from the centrifugal machine always give 
a test for starch, but the quantity of starch present is very minute. 
Satisfactory results could not be obtained by the diastase method, 
because it was impossible to break all the cells. The diastase did not 
have ready access to the swollen starch grains, and the complete 
washing out of dextrin was not possible. The direct extraction of the 
sugars by alcohol was tried, but was found less convenient than the 
water extraction. 
Other methods for the determination of starch in fruits have been 
deseribed, among which the methods of Browne and Lindet are given 
as worthy of special consideration. 
“ Bul. 73, p. 70, Bureau of Chemistry, U.S. Dept. of Agr. 
b Ibid, p. 65. 
¢ Bul. 65, p. 49, Bureau of Chemistry, U.S. Dept. of Agr. 
@ [bid, p. 58. 
