720 Journal of Agricultural Research vol. vi, No. 18 



prising the test, and the determinations of carbon dioxid, oxygen, and 

 heat in one period agree quite closely with those in the other, while the 

 discrepancies between the quantities found and those required are for 

 the most part small. The ratio of the volume of carbon dioxid pro- 

 duced to that of oxygen consumed in the test was 0.663, whereas the 

 theoretical respiratory quotient for the combustion of alcohol is 0.667. 



The only test in which less than 1 gm. of alcohol per hour was burned 

 for any considerable period was that on January 27, which continued 

 nearly 12 hours, at a rate of combustion averaging only 0.88 gm. per 

 hour. There was a close agreement between the quantities computed 

 and those determined in the measurement of gaseous exchange in this 

 test also, but the heat production was not determined. These results 

 are quite typical of all those obtained in tests of this character. In none 

 of them have there been wider discrepancies than these shown between 

 the measured and calculated quantities, the reasons for which were not 

 ascertained and which could not have been avoided. 



The accuracy with which heat generated in the calorimeter chamber 

 can be determined is tested also by converting a known amount of 

 electrical energy into heat in a resistance coil suspended in the chamber 

 and measuring the heat with the calorimeter. In a test made on Feb- 

 ruary 3, 1 91 4, a current of 0.087 ampere was passed through a resistance 

 coil of 1,680 ohms at an average pressure of 146.5 volts, generating 



10.97 Calories of heat per hour according to the formula - — r — = small 



Calories per second at 20 C. The quantity of heat measured by the 

 calorimeter was 11.04 Calories in the first hour and 11.08 Calories in the 

 second hour of the 2 -hour test. During the second hour the increase in 

 the temperature of the water that flowed through the heat absorber in 

 the chamber was measured by a potentiometer and the differential ther- 

 moelement installed in the resistance thermometers (see p. 713) as a 

 check on the measurement by the thermometers themselves. The aver- 

 age temperature difference was 1.42 as indicated by the resistance ther- 

 mometers and recorder and 1.40 by the thermoelement and potentiom- 

 eter. The discrepancy between the computed and the measured amounts 

 of heat in the second period of this test is wider than that in any other 

 electric test with this respiration calorimeter. The closest agreement 

 was that obtained in a test which continued only 1 hour, on November 

 2, 1 91 2, in which the amount of heat computed to have been generated 

 in the chamber was 7.54 Calories and that measured by the calorimeter 

 was 7.56 Calories. 



Both the electric and the alcohol tests indicate that measurements 

 can be made with this respiration calorimeter to a high degree of 

 accuracy. 



