Talk:Calefaction

This article was written by Clement Casciani (n°56, p497).

The steam- engine needs  a special apparatus for the production of steam, i.e. the boiler or generator which   is more or less large and may explose  ...  It was initially  these dangers of explosions that had to be evoided .. Boutigny, by a series of experiments,has showed that one of its causes, the principal one, consisted in the phenomenon of calefacion. We know  what it is if, after  heatig  to red a capsule or a metalic basin, and pouring  then a few grams of water,this water doesn't  spread out just like  it  does  at  ordinary temperature,, it takes the shape of a  flat sphere,  we say that it passes  into a  spheroidal state. In this state it moves round and round in  a fast gyratory movement, and it does not vaporize any more but  very slowly, that is to say fifty times less quickly than in the ordinary state at 200°. Lastly, if the capsule or the basin cools, it arrives one moment when the spheroid state ceases; then water wets surface  and a violent boiling, a kind  of explosion occurs suddenly. All the liquids can take the spheroid state at temperatures, according to their point of boiling ...

The experiment still succeeds when one practises it in vacuum... If one studies in experiments these curious phenomena one recognizes soon that the fact of the constitution of the spheroid state coincides with a separation of the liquid from the heated wall;  the released vapor  raises the drop, thus withdrawing it out of the action of gravity. These facts are very significant from the point of view of the power supply of the boilers. Indeed, when one heats to red  temperature a small boiler, closed by a  stopper with  a narrow opening by which a light vapor jet passes, the latter has only very weak tension, as long as the water put in the boiler is in a spheroid state,, when the temperature is lowered sufficiently so that water wets the walls, a  jerk passes by the opening, and the stopper is projected violently, in spite of the presence of this kind of   valve. Thus, vaporization, almost null initially, takes an enormous value suddenly as soon as the walls cool. The spheroid state ceases and the vapor mass formed in one moment can make  the boiler jump, exactly in the same way that the gases suddenly released in  the explosion of a sufficient quantity of powder...