39 
physical property, each depending on the volatility of the substance 
and the capacity of lowering the surface tension of water. 
Therefore it avails to measure at the same time the surface 
tension. In the case of pure substances it does not exert a special 
influence upon the shape of the curve. In the case of water it does. 
Mr. H. R. Knoops was kind enough to investigate this for the 
fatty acids. 
PAB LEV: 
Number of droplets falling from TRAUBE’s Stalagmometer 
the standard for water being 51. 
Fatty acids "Nog n. | Wag Me | "ggg n. 
Formic ac. | gls | 51 51 
Acetic ac. | 57 56 53 
Proprionic ac. 58 a) 93 
Butyric ac 70 | 68 | 53 
Valerianic ac. | 88 12 | 53 
Caproic ac. | = | 12 54 
bkr ke Es 
Caprylic ac. | an _ 53 
Ld 
In the series of fatty acids about which we know most, 
smell intensity and electric power agree in that, while running 
up in the lower terms, they first increase till they reach a maximum 
at a certain point, then suddenly weaken in order to fade out in 
the end. The factor, which, as I think, dominates the olfactory and the 
electrifying property, viz. that of lowering the surface tension, 
maintains itself till the series is far advanced, for myristin acid still 
reduces the surface-tension distinctly (if arrests the camphor-movement 
and, when added to water to saturation, its number of drops in a 
given volume is 60, that of water being 51), but it does not evoke 
the electrical phenomenon, and is at the same time inodorous. It is 
not improbable that this has something to do with its lack of 
volatility. I cannot say, however, which of the two properties: the 
electrical phenomenon or the olfactory capacity goes farther in the 
homologous series, as caprylic acid was the highest term at my 
disposal, and this substance still evinces both properties. According 
to Passy laurie acid is the terminal smell stimulus in the series. 
22* 
