TEMPERATURE DETERMINATIONS 



169 



molecules of a catalyst. 'Vhv catalysts repeatetllj^ involved in bio- 

 chemical reactions might thus be identified by determination of tem- 

 perature characteristics. Although many conijolex systems, involv- 

 ing serial reactions, have definite temperature characteristics, it is 

 seldom possible to assign the n value to a ])aiti('ular reaction in the 

 system. 



By rearranging the above equation, the temperature characteristic 

 of a reaction can be determined by measurement of reaction rates at 



1.5 



o 



I- I.I 

 o 



=J 



Q 



■^ 0.9 



5 0.7 



> 0.5 



o 



0.3 



0.0030 



0.0032 



0.0034 



Fig. 15. Typical Arrhenius graph. Reciprocal of absolute tem- 

 perature plotted against logarithm of velocity of anaerobic reduction 

 of methylene blue by bacteria in presence of sodium succinate as 

 source of hydrogen. Destructive effects evident above 50 °C. Tem- 

 perature characteristic, m, is 16,700. After Crozier; curve based on 

 data of Quastel and WTietham. 



two known temperatures. It is more practical, however, to deter- 

 mine fjL by plotting log k against 1/T for a series of observations at 

 several temperatures. The temperature characteristic will then be 

 the slope of the line obtained as shown in Figure 15. The temperature 

 characteristic has been determined for many physiological processes, 

 including cell division rates, rate of pupal development, heart rate, 

 velocity of ciliary movement, velocity of the nerve impulse, growth 

 rate, carbon dioxide production and oxygen consumption rates in 

 many plant and animal forms in vivo. It has also been determined for 

 many purely chemical or enzymic processes in vitro, such as the inver- 



