796 REPORTS ON THE STATE OF SCIENCE.—1912. IL.a. 
be conveniently dropped as a help towards understanding the cause 
of dissolution and the condition in which a substance exists in solution. 
As evidence is accumulated from the study of the subject on 
broad lines and the behaviour of non-aqueous solvents becomes better 
understood, the necessity arises of regarding dissolution as primarily 
a chemical process in which both solvent and solute undergo change 
and rearrangement: a change which, besides involving their reciprocal 
interaction, includes their degradation into simple molecules. 
IJ.—Metuops or DrreRMINATION, 
In Part I. of this Report (Sheffield, 1910) the attention of authors 
was directed to the importance of placing'on record a brief but exact 
description of their methods of working when publishing the results 
of solubility measurements. If quantitative work on this subject is 
to be of value to later investigators, it is absolutely necessary that 
the limits of accuracy should be made known. Only from such 
knowledge is it possible to judge whether legitimate use may be made 
of published data in any subsequent research. 
Within the scope of this Report it is not possible to refer to all 
the different methods of determining solubility which have been made 
use of from time to time: much necessarily depends upon the 
properties of both solvent and solute, and upon the temperature and 
pressure at which measurements are made. It is thought to be 
sufficient to include in this section only methods of more or less 
general application and those which present useful elements of 
novelty. 
A.—Solubility of Solids. 
When studying the solubility of solid substances in gases, earlier 
investigators made use of a modified form of Andrew’s apparatus.* 
1897 In the research on this subject carried out by Talmadge *’ the 
~<"* following method was adopted. A saturated solution of the 
solute (camphor) in the solvent (ether) was distilled from a flask 
connected to a condenser to which was attached a receiving vessel 
in connection with a pump and manometer; the solvent was heated 
slowly to the desired temperature, and the distillate, collected under 
reduced pressure, was analysed by a refractrometric method. 
It is sometimes stated that difficulty is experienced in preparing 
saturated solutions of a salt in the solution of another salt: this was 
noticed particularly by Léwenherz?* when determining the solubility 
of potassium sulphate in solutions of magnesium chloride. He 
emphasised the necessity of heating the solution above the tempera- 
ture at which determinations are to be made and then allowing it 
to cool, because the potassium salt dissolves only with difficulty in 
the solution of the magnesium salt. 
A modified form of ‘‘ Beckman apparatus ’’ has been described by 
Meyerhoffer,*” the new form being available either for determinations 
of freezing point or for solubility measurements. 
In the same year, a somewhat complicated form of apparatus was 
* Vide Part I., R. 80. 
