1915 J 



MERRILL DISTILLED "WATER 467 



desired for the most part. The method employed, therefore, 

 was to remove from the carefully stirred solution in the 

 tumbler a 25 cc. sample with a pipette of the same capacity, 

 the latter having previously been rinsed with the solution. 

 Using exactly the same amount for each determination further 

 reduced any possibility of error due to unequal dilution in 

 the conductivity cell. Between readings the pipette was kept 

 almost entirely immersed in redistilled water in a tall cylinder 

 attached to a stand in the water bath. After carefully pour- 

 ing the sample back into the tumbler, in case further readings 

 were to be taken, the cell was rinsed twice with doubly dis- 

 tilled water and rapidly drained before taking the next read- 

 ing, whether of the same or of a different culture. Any 

 minute amount of doubly distilled water that might be present 

 to dilute the next sample was a constant factor throughout all 

 the readings and was of course inconsequential. 



In using fresh batteries it was necessary to insert resis- 

 tance coils between the battery and the induction coil in order 

 to reduce the current. For this purpose German silver wire 

 was used. While polarization phenomena may possibly be 

 operative to a certain extent, such would be so small as to be 

 practically negligible, especially in view of the fact that the 

 effects from such a cause would be entirely relative and 

 would therefore not affect the validity of the results. 



Some of the conductivity results given in this paper are 

 shown in tabular form and others are plotted as curves. In 

 some instances the data are calculated as specific conductivity ; 

 in other cases the conductivity is represented by the value of 

 x on the Wheatstone bridge. To make it clear what x actually 

 represents, when the apparatus is set up as it was for the 

 determinations, the following proportion is given: 



R : R' : : x : 100 



■x 



R is the resistance in ohms inserted in the resistance box 

 R' is the resistance in ohms of the solution ; and x is the num 

 ber on the bridge wire (graduated in millimeters from t< 

 100 centimeters). As the position of x on the bridge varies 

 with R and R', the R for each series of curves or tables wil 

 be given (though in the great majority of cases it was 9,110) 



