APPARATUS AND METHODS USED IN THIS RESEARCH. 53 



dioxide absorbed from the ventilating air-current was determined from 

 the amount collected in the absorbing vessels, which were weighed at 

 the beginning and end of each period. The amount of oxygen admitted 

 to the apparatus was found from the change in weight of a cylinder of 

 oxygen, which was also weighed at the beginning and end of each 

 period, correction being made for the known impurities contained in 

 the oxygen. Correction was also made for the change in volume of 

 the spirometer, which, in the period represented by table 18, rose 1 mm. 

 corresponding to 23 c.c. or 0.03 gram of oxygen. This, for convenience, 

 is deducted from the corrected amount admitted from the cylinder. 



Measurement of the alcohol burned and the calculation of the products 

 of combustion. — The records of the alcohol burned and the calculation 

 of the products of the combustion during the first period of the experi- 

 ment are also given in table 18. The alcohol used in this experiment 

 was 92.56 per cent ethyl hydroxide by weight, the combustion pro- 

 ducing 1.769 grams of carbon dioxide for each gram of alcohol burned 

 and requiring 1.930 grams of oxygen for the oxidation. The readings 

 of the burette at the beginning and end of the period were respectively 

 0.590 c.c. and 2.770 c.c. at the average temperature of 21.05° C, or 

 2.169 c.c. at 15.6° C. The multiplication of this amount by the specific 

 gravity at 15.6° C. (0.81576) gives 1.769 grams as the weight of alcohol 

 burned. This amount, in turn multiplied by the factors 1.769 grams 

 for carbon dioxide and 1.930 grams for the oxygen, gives respectively 

 the theoretical amounts of carbon dioxide produced and oxygen con- 

 sumed as a result of the combustion. 



Comparison of the theoretical amounts of carbon dioxide produced and 

 oxygen consumed with those measured by the apparatus. — The amounts 

 of carbon dioxide produced and oxygen used as measured by the appa- 

 ratus are found by correcting the amounts of carbon dioxide absorbed 

 and the oxygen admitted for the change in the residual amounts present 

 in the chamber. Comparison of the amounts found with the theoretical 

 amounts as calculated from the weight of alcohol burned shows that for 

 the entire experiment 98.7 per cent of the carbon dioxide produced was 

 measured and 100 per cent of the oxygen used. The comparison is 

 given in table 19. 



As supplementary evidence on the alcohol check tests, measurements 

 made in four other experiments with the baby respiration apparatus 

 and one check test of two periods with another respiration apparatus 

 of exactly the same type but used for dogs are presented in table 20. 

 In considering the data for the experiment with the dog respiration 

 apparatus, it should be stated that the volume of air in the chamber is 

 over three times as large as the volume of air in the baby respiration 

 apparatus ; hence the errors incidental to accurate oxygen determinations 

 are greatly magnified. In spite of this, however, it can be seen that the 

 results for both forms of apparatus are very satisfactory, showing that 



