HYDROGEN-ION CONCENTRATION OF PROTOZOAN 



CULTURES. 



JOSEPH HALL BODINE, 

 ZOOLOGICAL LABORATORY, UNIVERSITY OF PENNSYLVANIA. 



The chemical changes taking place in ordinary hay infusions 

 used for protozoan cultures have been described by various 

 authors, among whom may be mentioned Peters 1 and Fine. 2 

 The points of interest discussed by these two authors are the 

 changes occurring in the titratable acidity and alkalinity of such 

 infusions. Changes in titratable acidity and alkalinity, however, 

 as is well known, do not give a correct expression of the changes 

 in concentration of hydrogen ions. Inasmuch as the hydrogen- 

 ion concentration of the medium with which organisms are in 

 contact is of great physiological importance, it was planned to 

 study this factor throughout the life of series of protozoan 

 cultures, and to see in how far such results agreed with those 

 obtained by titration methods. 



In the present study, therefore, determinations were made of 

 both titratable acidity and alkalinity, as well as of hydrogen-ion 

 concentration of series of cultures prepared in various ways. 



The titratable acidity was obtained by titrating 5 c.c. of 

 culture with o.oi N NAOH, using phenolphthalein as indicator. 

 The titratable alkalinity was obtained by titrating 5 c.c. of cul- 

 ture with o.oi N H 2 SO4, using bromphenol blue as indicator. Hy- 

 drogen-ion determinations were made by colorimetric methods, 

 using phosphate and acetate mixtures as standards, and phenol- 

 sulfonephthalein, brom-cresol purple and methyl red as indicators. 

 Series of cultures were prepared in various ways and determina- 

 tions carried out daily. In the case of hay infusion cultures with 

 hay, the same amount of hay (approx. 25 gms.) was used and 

 treated in the manner indicated in explanation of figures. The 

 soil in soil cultures was obtained from the greenhouse and was 



1 Peters, A. W., 1907, Amer. Jour. Physiol., 17 and 18. 



2 Fine, M. S., 1912, Jour. Exp. Zool., 12, p. 265. 



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