- 229 - 



factors are limiting and where not and I have preferred to reduce 

 all the estimations to 20° and to a G0 2 content of 0.55 mg pr. 1. 

 Since the temperature in the greater part of the experiments was 

 about 20°, the values of the corrections are small. On the whole 

 the assimilation curves will be about the same with or without the 

 corrections (The respiration values are not corrected for the G0 2 

 content of the air). 



The errors in the estimations are as follows: 

 1. Constant errors. By using very dilute solutions for titra- 

 tions (for instance — ^) an error will arise since the water 

 used in diluting acts as an acid. For instance : 20 cm 3 Baryta solution 

 corresponded with 19.9 cm 3 ^ HCl. After the solutions were diluted 

 ten times, 20 cm 3 of the Baryta solution corresponded with 19.4 cm 3 

 2^q HCl. Yet the significance of this error is not great and can here 

 be omitted. 



More important is the error arising from the fact that not the 

 whole amount of C0 2 is absorbed in the absorption tubes. The mag- 

 nitude of this error will be different for every single apparatus. To 

 estimate this error two methods can be used. Indirectly, the error 

 can be estimated by passing a definite amount of air through the 

 apparatus and titrating the content of each absorption tube sepa- 

 rately. The result of 3 experiments with 3 different systems of ab- 



sorption tubes was as 



follows. 









Content of 



Tube 1 



Tube 2 



Tube 3 



Tube 4 



the absorpt. tubes 







30 cm 3 Baryta sol. . . 



59 



28 



13 





» » » « . . 



69.7 



21.5 



8.8 





40 cm 3 Baryta sol. . . 



44.3 



27.1 



17.4 



11.2 



The figures indicate percent of the total amount of the absorbed 

 C0 2 . Hence it can be calculated, that the loss of C0 2 in the first 

 experiment is 11 %, in the second 9 % and in the third 20 % of 

 the estimated value. 



In the last experiment the diameter of the absorption tubes 

 was greater than in the 2 first experiments. To accomplish an effec- 

 tive absorption the absorption tubes should be narrow and the gas- 

 bubbles small. 



