PHYSIOLOGICAL AND BIOCHEMICAL TECHNICS 



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herein, although slight modifications may be advisable for the particular 

 problems which are under investigation. In any case, the appropriate 

 analytical method should be thoroughly tested and proved under the 

 particular conditions of application. 



In general terms, portions of the clarified solution referred to above are 

 subjected to several treatments. Disappearance of the substrate is 

 measured, as are the types of products listed in Table 19, according to the 

 procedure described below. The pH of the cleared solution containing 

 the dissolved dissimilatory products is adjusted to pH 7-8 and distilled 



Table 19 



* Ether-extractable at pH 7-8. 

 t Ether-extractable at pH 2-3. 



to obtain a fraction containing the neutral volatile products. The residue 

 is adjusted to pH 2-3 and steam-distilled to obtain the volatile acid frac- 

 tion. The nonvolatile products remain in the residue. 



Each of the products thus obtained is measured, taking into considera- 

 tion the possible effects of other products upon the particular analysis. 

 Partition chromatography may be used to separate and measure many 

 of the components of the mixtures; the volatile acids may also be meas- 

 ured by Duclaux distillation (Neish, 1952). 



After identification and quantitative determination of the dissimilatory 

 products, two types of balances are drawn up to check the accuracy of 

 the analysis. These are the carbon and oxidation-reduction (0/R) 

 balances. An example of such balances, taken from Johnson et at. (1949), 

 is given in Table 20. 



As a result of dissimilation, substrate carbon appears in the products 

 formed, and complete carbon recovery is to be expected if all products 

 have been identified and if the quantitative determinations are not in 

 error. Usually the analytical data are calculated on the basis of milli- 

 moles of product per 100 millimoles of substrate dissimilated ; micro- 

 moles are used in microanalysis. To calculate the carbon balance, 

 millimoles of any product are multiplied by the number of the carbon 



