TALKING OF PERFUMES AGAIN o HOH C X H I H ortho hydroxy para hydroxy benzaldehyde benzaldehyde Of course, this bonding or associating effect of molecules is not restricted to alcohols and phenols, but applies to many polar compounds, and it is important to remember that the effect will obtain also between different types of molecules. No doubt the fine blending properties of phenyl ethyl alcohol and certain carbinols can be attributed to a bonding phenomenon. Benzyl benzoate is, perhaps, the most used of our fixatives. It is in- expensive, a good solvent for our solid ingredients, and relatively free from odour. It is not the ideal fixative, but it will be known to all. Let us con- sider its practical function as a fixative. The following simple example demon- strates quite clearly that benzyl benzoate does have the power to retard the rate of evaporation of volatile substances. Six solutions were made as follows: A B C D E F Ethyl alcohol .... 9 8 9 8 8 7 Methyl amyl ketone .. 1 1 - - 1 1 Benzyl acetate .. - - 1 1 1 1 Benzyl benzoate .. - 1 - 1 - 1 The solutions were tested from smelling slips and, ignoring the odour of alcohol and benzyl benzoate, times were recorded for the length of life of the odour of methyl amyl ketone and benzyl acetate. COMPARING A WITH B Initially A was stronger. After 3 minutes B was stronger. In 5 minutes the odour of A had gone. The odour of B lasted for 8 minutes. COMPARING C WITH D Initially C was stronger in benzyl acetate. Gradually the strength approached equality, and at 40 minutes they were at the same strength. D then become stronger with time and after 75 minutes the odour of benzyl acetate in C had disappeared, whilst that in D was still strong. The odour in D remained for at least 3 hours. 199

JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS COMPARING E WITH F Immediately E was stronger, especially of methyl amyl ketone. After 4 minutes E was stronger in both methyl amyl ketone and benzyl acetate. After 6 minutes the methyl amyl ketone was stronger in F but the benzyl acetate was weaker. After 8 minutes only the benzyl acetate was in evidence in E, whilst the methyl amyl ketone was still apparent in F. After 12 minutes E was stronger, but both odours were of benzyl acetate. E remained stronger for 45 minutes and at 60 minutes the odour of benzyl acetate in F was definitely stronger. The benzyl acetate in E had disappeared in 80 minutes, but remained in F for at least 3 hours. On theoretical grounds we could imagine benzyl benzoate having an attraction for methyl amyl ketone as follows ß CH 3 •+ -- •C 0 I C•Hn I 1 OCH2CoH5 I o - + CoH5 Methyl amyl ketone benzyl benzoate For the benzyl benzoate/benzyl acetate association we imagine' C0HsCH•.Ox, C 0 CHa l l OCH•.CoH • 0 -- CoH5 On the evidence of these experiments benzyl benzoate retards the evaporation rate of both methyl amyl ketone and benzyl acetate. Further, the presence of benzyl acetate itself has some fixative properties for the methyl amyl ketone. 200