THE HYDROGEN-ION CONCENTRATION, CO^ TENSION, AND 

 CO2 CONTENT OF SEA-WATER.* 



By J. F. McClendon, C. C. Gault, and S. Mtjlholland. 



DEFINITIONS AND ABBREVIATIONS. 



Since the volume of water changes with the temperature, the most 

 accurate method of expressing the results of water analysis is to take 

 the kilogram of water as the unit. The older method was to express 

 results in grams per kilogram. In volumetric analysis it is more 

 convenient to express results in grams per liter, and this method is 

 equally accurate provided the water is brought to a standard tempera- 

 ature, preferably 20°, for analysis, or the temperature is recorded in 

 each case. Since the ratios of the weights of chemical elements or 

 radicals that will enter into chemical composition with one another 

 have been established with an accuracy more than adequate for oceano- 

 graphic work, it is still more convenient to express results in gram- 

 equivalents per liter. 



A normal solution (abbreviated to n) is a solution containing in 

 1 liter the quantitj^ of substance that will combine with 23 grams of 

 sodium or 35.46 grams of chlorine. A mol-liter solution (abbreviated 

 to m) is the molecular weight in grams (mol) of the substance con- 

 tained in a liter of the solution, and may or may not be a normal 

 solution, and where confusion is likely to arise, m and not n should be 

 used. For example: if enough H3BO3 is added to a normal solution of 

 NaOH to make a 2 m solution of the former, the result is a 0.5 m solution 

 of Na2B407. In the ordinary use of m we mean more correctly the 

 formal concentration — i. e., the molecular weight is taken from the 

 ordinary chemical formula, regardless of the fact that several molecular 

 species containing the substance in question may occur in the solution. 



AVhere a particular molecular or ionic species is intended, it should 

 be designated. Thus a normal solution of hydrogen ions contains 

 1.008 grams (or for practical purposes about 1 gram) of hydrogen ions 

 per liter, regardless of the amount of hydrogen in other chemical 

 states. It is not always possible to reduce such a quantity to a 

 standard temperature, since some hydrogen ions may disappear or be 

 formed during the change in temperature. This particular case is 

 simplified by the fact that the normal concentration of H ions per liter 

 is not changed very much by the ordinary changes in temperature, as 



*This investigation was aided by a grant from the research fund of the graduate school of the 

 University of Minnesota. Wc are indebted to Dr. H. A. Lubs and Professor L. G. Rowntree for 

 some indicators. 



23 



