2 Electrometric Titration of Blood 
outer end dips into a reservoir of saturated KCI solution con- 
nected with the saturated KCl-calomel electrode. The electrode 
proper is of gold coated with palladium black and connected to 
a platinum wire fused in one of the glass tubes. The wire is 
connected with the potentiometer. Lead glass was not used in 
sealing in the platinum wire owing to danger of reduction of lead 
thus making the platinum brittle. The 1 mm. glass tube was 
narrowed at one end so that the platinum wire would just go 
through. After insertion of the wire, a moment’s heating in a 
tiny blast flame sealed it in the end of the glass tube. About 
12 mm. of the platinum wire were allowed to protrude and a 
gold bead was fused on the end of it. This was accomplished by 
holding the end of a gold wire in a small Bunsen flame until a 
bead of the proper size formed, and advancing the end of the 
platinum wire into the flame until it touched the gold bead, then 
withdrawing it quickly. The gold bead was hammered to a dise. 
The finished electrode was put in place so that the gold disc hung 
down in the electrode vessel. Another glass tube, 1 mm. bore, 
was drawn to a dropping tip inside the electrode vessel and the 
outer end connected with a rubber tube of 1 mm. bore closed by 
a Langenbeck clip and connected with a 1 cc. pipette graduated 
in hundredths and filled with 0.1 N HCl or NaOH and used as a 
micro-burette. A glass tube of about 3 mm. bore served for the 
admission of hydrogen. 
In setting up the apparatus, the frame was set in place and 
weighted with lead so as to remain in position. 1 cc. of plasma 
was run into the electrode vessel and it was put in place by insert- 
ing the axle of the cork pulley in the vertical slot in the frame 
made to receive it. The cork pulley was connected by means of a 
string belt to a Tiffany motor. The micro-burette and connect- 
ing tube were filled with HCl and the rubber tube was filled with 
a saturated solution of KCl. The gold disc was coated with 
palladium black by electrolysis with a 2 volt current and a fairly 
strong solution of palladium chloride. When this solution be- 
came yellow it was evaporated until it appeared light brown in a 
layer about 2 cm. thick. The electrode was sprayed a moment 
with distilled water and the 10 mm. glass tube containing the 
four smaller tubes carefully inserted through the hole in the 
wooden frame and the hole in the electrode vessel. The 10 mm. 
tube fits tight in the hole in the frame and, owing to the downward ~ 
