. Carnegie Institution of Washington publication. The Hydrogen-ion Concentration, etc., of Sea-Water. 29 be good for 5 years, provided they are kept in the dark most of the Details of the indicator method and the colorimeter that we used are given on pages 44-46, and we will now pass on to the question of the duplication of our results by the indicator method. We found the PH of sea-water to be practically independent of salinity or temperature between 20° and 30°, and all of our experiments. 67891 X ID'10 x 10-* 5 6 7891 X10-' Hydrogen ion concentration 4 5 6 7 8 9 10 ' FIG. 4.—Results
. Carnegie Institution of Washington publication. The Hydrogen-ion Concentration, etc., of Sea-Water. 29 be good for 5 years, provided they are kept in the dark most of the Details of the indicator method and the colorimeter that we used are given on pages 44-46, and we will now pass on to the question of the duplication of our results by the indicator method. We found the PH of sea-water to be practically independent of salinity or temperature between 20° and 30°, and all of our experiments. 67891 X ID'10 x 10-* 5 6 7891 X10-' Hydrogen ion concentration 4 5 6 7 8 9 10 ' FIG. 4.—Results of electrometric titration of CCVfree sea-water plus indicator with CCVfree NaOH solution. A very slight excess of HC1 is added to the water and the CO2 driven off by boiling, the water is brought about to the neutral point (PH =7), and then titrated. On the ordinate is measured the logarithm of the number of cubic centimeters of normal NaOH added to 100 of the neutral, COs-free sea-water, and on the abscissa is measured thePH. At the bottom is a scale for conversion of the PH into normality of H-ion concentration. The titrations were made on sea-water from the following sources: A, artificial sea-water containing molecular boric acid. B, sea-water from Tortugas, Florida, C, artificial sea-water containing molecular boric acid. D, Tortugas sea-water in which diatoms and other Protista had been grown in a pyrex flask for about 6 months. E, sea-water collected somewhere off Hatteras and kept in the Princeton marine aquarium about 6 years, the evapor- ation being compensated by addition of rain-water. F, artificial sea-water without any non- volatile buffer. Later experiments showed these data to be merely relative. at 10° indicate that even this drop in temperature does not appreciably affect the PH. Our values given for 0° are extrapolated from C02 data on the assumption that the PH is independent of the temperature. We found the PH of sea-water to
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