JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS is perfectly feasible to keep it as a standard aqueous solution, say exactly 10 lbs. to 10 gallons, so that if you want to use 1 lb. of triethano- lamine for 1 cwt. of a cream or lotion, all that is necessary is to measure an exact gallon of stock solution. Many aliphatic hydroxy- lamines are hygroscopic and absorb carbonic acid, so should not be freely exposed in the pure state. If it is desired to make triethano- lamine stearate separately, it should be made as near the melting point of the stearic acid as possible say 55øC. for the stearic acid and 40øC. for the triethanolamine: if the mix- ture becomes too hot its colour will deteriorate. In making creams, the components should be stirred ener- getically only at the very start, then much more slowly. If stirred vigorously in the cold, the cream generally becomes thin. On the other hand fluid lotions may be homogen- ised, the best proportion of amine to fatty acid being carefully deter- mined. In the manufacture of special soaps, triethanolaminct soaps have very low alkalinity, and the oleate, ricinoleate, linseed oil soaps and so on are soluble in many oils and sol- vents and are used in dry-cleaning. As a guide to oil solubility, the triethanolamine soaps are more oil soluble than the monoethanolamine soaps, and the isopropanolamine soaps are more soluble than the cor- responding ethanolamine soaps. If we keep the amine tertiary and knock out hydroxyl groups, the soaps become progressively more oil soluble. It is possible to substitute larger hydrocarbon substituents as in diethylhexyl ethanolamine, be- longing to a class .of substances val- uable as corrosion inhibitors in oils. CONCERNING THE POLYGLYCOLS. Returning from our excursion among the nitrogen compounds, I would like to conclude this Dutch auction of the synthetic aliphatics in descending order of complexity with a brief survey of the compounds with two carbon atom chains. Apart from acetic acid and the vinyl poly- mers, these generally start, as al- ready indicated, with ethylene oxide, and a very numerous class of compounds is built up with these linkages. The simple glycols and glycol ethers are humectants, per- fumery, colour and lacquer solvents, and blending solvents for colours, oils and waxes, usually of mild odour. In recent years the process has been carried very much further. Ethylene and propylene oxides can be converted into polyalkylene gly- cols which can contain any number from three to seventy ethylene oxide linkages. In the polypropylene glycol series, hal/ the CH2 groups are substituted by CH.CHa, pro- bably with two secondary terminal alcohol groups (--CHOH 1 CH•). Now as we progress along such a series, several interesting and sometimes very useful changes be- come apparent. The prototype, diethylene glycol, is a liquid of low 136

INFLUENCE OF ALIPHATIC CHEMISTRY DEVELOPMENTS freezing point, b.p. 245*C., about as hygroscopic as glycerin, but, like propylene glycol, more resist- ant against mould growth it is very sparingly soluble in oils, and is ap- preciably toxic internally. As we advance up the series, (CH..OH)• (CH•OCH•)n the boiling point increases to around 350øC. or a little over, and the freezing point rises rapidly the pounds become less and less hygro- scopic, and up to about n -:: lg they become better solvents for oils and fats, for essential oils, and also for various resins and cellulose esters and ethers. Above n = 12 these solubilities seem to decline again, probably because of the size of the molecule. Doubtless for the same reason, toxicity very much declines. In the polypropylene series, water solubility declines rapidly and oil and resin solubilities are much more •narked. They are also much more fluid than the polyethylene glycols. This type of solvent may well prove very satisfactory for blending spirit soluble colours with oils and waxes, as in lipstick base. Where n ::= 20 and over, the poly- ethylene glycols become solid and •nay be called "water soluble waxes" --strictly of course pseudo waxes, They are totally insoluble in petro- leum, and only slightly soluble in me.st animal and vegetable oils the harder members are therefore use- fully incorporated in industrial bar- rier creams for operatives in engin- eening,. paint works, oil refineries, petrol stations or simply for clean- ing out the gas cooker. They are very good hair conditioners or emol- lients for hair shampoos or setting lotions. Their emollient effect is free from stickiness or hygroscopicity. They can also be used to suspend high proportions of inorganic astrin- gents, so obviating the difficulties of emulsion techniques in these cases. Polyglycols can be further modi- fied, either by after-treatment or by •ntermediate 'treatment, by substi- tuting one or both of the hydroxyl groups. Simple interpolymerised other groups•as for instance compounds made by catalysing alcohols with a large excess of alky- lone o,xides- yield a series of s•vn- thetic lubricants of very low freezing points and quite exceptional viscos- ity characteristics, reduction of vis- cosity with increasing temperature being less than with the very highest class of naturally derived lubricating oils due to the incidence of oxygen linkages they also oxidise readily and leave little or no carbon or tar behind. These compounds are sometimes soluble in water and sometimes in- soluble the water insoluble types disolve in dilute alcohol. All have strongly oily character and have one free hydro.xyl group. They therefore have some of the physical and sol- vent qualities of castor oil, and have been used in America as bath oils, constituents of lotions, and condi- tioners and fixatives for the hair, incapable of rancidity. POLYGLYCOL ESTERS AND ETHERS. Finally, by substituting long c•rbon chains, either of ether or ester type, 137