1922] NEWTON & GORTNER—TISSUE FLUIDS 443 
expected under this assumption, but it is preferred to use the 
theoretical value until further data on this point are available. 
It is assumed that the magnitude of the excess depression is a 
measure of the quantity of water held in such a way as to be unavail- 
able for the solution of the sugar. The values obtained may be 
calculated to percentage “bound” water. This represents the 
total water of hydration of all the substances in the sap, but has 
been found to correspond so regularly with the content of hydro- 
philic colloid as to indicate a close relationship. It seems probable 
that in most cases the water bound by substances other than colloids 
is of minor importance. 
In table I are reported the data for a number of the samples of 
expressed juice included in table I of the preceding paper, and in 
addition for a series of gum acacia sols prepared by weighing out 
the necessary quantities of highly purified gum acacia and distilled 
water. The percentage of total solids, as read directly by the 
refractometer, is given in column 2. The values for viscosity, 
recorded in column 3, were determined by a viscosimeter of the 
Ostwald type, in a constant temperature bath at 25° C.; the figures 
are the number of seconds required for 3 cc. to flow through a 
capillary tube, through which the same quantity of distilled water 
flowed in 204 seconds. In column 4 is given A, the freezing point 
depression of the freshly expressed juice; in column 5 A,, the 
freezing point depression after the addition of the sugar; in column 
6 A.—A, the actual additional depression due to the added sugar; 
in column 7 A,—(A+K,,), the amount by which the depression 
found on addition of the sugar is in excess of that expected on 
theoretical grounds. As previously noted, it has been assumed that 
sucrose forms sucrose hexahydrate in solution, and therefore Kp, 
the molecular constant for the depression of the freezing point, has 
been taken as 2.085° C. instead of the usual 1.86° C. The percent- 
age ‘“‘bound” water, given in the last column of the table, is con- 
veniently calculated from the value for actual additional depression 
due to the added sugar (A.—A). The calculations involved will be 
made clear in the following example, using the first item in the table. 
1.86°=A due to 1 mole dissolved in 1000 gm. water, but 1 mole 
sucrose combines with 6 moles water. Thus 1 mole sucrose dis- 
