Water Vaporized from Lungs and Skin. 139 



heat from the calorimeter, namely, the passing of cold water through a pipe 

 inside the chamber, may result in the condensation of considerable moisture 

 upon this pipe, particularly if the water vaporized from the lungs and skin is 

 large in amount. This is invariably the case in work experiments, but in rest 

 experiments, under proper conditions of ventilation, the relative humidity of 

 the air inside the chamber is usually fairly low, and the " dew-point " is as a 

 rule considerably below 10 C. Inasmuch as the ingoing water is commonly 

 kept at a temperature above 10 C. during rest experiments, there is rarely con- 

 densation upon these pipes. Finally, provision was made for actually weighing 

 the heat-absorbing system and noting the weight of water condensed upon it. 

 The difficulties attending the weighing of this apparatus which have been 

 elsewhere described, 1 were very great, however, and the results for water vapor- 

 ized, which in some publications have been corrected for these weights, must 

 of necessity have less value than the results for those experiments in which 

 there was no condensation upon the heat-absorbing system. 



In this connection it is of great importance to note in these experiments that 

 the chief value in determining the water-vapor in the outcoming air-current 

 has been to compute accurately the amount of heat that was required to 

 vaporize the water, since the heat measurements were of prime importance in 

 our experiments. It is obvious that if water is vaporized from the body and 

 subsequently condensed upon the absorbers, no interchange of heat so far as 

 the calorimeter as a whole is concerned has taken place. A certain amount of 

 heat, to be sure, has been required to vaporize the water as it leaves the body, 

 but an equal amount of heat was yielded to the heat-absorbing system as the 

 water was condensed upon it. Consequently no errors in the heat measurement 

 occur, even if there be considerable condensation of water upon the cooling 

 pipes of the heat-absorbing system. 



Such condensation does, however, interfere seriously with the accurate de- 

 termination of the water vaporized from the lungs and skin, a problem entirely 

 independent of the heat measurement. Accordingly it is possible to discuss 

 intelligently only the results obtained in those experiments in which there was 

 no condensation, namely, those during rest. In some of the previously recorded 

 work experiments, where the amount of water vaporized was very considerable, 

 doubtless the errors incidental to weighing the heat-absorbing system and the 

 corrections thereby applied to the water collected in the sulphuric-acid-absorb- 

 ing vessels were proportionately not large, inasmuch as large quantities of water 

 were being dealt with. In the rest experiments, where the water vaporized per 

 hour is not far from 40 grains, the condensation of 40 grams of water on the 

 heat-absorbing system introduces considerable error. In controlling these ex- 

 periments it was planned so to adjust the conditions of ventilation and the 

 temperature of the ingoing water that condensation on the pipes would be 

 avoided in all instances. 



1 Atwater and Benedict, loc. cit., p. 161. 



