APPARATUS AND METHODS USED IN THIS RESEARCH. 51 



ingly refined experimenting, the amount of carbon dioxide present in 

 the residual air. The protocol of a single alcohol check test by this 

 later quantitative method may serve to illustrate simultaneously the 

 method of calculation and the accuracy of the apparatus. 



DETAILS OF TYPICAL QUANTITATIVE ALCOHOL CHECK TEST. 



Measurement of the residual carbon dioxide and oxygen. — This experi- 

 ment consisted of two periods, the first from ll h 30 m a. m. to 12 h ll m 

 p. m., and the second from 12 h ll m p. m. to 12 h 51 m p. m. At the begin- 

 ning and end of each period of the experiment, observations were made 

 of the humidity conditions, the temperature of the apparatus, and the 

 barometric pressure. By means of these observations and the deter- 

 mination of the carbon-dioxide content of the air in the chamber, the 

 volumes of oxygen and nitrogen and of the carbon dioxide residual in 

 the apparatus were obtained for the standard conditions of 0° C. and 

 760 mm. pressure. The observations made at the end of the first 

 period are given in table 17. 



Table 17. — Observations at end of first period of alcohol experiment of October 9, 1913. 



Psychrometer: Dry bulb (h) 19.80° C; wet bulb (t 2 ) 15.91° C. 



Temperature at top of chamber (/,) 21.63° C. 



Temperature of apparatus (t t ) : h = 19.80° C; t s = 21.63° C; average, (t t ) 20.72° C. 



Barometer: Reading at end of period 767.05 mm. 



Tension of aqueous vapor in chamber. . . 11.10 mm. 

 Corrected barometer (p) 755.95 mm. 



Residual carbon dioxide and oxygen : 



Logs. 

 Total volume of apparatus 81 .5 liters = 91116 



Temperature of apparatus 1-1- n 00367 t ~ ^6817 



Corrected pressure ~gQ = 99768 



Corrected volume C0 2 + 2 + N 2 = 87701 = 75 . 34 liters. 



Per cent CO, (by analysis) 0.098 = 99123 



Residual C0 2 = 86824 - 0.07 liter. 



Residual 2 + N 2 75.27 liters. 



The temperature of the air in the chamber of the apparatus was not 

 determined with absolute certainty. The thermometer placed in the 

 top of the apparatus (t 3 in table 17) recorded temperatures which, 

 because of the position of the lamp and the warm air rising to the 

 bulb of the thermometer, were without doubt too high. The record 

 obtained from the dry-bulb thermometer (h of table 17) shows the 

 temperature of the air immediately after it left the chamber. It is 

 believed that the average of these two records (20.72° C. in table 17) 

 gives an approximate value for the temperature of the air in the appa- 

 ratus at the time the records were made and that the change in tempera- 

 ture from the beginning to the end of the period may by this means be 

 obtained. 



