28 Electrometric Titration of Blood 
flow about 5 minutes or more before beginning to titrate back 
with NaOH. The following table gives the minutes required, 
as shown by the rise in pH to an equilibrium. 
Min. pH Min. pH 
1 4.75 5) 5.40 
2 5.15 6 5.40 © 
3 5.30 7 5.40 
4 3.30 8 5.40 
Determinations may be made on 0.1 to 0.5 cc. of plasma using 
0.01 n HCl or NaOH. If the plasma does not cover the disc, 
it must be diluted with 1 per cent KCl solution until it covers 
the disc. | 
No undoubted cases of acidosis have yet been studied although 
I have agreed to do so. Plasma of lowered alkaline reserve was 
obtained by allowing the CO, to escape from the blood before 
centrifugation. ‘Two such experiments gave the alkaline reserve 
to equal 0.017 and 0.02 N respectively, but the alkaline reserve 
before exposure to air was not determined. As may be seen in 
the above pages, the normal seems to be about 0.03 if pH = 7 
is taken as the end-point. I do not, however, know the average 
normal and merely suppose certain samples to be normal since 
they were taken from patients without symptoms of acidosis. 
Van Slyke and Cullen give the average normal chemically bound 
CO, as 65 volume per cent, which I interpret as 0.029 n (since 
22.4 liters of CO: dissolved in 1 liter of 1 n NaOH would make a 
1 n solution of NaHCQ;). 
It was found that plasma kept for hours at room temperature 
and then placed in the refrigerator over night presented no 
difficulties the next day. Plasma kept 36 hours at room tempera- 
ture poisoned the hydrogen electrode so that no readings could be 
made. No HS was detected in this plasma, and the substance 
affecting the electrode was not determined. 
My thanks are due to members of the staff of the University 
Hospital for drawing samples of blood. 
