The impurity was called 0 when the impurity was less than .1 = about 1140 of a cubic centimetre, or = 1100,000 of the volume of the gases used.
The gases were measured moist, and the surface of the measuring vessel was kept thoroughly moist by washing the apparatus with distilled water in the evening and expelling the water, and then leaving it full of mercury and expelling what had risen through the night, so that no appreciable error was introduced from water present as such in the vessel. One advantage of working with moist gases and vessels with moist surfaces is that the gases can be so completely got rid of, none remaining as a film. When both manometer and measuring vessel were completely filled with mercury and the reservoir lowered so as to produce a Torricellian vacuum in both, it was usual for the mercury to remain for some time 300 to 400 millims. higher in the measuring vessel than in the manometer, the mercury not leaving the moist glass till a trace of gas from the stopcock 2 set it off.
The following experiments taken at random show the modes of measurement and calculation adopted.
August 24th, 1889. Experiment XXXIV., Series If. Apparatus with Variable Volume.
Oxygen from mercuric oxide—
Volume 50.0 = 3881.0.Temperature = 15.4° C.
| millims. | millims. | |||
| Height of mercury in manometer tube on scale | = | 71.3 | on cathetometer = | 10.0 |
| Height of„ mercury in„ volume tube on scale | = | 71.6 | on cathetometer„ = | 10.3 |
| Height of mercury in Correction | = | −0.3 | = | −0.3 |
| millims. | |||
| Barometer 777.1 − 26.0 | = 751.1 | ||
| Pressure of aqueous vapour | = 13.0 | ||
| ∴ | Pressure of oxygen = 751.1 − .3 − 13.0 | = 737.8 | |
Hydrogen from electrolysis of dilute hydrochloric acid—
Volume 45.3 = 3819.6.Temperature = 15.35° C.
| millims. | |||
| Height of mercury in manometer tube on scale | 118.5 | ||
| Height of„ mercury in„ volume tube on scale | 118.5 | ||
| Height of mercury Correction= | .0 | ||
| Barometer 777.4 − 25.8 | = 751.6 | ||
| Pressure of aqueous vapour | = 13.0 | ||
| ∴ | Pressure of hydrogen = 751.6 − 13.0 | = 738.6 | |
