42 CHEMISTRY AND PHYSICS IN RELATION 



If now we designate by R, a quantity of carbon and hydrogen, which belongs 

 to the formula C H. (like equivalents), we see immediately, that the composition 

 of alcohol can be expressed by that of pyroligneous spirit-j-2 R. 



Pyroligneous spirit, Alcohol. 



C 2 H 4 2 +C 2 H 2 = C 4 H 6 2 . 



While the composition of fousel oil may be expressed by that of pyroligneous 

 spirit -f 8 R. 



Pyroligneous spirit. Fousel oil. 



C 2 H 4 2 +C 8 H 8 = C 12 H K 2 . 



The formula of formic acid is C 2 H 2 O 4 , that of acetic acid C 4 H 4 O 4 , that 

 of valerianic acid C, H, O 4 . We easily perceive that the formula of the 

 acetic acid can be expressed by that of formic acid-f-2 R, the formula of valerianic 

 acid by that of formic acid + 8 R. In accordance with these experiments, a 

 boiling point increased 34 F. corresponds with the occurrence or excess of 2 equiv. 

 of carbon and 2 equiv. of hydrogen, or of 2 R. It may be seen that the relation 

 between this group is constant, and that a conjecture concerning their composition 

 may be made from the knowledge of the boiling point. The boiling point of the 

 formate of oxyde of methyle is 96 F., that of formate of oxide of aethyle, 100 

 F., the difference between the two, 34. From this it might be conjectured that 

 the composition of the latter differs from the former about C 2 H 2 or 2 R, and 

 such is the case, The formula for formate of oxide of methyle is C 4 H 4 O 4 , 

 that of the corresponding compound of aethyle C 6 H 6 O 4 , and therefore about 

 C 2 H 2 higher. But butyric acid boils at 311 F., and its boiling point is, therefore, 

 about three times 34 higher than that of formic acid. The comparison of their 

 formulae shows that butyric acid may be looked upon as formic acid -f 6 R. 

 Toluidine and aniline are two organic bases, both so far different in their compo- 

 sition, that aniline contains C 2 H 2 , or 2 R more than toluidine. The comparison 

 of their boiling points shows that the boiling point of aniline is 34 higher. 



THE LAW OF THE RELATIONS OF DEPENDENCE IS DISTINCT FROM 

 THE CAUSES BY WHICH THESE PHENOMENA ARE EFFECTED. 



No one will deny, from these examples, the existence of a natural law for this 

 group, nor can any one doubt that the qualities of a body stand in a definite rela- 

 tion to its composition, and that a change in a quality corresponds with a similar 

 deviation in its quantitative relations. It must be especially noticed here, that the 

 knowledge of this natural law is quite independent of the actual cause, or of the con- 

 ditions which, taken together, effect the constant boiling point, for we are as ignorant 

 of what relates to the boiling point, as we are concerning the conception of life. 



THE BOILING POINT, THE SPECIFIC GRAVITY, AND THE COMPOSI- 

 TION OF A BODY STAND IN RELATIONS OF DEPENDENCE TO 

 EACH OTHER. 



In the above examples we have only touched upon one of the relations of the 

 quality and composition of bodies, there being as many of these relations as the 

 body has properties. A law has been obtained for a large group of chemico organic 

 combinations, by which, from the knowledge of the boiling point, and the compo- 

 sition of the body, it has been established how many pounds a cubic foot of the 

 combination weighs, and that the property of the specific gravity, and consequently 

 of the pressure which the body exerts on equal spaces, stand in a definite relation 

 to two others, which are changed as it likewise is changed. 



SPECIFIC HEAT AND ATOMIC WEIGHT. 



A similar relation of dependence has been established in reference to the amount 

 of heat which different bodies need in order to rise to the same temperature, and 



