SOLVENTS, HUMECTANTS AND BLENDING AGENTS its use, make it evident that there is still cause for further work in this field. Fortunately the more recent papers on the subject provide evi- dence of a wider and more logical approach to the problem and inter* esting developments may still be anticipated. Table 3, which lists the solubility of tetrabromofluorescein in a wide range of liquids, has been compiled from the work of Lower -• and ex• tended by results available to the authors from tests on a highly puri- fied grade of dyestuff. TABLE 3. SOLUBII,ITY OF TETRABROMOFLUORESCEIN AS W/W % AT 20øC. Alcohols Benzyl alcohol 6 fi PhenylethanoI 8 Terpineol 1.9 Furfuryl alcohol 3.0 Tetrahydrofurfuryl alcohol 2 Lauryl alcohol O. 7 Myristyl alcohol O. 6 Stearyl alcohol 0.5 Oleyl alcohol 1.0 Ketones Acetone 3.5 Diacetone alcohol 6.5 Benzophenone 3.5 Cyclohexanone 1.6 Glycols and Derivatives Ethylene glycol 1.0 Ethylene glycol oleate acetate 0.4 Ethylene glycol oleate 0.1 Ethylene glycol diricinoleate 1.9 Diethylene glycol 2.5 Diethylene glycol monostearate 1.0 Diethylene glycol ethyl ether 10.5 Triethylene glycol 4 Tetraethylene glycol 5.7 Hexaethylene glycol 9 Polyethylene glycoI' 400 ' 10 Polyethylene glycol '1500' 10 Polyethylene glycol '4000 ' •12 Propylene glycol 1.7 (propane 1.2 diol) Butylene glycol 20 (butane 1.3 diol) Hexylene glycol 6.0 (2 methyl pentane 2.4 diol) Hexylene glycol mono acetate 5.0 Hexylene glycol monostearate 1.0 Octylene glycol 5.0 (2 ethylhexane 1.3 diol) Acids Lauric acid 0.3 Myristic acid 0.3 Aldehydes Citral 4 Hydroxycitronellal 4 Esters Tetrahydrofurfuryl acetate. 2 Cetyl acetate 0.3 Butyl laurate insol. Ethyl myristate 0.5 Isopropyl myristate 0.5 Ethyl stearate 0.2 Butyl stearate 0.5 T.H.F. stearate 0.5 Methyl rincinoleate 1.0 Ethyl oleate 0.3 Methyl acetyl ricinoleate 1.0 Ethyl acetyl ricinoleate 1'4 Butyl acetyl ricinoleate 0.5 Methyl lactate 1.0 Diethyl sebacate 1.3 Tributyl citrate 0.2 Glycerol Series Glycerol a methyl ether 2.0 Glycerol monolaurate 1.0 Glyceryl monostearate 1.0 Castor oil 0.2 Cocoa butter 0.3 111

JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS PERFUMERY SOLVENTS AND FIXATIVES In the field of perfumery and lotion vehicles, ethanol so well fulfils its purpose as a safe, cheap, and mild odoured volatile liquid, suitable as a carrier and means of application of the requisite small amount of fixa- tive and perfume, that it is doubtful if any other organic solvent can seriously challenge its position. Per- haps the inflammable nature of this solvent, together with the rigid fiscal regulations attending its use, are its only disadvantages. Isopropanol, which in other fields is sometimes employed to. avoid the regulations restricting the use of spirit, has some advantages to. merit consideration in certain cases, especially where high tolerance for water is required, but its persistent odour is definitely against it. Developments in this sphere have been directed mainly to replacing all or part of the ethanol used by water and this entails the careful selection of a blending agent either of conven- tional type or from the class of sur- face-active agents where the mech- anism involved is 'that of micro-dis- persion or solubilisation. The fixation of perfumes has been practised since the early history of perfumery and the original fixatives (ambergris, musk and civet extracts, etc.) are still widely accepted as highly efficient. Since natural fixa- tives are usually odorous materials they do impose some limitation on the character of the finished product prepared from them and the use of synthetic fixatives typified by diethyl phthalate has developed. The odour- less synthetic fixatives besides being economically attractive permit greater freedom and variety in compounding. There are many characteristics desirable in a fixative among which may be noted the following. A fixa- tive should be relatively non-volatile and free from unpleasant odour. It should act as a suitable medium for blending the various odorous com- ponents, effectively reduce their evaporation and restrain the com- ponents so that each persists until all have dispersed. It is probably impossible to achieve this state of affairs except by painstaking empiri- cal methods of trial and error. The mechanism involved in fixation does not appear to have received much attention although Moncrieff •ø has recently drawn attention to some of the factors involved. The variation of the vapour pres- sure of a binary mixture with its composition is postulated by Raoult's Law as proportional to the molar fractions of the components. Thus referring to Fig 1, volatile liquids A, B, C, D on coml•ounding with a liquid F of low vapour pres- sure (hence high molecular weight) give binary mixtures in which the vapour pressure of A, B, C or D is reduced according to the amount of F present. Furthermore, the vapour pressures of such mixtures are more nearly comparable than are those of the pure components A, B, C and D. Since this relation is postulated to hold for concentration measured in 112