
RESPIRATION CALORIMETER AND EXPERIMENTS. 223 
lowered by a walking beam. The inner cylinder is also covered at the top, but 
through this cover are two circular apertures opened and closed alternately by 
an automatic valve, actuated by a compressed air mechanism underneath. 
Connected with these apertures are pipes passing downwards through the inner 
cylinder. One serves to convey the air, as it comes from the chamber, into the 
pump as the central cylinder rises. As the cylinder falls the other pipe conveys 
the air outward and thus plays the part of a discharge pipe. The automatic 
valves open and close the inlets and discharge pipes so that with each stroke of 
the inner cylinder the air is cut off at the proper time. The length of the stroke 
of the cylinder is determined exactly by rods, provided with stops, these rods 
playing through guides on two sides of each cylinder, and by this arrangement 
the only variation is that which comes with the very slight changes in the length 
of the rods due to changes of temperature. The air coming from the discharge 
pipe, escapes into the room, but by a special device the air of each fiftieth stroke 
of each pump is diverted into a receptacle, from which it is being constantly 
drawn for analysis. The dotted lines in the picture indicate the position of the 
pipes through which the air passes into and out of the pump. The details of 
this apparatus will be more appropriately described in another place. It will 
suffice to say here that the results obtained from its use are very satisfactory. 
Cooling apparatus.—It is desirable that the ventilating current of air shall 
enter the respiration chamber as dry as possible. To this end it is cooled toa 
temperature of —I9 to —22 degrees C. (—2 to —8 degrees F.), by passing 
through copper cylinders which are immersed in brine in the tank shown in 
figure 9. ‘The brine is cooled by use of an ammonia refrigerating apparatus.* 
The air after passing out of the cylinder is warmed before entering the chamber 
in the way described. On coming out of the chamber the air current is again 
passed through copper cylinders immersed in the brine, and thus practically all 
of the water which has been imparted to it within the chamber is removed. 
The same brine is used for cooling the. current of water which passes through 
the absorbers and conveys away the heat from the chamber. 
Analyses of air, determinations of carbon dioxide and water.—The methods 
used for these purposes are essentially the same as described in the Report of 
Storrs Experiment Station and Bulletin 44 of the Office of Experiment Stations 
of the U. S. Department of Agriculture above referred to. ‘It will therefore 
suffice to say here that the larger part of the water is caught in the copper 
cylinders, immersed in the cooling brine as above described, and its amount 
found by weighing. The residue of the water of both the incoming and outgo- 
ing air current is determined in samples by passing through U tubes containing 
pumice stone and sulphuric acid. The carbonic acid is in like manner deter- 
mined by passing through U tubes containing soda lime. 
In the ordinary experiments the determinations of water, carbonic acid and 
heat are made for periods of six hours. 

* See description of the arrangements for cooling in Report of the Storrs Experi- 
ment Station for 1896, p.92, and Bulletin 44 of the Office of kxperiment Stations of the 
U.S. Department of Agriculture, p. 22. 
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