TENSION-EQUALIZER UNIT. 33 



To determine the completeness of absorption, so-called efficiency tests 

 are made, as follows: The weights of the soda-lime container and the 

 accompanying water-absorber are each taken separately. The two 

 absorbers are then connected with the rest of the apparatus and the 

 ventilation is continued for 15 or 20 minutes. If the water-absorber is 

 efficient, the loss in weight of the carbon-dioxide absorber and the gain 

 in weight of the water-absorber are equal. In general practice they 

 agree within 0.02 gm., which is the limit of weighing. Occasionally 

 the absorption has been incomplete, and this of course is indicated by 

 the fact that the increase in weight of the sulphuric-acid container is 

 less than the decrease in weight of the soda-lime container. It also 

 sometimes happens that the Wolff bottles, i. e., the first two water- 

 absorbers or air-driers, are deficient. This is shown by the fact that 

 the increase in weight of the acid-container accompanying the soda- 

 lime container is greater than the decrease in weight of the latter. In 

 the later experimenting with this apparatus, the common practice has 

 been to test the efficiency of the Wolff bottles by weighing the carbon- 

 dioxide absorber and the third water-absorber together; if no change 

 in weight is found during the 15 or 20 minute test, it is assumed that 

 all parts of the apparatus are efficient. There is, of course, the slight 

 possibility that the actual loss through the two Wolff bottles may be 

 equivalent to an actual loss in the third water-absorber. Even if 

 this occurs, however, it will not in any way affect the carbon-dioxide 

 determination, as the net result will be the same. 



GENERAL ROUTINE OF AN EXPERIMENT. 



The general method of determining the respiratory exchange of a 

 subject with this apparatus is as follows: The subject assumes the 

 position which he is to maintain during the experiment, lying or sitting, 

 as the case may be, and should maintain that position for at least half 

 an hour previous to the experiment. After the preliminary test for 

 tightness, the nosepieces or mouthpiece is inserted, and the subject 

 breathes into the open air until the experimental period begins. The 

 carbon-dioxide absorbers are weighed; the oxygen cylinder, if used, is 

 also weighed, or if the meter is used a reading is made before the 

 experiment begins. After a few minutes of quiet and regular respi- 

 ration, the three-way valve is turned by an assistant, who does this in 

 so far as possible exactly at the end of a normal expiration. The 

 subject then breathes into the apparatus, and the experiment is con- 

 tinued the determined length of time. At the conclusion of the experi- 

 ment, the valve is again turned at the end of a normal expiration. 

 During the experiment oxygen is admitted occasionally or continuously 

 at such a rate as to prevent the rubber diaphragm touching the bottom 

 of the tension equalizer. Toward the latter part of the experimental 

 period a test is made for the completeness of the absorption of carbon 



