EXPERIMENT STATION BULLETINS. 571 



nations of carbon dioxide and for obtaining other data necessary to 

 show the influence of ammonia upon the respiratory quotient of tlie 

 beetles, was worked out: 



A group of three or four beetles was weighed and the respiratory 

 quotient for the group in air was found in the usual manner. A stock 

 preparation of ammonia-air, containing the desired percentage of 

 ammonia for the experiment, was prepared in a large container. The 

 group of beetles, having been left in fresh air for a time, was now 

 placed in a respiration container. The mercury was forced up around 

 them until all the air was expelled and a measured amount of the pre- 

 pared ammonia-air was quickly drawn into the container with the in- 

 sects. No carbon dioxide was in this air at the beginning, and the 

 percentages of ammonia, oxygen, and nitrogen were determined. At 

 the end of the experiment, the oxygen and nitrogen percentages were 

 again determined as was also the percentages of carbon dioxide, or 

 ammonia — only one of the latter gases would be present in decidedly 

 measurable amounts in the respired air. For determining the per- 

 centages of the component gases, two samples of the respired air were 

 taken. One sample of 70 to SO cubic centimeters was passed into a 

 measured quantity of standard barium hydrate solution and the car- 

 bon dioxide, if present, was then determined by the titration method 

 already described. The other similar sample was first passed into a 

 sulphuric acid pipette (Ho S O^ of Sp, gr. 1.84 diluted one-half), then 

 into a potash pipette and finally into a phosphorus pipette. Any am- 

 monia present was absorbed by the sulphuric acid and its percentage 

 could be found. Of course, measurements of the remaining gas were 

 made after each absorption. Any carbon dioxide was taken up in the 

 potash pipette. Besides, a check estimation of the latter gas, if present, 

 had already been made by the barium hydrate method. The percentage 

 of nitrogen and oxygen (also the per cent of oxygen used) could be 

 figured out in the way described for former estimations of these gases. 



All the gas contained with the insects at the end was measured. 

 Since the volume of the air at the beginning and at the end was known, 

 then, it was possible to determine the total amount of ammonia that 

 had been taken up by the insects during the experiment, the total 

 amount of oxygen used, and the total amount of free carbon dioxide 

 (when present) in the respired air. 



For determining the amount of carbon dioxide and ammonia that 

 were retained within the beetles, the apparatus represented in Fig. 

 6 was used. In this apparatus, the large jar (j) was a carbon dioxide 

 filter. Before the experiment was started, the apparatus was all con- 

 nected up and the tube "E" was attached to a Chapman air-pump which 

 was kept going until the entire apparatus w^as free from carbon dioxide. 

 A measured amount of standard barium hydrate was then placed into 

 flasks ''a" and "b," and a measured amount of ^ sulphuric acid was 

 placed in ''C." The distilling flask ^'D" was made ready with about 

 150 cubic centimeters of boiling-hot distilled water. 



As soon as the last of the respired ammonia-air mixture had been 

 measured, the beetles were quickly dropped into flask "D" and the 

 distillation was started; also, the air pump connected with ''E" was 

 started at the same time. "D" was kept distilling at a boiling tem- 

 perature for one hour. In that time, it was found, practically all the 



