EXPERIMENT STATION BULLETINS. 559 



adsorption. In complex sy.stems special conditions would arise and in- 

 troduce errors which would have to be rectified in some way, in order to 

 make this method applicable. 



Certain physiologists, pathologists, biochemists, and others have made 

 use of conductivity methods, but, because of inaccuracies and difficulties 

 attendant upon a measurement, comparatively little work except of a 

 general nature has been done. Tlie names of Roth (33), Bugarzkv and 

 Tangle (3), Sjoquist (37), Stewart (35), Woefel (4.5), Oker-Bloui (18) 

 and McClendon (10) stand out prominentl3\ Their work was mostly 

 concerned with the blood of animals and the eggs of sliell fish. Osterliout 

 (19-31), True and Bartlett (39-40), Dixon and Atkins (6-7), Stiles and 

 Jorgensen (36), Bouyoucos (2), and others have entered the field from 

 the botanical side. Bayliss has collected data on the hydrolysis of vari- 

 ous proteids by tlie action of trypsin. He measured the increase in con- 

 ductivity brought about by the reaction of the enzyme. Ziegel (46), 

 van Suchtelen and Itano (41) have described electro-titrametric methods 

 for determining the end point in reaction. Kiister and Griiters (15) used 

 the conductivity method as an indicator of neutrality in tlie titration of 

 weak acids by strong bases. They also used the same method to determine 

 the acidity of colored liquids where the color change of the indicator 

 would be masked. Hall and Bell (S), and Patten and Kobiiison (.32) 

 working independently of each other applied the method of conductance 

 to the determination of the neutrality of ammonium citrate solution. 

 The work of Whitney and Means (44) and Davis and Bryan (4a) was 

 along the line of developing a simple and efficient Wheatstone bridge that 

 could be used in the field. This resume of the literature does not claim 

 to be exhaustive, the only purpose being to indicate the lines of study 

 and direction of investigation. 



Since the problems, which in all probability will lend themselves to 

 solution through the aid of conductivity measurements, are numerous, 

 and since so few have considered the results commensurate with the time, 

 labor and patience in making a measurement, it is evident that any iin- 

 ]n'ovement of the old method will tend to enhance its value and lead the 

 way to a clearer understanding of some of the little known biological 

 problems. The old method, as has been admitted, is not free from many 

 sources of error. It is not an easy matter to make a measurement and 

 more time than ought to be necessaiy is consumed in making it. Besides 

 the nerves of the operator are constantly under strain. With the changes 

 suggested in the following pages, one is now able to obtain a high degree 

 of precision with greater rapidity and mucli less strain on the nerves. 

 The correct bridge setting is determined by the aid of the eye instead of 

 the ear, a change which will no doubt greatly commend the method. 



In the spring of 1913, by permission of the Director of the Experiment 

 Station, a preliminary paper by the senior author (10) was published 

 in the 15th report of the Michigan Academy of Science. Shortly before 

 this, and while we were still working on the problems, there appeared in 

 the February number of the Journal of the American Chemical Society a 

 paper on ''An Improved Apparatus for Measuring the Conductivity of 

 Electrolytes," by E. W. Washburn and J. E. Bell (42). Tlie method 

 outlined in this paper was based upon three important changes in the 

 customary apparatus. Working independently of these investigators, 

 we made our changes along the same general line. However, our studies 



