THE CALORIMETER. 45 



and states that the " probable error " of values computed from this formula 

 is 0.5 joule. The results are expressed in international joules, that is, in 

 terms of the international ohm and 1.43400 for the E. M. F. of the Clark 

 cell at 15° C, and assuming that the mean calorie is equivalent to 4.1877 

 international joules,* the formula reads 



L (in mean calories) =597.44-0.580 T 



With this formula Smith calculates that at 15° the heat of vaporization 

 of water is equal to 588.73 calories; at 20°, 585.84 calories; at 25°, 582.93 

 calories; at 30°, 580.04 calories ;f and at 35°, 577.12 calories. In all of 

 the calculations in the researches herewith we have used the value found 

 by Smith as 586 calories at 20°. Inasmuch as all of our records are in 

 kilo-calories, we multiply the weight of water by the factor 0.586 to obtain 

 the heat of vaporization. 



THE BED CALORIMETER. 



The chair calorimeter was designed for experiments to last not more 

 than 6 to 8 hours, as a person can not remain comfortably seated in a 

 chair much longer than this time. For longer experiments (experiments 

 during the night and particularly for bed-ridden patients) a type of calo- 

 rimeter which permits the introduction of a couch or bed has been devised. 

 This calorimeter has been built, tested, and used in a number of experi- 

 ments with men and women. The general shape of the chamber is given 

 in fig. 26. The principles involved in the construction of the chair calo- 

 rimeter are here applied, t. e., the use of a structural-steel framework, inner 

 air-tight copper lining, outer zinc wall, hair-felt insulation, and outer 

 asbestos panels. Inside of the chamber there is a heat-absorbing system 

 suspended from the ceiling, and air thermometers and thermometers for the 

 copper wall are installed at several points. The food-aperture is of the same 

 general type and the furniture here consists simply of a sliding frame upon 

 which is placed an air-mattress. The opening is at the front end of the 

 calorimeter and is closed by two pieces of plate glass, each well sealed into 

 place by wax after the subject has been placed inside of the chamber. 

 Tubes through the wall opposite the food-aperture are used for the intro- 

 duction of electrical connections, ingoing and outgoing water, the air-pipes, 

 and connections for the stethoscope, pneumograph, and telephone. 



The apparatus rests on four heavy iron legs. Two pieces of channel iron 

 are attached to these legs and the structural framework of the calorimeter 

 chamber rests upon these irons. The method of separating the asbestos 

 outer panels is shown in the diagram. In order to provide light for the 



♦Philosophical Transactions, vol. 199, A, p. 149. (1902.) 

 t This is in agreement with the value 579.6 calories found by F. Henning, Ann. 

 d. Physik, vol. 21, p. 849. (1906.) 



