The apparatus was very simple. It consisted of a pump which would propel air towards the ether bottle; a glass bottle containing ether, the roof of which was pierced by two tubes, one of which carried the air from pump to bottle, and the other from bottle to a Waller’s tube, where it was collected. The percentage of ether in the air was then estimated by Waller’s gravimetric method. The ether jar stood in a water bath which could be either left otherwise empty or filled up with water of known temperature. The following tables show some of the results. In each case, the air was propelled for five minutes, by which time the cooling effect upon the ether was very marked; the figures given are averages taken from several observations.
TABLE A.
Air Blowing over Surface of Ether.
| Temperature of Bath (Fahr.) before experiment. | Quantity of ether before experiment. | Rate of pump. | Temperature of ether (Fahr.) at end of experiment. | Percentage obtained. |
| 75 | 100 c.c. | 30 | 50 F. | 12·7 |
| 85 | 100 c.c. | 30 | 52 F. | 12·8 |
| 75 | 100 c.c. | 90 | 45 F. | 8·7 |
| 85 | 100 c.c. | 90 | 45 F. | 8·8 |
| No water in bath | 100 c.c. | 30 | 32 F. | 8·2 |
| No water in bath | 100 c.c. | 90 | 23 F. | 5·4 |
| No water in bath | 200 c.c. | 30 | 38 F. | 9·6 |
| No water in bath | 200 c.c. | 90 | 29 F. | 6·6 |
TABLE B.
Showing increased percentage obtained by “bubbling through” instead of “blowing over” ether—
| Water Bath at 75° Fahr. | |
| Quantity of ether. | Rate of pump. |
| 100 c.c. | 30 |
| Air blown over surface of ether gave percentage of ether | 12·8 |
| Air bubbled through ether | 23·8 |
TABLE C.
Showing amounts of ether vaporised at varying pump rates. In each case, the temperature of the water bath was 75, and the initial amount of ether was 100 cc.—
| Pump Rate. | Amount of Ether Vaporised. |
| 30 | 30 c.c. |
| 90 | 38 c.c. |
These experiments justify one in drawing the following conclusions:—
1. The effect of a water bath has a marked effect in increasing the strength of the vapour yielded, but small variations in the temperature of the bath (as between 75 and 85 Fahr.) have but little effect.
2. If ether is vaporising quickly, it cannot pick up heat from the water bath as quickly as it is losing its own heat. Though not shown in the tables, the actual loss of temperature on the water bath was small—about 2 degrees Fahr. during the five minutes experiment.
3. The more forcible the blast of air blown over or through the ether, the less the percentage of ether yielded. Table C shows that this loss of percentage is not compensated for by an increase in the total amount vaporised.
Of course, these results only apply to the case of a strong current of air. If the current of air were very small, the ether could pick up heat as fast as it parted with it, and within moderate degrees a little increase of the air stream would increase the total amount of ether vaporised without reducing the percentage strength.
These results are of some practical importance in connection with so-called “vapour anæsthesia” as given for instance by Shipway’s instrument (page 90), and in devising and using the ether chambers of intratracheal apparatus.