Chem.), after an exhaustive review of the material at hand, concluded that simple additive relations did exist but with considerable deviations, which he ascribed to differences in structure.
The critical volume provides data which may be tested for additive relations.
Schroeder the silver salts of the fatty acids exhibit additive relations; an increase in the molecule of CH2 causes an increase in the molecular volume of about 15'3.
They are characterized by their additive reactions: combining with water to form acids, with alcohols to form esters, and with primary amines to form amides.
The most direct manner in which to test any property for additive relations is to determine the property for a number of elements, and then investigate whether these values hold for the elements in combination.
While certain additive relations hold between some homologous series, yet differences occur which must be referred to the constitution of the molecule.
Walden (ibid.) has shown that certain salts dissolve in liquid sulphur dioxide forming additive compounds, two of which have been prepared in the case of potassium iodide: a yellow crystalline solid of composition, KI 14 S0 2, and a red solid of composition, KI 4S0 2.
Kopp, begun in 1842, on the molecular volumes, the volume occupied by one gramme molecular weight of a substance, of liquids measured at their boiling-point under atmospheric pressure, brought to light a series of additive relations which, in the case of carbon compounds, render it possible to predict, in some measure, the cornposition of the substance.
The molecular volume is additive in certain cases, in particular of analogous compounds of simple constitution.
Kopp systematized the earlier observations, and, having made many others, he was able to show that the molecular heat was an additive property, i.e.