107 
on metiylnonylacetaldyde. The Rieanaton of an i ubylene linking of the aldehyde group 
nfluences the smell to a great extent. For examiple, there is but little difference 
i the smell of decyl and undecylenaldehyde (double linking - ‘in 9, 10-position), 
whereas it is quite - marked between nonylaldehyde and «,@-nonylenaldchyde, as 
well as between caprylethyl ester and-heptincarbonethyl ester (acetylene linking in 
> «,8-position). The difference in smell is likewise’ considerable between citronellal and 
_ citral, less so between citronellol and geraniol. In the case of cyclic compounds, 
the | position of the double bond is of influence upon. the smell, for instance with 
_a@- and p-ionone, in: the latter of which there are Po ninested double bonds, but not 
in the former. 
For further instances, we beg éB refer to fie original 
a 
y Th. H. -Durrans?) has published an. “ eadenlstee® traatige on the Ee Neate between 
- composed of carbon, hydrogen and oxygen. For most of. the numerous bodies 
_ mentioned by him, he has been compelled to cull from previous - publications the 
notes regarding smell, which for the reasons stated. before are not very reliable. 
e - In the introduction he points out that the smell of most bodies has been. judged 
ae: ordinary temperature, whereas the degree of volatility is decisive in many cases_ 
- for the fact, whether a substance smells or not. Inodorousness is sometimes caused 
by insufficient vapour pressure. Most likely chemical bodies like ether, ethyl -acetate 
and acetone are inodorous at a low temperature and perhaps all compounds have no 
~ smell if the temperature be sufficiently low”). G. Woker’s supposition’) that smell 
Berend upon volatility is not correct, according to Durrans, for it does not agree 
with the fact that high-boiling compounds with consequently low. vapour pressure 
Bat an ordinary temperature, such as” reid santalol, meine 8c., smell. quite 
- specially strongly. ; 
- Durrans further discusses the fact that there does not seem to be any connection 
between smell and colour, although some bodies exist, like quinone and chromane, which 
- “smell strongly and are coloured intensely at the same time. | 
After a critical review of previous publications on the connection between smell | 
and chemical construction, the author gives a systematic: summary of the odoriferous 
~ properties of aliphatic, aromatic and hydroaromatic hydrocarbons, saturated and 
_ unsaturated aliphatic alcohols, aromatic alcohols, hydroaromatic alcohols, phenoles, 
_ aliphatic and aromatic aldehydes, aldehyde hydrates and acetals, ketones, ketenes, © 
~ polymethylene ketones, acids, esters, acid anhydrides, ethers and oxides, in all about 
a ~ 1000 chemical bodies. A full report on his consecutive theoretic reflections would 
lead us too far, so that we shall only extract some particulars 
. With aliphatic hydrocarbons, the acetylene linking, as arule, produces a hienarecabte’ 
_ smell, which is not the case with aromatic hydrocarbons, Hydrogenization of the 
_ benzene ring has a considerable effect, which is the greatest if two hydrogen atoms 
are added; with the naphthalene ring, the effect is quite the opposite. With aliphatic 
~ alcohols, the same as with many. other types of compounds, the intensity of smell 
_ Tises with the number of carbon Loaelield reaching its maximum at Cio. ‘A tertiary carbon 
_ whether a substance which at ordinary temperature is inodorous would become odorous at a higher temperature, 
ae. with increasing vapour pressure. ‘This will have little importance, however, for practical purposes, as 
Ost aromatics are used only at an ordinary temperature. — %) Jow'n. of physic. Chem. 10 (1906), 455; Report 
ih 1907, 113. . | ; 
4 
Pe = ; - ¢ . 
‘ ie. 1) Perfum. Record 10 (1919), 104. — *) From a theoretical point of view, it is very important to know, 
b 
Es 
%, 
ae D 
— odour — and chemical. constitution. He has studied quite specially the compounds is 
