62 A RESPIRATION CALORIMETER. 



thermometers are graduated in degrees and read to tenths of a degree. 

 That used in the Elster meter is read to hundredths of a degree. As 

 the temperatures at which they are used rarely exceed 25, it was found 

 expedient to calibrate them, together with a number of others used for 

 incidental work, such as in the specific gravity of alcohol, etc., simul- 

 taneously with the water thermometers, and a table of corrections for 

 each thermometer in use in the laboratory was thus obtained under con- 

 ditions exactly similar to those described for the water thermometers. 

 (See p. 133.) All temperatures read by observers are subject to these 

 corrections before use in the calculations. 



In regard to the temperature observations on that portion of the air- 

 circuit outside of the respiration chamber, it is found that under certain 

 conditions of experimenting, especially those in which large quantities 

 of carbon dioxide are being absorbed, the temperature of the carbon- 

 dioxide absorbers is considerably increased. In one experiment the 

 bulb of a thermometer was placed on the exterior of the absorber, the 

 bulb covered with a piece of hair felt, and the temperature noted. A 

 temperature of 47.5 was observed during this experiment, and an 

 observation on another day gave a temperature of 53.3. 



As stated previously (p. 31), all three carbon-dioxide absorbers dur- 

 ing a work experiment become more or less heated, although usually 

 the excessive heat is confined to one absorber. In consideration of the 

 lack of more data, it has been assumed that, while the carbon dioxide 

 was being absorbed from the air current during a period in which the 

 subject was engaged in excessive muscular exercise, one-half of the air 

 in the soda-lime absorbers reached a temperature of 50, the rest 

 remaining at 20. It has been computed that about 0.4 liter of air is 

 thereby added to the system at each change in the absorbing system 

 after a period of heavy work. In an alcohol check experiment, or in a 

 rest experiment, the rise in temperature is so slight that no correction 

 is necessary. 



In the first water-absorber there is always a slight rise in temperature 

 above the initial temperature. The amount of water absorbed in the 

 course of a two-hour period is too small, however, to cause any great 

 increase in temperature, and consequently it is not considered in the 

 calculations. 



