86 CALORIMETERS FOR STUDYING RESPIRATORY EXCHANGE, ETC. 



where the composition of the air in the chamber is much more nearly nor- 

 mal, this correction is without special significance. Furthermore, in the 

 two forms of calorimeter now in use, the experiments being of but short 

 duration, provision is made to render it unnecessary to open the food- 

 aperture during the experiment proper. Consequently at present no cor- 

 rection for interchange of air in the food-aperture is made, and for the 

 same reason the slight alteration in volume resulting from the removal or 

 addition of material has also not been considered here. 



USE OF THE RESIDUAL BLANK IN THE CALCULATIONS. 



To facilitate the calculations and for the sake of uniformity in express- 

 ing the results, a special form of blank is used which permits the recording 

 of the principal data regarding the analyses of air in the chamber at the 

 end of each period. Thus at the head of the sheet are recorded the time, 

 the number of the period, kind of experiment, the name or initials of the 

 subject, and the statement as to which calorimeter is used. The barometer 

 recorded in millimeters is indicated in the column at the left and imme- 

 diately below the heading, together with the temperature of the calorimeter 

 as expressed in degrees centigrade. The temperature of the calorimeter as 

 recorded by the physical observer is usually expressed in the arbitrary 

 scale of the Wheatstone bridge and must be transposed into the centigrade 

 scale by means of a calibration table. 



The apparent air-volumes in the subsections of the ventilating system 

 are recorded under the headings I, which represents the volume of air con- 

 taining water-vapor and therefore is the air in the chamber plus the air in 

 the piping to the surface of the acid in the first sulphuric-acid absorber; 

 I-II, which represents the air containing carbonic acid and includes volume 

 I plus the volume of the air in the first sulphuric-acid vessel and the 

 volume of air in the potash-lime absorber; I-II I, which includes the total 

 confined volume of the whole system, since this air contains both oxygen 

 and nitrogen. These volumes change somewhat, depending upon the size 

 of the body of the subject, the volume of the materials taken into the 

 chamber, and the type of calorimeter. 



The data for the residual analyses are recorded in the lower left-hand 

 corner : first the weight of the water absorbed from 10 liters of air passing 

 through the meter ; to the logarithm of this is added the logarithm of volume 

 I ; the result is the logarithm of the total weight of water-vapor in the venti- 

 lating air-current. To convert this into liters the logarithmic factor 09462* 

 is added to the logarithm of the weight of water and (a) is the logarithm 

 of water expressed in liters. A similar treatment is accorded the weight 

 of carbon dioxide absorbed from the air-sample, (b) being ultimately the 

 logarithm of the volume of carbon dioxide. 



* In the use of logarithms space is saved by not employing characteristics. 



