76 BOTANICAL GAZETTE [JANUARY 
the quantity of principal salts present, and by means of their 
osmotic equivalents to calculate roughly the osmotic value of the 
sample of sea water used in this work. 
PFEFFER has calculated the osmotic equivalents of solutions of 
the common salts, giving the atmospheres of pressure exerted by 
1 per cent solutions made up on the basis of 1 gm. of salt in 100 ccm. 
of solution. The recalculation of the osmotic value of NaCl by 
RENNER already referred to has given a considerably increased 
value for this salt. There has been no similar recalculation for the 
other sea salts known to the writer, but since the quantities of salts 
other than NaCl are small, but a relatively small effect would result 
from their correction. MgCl, present in second largest quantity, 
namely, 0.32 per cent in the sample of water here concerned, was 
recalculated by the writer in a very approximate way from freezing 
point values given in LANDOLT-BORNSTEIN-RotTH’s (13) tables for 
the temperature of 22° C., and a value somewhat greater than that 
given by PreFreR was obtained. The values here discussed are 
brought together for convenient reference in table I. A glance at 
TABLE I 
“Challenger” Quantity i Atmos. press. —_ Qemotic values | Osmotic values 
Salts | proportions sample used ferent sol. “"éeer | "recalculated 
NaCl -.| O:777 ha. =o = 2, = per cent <6. — =13.8 atmos.} 17.30 atmos. 
MgCl... ‘ae. oe 85 = 0.3 X4 = 1.6 2.16 
re 0.048 X 2.93 = a4 Sega = 0.3 0.30 
Cas)... = 0.036X2.93 = 0.10 © X 2.00( ?) = 0.2 ©. 20 
K,SQ,....| 0.025X2.93 = 0.07 “a.92 = 0.2 ©. 20 
| 0.905 2.gopercent equals . 16.1 atmos.| 20.16 atmos. 
this table shows that if PrerreR’s osmotic values are accepted, the 
osmotic pressure of sea water falls short of that contained in the 
experiment described by a ratio of 16.1 to 22.3. Onrecalculating, 
the total pressure derived from analytical data exceeds 20 atmos- 
pheres. 
In this connection it is of interest to compare with these values 
those obtained by GarRey (10), using the freezing point method. 
As a result of several freezings, he concluded that for the water of 
the basin of the United States Fish Commission the average lower- 
