Miscellanies. 403 



^application of heat may cause the liquid to dilate, to contract, or 

 remain stationary. 



These anomalies have furnished the means of verifying the num- 

 bers which the preceding researches had given relative to dilatation 

 and vaporization. According to these numbers, the point of equi- 

 librium above v^^hat the liquid increases and belovv^ what it diminishes 

 by the addition of heat, results from such a proportion between va- 

 cuity and fullness that at zero the stratum of liquid occupies |f of 

 the whole tube. If the liquid occupies at zero the third of the tube, 

 we have a retrograde thermometer whose fluid increases by cold and 

 diminishes by heat. If the liquid occupies at zero two thirds of the 

 tube, we have a normal thermometer, — one in which the fluid in- 

 creases and diminishes according to the laws of dilatation. The play 

 of this thermometer is limited to +30 Cent. ; for at this tempera- 

 ture the tube is entirely filled by the liquid. 



A thermometer of this kind would have a great advantage over 

 common thermometric instruments, in determining the temperature 

 of cellars and similar places below +30° Cent. 



Specific gravity. — Liquefied gas, whose specific gravity at 0° is 

 .83, (water being taken for unity,) presents the unique phenomenon 

 of a liquid, which, from —20° to +30 Cent, runs over the scale of 

 densities from .90 to .60. 



Action of liquid carbonic acid on other substances. — While it 

 remains liquid it is absolutely insoluble in water, with which it does 

 not mix, but floats above it. It is the same with respect to the fat 

 oils. 



It is soluble in all proportions in alcohol, ether, naphtha, spirits of 

 turpentine, and carburet of sulphur. - 



It is decomposed, when cold, with effervescence by potassium ; it 

 has no sensible action on lead, tin, iron, copper, &c. 



Cold produced by liquid carbonic acid in its transition from the 

 liquid to the gaseous state. — -When a jet of the liquid acid is direct- 

 ed upon the bulb of an alcoholic thermometer, it rapidly sinks to 

 — 90° Cent. But the frigorific effects do not respond to this abase- 

 ment of temperature, a fact which is explained by the almost abso- 

 lute want of conducting power of the gases and their low capacity 

 for heat ; hence the intensity or tension of cold is enormous, but the 

 sphere of activity is limited in some sort to the point of contact. 

 The congelation of the mercury is confined to small portions of it, 

 and if a finger is exposed to a jet of the liquid a sensation of burn- 



