CAL 



CAL 



All solid bodies, a very small number ex- 

 cepted, may be converted into liquids by 

 heating them sufficiently ; and, on the 

 other hand, every liquid, except spirit of 

 wine, is convertible into a solid body, by 

 exposing it to a sufficient degree of cold. 

 All liquid booses may, by heating them, 

 be converted into elastic fluids, and a 

 great many solids are capable of under- 

 going the same change ; and lastly, the 

 number of elastic fluids, which by cold 

 are condensible into liquids or solids, is 

 by no means inconsiderable. These facts 

 have led philosophers to form this general 

 conclusion, " that all bodies, if placed in 

 a temperature sufficiently low, would as- 

 sume a solid form ; that all solids be- 

 come liquids when sufficiently heated; 

 and that all liquids, when exposed to a 

 certain temperature, assume the form of 

 clastic fluids." The state of bodies then 

 depends upon the temperature in which 

 they are placed ; in the lowest tempera- 

 tures they are all solid ; in higher tempe- 

 ratures they are converted into liquids ; 

 and in the highest of all they become 

 clastic fluids. The particular tempera- 

 tures at which bodies undergo those 

 changes are exceedingly various, but 

 they are always constant for the same 

 bodies. Thus we see that heat produces 

 changes on the state of bodies, convert- 

 ing them all, first into liquids, and then 

 into elastic fluids. 



When solid bodies are converted by 

 heat into liquids, the change in some 

 cases takes place at once. There is no 

 interval between solidity and liquidity ; 

 but in other cases a very gradual change 

 may be perceived: the solid becomes 

 first soft, and it passes through all the 

 degrees of softness, till at last it be- 

 comes perfectly fluid. The conversion 

 of ice into water is an instance of the 

 first change ; for in that substance there 

 is no intervening state between solidity 

 and fluidity. The melting of glass, of 

 wax, and of tallow, exhibits instances of 

 the second kind of change ; for these 

 bodies pass through every degree of 

 softness before they terminate in per- 

 fect fluidity. In general, those solid bo- 

 dies which crystallize or assume regular 

 prismatic figures, have no interval be- 

 tween solidity and fluidity ; while those 

 that do not usually assume such shapes 

 have the property of appearing succes- 

 sively in all the intermediate states. 



Caloric not only increases the bulk of 

 bodies, and changes their state from 

 solids to liquids, and from liquids to 

 elastic fluids, but its action decomposes 



a great number of bodies altogether, 

 either into their elements, or it causes 

 these elements to combine in a different 

 manner. Thus, when ammonia is heated 

 to redness, it is resolved into azotic and 

 hydrogen gases. Alcohol, by the same 

 heat, is converted into carbureted hydro- 

 gen and water. 



This decomposition is in many cases 

 owing to the difference between the vo- 

 latility of the ingredients of a compound. 

 Thus, when weak spirits, or a combina- 

 tion of alcohol and water, are heated, the 

 alcohol separates, because it is more vo- 

 latile than the water. In general, the 

 compounds, which are but little or not at 

 all affected by heat, are those bodies 

 which have been formed by combustion. 

 Thus water is not decomposed by any 

 heat which can be applied to it ; neither 

 are sulphuric, phosphoric, or carbonic 

 acids. Almost all the combinations into 

 which oxygen enters, without having oc- 

 casioned combustion, are decomposable 

 by heat. This is the case with nitric 

 acid, hyperoxymuriatic acid, and many of 

 the metallic oxides. 



All bodies that contain combustibles 

 as component parts are decomposed by 

 heat. Perhaps the metallic alloys are 

 exceptions to this rule ; at least it is not 

 in our power to apply a temperature high 

 enough to produce their decomposition, 

 except in a few cases. 



When two combustible ingredients and 

 likewise oxygen occurtogetherin bodies, 

 they are always very easily decomposed 

 by heat. This is the case with the 

 greater number of animal and vegetable 

 substances. 



Having examined the nature, and some 

 few of the properties and effects of calo- 

 ric, as far as the subject has been hitherto 

 investigated, it now only remains for us 

 to mention the different methods by 

 which caloric may be evolved or made 

 sensible, or the different sources from 

 which it may be obtained. These sour- 

 ces may be reduced to five : it radiates 

 constantly from the sun ; it is evolved 

 during combustion ; and it is extricated 

 in many cases by percussion, friction, and 

 mixture. The sources of heat, then, are, 

 the SUN, COMBUSTION, PKRCUSSIOX, FRIC- 

 TION, MIXTURE, which see. See also 

 CAPACITY. 



CALORIMETER, in chemistry, an in- 

 strument contrived by Lavoisier and La 

 Place for measuring the comparative 

 quantities of caloric in bodies. 



CALTHA,in botany, a genus of the 

 PolyunUria Polygynia class and order. 



