280
GILBERT D. MILES A S D J O H S ROSS
FO-All ST-%BII,ITTOF POL'UTIOSS O F SOLIPS OF PURE FA\TTT A\CIIDS GILBEET D . MILES
ASD
J O H S ROSS
Colga t c -PaI tti o 1c'i:e- P e e t Co , J c rs e y C if y , S e IC J c r se u ~
Ileceiwd Jfci ii 24, 1.944
I n order to determine some of the factors 11-hich influence the foam stability of solutions of soaps, the authors have applied a compar:itivr method (9) for nieasuring relative foam stability to solutions of t h e sodiuix salts of pure fatty acids. The n-ork presented in this paper includes the examination of the influence of such vaiiables as p H , temperature, concentration, the presence of calcium and magnesium soaps, and combinations of soaps on the foam stability of soap solut'ions. The inadequacy of previous methods for evaluating foams 17-ith the high order of stability usually associated with soaps is emphasized by the absence of any directly relevant, published n-ork. C. I,. Baker ( 2 ) has presented some observations on the influence of p H on the foam stability of sodium stearate as part of a study on silicates as detergents. These results n-ith regard t,o foam stability are too anibiguous t,o permit detailed discussion here. We recognize that foam stability is a composite manifestation of several surface phenoniena. However, we have learned that changes in foam stability provide exceedingly useful clues to the possible mechanisms involved in certain phases of surface activity. 31.1TERIALS
The fatty acids used in this ~ o r l Jvere r deriwd from natural fats and n-ere purified by different methods, according to the nature of the fatty acid. The saturated fat,ty acids xere converted into the methyl esters and these were treated n-it,h potassium permnnganate in acetone solution in order t o remove the unsaturated impurities. The recorered neutral methyl esters were then fractionally distilled through a 5-foot modified Fenske fractionating column.
Methyl s t e a r a t e . . . . . . . . . . . . . . . . . . . . . . . . . . l Methyl palmitate. . . . . . . . . . . . . . . . . . . . . . ' llethq-1 inyristate. . . . . . . . . . . . . . . . . . . . . . Met,hyl laurate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Capric L1cid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
175.5 at 160.5 a t 132.5 a t 109.8 at 132.5 a t
Methyl Methgl Methyl Elaidic
118.5 a t 0 . 8 mm. 210.0 a t 1 . 0 mm. 105.4 a t 3 . 3 mm. 1n.p. 4 3 . 5 ~ .
oleate. . . . . . . . . . . . . . . . . . . . . . . . . . . . ricinoleate. . . . . . . . . . . . . . . . . . . . . . . . undecylenate.. . . . . . . . . . . . . . . . . . . . . . acid. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
' 1 .I
3 . 0 mni. 2 . 9 mm. 1.8mm. 3 . 2 min. 4 . 3 inm.
il ~b
11 iJ I
1
>os
Appros. 95 S p p r o x . 95 Appros. 98
