430 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS C yclop entadeca none P entadeca nol ide CH•, CH• CH2 I I (cH2)., co (XIX) (XX) This compound is extremely woody in odour. In addition to the typical clean musk odour there is a strong woodiness. Other macrocyclic chemicals possess woodiness of odour but the effect is usually towards santalol. In this case, the cedrol note is strongly in evidence. This possesses the musk intensity of ambrette but is strongly santalol- hke with a touch of cedrol. 12-oxa-hexadecanoli& CH •, I (CH2)a--O--(CHa)•0 (xx) Very suggestive of blackberries. 4-oxa-pentadecanolide 0 CH• 0 I I CO (CH•,)•o--O--(CH•,)•-- CO (XXII) This chemical possesses a fine musk odour with a back-note of santalol. It also possesses a slight fruity note. A medium strength sweet musk with a distinct woodiness. Ethylene brassilate CH• 0 1 CH•--O--C--(CH•)n -CO 0 (XXIII) A sweet intense musk with a suggestion of ambrette and blackberries. The woodiness is quite absent. FIXATIVE PROPERTIES OF THE MUSKS For a long time the nitromusks were regarded as fixatives for other more volatile odours. In recent years it has been said that these chemicals although persistent in odour themselves had no power to inhibit odour loss in other chemicals. However, most writers include the nitromusks in their lists of fixatives. The following experiment gives some indication of the fixative power of musk xylol. Four samples were examined from a smelling slip.

THE MUSK ODOUR 431 1. Pure benzyl acetate. 12. Benzyl acetate plus 10% musk xylol. 3. Benzyl acetate plus 10% benzyl benzoate. 4. Benzyl acetate plus 5•o musk xylol and 5% benzyl benzoate. Under the conditions of this particular test the odour of benzyl acetate itself remains for approximately 600 minutes in the presence of 10% of musk xylol, 750 minutes and in the presence of benzyl benzoate 840 minutes. The test, which included both musk xylol and benzyl benzoate, was made to obviate the tendency for the musk xylol to crystallize from the solution. The solution containing both musk xylol and benzyl benzoate retained its odour of benzyl acetate for about 960 minutes. A similar set of experi- ments were made but in this case a more volatile solvent (namely methyl amyl ketone) was employed. Examined olfactorily from slips, methyl amyl ketone maintained its odour for 17 minutes. The presence of musk xylol increased the odour life to 20 minutes, the benzyl benzoate to 22 minutes and the combination of musk xylol and benzyl benzoate also to 22 minutes. From these tests, it appears that musk xylol does exert some fixative effects although these effects are less positive than those given by benzyl benzoate. The fixative effects of a number of musk-like compounds were examined employing methyl amyl ketone as the solvent. The results are shown below :- Table 1 ODOUR RETENTION TIME OF METHYL AMYL KETONE Retention time Composition of solution in minutes Methyl amyl ketone pure 17 Methyl amyl ketone -t- 10% benzyl benzoate 22 Methyl amyl ketone + 10% musk ketone 21 Methyl amyl ketone + 10% 1.1.4.4-tetramethyl-6- ethyl-7-acetyl- 1.2.3.4 -tetra- hydronaphthalene 28 Methyl amyl ketone + 10% 4-acetyl-l.l-dimethy-6- tertiary-butyl-indane 27 Methyl amyl ketone d- 10% 3.5-ditertiary-butyl- acetophenone 26 Methyl amyl ketone + 10% Pentadecanolide 28 It will be seen that musks drawn from the benzene, tetralin, indane and macrocyclic range have the ability to reduce the rate of odour loss of methyl