1920] 
DUGGAR—INSOLUBLE SALTS IN BALANCED SOLUTIONS 327 
cases ferric citrate has proved equally veluable. Certain fer- 
mentation processes may occur in cultures in which these com- 
pounds are employed and a further study of the influence of 
those changes is necessary. 
Except in the cultures containing K,PO, or MgCO, the hydro- 
gen-ion concentration of all combinations used in the three series 
here reported ranges from 5.6 to 8.0, and after the growth of 
test plants there is usually a shift in the Py toward alkalinity 
or greater alkalinity. 
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