678 Scientific Proceedings, Royal Dublin Society. 
about by the principle of closest-packing is immediately productive 
of a change to the linked condition not produced by any less close 
and symmetrical juxtaposition. Now, in order that the new 
molecules formed when a chemical synthesis takes place may all 
have the like composition, it is manifest that the atoms which 
combine to form them must, as an antecedent condition, by some 
means or other come to be distributed through space in the precise 
proportions obtaining in these molecules. Consequently this 
uniform intermixture of the combining atoms or complexes which 
accompanies or precedes the act of chemical synthesis may be 
instanced as greatly resembling the combination in precise pro- 
portions of two fluid assemblages which paves the way for a change 
of state as described above.’ 
This change of state, which stereotypes the homogeneous 
arrangement reached by the assemblage, has its representative in 
the chemical change or act of synthesis whose occurrence is. 
evidenced by change of properties and manifestation of energy, 
The intermixture which accompanies or precedes the produc- 
tion of definite compounds containing water of crystallization, or of 
those double salts whose constituent salts are held together so 
loosely that the tie does not survive the passage to the liquid state, 
also furnishes a resemblance to the symmetrical intermixture 
leading to change of state above referred to; the only difference 
is that in the fluctuating or liquid state there will be at least two 
kinds of separate groups present in a compound assemblage which 
is paralleled by the last-named cases, and not one kind of group 
only.” 
The change known as polymerisation resembles the symmetrical 
compounding of groups occurring in a simple assemblage in the 
way above described, e. g., 
38C,H,O = C;H,.0; 
3 mols. acetaldehyde = 1 mol. paracetaldehyde. 
When the homogeneity produced locally is not stereotyped as. 
it arises by a contemporaneous change of state, and thus the 
1 See note 1, p. 675. 
* Comp. Pope’s translation of Fock’s ‘‘ Chemische Krystallographie,”’ pp. 36, 37, &c. 
