24. Electrometric Titration of Blood 
method. Measuring 1 cc. of the oxalated plasma into the electrode 
vessel and cleaning and recoating the disc takes but a few moments. 
If 0.4 cc. of 0.1 n HClis added at the start the titration back with 
alkali takes 4 minutes. If the titration is made with HCl the 
speed with which the pH rises after the addition of acid indicates 
the amount of acid that it is safe to drop in the next time. The 
following example shows the time required for titration to the 
nearest hundredth of a cc. The final two pH readings give a pos- 
sible method for estimating to thousandths of a cc., but whether 
such an estimation can be duplicated has not been determined. 
In some cases a weaker HCI solution was used to ensure more 
accurate volumetric measurement. In the following table, since 
seconds are not recorded, in some cases, two operations are placed 
opposite the same minute. 
Hour, p.m. |Burette reading. pH Hour, p.m. |Burette reading. pH 
3.49 0.1 3.54 6.96 
3.50 7.90 3.55 7.00 
3.50 0.2 3.56 7.02 
3.51 [GOs 3.56 0.31 
3.51 0.3 3:57 6.85 
3.02 6.50 4.00 6.87 
3.53 6:90 4.05 6.87 
The titration in this case took 16 minutes and the alkaline 
reserve was found to be between 0.03 and 0.031 nN. It is not al- 
ways possible to find the end-point with only four additions of 
acid, but it is only after the last two burette readings that it is 
necessary to wait for the definitive pH to be reached. In the 
following titration six additions of acid were required but the 
time spent was the same. 
Hour, a.m. |Burette reading. pH Hour, a.m. |Burette reading. pH 
10.15 0.1 10.21 7.05 
10.16 7.4 10.21 0.32 
10.16 0.2 10.22 6.95 
10317, 1220 10.25 7.05 
10.17 0.25 10.25 0.33 
10.18 7.10 10.26 6.85 
10.18 0.30 . 10.30 6.85 
