gß J. Lindhard. 



burette, that there was an excess of pressure in this when the mer- 

 cury stood in the narrow tube. Thereafter I brought the mercury 

 cohimn to one of the marks on the wide tube, opened the upper 

 tap of the burette for a moment, to equahze the pressure, and then 

 brought the absorption-Hquid to the mark in the wide tube of the 

 absorption-pipette by means of the movable receiver connected with 

 the pipette. After absorption of the carbonic acid the absorption- 

 liquid was again brought to this mark by means of the mercury. 

 The manometer was thus not used in these analyses. 



A source of error is introduced when the analysing apparatus 

 is used in this way, since the temperature of the water-bath is of 

 importance for the volume of air noted. This water-bath always 

 contained plenty of glycerine or cooking-salt, owing to the cold at 

 nights in the cabin, and its temperature was practically always 

 lower than the temperature of the air. During the analysis, when 

 the warmer air of the room was constantly being pumped through 

 the bath, the temperature of the latter rose, usually by some few 

 tenths of a degree. The temperature of the bath had therefore to 

 be read directly after each reading of the amount of the air-sample. 

 In calculating the results of the analyses a correction is made for 

 these temperature changes and thus no uncertainty worth mentio- 

 ning is introduced by these into the experiments. 



The fact, that the absorption-liquid, owing to great changes in 

 the air-pressure, may absorb or give off a measurable amount of 

 other gases than carbonic acid, might occasionally introduce an 

 uncertainty in the carbonic acid determination, which cannot be 

 calculated but which may nevertheless be approximately estimated. 

 Some examples of this will be shown in the discussion of the sepa- 

 rate experiments. Apart from such errors, the importance of which 

 must be judged in each separate case, we may most probably con- 

 clude, that the total error in the determination does not exceed -^ 

 005 "^/o CO 2- With regard to the ordinary use of the analysing appa- 

 ratus, I may refer to Krogh's paper cited above. 



The respiration experiment, which as a rule lasted 30 

 minutes, was carried out in a kneeling position, on account of the 

 space available, with both arms resting and the face leaning against 

 the respiration-mask. This position, after I had learnt to know it 

 in the preliminary experiments, was convenient and easy to take 

 up, so that it was almost exactly the same from day to day. Without 

 changing the position of the body my right hand was able to move 

 the balls on the "counting-machine", as also to reach the watch and 

 a small glass which showed me whether the valves in the respira- 

 tion-apparatus were working properly; with the left hand I could 



