808 REPORTS ON THE STATE OF SCIENCE.—1912. IV.a. 
by Hulett.°* This observer showed that the solubility of gypsum in 
water is appreciably greater when the particles do not exceed 
0°00003 cm. than when they are as large as 0°0002 cm.: the solubility 
of barium sulphate is affected in the same way. This subject was 
further discussed in a publication by Marie.1™4 
From experiments with alabaster Bruner and Tolloczko 1°? show 
that the velocity of dissolution is dependent on the structure, crystal- 
line or granular, of the solid substance used as solute. 
1902 In the following year Schick 1°? compared the solubility at 
" 25° and 100° of the red and the yellow forms of mercuric oxide, 
and found them to be identical. Pomeranz '*! contributed a mathe- 
matical discussion of the relationship between the solubility of the salts 
of an optically active monobasic acid and of the mixture of the salts of 
the d- and l-acids. He established a mathematical relationship— 
L= l.,/2; in which L represents the solubility of the inactive 
mixture, and | that of either the d- or I-salt. When the non-dissociated 
portions were taken into account by the author the equation became 
L=1 {2(l—a) + V2a} ; 
this formula was applied to silver valerate. 
An influence on solubility, due to the size of the particles, was 
1903 detected by Béttger 1** when measuring the solubility of spar- 
* ingly soluble salts. The observed effect was small, amounting 
to about 1 to 2 per cent. Further work on this subject was published 
1904 by Hulett,’®* who, after taking every precaution against errors, 
‘ affirmed that finely divided gypsum is more soluble than gypsum 
plates, and that the concentration of the solution saturated with finely 
powdered gypsum gradually falls, owing to an increase in the size of 
the particles in contact with the solution. This author’s criticism of 
Kohlrausch’s * work appears to have been based on a misunderstand- 
ing.1°? When discussing the solubility of silver chloride with refer- 
5 ence to atomic weight determinations, Richards and Wells 7° 
1909. state that freshly precipitated silver chloride is more soluble than 
that which has been standing: probably this depends upon a change in 
size of the particles. 
Holty ?°° adversely criticised this conception of small particles 
having a greater solubility than larger particles; he based his opinion 
upon experiments made with sucrose dissolving in pyridine. 
1907 When in the amorphous state the sulphides of the heavy 
’ metals were found by Weigel ?°° to be more soluble in water than 
when they are in the crystalline state—a result which is not in harmony 
with Bodlinder’s formula. + 
The solubility of a colloid was defined by Duclauz **? as the 
1909. concentration at the point when no more solvent can be removed 
from the solution by filtering through collodion under increasing 
pressure, and by this method he determined the solubility of such 
different colloids as-gelatin and ferric oxide. He was able to show that 
the solubility, thus defined, is related to the size, composition, and 
electric charge of the molecular clusters which compose the colloid. 
* Zeit. phys. Chem., 44, 199. + Ibid., 27, 55. 
