339 



never ruffled. In the 35 cc. of air there was found a per- 

 centage of CO,, = 0.03 "/0. 



The percentage of carbonic acid in the atmospheric air 

 used in these experiments was found by two analyses to be 



0.06 ^/o or 0.055 %. 



It appears that seawater may be shaken with an equal 

 volume of air and absorb ^/з of the carbonic acid contained 

 without the tension being perceptibly altered, and I therefore 

 adopted the following method as perfectly reliable: The sample 

 of water is taken into a bottle of 1 liters capacity and provided 

 with a thermometer. So much air as will be sufficient for an 

 analysis is left above the water, and the bottle is shaken vigour- 

 ously for 2 minutes. The air is then transferred to the analysis- 

 apparatus and the percentage of carbonic acid determined. The 

 percentage found is the tension of carbonic acid in the sample 

 of water at the temperature observed afler the shaking. For 

 the sake of convenience I take the Vioooo of the normal atmos- 

 pheric pressure as a unit. A tension given in the present 

 paper as 2.3 means therefore 0.023 °/o of the normal atmo- 

 spheric pressure. 



I hope that 1 shall be able to show in the present and the 

 following paper that researches on the tension of carbonic acid 

 in natural waters, and especially in the ocean, will very pro- 

 bably give important results, when they are extended over a 

 larger area of the globe. For the sake of those who might 

 wish to take up this subject I shall now proceed to give very 

 full particulars regarding the most suitable methods, the pre- 

 cautions necessary in their application and the degree of accuracy 

 desirable and obtainable. 



The samples of water are taken into glass-stoppered bottles 

 of one liters capacity. If the sample must be kept for some 

 time I recommend the use of resistance-glass which has the 



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