504 STATE BOARD OF AGRICULTURE. 



insect or group of insects in pure air uudei- certain conditions of 

 iemperature, moisture, etc., and then it was found for the same Insects 

 under the same conditions, as nearly as possible, but with the vapor 

 of the insecticide present in the air respired. Gasoline and kerosene 

 vapors were used first. A stock supply of gasoline or kerosene air 

 was prepared in one of the large containers. Enough of this stock 

 supply of vapor-air for several estimations would be drawn into a con- 

 tainer with the insects. By connecting the respiration container with a 

 similar gas-container through a capillary transfer tube, the gas could 

 be passed back and forth until thoroughly diffused; then a sufficient 

 amount could be kept in the gas-container for two or three estima- 

 tions. In this way, checks of the percentage values of carbon dioxide, 

 oxygen, gasoline or kerosene vapor, and nitrogen present at the be- 

 ginning of the experiment might be obtained. The component gases 

 were estimated at the beginning and at the end of each experiment in 

 a certain order. Between 75 and 100 c. c. of the vapor-air was meas- 

 ured off in the measuring-compensating burette. The carbon dioxide 

 was absorbed with a potash pipette in which some of the vapor-air to 

 be absorbed had been previously standing, and the remaining gas was 

 again measured. The kerosene or gasoline-vapor was next destroyed in 

 a fuming sulphuric acid pipette; several minutes were required to do 

 this completely-. With a potash pipette, used only for that purpose, 

 the fumes of the sulphuric acid were absorbed and the gas was again 

 measured. Finally', the oxygen was absorbed with either a phosphorus 

 or a potassium pyrogallate pipette — phosphorus Avas used mostly. The 

 remaining gas was the nitrogen present. 



One-tenth cubic centimeter of water was used in the measuring 

 burette above the mercury, and the burette was washed out after each 

 complete gas estimation. The water was necessary in order to insure the 

 air being measured moist after treatment with the sulphuric acid. By 

 using every precaution, after much practice, the possible error could be 

 kept below 0.2% as shown by duplicate estimations. The greatest source 

 of error came in using the fuming sulphuric acid. 



The record for a single estimation of respired gasoline-air is given 



here. 



Took 82.4 c. c. respired gasoline-air. 

 77.05 after KOH pipette. 



5.35 c. c. CO. = 6.49% COj. 

 69.65 after HoSO^ and KOH pipettes. 



7.4 c. c. gasoline vapor = 8.98% gasoline vapor. 

 59.3 — after Phosphorous pipette = 71.96% nitrogen. 



10.35 c. c. O, = 12.56% oxygen. 

 At the beginning, estimations gave 0.04% COo, 9.22% gasoline, 71.79% nitro- 

 gen and 18.95% oxygen. 



71.96 



Nitrogen ratio =: 



71.79. 

 71.96 



0.04 X = 0.04 c.c. CO., at beginning, to each 100 c. c. respired air. 



71.79 



71.96 



9.22 X = 9.24 c.c. gasoline vapor, at beginning, to each 100 c. c. respired 



71.79 air. 



71.96 



18.95 X = 18.99 c.c. oxygen, at beginning to each 100 c. c. respired air. 



71.79 



