f 



THE CALORIMETER SYSTEM AND MEASUREMENT OF HEAT. 1 19 



connecting the unions, each pipe can be sprung a little and thus readily 

 removed. 



The heat-absorbing capacity of the mass of water in the pipe is very 

 great, much more so than that of the metal of the pipe itself, since the 

 specific heat of water is about ten times that of the pipe. Consequently, 

 in order to secure a quick and easily controlled heat absorption, it is 

 necessary to provide for the rapid draining out of the water in the cool- 

 ing system. As the water leaves the valve connected with the water 

 main it traverses the section of the pipe with which the valve is con- 

 nected. When the valve is shut off a check-valve attached to an upright 

 section of pipe (see fig. 37) opens, allowing air to enter. As each section 

 is purposely piped in such a manner as to allow a free outflow of the 

 water, the water in the pipes quickly drains out, and thus the cooling 

 effect is much more rapidly arrested. 



TEMPERATURE REGULATIONS IN THE OUTER AIR-SPACE. 



The temperature regulation of the air-space next the zinc wall is 

 affected by the fluctuations in temperature inside the metal chamber, 

 and also, in spite of the insulating of the wooden walls papered with 

 asbestos, by the temperature of the calorimeter laboratory. The outer 

 air-space, i. e., that between the inner and outer wooden casings, 

 dampens the effect of sudden changes in temperature of the calorimeter 

 laboratory, but to aid in regulation provision is made to heat and cool 

 the outer air-spaces at will. The heating and cooling circuits in these 

 spaces are of exactly the same nature as those described above for the 

 inner spaces, except that, since the delicate control of the temperature 

 in the outer air-space is much less important, no provision is made for 

 draining the water out of the water-pipes installed in this air-space. 



The necessity for heating or cooling the outer spaces is likewise 

 determined by deflections on a galvanometer connected with a series of 

 thermo-electric elements. These are inserted in the inner wooden walls, 

 one end of the junctions being in the inner and the other end in the outer 

 space. There are fifty-four such elements (containing each four pairs 

 of thermal junctions) distributed throughout the six inner panels at 

 equal distances from each other, so as to assume more nearly the average 

 temperature of the air-space. The black irregular line (not to be con- 

 fused with the series of parallel black iron pipes) on the right-hand 

 inner wall in figure 31 shows the method of connecting these elements. 

 Along the upper portion of the panel, running parallel to the iron pipes, 

 is one straight row of four elements. A somewhat different view is 

 given in figure 30, and the distribution on the inner rear panel may be 

 seen in figure 25, in which the panel is removed and standing at the right. 



