GAS INTERCHANGE. 



69 



closely similar, but the actual amount of acid present was less fluctuating 

 (table 53). Four series were carried on simultaneously and at three tempera- 

 tures, namely, 15, 25, 40 C. Expressed in cubic centimeters per gram-hour 

 fresh weight, the averages of the series are shown. 



It will be seen that the ratio rises with the temperature or, in other words, 

 the production of carbon dioxide increases more rapidly than does the absorp- 

 tion of oxygen. This is in agreement with the results of Aubert. 



It is interesting to note in this connection the acceleration of interchange 

 of gases in comparison with that of other chemical reactions. The doubling 

 of rate called for by the ordinarily accepted idea of van't Hoff's statement 

 regarding reaction velocities is not attained, but, as Barry has said, many 

 circumstances may condition the speed of reactions in such complicated physi- 

 ological processes. At 25 the amount of carbon dioxide produced is 83 per 

 cent higher than at 15, while at 40, where an increase of the.original rate of 

 600 per cent would be predicted, there is an actual increase of 550 per cent. 

 On the other hand, there are individual experiments in which the difference 



TABLE 44. 



between the rates at 15 C. and 25 C. is almost exactly 100 per cent. In 

 one case the evolution of carbon dioxide at 15 C. is 0.066 c.c. per gram-hour 

 and at 25 C. it is 0.134 c.c. for the same unit. In another case the figures at 

 15 C. and 40 C. are 0.075 c.c. and 0.45 c.c., respectively, which is an increase 

 of exactly 600 per cent. 



It is obvious since the ^ ratio rises, that the reactions involved in the 

 absorption of oxygen from the air do not keep pace with those concerned in the 

 production of carbon dioxide. The amount of oxygen taken in at 25 C. is 

 only 32 per cent more than at 15 C., while at 40 C. it has risen only to 220 

 per cent. It would, however, be unsafe to say that the actual oxidation does 

 not proceed in something like geometrical ratio with rising temperature, for 

 at higher temperatures it is not impossible that some of the necessary oxygen 

 is supplied, as it is in intramolecular respiration. 



In connection with the discussion of temperature effects, it is well to turn 

 back to an examination of the general mass of determinations from the stand- 

 point of increased carbon dioxide formation. In comparing the group^ of 

 experiments carried on at 23 to 24 C. with those which were made at 33 to 

 34 C., approximately the same increase is noted as above described, irre- 

 spective of acidity or other consideration. However, as has been pointed out, 

 the ^ ratio is greatly affected by the degree of the acidity, so that it is evi- 



"Barry, F. The influence of temperature on chemical reaction in general. Amer. Journ. of 

 Bot., vol. i, pp. 203-225, 1914. 



