dol 
Physiology. — “The Electrical Phenomenon in Smell-mirtures’’. 
By Prof. Dr. H. ZWAARDEMAKER. 
(Communicated in the meeting of September 30, 1916). 
In ordinary life it has long been known that there are certain 
smells that neutralise each other. It is very diffieult, however, to 
mix them experimentally in the right proportion to find the cons- 
pensation-point i.e. the point at which they cancel each other com- 
pletely. This is 1. because the constituents mostly volatilise unevenly 
(directly after the mixing because the solubility is mutually modified ; 
later on through a difference of evaporation); 2. because the migrat- 
ing odorous molecules generally diffuse with various rapidity ; 3. 
because of the disproportionate adsorption of the smell-mixtures to 
the sides of phials, beakers ete., used in examining the mixture. 
The difficulties to be obviated, are such as to render it next to 
‘impossible to find the compensation-point by mixing odorous fluids. 
In the perfume-industry and in pharmaceutical practice a moderate 
stability of the resultant odour should, therefore, be valued as a 
fairly satisfactory result. 
The ascertainment of these proportions induced me, in the year 
1888, to produce inodorousness by mixing the odorous gases them- 
selves. Well-known, purely chemical odours were then combined in 
a double olfactometer made of metal, glass, and filter-paper. A sur- 
prisingly great number of complete compensations were achieved 
with it. 
If one type were taken of each of the nine complemented classes 
of Linnazkus’ classification of smell qualities, numerical values could 
be established for 4?— 36 combinations *). Afterwards J. HERMANIDES ”*) 
2 
4 
did the same in his thesis for a doctor's degree. With three combi- 
nations his results coincided with mine and with those of a third 
observer (Herinea). Sinee then I examined terpineol, guaiacol and 
valerianie acid chiefly with these odours in paraftin solutions. 
Much greater accuracy together with sufficient persistence can be 
secured, when replacing paraffin solutions by a saturated aqueous 
solution in which there is a slight excess of odorous matter. The 
olfactometer then contains a system of phases, viz. air, water, odorous 
matter, which after a few days will be equilibrated and which 
moreover maintains its equilibrium against the adsorption of the 
filter-paper. 
1) H. ZWAARDEMAKER, ti. d. Proportionen der Geruchscompensation, Arch. f. 
Anat. u. Physiology. 1907, Suppl. p. 60. 
2) Utrecht 1909. See also Proc. Roy. Ac. Amst. May 29 1909, Vol, 18, p. 53. 
