Why do liquids boil in open space

The process of heating and boiling the liquids. Persistence of the free heat of the steam of boiling water. Fixed, volatile bodies. Gas. Steam. Permanent, coërcible gases

Chemico-Pharmaceutical Education pp 28-32 | Cite as

Part of the First Class of the Pharmacist book series (EUP, volume 1)


The vapors rising from a boiling liquid generally have the same amount of free heat that the boiling liquid exhibits. A liquid which boils under normal atmospheric pressure, i.e. in an open vessel, cannot be brought to a temperature above its boiling point by further heating. Whatever more heat flows into it is used as latent heat to form the steam. With a stronger fire we cannot raise the boiling point, but we can accelerate and increase the formation of steam. If this happens to the fullest extent, the liquid boils over in narrow vessels as a result of the rapid and increased formation of vapor bubbles, it rises out of the cooking vessel. Take a test glass in hand, fill it halfway with water and hold it by means of a test glass holder, after warming up with the lower end, without any movement, in a spirit flame. Immediately smaller steam bubbles begin to rise from the bottom of the glass, the water boils, the steam bubbles become bigger and bigger and finally so big and fast that they throw most of the water out of the sample glass. By gently moving and shaking the water, the formation of large steam bubbles is disturbed, and small steam bubbles only cause the water column to stir gently. Therefore, if you want to boil liquids in test glasses, always heat them with a flame while moving the glasses back and forth.

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© Springer-Verlag Berlin Heidelberg 1877

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