606 Philippine Journal of Science 1920 
Table 1. — Number of gram molecules of each salt reqtiired in 1 liter of 
water, to produce from 0.1 to 0.8 of a total osmotic concentration of 
approximately 0.5 atmosphere. 
Tenths of 0. 5 atmosphere. 
Ca(H2P04) 2. 
(NH4)2S04. 
K2SO4. 
1 
0. 00081 
0. 00081 
0. 00081 
2 
0.00161 
0. 00161 
0. 00161 
3- — — 
0.00242 
0.00242 
0. 00242 
4 
0. 00323 
0.00323 
0. 00323 
5 • - 
0.00404 
0. 00404 
0. 00404 
6 - 
0. 00485 
0. 00485 
0. 00485 
7 - 
0.00566 
0.00666 
0.00566 
0. 00647 
0. 00647 
0.00647 
The amount of each salt needed to produce the required par- 
tial concentrations has been approximately calculated by means 
of the van’t Hoff equation for osmotic pressure. The general 
method used in such calculations is presented in detail in the 
paper by Tottingham previously mentioned. Table 1 gives the 
calculated number of gram molecules of each salt required to 
produce from 0.1 to 0.8 of the total osmotic concentration of 
approximately 0.5 atmosphere in 1 liter of water. The cul- 
ture medium used was composed of saturated soil with water 
standing to a depth of about 3 centimeters on the surface, and 
occupied a volume of approximately 19 liters. Accordingly, the 
values given in Table 1 were multiplied by 19 to obtain the 
amount of each salt required for each of the thirty-six cultures 
of these tests. The values thus calculated are shown in Table 
2, where %iey are expressed both in terms of gram molecules 
and in terms of grams, for each of the salts. 
Table 2. — Amount of each salt, expressed in grams and in gram molecules, 
that was added to the 19 liters of water-saturated soil of each culture. 
Tenths of 0. 6 atmosphere. 
Ca(H2P04)2. 
(NH4)2S04. 
K2SO4. 
gm. mol. 
gm.^ 
gm. mol. 
gm. 
gm. mol. 
gm. 
1 
0. 0154 
3.60 
0. 0164 
2.03 
0.0164 
2. 68 
0. 0307 
7. 19 
0. 0307 
4.05 
0. 0307 
5.35 
0.0461 
10.78 
0.0461 , 
6.08 
0. 0461 
8.02 
0.0614 
14.37 
0.0614 
8.11 
0. 0614 
10.70 
0. 0768 
17.97 
0. 0768 
10. 14 
0. 0768 
13.38 
fi 
0. 0922 
21. 67 
0. 0922 
12. 16 
0. 0922 
16.06 
0. 1075 
25. 16 
0. 1076 
14. 19 
0. 1075 
18.73 
0. 1228 
28.75 
0. 1228 
16. 22 
0. 1228 
21. 40 
“ Grams of the anhydrous salt. 
