EXPERIMENT STATION BULLETINS. 565 



6.49 — 0.04 = 6.45 c. c, gain in CO; for each 100 c. c. respired air. 



loss in gasoline-vapor for each 100 c. c. respired air. 



loss in Go for each 100 c. c. respired air. 



6.45 



= — 1.003 



O, 6 . 43 



Nine sets of experiments were carried out to determine the influence 

 of kerosene and gasoline vapors in air upon tlie respiratory quotient 

 of P. cornutus. Five of these sets are recorded in Table V, (page 36). 



It will be seen that the percentage of oxygen present in the vapor- 

 air respired was still comparatively high at the end of the experiments. 

 A quotient of 0.89 as given in set No. 5 was the largest obtained when 

 using kerosene vapor. None in any set fell below the average ratio for 

 the beetles in air. In case of the other experiments with gasoline 

 vapor, the results ran very similar to those recorded, except in two in- 

 stances. All quotients influenced by the latter vapor "are higher than 

 those obtained when using kerosene vapor. Note also that when the in- 

 sects were deepest under the influence of the vapor and nearly dead, the 

 respiratory ratio was highest. It was in testing out this last point that 

 the two exceptions mentioned occurred. Two estimations of oxygen 

 made for a period when the beetles were nearly dead, indicated that no 

 oxygen was absorbed while a rise of 0.43% of carbon dioxide was 

 found. In fact, the percentage of oxygen at the end seemed slightly 

 higher than at the beginning of the experiment, but that might be at- 

 tributed to experimental error. Kerosene did not give a very high 

 percentage of vapor at the temperature used and it did not bring the 

 insects deeply under its influence rapidly as was the case with the more 

 volatile gasoline. 



CO 

 INFLUENCE OF HYDROCYANIC ACID IN AIR UPON THE —?^ OF PASSALUS 



CORNUTUS. 



• 



The influence of hydrocyanic acid gas in air upon the respiratory 

 quotient of Passahis cornwtus was next studied. Enough air-hydro- 

 cyanic acid mixture was confined with the insects to make at least two 

 complete estimations — one at the beginning and one at the end of the 

 experiment. 



About 75 c. c. of the air-mixture to be estimated was drawn off and 

 measured accurately by the use of the compensating burette. This volume 

 (V) was for the estimation of the hydrocyanic acid alone. It was passed 

 slowly into a small amount of potassiuan hydrate solution in a flask, 

 which was set aside. As quickly as possible another measure (V) of 

 75 to 80 c. c. of the same mixture was made. The hydrocyanic acid 

 gas and carbon dioxide present in this volume were absorbed in a 

 potash pipette and the percentage of the two gases, together, deter- 

 mined. Oxygen was absorbed from the remaining gas in a phosphorus 

 pipette and its percentage, as also that of the nitrogen, was found in 

 the manner described for former estimations. 



Silver nitrate was afterward added to the alkaline solution that had 

 been set aside; the contents of the flask were then acidified slightly 

 with nitric acid and filtered. The filtrate was dried, ignited in a por- 



