The Hydrogen-ion Concentration, etc., of Sea-Water. 53 



bore with a stopcock at one end and the other end fused to a short tube of 

 exactly 24 mm. bore, containing the palladized gold disk and closed with 

 a minute ungreased stopcock. About 11 to 12 c.c. of sea-water contain- 

 ing the indicator were sucked up into it and it was clamped with the 

 small tube downward (which then contained a column 30 cm. high of 

 sea-water). The mixture of CO2 and H2 was passed in at the bottom in 

 small bubbles, and the flow regulated so that the sea-water did not rise 

 into the large tube. The gas mixture escaped at the top through a 

 trap connected to the stopcock by a short rubber tube, to prevent the 

 backward diffusion of air. The gas pressure of the bubbles varied from 

 the barometer reading to the barometer + 300 mm. of water, the 

 average being barometer +150 imn. of water or about barometer -f- 

 11.5 mm. of mercury. 



We tested equilibrium by first starting with sea-water of a known 

 lower CO2 tension than the gas mixture, and making a second deter- 

 mination on sea-water of a known higher CO2 tension than the gas 

 mixture. If the final Pg was the same in both cases we concluded that 

 equilibrium had been sufficiently approximated, but in all later 

 experiments we about doubled this time. 



In making the electrometric reading the electrode was simply 

 inverted so that the sea-water ran down into the large tube, the 

 ungreased stopcock immersed in the KCl bath, and a platinum-tipped 

 wire hooked into the platinum loop to connect to the potentiometer. 

 If the reading was taken with the disk out of the water, the H2 and CO2 

 partial pressures were the same as in the original gas mixture, but if 



the disk was immersed, 11.5 was added to the H2 pressure and p ( r-— ) 



was added to the CO2 pressure in making the calculations. The 

 pressures were always corrected for vapor tension of water before the 

 final calculations. 



The gas mixture was made in the apparatus shown in figure 17, 

 holding about 25 pounds of mercury. This consisted of a liter separa- 

 tory funnel with a narrow tube and 3-way cock attached at the top, 

 and wrapped with wire passed through hot sealing-wax to increase its 

 strength. By graduating the narrow tube in tenths of a cubic centi- 

 meter and making a mark, M, near the lower end of the separatory 

 funnel to denote a total volume of a liter, it was possible to measure the 

 CO2 in parts per 10,000. The CO2 was washed with NaHCOs solu- 

 tion and the H2 with HgCl2 solution and again in H2O in wash bottles 

 shaped hke pyknometers, and passed through traps (0, fig. 17) to 

 insure atmospheric pressure. The apparatus was filled with mercury by 

 raising the levehng bulb by means of a rope passing through a pulley 

 in the ceihng. The CO2 apparatus was attached to the 3-way cock and 

 the air was washed out of the connections. The 3-way cock was now 

 turned as in figure 17, so that CO2 entered the narrow tube when the 



