HYDROGEN-IOiN CONCENTRATION AND ELECTRICAL 



CONDUCTIVITY OF THE SURFACE WATER OF 



THE ATLANTIC AND PACIFIC. 



By Alfred Goldsborough Mayor. 



The hydrogen-ion concentration of sea-water was determined by 

 placing 0.4 c. c. of 0.1 per cent of the red dye thymolsulphoneph- 

 thalein in 70 per cent alcohol, in a test-tube of resistance glass, 24 mm. 

 in caliber, then adding sea-water so as to make up 30 c. c. of solution. 

 The more alkaline the sea-water the more blue the solution, while a 

 yellow color appears more and more pronounced in less and less 

 alkaline sea-waters. Thus comparing the color of the solution in 

 the test-tube with a graded series of sealed tubes whose colors cor- 

 respond with known hydrogen-ion concentrations of sea-water, we 

 can readily determine the hydrogen-ion concentration of our sample. 

 A series of such tubes, ranging from 7.95 to 8.3 Ph, was standardized 

 by Professor J. F. McClendon and kindly presented to the author 

 in 1917, and I have since then restandardized these tubes at intervals 

 of two years by comparison with determinations of Ph made by a 

 Leeds and Northrup potentiometer, but the color of the tubes has not 

 changed appreciably in the interval. When not in use the tubes are, 

 however, kept in the dark to avoid the possibility of light changing 

 their color. 



The method for making up the solutions in these standard colori- 

 metric tubes is described by McClendon, Gault, and MulhoUand in 

 publication No. 251, page 44,Carnegie Institution of Washington, 1917. 



As is well known, Kohlrausch found that in the purest distilled 

 water the molecules are only slightly dissociated, so that there is 

 only about 1 gram of hydrogen ions in 10,000,000 liters of water; 

 or the hydrogen-ion concentration is about 10^ These hydrogen 

 cations are of course balanced by 10^ concentration of OH anions in 

 the water. In sea-water, however, the hydrogen-ion concentration 

 is about 10^ and the OH-ion concentration 10^ 



In order to avoid writing negative exponents, Sorensen (1909, 

 p. 28) devised the symbol "Ph" to indicate the negative logarithm 

 of the hydrogen-ion concentration. Thus 10~^ would be Ph 8 in 



Sorensen's system, and a hydrogen-ion concentration of — — ~ 



= 0.4 X 10-« would be written Ph 8.398, because 0.398 is the loga- 

 rithm of 2.5 and 8.0 is the logarithm of 10«; hence 8.0 + 0.398 = 



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