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



61 



gas-bubbles rise from the little sea-water above the mercury. We 

 prefer the half-normal solution, however, because it is completely 

 neutralized and washed out at the end of an experiment by the sea- 

 water from the trap T, and it is only necessary to grease the stopcocks 

 before another determination. In reading the gas-volume after ab- 

 sorption it is necessary to level the bulb, reckoning -^ of the NaOH 

 column as mercury. 



The calculation of the results are a little compUcated, but it was 

 impossible to make a conversion table possessing great accuracy. We 

 found the gas burette in one apparatus correct for the upturned 

 meniscus, but it was therefore incorrect for measuring the water 

 between the upturned and downtumed menisci. A small correction 

 in cubic millimeters given in the following table must be added to the 

 volume of water above the mercury as measured by the scale on the gas 

 burette B, depending on the total length of this scale in centimeters. 



In order to make certain corrections, it is necessary to know the 

 absorption coefficient of neutralized sea-water for CO2. Since the 

 half-normal HCl added to the sea-water has about the same absorption 

 coefficient for atmospheric gases as neutralized sea-water, we assume 

 that it does not seriously affect the absorption coefficient of the sea- 

 water when 1 c.c. is added to 10 c.c. of the latter. Bohr's data were 

 plotted for this purpose on the assumption that the absorption coeffi- 

 cient of neutralized sea-water for CO2 is the same as that of NaCl 

 solution of the same CI content. The isotherms form characteristi- 

 cally curved lines, but in the small portion included in figure 22 the 

 curvature was hardly perceptible and was later obliterated by the use 

 of a straight-edge in inking-in the pencil drawing. 



It is necessary to know capillary depression of the mercury in B, 

 which is easily determined by opening all stopcocks and measuring the 

 vertical distance between the mercury meniscus in B and the plane of 

 the mercury surface in the leveUng bulb. A mercurial barometer with 

 glass scale is preferable, and the capillary depression must be sub- 

 tracted from the reading. 



In the following tablefor reducing the final gas-volume toO°, 760 mm., 

 and dryness, the temperature correction for the glass scale barometer 

 is included. The moist gas-volume at designated temperature and 



