56 



Papers from the Department of Marine Biology. 



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FIG. 20. Table for conversion of millivolt readings into P H when using a hydrogen electrode 

 connected with a 0. 1 n KC1 calomel electrode. A correction for the concentration of hydrogen 

 gas must be added to millivolt reading before using the table. The large figures from to 10 

 denote P H , the figures from 338 to 950 denote millivolts, and the temperature lines are 

 designated at the bottom. The double scale at the top is for conversion of the fractional part 

 of P H into the digits used in the decimal system, the decimal-point being determined by the 

 integral part of the P H . We see no advantage in the decimal system over the logarithmic 

 (PH) system of expressing H-ion concentration, but have added this scale for comparison of 

 results expressed in the two systems. In the upper double scale the arrow-heads denote 

 tenths of a P H and the lower scale the digits of the decimal system. Thus P H =8.7 is about the 

 same quantity as H'conc. =0.2 XlO~ 8 . PH 7 was misplaced. 



