260 On the Spheroidal Condition of Liquids. 



liquid is in the ordinary spheroidal stale. The reason of this 

 I rendered apparent by first heating the water to the boiling- 

 point, and then immersing the red-hot platina, which in that 

 case produced a rapid ebullition during the time that the metal 

 remained incandescent and separated from the water by the 

 usual atmosphere of steam. The absence of ebullition in M. 

 Boutigny's experiment is obviously therefore simply owing 

 to the steam being condensed by the coldness of the water, 

 as soon as it recedes beyond the influence of the heated 

 platina. 



It is instructive also to observe the different effect produced 

 by the partial and the total immersion of the red-hot platina 

 in water heated to 205°, which it will be recollected is the 

 maximum temperature that water acquires in the spheroidal 

 state. If the heated metal be only partially immersed, there 

 is no ebullition, and the temperature of the liquid remains 

 stationary ; but if the platina be wholly sunk in the water, then 

 the temperature rises and ebullition takes place. The reason 

 of this difference is very evident: when the platina is not en- 

 tirely covered by the water, the steam it produces has an out- 

 let, and the conditions resemble those of water in the sphe- 

 roidal state ; but when the platina is submerged, the heated 

 steam is compelled to bubble up through the water, and 

 thereby not only produces ebullition, but also imparts in its 

 passage additional heat to the liquid. 



1 easily succeeded in showijig M. Boutigny's remarkable 

 experiment of freezing water in a red-hot platina capsule by 

 the agency of sulphurous acid, which boils at a temperature of 

 18° below the treezing-point of water. This singular experi- 

 ment is entirely dependent upon the peculiar mode of evapo- 

 ration, which is incident to liquids in the spheroidal form. 

 When the acid is poured into the red-hot vessel, its inferior 

 surface is instantly vaporized, and the resulting stratum of in- 

 terposing vapour prevents the liquid from touching the metal, 

 and causes it to pass into the spheroidal form. In this condi- 

 tion the acid consumes by evaporation part of its own sensible 

 heat, and its temperature in consequence suffers a further de- 

 pression of about 5°. The acid is thus maintained at an ex- 

 tremely low temperature in the heated capsule, so that when 

 water is also poured into the red-hot vessel, it is immediately 

 congealed by the intense cold of the contiguous liquid. 



M. Boutigny attempts to account for the explosion of steam- 

 boilers by reference to the spheroidal condition of water. He 

 supposes that wlien water is admitted into an over-heated 

 boiler, it assumes the spheroidal state; and that afterwards, 

 on the partial cooling of the boiler, it is brought into contact 



