560 



Carbon dioxide can be bought in tanks and used directly from them, 

 but it is necessary to make the monoxide. This was done by the com- 

 mon method of heating oxaHc acid with five to six times its weight 

 of concentrated sulphuric acid. In the reaction both the dioxide and 

 the monoxide are formed ; the dioxide is removed by passing the gas 

 through two wash bottles containing concentrated NaOH, and the 

 gas remaining was also led through two wash bottles containing dis- 

 tilled water before it was collected in large 20-liter bottles over water. 

 Analysis of the gas showed it to be 95 per cent. CO and 5 per cent, 

 atmospheric gases in the proportion in whicl\ they dissolve in water 

 from the atmosphere. These latter gases must have come out of tlie 

 Vvater over which the CO was collected. The generation of the gas 

 and the experiments were performed with a canary bird at hand, the 

 gas being particularly poisonous to birds. 



Figure I illustrates the method used in introducing the CO into 

 the water that flowed through the experimental bottles. The method 

 may be useful wherever the introduction of small amounts of any 

 substance, especially a volatile one, into a stream of running water 

 is desired. It reduces the exposure to the atmosphere to a minimum, 

 and the concentration can thus be kept relatively constant. The steps 

 in introducing the CO were as follows: — (i) Water from J was 

 siphoned into A. which was already full of CO. The clamp between 

 A and B was kept closed, and thus the water in A was subjected to 

 some pressure. After some hours the water was found to be satu- 

 rated with CO. (2) B was now lowered, and the pinch clamp be- 

 tween A and B was loosened. The water in A now ran into B, dis- 

 placing the air through the glass tube leading to the top of B. More 

 water from J flowed into A at the same time; but if the exchange 

 was made rather slowly, practically no mixing took place and analysis 

 showed the water in B to be saturated or even slightly supersaturated 

 with CO. (3) The clamp between A and B was closed, B was 

 raised to the position shown in the figure, and the clamp between B 

 and the burette was opened. The water now ascended in the burette 

 till it reached the level of the water in B. (4) By opening the burette 

 cock the saturated water was now run into the glass tee at C, where 

 it mixed with the tap water. The rate of flow from the burette was 

 determined by counting the drops per minute, the number of drops 

 per c.c. having previously been determined. (5) The mixture then 

 flowed through the experimental bottles of which D is the first. (6) 

 Finally, as has been stated before, the actual concentration of gas in 

 the water in the experiment was determined by analysis. 



