140 REPORTS ON THE STATE OF SCIENCE.—1918. 
tions in the internal pressure, compressibility, viscosity, solubility, 
&c. The phenomena are not in relation to the valency of either ion, 
but follow a series known as that of Hofmeister (18388). The order 
of activity in anions is :— i 
SCN <I<C10;<NO3<C1<CH;COO <SO, <tart. <citrat. 
In cations .— 
NH, <Li<Cs<Na<Rb<K. 
But the difference between individual cations is less marked than 
that between anions. This series is met with in many phenomena 
in which emulsoid colloids play a part. The action appears to be 
preceded by adsorption. 
The effect of acid and alkali in increasing the amount of water 
taken up in the swelling of emulsoid colloids has been the subject of 
experiments by Martin Fischer and G. Moore (1907), Chiari (1911) 
and others. According to Pauli (1912), the swelling is due to the 
formation of electrolytically dissociated salts and the affinity of the 
protein or other colloidal ion for water. If this be the case, we see 
how little importance the process can have in the phenomena of 
cedema or of “acidosis,” where the possible increase in hydrogen-ion 
concentration is far too small to result in any salt formation with 
proteins. The experimental results of Fischer and Moore show, 
moreover, that a fairly high degree of acidity is necessary to produce 
any significant effect. Pauli’s point of view is rendered doubtful 
also by the fact that the swelling occurs in solids, as well as dispersed 
molecules. It seems more likely that it is due to a change in the 
properties of water at the surfaces of the constituent elements of the 
colloidal masses, a change conditioned by the adsorption of inorganic 
ions at this situation. 
The opposite effects which sodium and calcium salts have in 
reversing the phases of oil and water systems and on the permeability 
of the cell membrane have been referred to in the preceding section, 
together with the necéssity for the presence of both for maintenance 
of the normal cell processes. If we confine our attention only to the 
cation in its action on emulsoid systems, it is difficult to understand 
why there should be, not merely a quantitative difference between 
univalent and bivalent ions, but an opposite effect. Clowes (1916, 
p. 408) holds that the opposition is really one between anions and 
cations, a more intelligible view. In the case of calcium chloride, 
for example, the cation is more powerfully adsorbed and reactive 
than the anion; in that of sodium chloride, the anion is adsorbed to 
a greater degree than the cation. Hence the possibility of obtaining 
a balance between the two effects and the reason why a small con- 
centration of calcium chloride balances a much larger one of sodium 
chloride. This view is confirmed by the fact that much less sodium 
citrate than of sodium chloride is required to counteract the effect 
of calcium chloride, because the citric anion is more powerfully 
adsorbed than the chlorine ion. But the possibility of the production 
of complex ions, containing calcium and the citric ion, must not be 
overlooked. 
A certain difficulty arises with regard to potassium. It is found 
that to maintain normal cell processes and to permit growth the 
