123 
faction before mixation ; and the influence of heat 
upon the action was considered. 
5. In catalytic actions the force sometimes produces 
decomposition, at others synthesis. When contact 
produces decomposition, as when binoxide of manga- 
nese facilitates the evolution of oxygen from chlorate 
of potash, the molecular affinity of the catalyte is 
probably greatest for one of the constituents of the 
substance acted upon, and it attracts this to such an 
extent as to enable it to gain its freedom. When 
synthesis results, as in the oxidation of alcohol by 
means of platinum black, the catalyte draws the 
particles together, or it may be able to concentrate 
upon itself one of the elements so exclusively that it 
may appear in an undiluted or liquid form. 
6. The phenomena of osmose were fully investigated, 
and were referred to the mutual attractions of the 
two fluids and of the septum itself. 
7. Dialysis probably differs from osmose, in consequence 
of the peculiar molecular properties of colloid 
substances. 
8. The attraction of colloids, and of heated metals for gases 
and vapours, was illustrated by the recent researches 
of Dr. Graham and Messrs. Dumas and St. Clair 
Deville. 
(B.) Molecular conditions favourable to catalysis. Since 
molecular attraction is independent of mass, and since its 
power is only exerted at very small distances, it is evident 
that molecular attraction can only be exerted at the surfaces 
of the acting body, the second stratum of molecules will 
scarcely, if at all, affect substances lying on the surface; 
hence a large extent of surface is an important aid to mole- 
cular actions. Points of matter possess still greater advan- 
tages from their power of undisturbed action. These 
remarks were attested by observations upon catalytes, by 
