ACYLATED AMINO ACIDS IN SHAMPOOS 413 ness may be developed by incorporating as little as 10 per cent lauroyl safcosine acid in the sodium lauroyl sarcosinate or alternatively by lower- ing the pH. As an approach to measuring one aspect of what is obviously a complex property, lathers have been beaten up in a Waring blender and the rela- tive viscosity of the foams produced was measured by noting the sinking time of a magnesium strip. No claims are made for the meaningfulness of Figure 7. TEA-SABKOSYL L 300 •'• "'- • ß 200 •. 100 • I 100 75 50 25 0 % ALKYLABYL SULFONATE 400 ,100 200 1oo Figure 8. ,•••... SARKOSY• SOAP • DISTILLED •ATER 100 75 50 25 LAURYL SULFATE

414 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS this simple test, but it has been found that under the static conditions of the test, lauroyl sarcosinate foams are more viscous than lauryl sulfate or soap foams. Water hardness up to 250 p.p.m. calcium carbonate is with- out effect on either foam volume or foam viscosity. Viscous, creamy lathers are actually best obtained by incorporating small amounts of fatty amides or polyethyleneglycol fatty acid esters. Of the various products tested, Altosol C* produces the most desirable end effect, including ex- tended inhibition of crystallization of magnesium and calcium salts in very hard water. For formulation of cream shampoos, hydroxyethyl- stearamide seems to be best suited, combining opacifying, thickening and foam stabilizing functions. Fisur• •. 400 := 300 ,• 200 1oo 100 7,5 50 25 0 % LAURYL SULFATE In testing the sensitivity of lauroyl sarcosinate and other surface-active agents to defoamants such as water hardness, mixtures of neutral and par- tially hydrolyzed fatty glycerides, or carpet sweepings, a shake test using relatively dilute solutions (0.1 per cent) gave more significant results than the Waring blender. Sodium lauroyl sarcosinate at neutral and mildly alkaline pH's offers no special advantage over lauryl sulfate but mixtures of sodium lauroyl sarcosinate and lauroyl sarcosine acid have been found to have excellent foam stability under a wide variety of adverse conditions. Of some interest is a comparison of the foaming properties of mixtures of sulfur containing detergents with soap on the one hand and with lauroyl * An alkylolamide available from Geigy Industrial Chemicals.