HEAT OR CALORIC 1 . 49 



fa.) The antagonist power is cohesion. 



Therefore, as regards all the three forms of matter, solid, 

 fluid, and gaseous, the expansion varies with the ratio of these two 

 forces ; only one of which exists in the gases. 



6. GASES AND ALL AERIFORM BODIES EXPAND ALIKE.* 



(a.) One body, of this class, corresponds with one of another class; 

 e. g. carbonic acid gas with hydrogen, steam with vapor of alcohol, &c. 



(b.) The same body corresponds with itself, equal variations of 

 temperature producing equal variations of volume, in different parts 

 of the scale. 



(c.) The reason of this exception is obvious, as in aeriform bodies 

 there is no cohesion to overcome; the power of the heat is, therefore, 

 the same upon them all. 



7. Fluids expand very unequally. 



(a.) In general, the lower the boiling point of a fluid is, the more 

 it is expanded by heat, and vice versa, as is seen in ether, alcohol, 

 water, and mercury. 



(b.) In general, also, the expansibilities of liquids are inversely as 

 their boiling temperatures. Thomson. 



(c.) In any given liquid, the expansibility increases with the rise 

 of temperature, and those are the most equal, whose boiling point is 

 the highest. 



(d.) The expansibility of fluids does not follow the ratio of the 

 density. 



(e.) It increases very rapidly as we approach the boiling point. 



* Mr. Dalton of Manchester, (Eng.) and Gay Lussac of Paris, ascertained, by 

 numerous experiments, that the expansion of all bodies, in the form of air, is the 

 same, for equal additions of heat; and moreover, that the expansion of any one agri- 

 form body is nearly, although not perfectly, equable for equal additions of heat, in 

 different parts of the scale. 



It was formerly believed, that every different gas was affected differently by heat, 

 and tables of expansion of the different gases were constructed, but this variation 

 was owing to the presence of water in all experiments before those of Dalton and 

 Gay Lussac, as the vapor mixing with the gas under examination, must neces- 

 sarily falsify the result. 



100 cubic inches of common air, in passing from 212 to 1035 become 250. cub. in. 

 100 do. common air, " " 32 " 212 137.5 



100 do. water, " " do. " do. " 104.5 " 



100 do. iron, '* " do. " do. " 100.1 



The expansion of air is then eight times greater than that of water, and that of 

 water forty five times greater than that of iron. The expansion of any one gas ap- 

 parently diminishes a^little as the temperature increases; it is however probable 

 that this difference, as it is so very small, is only apparent. 



Dalton informs us that the expansion of 100 cubic inches of air, from 55 to 133, 

 or for the first 77<| , was 167; and from 133 to 212, or the second 77^, it was 

 only 158 : but if this difference be imputed to inaccuracy, we may conclude that the 

 expansion is equable. Aeriform bodies expand one four hundred and eighty third 

 part of their volume for every degree of Fahrenheit between freezing and boiling. 

 Vide Manches. Memoirs, V. 593 ; Th. 1. 338 ; and Ann. de Chim. xliii. 137, and v. 43. 



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