PRELIMINARY NOTE ON THE USE OF SOME MIXED 

 BUFFER MATERIALS FOR REGULATING THE 

 HYDROGEN ION CONCENTRATIONS OF CULTURE 

 MEDIA AND OF STANDARD BUFFER SOLUTIONS 



M. R. MEACHAM, J. H. HOPFIELD and S. F. ACREE 



New York State College of Forestry, Syracuse University, Syracuse, New York 



Received for publication April 13, 1920 



In 1914-1915 Pieper (1917) began, with Humphrey and one of 

 us, the use of a mixture of phosphoric and asparaginic acids in 

 culture media and a number of other buffer mixtures were also 

 employed. Pieper did not have our hydrogen electrode equip- 

 ment set up to regulate the hydrogen ion concentrations, but this 

 work was already planned. Meacham (1918) then began and has 

 now finished investigations on this very important problem in- 

 volving the relation between the rate of growth of fungi and the 

 hydrogen ion concentration of culture media containing mate- 

 rials which enable any one now to regulate the hydrogen ion con- 

 centration at any desired value with great precision and repro- 

 ducibility without using the hydrogen electrode or indicator 

 methods. The result of his investigations on the growth of 

 Endothia parasitica, Lenzites sepiaria and other organisms will 

 appear in other articles. 



It is desired to point out here the advantages to be derived by 

 using a single solution of possibly two or three acids for giving a 

 smooth curve relation between (a) the hydrogen ion concentrations 

 from 10 -1 to 10~ 14 and (b) the amount of alkali added to such 

 mixture 1 of acids. The desirability of using 2 such a buffer mix- 



1 See also Prideaux (1916), whose excellent work was done after Pieper's 

 but who did not suggest the use of his mixture with culture media. We did not 

 discuss these physio-chemical relations in Pieper's article because he had no 

 opportunity to regulate his media with the hydrogen electrode, this new important 

 phase being taken up by Meacham in 1916-18. 



2 The mathematical side of the theory of buffer mixtures has now been de- 

 veloped in articles already completed, and applied in the measurement of the 



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