656 
a very long time. Neither did pyridin attach itself to aluminium, to 
which seatol again was largely adsorbed, although there was much 
less of it in the air. Iso-amylacetate was adsorbed to iron and tin 
only for a short time; scatol again for a long period, in spite of 
the small difference in the partial density of the air. Porcelain, on 
the contrary, attracts iso-amylacetate more than any other substance, 
scatol least of all. 
When, as was the case just now, the adsorption of the first sort 
is ascribed entirely to the presence of the condensation-layer, the 
duration of the adsorption will be a function 1. of the lowering of 
the surface-tension of water together with what had already been 
dissolved in it; 2. of the solubility of the odorous matter in water; 
3. of the thickness of the condensation-layer; 4. of the volatility of 
the odorous matter from water. 
The possibility of this differentiation proves the existence of a 
specificity. 
As said already, there are some solids without a condensation- 
layer, or if they have any it seems to be so inappreciable that no 
ions are available to conduct the electricity so that they may serve as 
insulators for static electricity. For this purpose amber, paraffin 
solidum and sulphur are used. These substances are not moistened 
by water *), for when tracing a channel in these substances by means 
of a darning needle no water will appear in it. This is indeed the 
case with a certain number of other odorous substances. With the 
method previously described we were able to demonstrate that a 
rather considerable number of odorivectors added to the air that 
passes through a tube of amber, sulphur or paraffin, is adsorbed to 
the inner surface of such a tube. To amber e.g. borneol! scent is 
retained 1 inin., creosol 1 min., geraniol 8 min., vanillin 29 min., 
nitrobenzol 37 min. Broadly speaking bere also the different degree 
of adsorption must depend on the difference in the lowering of the 
surface tension of the solid surface. 
In the case of the first sort as well as in that of the second the 
odorous substance must at length be dissolved also in the lower 
layers. In the first case it is the condensation-layer that is saturated 
with odorous matter and finally imparts a small portion of the 
dissolved substance to the sublayer. In that way the odorous matter 
can be retained almost for ever and it appears that the adsorption 
continues also after removal of the condensation layer. This phenomenon 
1) Vide: R. S. WorLows & F. HATSCHEK, Surface Tension and Surface Energy, 
2nd edition, London 1919, p. 89. 
