Jan. IS. 191S Changes in Sweet Potatoes During Storage 335 



dried for 20 hours at 60° C. and subsequently were allowed to stand in 

 the laboratory at least 48 hours, in order that the material might come 

 to a state of moisture-equilibrium with the air. The thimbles were then 

 weighed and the material was quantitatively transferred to a mortar and 

 ground to a fine powder. The starch was determined as glucose by the 

 acid-hydrolysis method (Wiley, H. W., et al., 1908) in two accurately 

 weighed fractions of this powder, each representing about one-half of the 

 extracted residue before it was ground. 



Sugar. — For the determinations of sugar, samples of 25 gm. were 

 washed into 250 c. c. volumetric flasks with enough neutral 70 per cent 

 alcohol to bring the volume up to about 200 c. c. About i gm. of calcium 

 carbonate was added to each flask. The flasks were then boiled in the 

 water bath for 10 minutes and on the following day were cooled to 20° C. 

 and filled to the mark. After being stoppered they were allowed to 

 stand for a few days, during which they were occasionally shaken to insure 

 uniformity of concentration of sugars in the solid and the liquid portions 

 of the contents. The solutions were subsequently treated essentially 

 according to the method described by Bryan, Given, and Straughn (191 1). 

 Reducing sugars and total sugars were determined according to the 

 method of Allihn (Wiley, H. W., et al., 1908). The cane sugar was 

 calculated from the difference between the total sugar and the reducing 

 sugars. 



Temperature. — The temperature of the two storage rooms was 

 recorded by thennographs. The curves obtained in the warm storage 

 room were integrated with a planimeter to obtain the average weekly 

 temperatures, which are given in Tables I and II. The average weekly 

 temperatures for the cold-storage room were written down from inspec- 

 tion of the records, since the tracings in this case were practically straight 

 lines. 



EXPERIMENTAL DATA 



The data showing the seasonal changes in the composition of sweet 

 potatoes stored in the farm cellar at a temperature varying mostly 

 from 11.7° to 16.7° C. are given in Table I. The percentages of car- 

 bohydrates have all been referred to the original moisture content of 

 the potatoes. The loss of solid matter by respiration had, of course, to 

 be disregarded. The numbers expressing the total content of carbo- 

 hydrates were obtained by the addition of the numbers representing the 

 starch (as glucose) and the total sugars (as glucose). 



