FATTY ACID ALKYLOLAMIDES In this case, the hydrophilic nature of the "head" may be controlled by controlling the number of ethylene oxide molecules employed. Once again, as in all surface-active matters, it is the balance in the molecule of the hydrophilic "head" as against the hydrophobic "tail" that counts. Where the R-CO is derived from laurie acid or the mixed fatty acids of coconut oil, the compound, where the addition of ethylene oxide has been controlled so that n in the formula (2) equals 5, shows the best wetting characteristics at 25 ø C. Where, however, R-CO is derived from oleic acid, the best figures are shown where n equals 10. It must not be assumed, however, that the compounds showing the best wetting figures are necessarily the most effective for all purposes. Compounds of the type represented by formula (2) are effective emulsifying agents for a variety of purposes. The products where R-CO is derived from oleic acid and where n equals 5, are effective emulsify- ing agents for producing oil-in-water emulsions of mineral or vegetable oil extending the number of molecules of ethylene oxide in the compound diminishes the value as an emulsifying agent for these oils, but makes the compounds effective when used with kerosene or turpentine. The relatively water-insoluble compounds falling within our classification (b) are usually derived from a mono-alkylolamine such as monoethanolamine, mono-isopropanolamine or mono-isobutanolamine and a fatty acid. Whilst they are too insoluble to be used as detergents in their own right, the products derived from C•/C•4 saturated fatty acids, when used in conjunction with the sulphated or non-ionic detergents in common use, exert a most pro- nounced effect. Indeed, it is this type of material that has made possible the modern heavy-duty detergent washing powder for domestic use. Natur- ally enough, patents exist in this field. These relatively water-insoluble compounds increase not only the soil removal efficiency, but also in many cases the lathering power. In point of fact, as the figures to be quoted show, they are actually more efficient in some instances for improving the lathering power in the presence of grease than the derivatives of diethanolamine previously discussed. Their use, however, in liquid preparations is limited and must be formulated with great care, since under certain conditions, and particularly at low temperatures, they can give rise to clouding. These foam tests were carried out in the presence of oil, using an active detergent concentration representative of that used in domestic operations such as dishwashing, or the washing of fine fabrics, but rather lower than is usually employed for shampooing. In the tests 10 per cent by weight of an acyl- alkylolamide was added to a dodecyl benzene sulphonate preparation con- taining 37 per cent active matter. The resulting mixture was then diluted with water until at its final dilution the mixture cost the same per kilo as the dodecyl benzene sulphonate preparation without additions. In this way, of course, the preparations containing the acyl-alkylolamides comprised less active matter. From a commercial standpoint, however, it is important 175

JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS when assessing the effectiveness of an acyl-alkylo!amide to consider that these substances are frequently more expensive than the commercial detergents in common use. A cyl-alkylolamide Initial After After After added foam 15 mins. 30 mins. 1 hour None ...... 120 c.c. 50 c.c. 25 c.c. -- Lauric diethanolamide .. 130 c.c. 75 c.c. 50 c.c. -- Lauric mono-ethanolamide 190 c.c. 160 c.c. 155 c.c. 130 c.cs. In fairness, it should be pointed out that these tests were carried out in distilled water and consequently do not reveal the preparation containing the lauric diethanolamide as showing such a big advantage over the untreated dodecyl benzene sulphonate preparation. If the tests are repeated in hard water, or at a higher concentration such as is used in shampooing, the per- formance of the compositions containing either of the alkylolamides is shown significantly better than that of the untreated dodecyl benzene preparation. In detail, the tests were carried out at 30 ø C. in 300 c.c. capacity standard foam cylinders. 100 c.c. of liquor were present containing .7 grams of the detergent preparation and .2 grams anhydrous sodium carbonate, and 2.5 grams of groundnut oil were added. The sodium carbonate was present to ensure a uniform alkalinity throughout the tests. Ten uniform shakes were given to the cylinders in each case and the above figures are averages of results which duplicated well. Derivatives of mono-alkylolamines and fatty acids of the C • 4/C • 8 unsatur- ated type with one or more double bonds are extremely effective emulsifying agents for the production of water-in-oil emulsions, using mineral oil. As little as 3 per cent on the oil phase of oleic mono-ethanolamide is capable of yielding a stable emulsion, even when the final ratio of water phase to oil phase is as high as 4: 1 or more. The same compounds may also be used as stabilisers for oil-in-water emulsions, when used in conjunction with water- soluble surface-active materials, such as soaps or anionic detergents. A recent novel use for the insoluble fatty acid alkylolamides of our classi- fication (b) is as dye solvents in the formulation of lipsticks* and other cosmetics. It has long been a problem to the cosmetics chemist that the halogenated fluoresceins which he wishes to incorporate in lipstick composi- tions are insoluble in all the oils or waxes normally employed (except castor oil, which shows a small solvent power). A purely physical incorporation by grinding the dyes in the form of a fine powder with the lipstick base is only partially successful, and the maximum staining power is not obtained from the dye. In order to remedy this, chemists have resorted to the use of organic solvents rather akin to cellulose lacquer solvents, which can dissolve substantial amounts of halogenated fluoresceins. These organic solvents * B.P. 719,300. 176