390 
TasLe IX | 
Values of pH corresponding to varying concentrations of free carbonic acid and 
bicarbonates calculated by the mass-law equation. (Table prepared by Greenfield and 
Baker.) Near-neutrality in bold-face figures. V. E. 8. 
CO., parts per million 
HCO, 
p.p.m. 
CaCO, 
0 1 2 4 6 8 10 12 14 16 20 30 | 40 
Ge SY EE as Ne i 
10 8.00 | 7.30) 7.05) 6.77 |6.60|6.48| 6.39 | 6.31/6.24/6.19 | 6.09 |5.92/5.79 
20 8.00| 7.52) 7.30|7 05|)6 89|6.77| 6.68)| 6.60/| 6.54 | 6.48 / 6.39 | 6.21) 6.09 
40 8.00) 7.70) 7.52) 7.22|)7.15|7 05) 6 96/|6.89/6.82|6.79 | 6.68) 6.51) 6.39 
60 8.00| 7.78| 7.63 | 7.48 | 7.380] 7.20] 7.12|7 04|6.98|6.93| 6.84) 6.68) 6.56 
70 8.00| 7.80) 7.67| 7.48 | 7.385| 7.25) 7.17) 7.10|7 04) 6.99 | 6.90/| 6.74/| 6.62 
80 8.00| 7.82) 7.70|7.52|7.40|7.30| 7.22) 7.15|7.10|7 05| 6.96 | 6.80) 6.68 
90 8.00) 7.84) 7.72 |7.56| 7.43 | 7.34) 7.26) 7.20|7.14|7.09|7 00) 6.84) 6.73 
100 8.00| 7.85) 7.74) 7.58) 7.47| 7.388) 7.30] 7.24) 7.18] 7.13 | 7.05) 6.89| 6.77 
120 8.00) 7.87) 7.78 | 7.63 | 7.52 | 7.44) 7.36] 7.30] 7.25| 7.20) 7.11| 6.96| 6.84 
140 8.00| 7.89] '7.80| 7.67] 7.57| 7.48 | 7.41] 7.35] 7.30| 7.25| 7.17| 7.02) 6.91 
160 8.00) 7.90} 7.82|7.70| 7.60] 7.52 | 7.46] 7.40] 7.35] 7.30) 7.22} 7.07} 6.96 
180 8.00| 7.91| 7.84] 7.72| 7.63] 7.56) 7.49| 7.43] 7.39| 7.384) 7.26) 7.12|7 00 
3. Relations of pH to putrescibility and pollution—Under ordinary 
conditions putrescibility accompanies high free CO,. This is determined 
partially, however, by alkalinity, but with a constant alkalinity, CO, 
usually varies directly with the putrescibility. In the Illinois River, with 
an alkalinity of 100 to 140 p.p.m. of CaCO,, samples show pH values 
up to 7.2 with CO, at 8 p.p.m. several days after being shipped from 
points above Chillicothe. Here the calculated values were about 3 points 
too high, which was probably because the formula gives incorrect results 
in the presence of free ammonia. The low CO, values are surprising for 
the Illinois River.* Farther down the stream, at Chillicothe, September 
6, 1919, I found pH 6.8 at the surface, and 6.9 at the bottom with green 
algae in evidence, and O, .9 c.c. per liter at the bottom, 20 feet from the 
west shore. On September 3, at Liverpool we found pH 6.9 at the 
bottom and O, .96 c.c. per liter, with the bottom fauna destroyed. The 
fact that CO, values appear to be small in this stream makes the calcu- 
lated pH values too high. In this case, therefore, pH determinations 
would appear more significant than CO, determinations. Calculated 
values should not be used except where determinations are not practi- 
cable—e. g., in working over old data. Too many waters contain ammonia 
or other disturbing substances. 
* Weston and Turner (’17) found high COs. in a polluted stream, but fail to give the 
alkalinity. 
