BOILING POINTS OF FLUIDS INFLUENCED BY FRESSURE. 93

1. The loiling points of different fluids are influenced ly atmos-pheric pressure.

The boiling point or the conversion of fluids into gases alwaystakes place at certain temperatures, which is different in differentfluids provided the pressure of the atmosphere be the same.

Experiment I.

Put any quantity of sulphuric ether into a Florence flask,suspend a thermometer in it, and hold die flask over an Argand’slamp, the ether will immediately begin to boil and the diermo-meter will indicate 98 0 , if the ether has been highly rectified.

Experiment II.

If highly rectified ardent spirit is heated in a similar manner,the thermometer will rise to 176°, and there remain stationary

Experiment III.

If water is substituted it will rise to 212°.

Experiment IV.

If strong nitrous acid of commerce be made use of, it will befound to boil at 248°;—sulphuric acid at 546°;—and mercuryand linseed-oil at 600°, See.

2. The boiling point of fluids is retarded l-y pressure.

Mr. Watt heated water under a strong pressure to 400°. Yetstill when the pressure was removed only part of the water wasconverted into vapour, and the temperature of this vapour, aswell as that of the remaining fluid, was no more than 212°.There was therefore 188° of caloric suddenly lost. This caloricwas carried off by the steam, Now as only about y of the water