•2MULS]•ONS AND THE COSMETIC perfume in water, but also one which will function as an efficient emulsi- fier. If a surface active agent such as sodium lauryl sulphate is chosen, the solubilising effect is good (in the presence of an efficient peptiser, such as carbitol) but the ultimate dilution in water will not be an emulsion and may well actually be clear. On the other hand, the alkali soaps such as potassium ricinoleate are efficient solubilisers and emulsifiers. This difference has been explained in the earlier stages of the article. As a perfume is compounded from materials which are almost insoluble in water (terpenes, etc.) and sub- stances which are partially soluble (alcohols, etc.) it must be appre- ciated that the perfume itself will have an effect upon the nature o[ the system. Thus it will not be pos- sible to establish a formula indicating the quantities of water-soap-solvent, and perfume to be used, as the vari- ous ratios will depend upon the nature of the constituents of the per- fume employed. "Sulphonated" Castor Oil (T.R.O.) is a good dispersing medium but a rather poor emulsi- fying agent. It is sold usually as the di sodium salt containing vary- ing amounts of water. Most per- fumes will dissolve in this body to the extent of 10% and will produce clear solutions in distBled water al- though these solutions will rapidly cloud. The presence of free sodium ricinoleate results in a strong opales- cence in tap water. Larger amounts of perfume may be added, especially in the presence of certain hydroxylic compounds such as glycols, ete, Benzyl alcohol will be found useful to clarify dispersions of perfume and T.R.O. The non-ionic agents are of great use in solubilising oils, although relatively expensive. Where an expensive bath essence is concerned, the cost of the dispersing agent is of less significance. Three or four parts of proprietary Sorbitan mono laurate poly oxyalkylene derivatives are recommended by the makers to solubilise one part of perfume. Mono o!eates of high molecular weight poly ethylene glycols are said to confer spontaneous emulsification upon mixtures of essential oils. The poly ethylene glycol and poly oxyalky- lene chains, when used in conjunc- tion with long chain fatty acids or alcohols, confer solubilising action upon these emulsifiers. An interesting and instructive experiment was carried out on the following lines: Solutions of triethanolamine oleate in Carbitol, water, benzyl acetate and benzyl alcohol were prepared and placed in burettes. In one sehes the triethanolaminc oleate was used at the rate of 5% in each solvent. In the. second series the soap content was increased to. 10%. A number of experiments were made commencing with a constant volume of the benzyl acetate/soap solution and making various additions of the aqueous solution. In each case the mixture was titrated with the Carbitol solu- tion until a clear solution was obtained. The series was extended to cater for varying amounts of the 155

JOURNAL OF THE $OCIET'¾ benzyl acetate solution. These experiments were repeated with a benzyl alcohol solution in the place of the benzyl acetate soiution and further extended with mixtures of the benzyl alcohol/benzyl acetate solutions. On obtaining a clear solution in each separate experiment, the mix- ture was shaken with nine times its volume of water and the type and stability of each dispersion noted immediately and after one week. By plotting the oil/water ratio for each system against the Carbitol/oil + water ratio, a number of graphs were drawn. These graphs show the proportions of the four ingredients of the system required to produce clarity and maximum emulsification on subsequent dilution with water. OF CO$3IEIIC CilE3•ISI$ Benzyl alcohol exerts a considerable influence upon the system, since it is dispersed in wat.er by relatively small amounts of soap and Carbitol. Its presence, in conjunction with benzyl acetate, greatly facilitates the dispersal of the latter. These experi- ments demonstrate the influence -which the ingredients of the perfume have upon the final dispersions in water. Perfumes which contain large amounts of alcohols--rose, lilac, lily--for example, are more easily dispersed than colognes. It is realised that this short dis- cussion will not have presented the reader with a definite formula for a bath essence, but the manner in which the problem of formulation may be approached has at least been indicated. This apparatus for use in the determination of the apparent melting point of resins, waxes, etc., is described on the oppo- site page. 156 :