HEAT OR CALORIC. 85 



sulphuretted hydrogen, carbonic acid, nitrous oxide, cyanogen, muri- 

 atic acid, and chlorine.* 



Strictly, the distinction between vapors and gases, although conven- 

 ient in description, is unimportant. A vapor is derived from a body 

 whose vaporific point is within our reach ; but that of a true gas, is 

 lower than our means will enable us to go. 



(b.) Caloric converts both^ solids and fluids into gases, and vapors. 

 Camphor, benzoic acid, and carbonate of ammonia, are easily 

 converted into vapor, by being thrown upon a warm iron ; a bell 

 glass may be placed over them to catch the vapor. Some solids are 

 volatilized without previous fusion sal ammoniac and arsenic are of 

 this number. 



(C.) WlTH EQUAL PRESSURE AND PURITY, EVERY LIQUID HAS A 



FIXED BOILING OR VAPORIFIC POINT ; c. g. water, the barometer be- 

 ing at 30 inch, boils at 212 ; ether, at 96 or 98 ;{ alcohol, 173 

 to 176. 



Water in a glass vessel boils at 214 or 216 in a metallic ves- 

 sel, at 212. The boiling point in most liquids, is lowered several 

 degrees by putting in chips of wood, coils of wire, metallic filings, 

 pounded glass, &c. The bubbles of steam are thus broken, and the 

 heat escapes more rapidly. Dr. Bostock thus reduced the boiling 

 point of ether, 50, and that of alcohol, 30. || 



(d.) The steam or vapor, is of the same temperature with the boil- 

 ing liquid. 



(E.) PHENOMENA OF EBULLITION explained by the instance of 

 water. As the water is warming from the common temperature, it 

 is first thrown into currents by the change of specific gravity, and 

 when it arrives at 2 12, IT elastic vapor then forms at the bottom of the 

 fluid, and from its levity ascends, is condensed and disappears ; it is 

 followed by other bubbles, and when the water is thus all heated to the 

 boiling point, the vapor passes through uncondensed, and is dissipated 

 at the top. The water remains at 212 till the last drop is exhaled. 



The old theories of palpable fire, or matter of caloric, of air bub- 

 bles passing through the water, and thus causing its agitation, &c. 

 are untenable, and unworthy of discussion. Water, in the aeriform 



* See Mr. Faraday's experiments in Philos. Transac. part II. for 1822, and Am. 

 Jour. Vol. 7 pa. 352. 



t Dr. Black laid the foundation of the philosophy of vapors and gases, or in other 

 words, of aeriform bodies, by his discoveries respecting latent heat, and by proving 

 the distinct existence of an auriform body, different from common air, namely, carbo- 

 nic acid gas, called by him, fixed air. The period of this discovery was 1757. 



t Dr. tire says 100. 



For exceptions, See Henry, 10th Lond. Ed. Vol. I. pa. 114 ; Ann. Philos. new 

 series, IX. 296. Ann. de Chim. et de Phys. torn, VII. pa. 307; and Jour. Science, 

 Vol V. pa. 361. || Ann Phil. N. S. Vol. IX. 



IT And also, when the vapor has acquired elastic power sufficient to lift both the 

 atmosphere and the superincumbent fluid. 



