NOTES ON SCIENTIFIC RESEARCH. 55 
It is due to this fact that the solution begins to show alkaline reaction even before 
the phenol is completely bound.to the alkali. Therefore there is no sudden change 
from colourless to red, but a gradual transition through pink takes place and it is 
difficult to say which particular shade of colour is to be considered as the end of the 
reaction. A correct result cannot be obtained in this manner. If titration is stopped 
as soon as the first permanent pink coloration is observed, values are found, even 
with pure vanillin, which are invariably below 100 p.c.; the figures ascertained by us 
ranged between 96 and 98 p.c. We consider it quite out of the question that even 
fractions of percents of foreign matter could be proved in vanillin in the above- 
described manner; on the contrary, it may happen that quite a wrong verdict is arrived 
at if the examination is confined to titration. 
Notes on Scientific Research in the Domain of the 
Terpenes and Essential Oils. 
General. 
Selection of aromatics for covering nasty smells. 
How nasty smells may be covered with the aid of synthetic aromatics has been 
discussed by R. Marchand in a short article’). As even the finest flower odours 
always contain subtances which in themselves have a disagreeable smell, the direction 
is given which one has to follow in order to cover a smell successfully. Jasmin, e. g. 
contains indole, which in itself smells of faeces. If therefore a faecal-like odour has to 
be covered, it can best be done with artificial jasmin free from indole. Very often the 
odour of fish oil has to be covered. If one takes into consideration that white haw- 
thorn contains a body of a similar smell as fish oil, one comes to the conclusion that 
odoriferous substances of the white hawthorn class, such as aubépine and p-cresol 
methyl ether may serve to cover the odour of fish oil. Once the odour is covered, 
other substances may be added in order to obtain a different perfume. 
The odour of light petroleum ought not always to be covered with the aid of 
turpentine oil, but the selection should thus be made that the perfume is adequate 
to the final product in view. When turpentine is cheap, one often tries to cover its 
odour. [If articles like boot polish, leather grease, &c., are concerned, Russia leather 
perfume is most appropriate. 
The chemistry of colloids and the manufacture of perfumes. 
P. Rohland*) has published an article on the importance of the chemistry of 
colloids for the perfume industry. The most interesting feature in it is the absorption 
of odours by colloids and of bodies inclined to become colloidal. The absorptions 
are due to the fact that these bodies, especially in contact with water, form and 
contain numerous colloidal substances, which have to be considered as dense tissues. 
1) Deutsche Parf.-Ztg. 1 (1915), 160. — 2) Deutsche Parf.-Ztg. 1 (1915), 116. 
