Avcust 9, 1918] 
degree. When potassium and sodium soaps 
are compared, it is found that an added al- 
kali will produce the series of changes earlier 
in a sodium soap than in a potassium soap. 
Similarly, if the effects are compared of add- 
ing equinormal solutions of potassium or 
sodium hydroxide to a given soap the former 
is found not so effective (in other words, a 
higher concentration is demanded to produce 
the series of changes noted above) as the 
latter. When solutions of the hydroxides of 
the bivalent or trivalent metals are used, the 
effects of the metallic radicals and the forma- 
tion of metallic soaps with their low hydra- 
tion capacity dominate the picture. Such hy- 
droxides, therefore, lead uniformly only to 
decrease in viscosity and separation of the 
slightly hydrated soap from the dispersion 
mediums. 
2. The addition of salts of the bivalent and 
trivalent metals to potassium, sodium, ammo- 
nium and lithium soaps leads to a clouding 
of the mixtures, a decrease in viscosity and a 
decrease in power to gel. The picture is again 
dominated, in other words, by the production 
of the metallic soaps with their low hydration 
capacities. A more careful study of the hy- 
dration and dehydration of the soaps of the 
alkali metals under the influence of various 
salts is therefore, limited to the salts of the 
alkali metals. As generally known in techno- 
logical practise, these salts lead to a “ salting 
out” of the soap, or, when used in smaller 
amounts, to a “gumming” or “stringing” 
of the soap. We were able to confirm and 
amplify here the investigations of other work- 
ers in this field which have shown that such 
gumming and ultimate salting out are depend- 
ent upon the concentration and the chemical 
nature of the salt used. With rare exceptions 
(more particularly those salts which in aque- 
ous solutions are not “neutral’’) all the or- 
dinary salts of potassium, sodium, lithium, 
ete., at first increase the viscosity of a potas- 
sium or sodium soap to a point where at 
proper concentration a soap jelly results, be- 
yond which further increase leads to a fall in 
viscosity (liquefaction) until, in still higher 
concentrations of the salt, the soap begins to 
SCIENCE 145 
separate from its clear dispersion medium, at 
first as a cloudy jelly and then as a (prac- 
tically dry) dehydrated soap mass swimming 
upon the clear “ solvent.” 
The intensity with which these successive 
changes are brought about again varies, at 
the same concentration of salt, with the fatty 
acid in the soap, the nature of the basic 
radical in the soap and the basic radical of the 
salt used. Potassium salts, for example, are 
less effective in bringing about the series of 
changes than the corresponding sodium or 
lithium salts. 
The acid radical (fluoride, chloride, bro- 
mide, iodide, nitrate, sulphocyanate, sulphate, 
acetate, tartrate, citrate) in the series em- 
ployed by us seems to influence the end re- 
sults so little as to come within the limits of 
experimental error. In other words, with salts 
of a given base the acid radical is practically 
of immaterial importance. 
When an alkali and a salt are together added 
to a soap, the action of the two is found to be 
algebraically additive. An alkalinized soap 
may be salted out by adding a neutral salt 
and at a concentration of the latter which 
would not by itself have proved effective. 
Vice versa, a partially salted soap may be com- 
pletely dehydrated by adding an alkali to a 
concentration at which the alkali alone would 
have produced no such effect. 
It is also of interest that all these effects of 
alkali, of Salts, ete., are largely reversible. A 
soap dehydrated by an alkali or a salt can be 
rehydrated by merely adding water; a soap 
partially dehydrated by a sodium salt can be 
rehydrated by substituting a potassium salt, 
ete. Most interesting, however (and phys- 
iologically important), is the fact that mag- 
nesium, calcium and even iron and copper 
soaps can, through the addition of the proper 
salts or hydroxides of the alkali metals, be 
slowly brought back into the more highly hy- 
drated soaps of these alkali metals. 
3. The non-electrolytes (alcohol, glycerin, 
dextrose, saccharose, lactose, urea) as com- 
pared with the electrolytes have at the same 
concentration relatively little effect upon the 
hydration and dehydration of soaps. They 
