1915] 



MERRILL DISTILLED WATER 465 



measurements could be made only by means of a continuous 

 current. Because of the resulting polarization effects, how- 

 ever, the resistance of the solution increased to such an ex- 

 tent as to introduce serious errors into the results. But 

 thanks to the classical work of Kohlrausch and others, the al- 

 ternating current method was devised and perfected, whereby 

 the determinations became practically independent of polar- 

 ization effects. A vast amount of work has since been done 

 in the realm of physical chemistry on conductivity measure- 

 ments, a review of which, however, is outside the scope of 

 this paper. For a clear and concise discussion of this sub- 

 ject see Jones ('09), Walker (10), or Findlay (10). 



In addition to the investigations already cited which deal 

 with the practical applications of conductivity work, there 

 might well be mentioned in this connection the work done by 

 investigators in the Bureau of Soils of the U. S. Department 

 of Agriculture: Whitney, Gardner, and Briggs ('97); Whit- 

 ney and Briggs ('97) ; Whitney and Means ('97) ; and Gard- 

 ner ('98). Heald ('02) used the Kohlrausch method for de- 

 termining the conductivity of plant juices in order to get 

 indications regarding the dissolved mineral substances in 

 different parts of the plants under experimentation. Nicolosi- 

 Roncati ('07), Bouyoucos (12), Dixon and Atkins (13, 

 13 a ) and others have also carried on conductivity determina- 

 tions with different plants and under various conditions. 



Sjoqvist ('95) was the first to use the conductivity method 

 in enzyme investigations, which he did in his work on the 

 action of pepsin on protein solutions. Similar work was 

 done by Oker-Blom ('02), who also extended the applications 

 of this method. Oker-Blom (12) has recently given an 

 account of his own and previous investigations in the 

 field of bacteriology, wherein the electrical conductivity 

 method was used. Various other investigators have also 

 made use of it, among whom may be mentioned Bayliss 

 ('07). Stiles and Jorgensen (14) give a partial review of 

 some of the historical aspects of this subject as it pertains 

 to plant work. 



