GORTNER AND Harris: FRUITS OF PASSIFLORA GRACILIS 29 
at the temperature of boiling water and then completing the 
desiccation by heating to 105° C. for several hours.* 
Depression of the freezing point, A, specific gravity, d(20°/20°), 
and total solids in 100 c.c. of juice, s, are the only direct deter- 
minations entered in the table. From these, osmotic pressure in 
atmospheres, P, and the average molecular weight of the sub- 
stances dissolved in the plant sap, M, have been calculated by the 
formulae 
P = 12.060A — 0.0214? 
M = 1890 erage (A 
1OG: = d | 
*It may not be amiss to consider the accuracy of our numerical data. Inas- 
much as we were not concerned with the absolute depression of the freezing point, 
but only with the sign and amount of variation between normal and abnormal 
juices, we have not taken all of the precautions which would be necessary were the 
absolute values desired. We have found that the degree of pressing the fruits has 
no influence on the relative values, providing that the normal is treated in the same 
manner as the abnormal. For example: a sample was pressed lightly and the freezing 
point of the expressed juice determined; then the residue was pressed so that a 
considerable amount of juice was again obtained, and this juice was added to that 
from the first pressing. The absolute values are much different but the relative value 
remains approximately the same. 
| Abnormal | Normal Difference 
' 
Light pressing. .. .. | A =0.677° C. A = 0.603° C. | + 0.074° C. 
eave eteaiee. A A =0.705° C. | A = 0.628° C. + 0.077° C. 
A constant relative value is also obtained when large samples are divided into 
two portions and the juice expressed from the second portion after an interval of 
four days, showing that holding the fruits for several days does not affect the relative 
values. The absolute and relative values of a pair of samples treated in this manner 
follow: 
| Abnormal | Normal | Difference 
. Set aoe os i Cc 
First value.......- A = 0.587° C. | A = 0.618° C, | 0.031° C. 
Four days later.... | A =0.677° C. A = 0.713° C. — 0.036° C, 
We have not corrected the depression of the freezing point for the amount of 
supercooling before freezing, for the same reason. That is, we are concerned only 
ith a relative value. We have had occasion in several instances to repeat a deter- 
mination, sometimes as much as twenty-four hours later, on the same sample of 
ie ae ee roa 3 vary from th igi oe | 7 at 
juice, and in ty ; 
J y one < See : ‘ 
Weaw bss 
