66 



Papers from the Department of Marine Biology. 



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Fig. 20. — Table for conversion of millivolt readings into Ph when using a hydrogen electrode 

 connected with a 0.1 n KCl 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 Ph, 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 Ph into the digits used in the decimal system, the decimal-point being determined by the 

 integral part of the Pg. 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 sj^stems. In the upper double scale the arrow-heads denote 

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

 same quantity as H"conc. =0.2X10—*. Ph 7 was misplaced. 



