Nov. 22, 1915 



Improved Respiration Calorimeter 



345 



accuracy of the determinations when heat was produced in the chamber 

 at a rate of about 1 20 calories per hour. For all four factors the quan- 

 tities determined were slightly larger than those computed from the 

 composition of the alcohol, the discrepancies amounting to 1.5 per cent 

 for oxygen, 0.7 per cent for water, and the same for heat, and 0.2 per 

 cent for carbon dioxid. The respiratory quotient — i. e., the ratio of the 

 volume of carbon dioxid produced to that of oxygen consumed in the 

 combustion of alcohol — is 0.667; in the test the ratio of the values found 

 was 0.658. Similarly, the ratio of the number of Calories of heat pro- 

 duced to the number of grams of carbon dioxid produced is theoretically 

 3.705, whereas in the test it was 3.725. 



Table II. — Data obtained iu the combustion of alcohol in the respiration calorimeter 



In February, 191 5, in a 6-hour period, 85.35 gm. of commercial alcohol 

 containing 88. 25 per cent of ethyl hydroxid were burned, the rate of pro- 

 duction of heat being about 90 Calories per hour. In this test the heat 

 measured by the calorimeter was nearly 0.5 per cent greater than that 

 computed, whereas the quantities of oxygen, water, and carbon dioxid 

 measured were i to 1.3 per cent lower than those computed. 



Another test made at frequent interv^als provides a check on the accu- 

 racy of the calorimetric function of the apparatus. Electric energy is 

 converted into heat within the chamber, and the amount produced in a 

 given period, which can be computed very accurately, is compared with 

 that measured by the calorimeter during the period. The electric energy 

 is converted into heat in a coil of resistance wire suspended in the cham- 

 ber. The amount of energy that is dissipated is computed from the 

 values for the voltage and amperage of the current in the coil, the time 

 in seconds, and the factor for converting watt seconds to small calories 

 at 20° C, as explained on p. 342. 



The resistance of the heating coil depends upon the desired heat pro- 

 duction, the majority of the tests having been made with a coil having a 

 resistance of 440 ohms, which allows 0.5 ampere of current to flow with 

 a fall of potential of 220 volts. The resultant heat is approximately 95 

 Calories per hour, or about that produced by an average man sitting 

 still. That the rate of production of heat may be constant, the voltage 

 of the current is controlled by an automatic regulator; but the actual 

 fall in potential is measured by a voltmeter connected to the terminals 



