88 J. Thomsen’s Thermochemical Investigation 
involves, a certain amount of heat is lost on balancing the ac- 
count. The further conclusion that the ultimate loss of heat. 
is precisely the same as it would be if sulphuric acid could be 
made by the direct union of its elements, is an inference from 
the general theorem to which we have referred, and which may 
be stated thus: 
Whenever a system of bodies undergoes chemical or physical 
changes and passes into another condition, whatever may have been 
the nature or succession of the changes the quantity of heat evolved 
or absorbed depends solely on the initial and final conditions of the 
system provided no effect has been produced on the bodies outside. 
Hence when the initial and final conditions are the same, 
this would give us what we have so long sought, a measure 0 
the forces which determine the union of the elementary atoms. 
e might then be able to find the amount of heat which 
would be evolved by the union of 82 grams of isolated sul- 
phur atoms, 64 grams of isolated oxygen atoms, and 2 grams of 
isolated hydrogen atoms, to form 98 grarhs of isolated mole- 
cules of sulphuric acid. The comparison of such data woul 
give us what we may appropriately call the thermal potentials 
of the isolated atoms in their several relations, and this would 
of investigating molecular structures. We should thus obtain 
a certain criterion for determining the order and the nature of 
the bonds by which the atoms are united in any molecule. 
In a recent notice (this Journal, vol. xix, 264, April, 1880), we 
wrote: “The problem of finding what we have called the 
thermal potential of the atoms is not more remote than many 
roblems which have been successfully solved in organic sy? 
thesis,” and we have thus soon the pleasure of calling attention 
to a partial solution of the problem then stated. 
As is well known, in the molecules C=C; HC=CH; H,C= 
CH,; H,C-CH,; H,C | CH, (the first representing an assumed 
molecule of carbon in an aeriform condition, and the last repre 
senting two molecules of marsh gas) our present theories rega! 
the two carbon atoms as united by four, three, two, one an 
bonds respectively ; and in the paper we are noticing Thomse? 
