144 
fied, our standard soap mixtures contain the 
proportions represented by a mol of the fatty 
acid neutralized by the gram equivalent of the 
proper metallic hydroxide, oxide or carbonate 
in the presence of a little water. 
As long known from empiric practise, the 
different soaps bind totally different quantities 
of water. We first determined the absolute 
amounts of water that are absorbed by equi- 
molar amounts of different oleates when pre- 
pared as described above. If that capable of 
holding most water is named first, the order 
in which these different soaps absorb water is 
about as follows; potassium, sodium, ammo- 
nium (2), lithium, magnesium, calcium, lead, 
mercury. Under the conditions of our ex- 
periments the first four bind all the water 
offered them (several hundred per cent.). 
Magnesium, however, holds but sixty per cent. 
its weight of water, and calcium oleate but 
forty. Even lower figures (about 10 per cent.) 
are obtained for the oleates of mercury and 
lead. 
This general order in which the oleates with 
different basic radicals hold water is repeated 
by the palmitates, margarates and stearates. 
If the amount of water used in the prepara- 
tion of the molar equivalents of soap is sufii- 
ciently reduced (to one fourth that stated 
above) then this same order may also be dis- 
covered in the case of the caprylates. These 
general findings seem therefore to justify the 
conclusion that a first factor in the determi- 
nation of the amount of water held by any 
soap resides in the nature of the basic radical 
combined with the fatty acid. 
We tried next to determine the effect of 
combining the same basic radical with differ- 
ent fatty acids of the same series. In these 
experiments we again neutralized one mol of 
the fatty acid with an equivalent of the nec- 
essary base (sodium or potassium hydroxide) 
in the presence of a constant volume (one 
liter) of water. The absolute amount of water 
taken up by a mol of any of these salts, as 
determined by discovering the maximum 
amount of water which such will take up at 
room temperature and yield a stiff jelly, in- 
creases progressively with the increase in the 
SCIENCE 
[N. S. Von. XLVIITI. No. 1232 
molecular weight of the fatty acid used. The 
absolute amounts of water absorbed vary 
enormously. From the lower members of the 
series (from the formates through the eap- 
roates) no colloid jellies at all can be ob- 
tained. The crossing line is well marked by 
sodium or potassium caprylate. These soaps 
form clear (molecular) solutions in twice their 
weight of water but they form jellies with 
once their weight of water. The amount of 
water that will be thus taken up and yield a 
jelly imereases progressively as acids above 
caprylic are used so that by the time stearic 
acid is reached, one part of soap will easily 
take up a hundred or even two hundred times 
its weight of water and form a solid mass. 
Experiments with fatty acids beyond stearic 
are not yet completed. Obviously then, with 
a given base, a second element in the amount 
of water held by a soap depends upon the na- 
ture of the fatty acid contained in the soap 
and its height in the series. 
We tried next the effects of different al- 
kalies, of different neutral salts and of differ- 
ent non-electrolytes upon the hydration capac- 
ity of different soaps (caprylates, laurates, 
oleates, palmitates, margarates and stearates 
of sodium and potassium). Our conclusions 
under this head may be summed up as follows: 
1. The addition of any alkali to a “solu- 
tion” of any of these soaps at first increases 
its viscosity or (in a limited volume of water) 
leads to its gelation; with higher concentra- 
tion of the added alkali, there follows a de- 
crease in viscosity (“liquefaction”) which 
change is succeeded, at sufficiently high con- 
centration of the alkali by complete separation 
of the soap from the dispersion medium as a 
dry mass floating upon the “solvent.” When 
equimolar solutions of the different soaps 
are compared it is found that the effects of an 
added alkali vary with (a) the fatty acid in 
the soap, (b) the base combined with the soap 
and (c) the basic radical of the added alkali. 
The lowermost members of the fatty acid 
series neither gel nor come out of “solution” 
upon addition of an alkali. The caprylates 
gel and come out easily while the higher soaps 
show these changes in increasingly marked 
