143 
then apparent. The mercury, immediately after the reaction 
is over, generally presents a bright, or but slightly tarnished 
surface, but on remaining in contact with the liquid is soon 
covered with a black coating of sulphide. No mercury 
enters into solution during the reaction. 
I believe that the reduction of sulphuric acid in the begin- 
ning is not gradual and successive, but is explained by the 
simple formula,— 
SO,H, + 4(H,) = 4H,0 + HS. 
The following paper was read, 
On the Role which Chalk plays in Butyric Fermentation, 
By O. Loew. 
It is a well-known fact, that a solution of sugar, when not 
protected against the access of air, develops gradually a smell 
of butyric acid and the formation of micro-organism. 
Béchamp* found that 1-2 drops of creosote or phenol are 
sufficient to prevent, in 100 cc of sugar solution, the deyvel- 
opment of infusoria and fungi, but that such a small quantity 
of creosote would not be sufficient to prevent a regular fer- 
mentation by yeast. For the latter purpose, much greater 
quantities of creosote would be necessary. 
Béchamp concludes from this observation that small quan- 
tities of creosote would kill imperfectly developed micro- 
organisms, but not the better developed cells of the yeast 
plant. A series of experiments, however, haye shown me 
that the real cause of the above-named fact, depends simply 
upon the relative proportions of the antiseptic substance and 
the quantity of the micro-organisms. The quantity of the 
spores falling from the air into a sugar solution, is small in 
comparison with the number of cells in a few cubic centi- 
metres of yeast. That a given quantity of creosote or 
phenol can only have a definite and limited antiseptic influ- 
ence is self-evident, but, as regards these limits, few investi- 
* Jahresber., 1865. 
