942 
action of many metals and oxides of the 
metals. A few such reactions will be given : 
Alcohol is oxidized to acetic acid by the 
oxygen of the air, both by the ferment my- 
coderma aceti, and by finely divided plati- 
num. Calcium formate is decomposed into 
calcium carbonate, carbon dioxide and hy- 
drogen, not only by certain bacteria, but 
also by finely divided iridium, rhodium 
and ruthenium. Dilute solutions of oxalic 
acid are decomposed by palladium plati- 
num and silver sponge, and also by certain 
fungi, and the list of such reactions could 
be very greatly extended. From this it is 
obvious that analogies between the action 
of finely divided metals and organic fer- 
ments were not entirely wanting when the 
work under review was begun. 
Bredig then attempted to determine how 
close these apparent analogies really are, 
by studying very carefully and thoroughly 
the decomposition of hydrogen dioxide by 
finely divided platinum. 
It has already been pointed out that a 
very small amount of platinum can decom- 
pose a large amount of hydrogen dioxide, 
just as a small amount of a ferment can 
effect a large amount of chemical transfor- 
mation. 
It has also been shown that the finely 
divided platinum does not enter into the 
reaction, just as a ferment does not enter 
as such into the reaction. 
The presence of electrolytes affects the 
colloidal condition of the platinum,and, con- 
sequently, its activity. They have the same 
influence on ferments. 
But the most striking analogy between 
the action of these colloidal solutions of the 
metals and organic ferments is to be found 
in their conduct in the presence of certain 
poisonous substances. 
Bredig and Reinders showed that hydro- 
gen sulphide in very small quantity, can 
diminish the catalytic action of the finely 
divided metal. An akaline solution, con- 
SCIENCE. 
[N.S. Von. XIII. No. 337. 
taining one gram-atomic weight of sulphur 
in ten million litres of water, can produce an 
appreciable diminution in the catalytic ac- 
tion of the metal. Schonbein has shown 
that small quantities of hydrogen sulphide 
can appreciably diminish the action of 
organic ferments on hydrogen dioxide. 
Bredig and von Berneck have shown that 
hydrocyanic acid has a remarkable influ- 
ence on the catalytic action of platinum. 
Thus, one gram-molecular weight of hydro- 
eyanic acid in twenty million litres of water 
diminishes to one-half the velocity of the 
decomposition of hydrogen dioxide by col- 
loidal platinum. This again is strikingly 
analogous to the action of hydrocyanic acid 
on organic ferments. Schonbein showed 
that very small quantities of hydrocyanic 
acid very materially lessen the action of all 
organic substances which decompose hydro- 
gen dioxide catalytically ; and quite re- 
cently Buchner has shown that hydrocyanic 
acid diminishes the action of the ‘ pressed 
juice’ of yeast on hydrogen dioxide and on 
other substances. 
The ‘ poisonous’ action of a number of 
other substances, such as bromine, iodine, 
analine, arsene, arsenious acid, phosphene, 
phosphorus, carbon monoxide, oxalic acid, 
mercuric chloride, etc., on the colloidal 
platinum and on organic ferments was 
studied, with the result that a general an- 
alogy between the two was undoubtedly 
shown to exist. 
The conclusion reached by Bredig as the 
‘result of this work can best be stated in 
his own words : 
“All these facts point to an unmis- 
takable analogy between the contact ac- 
tions in the inorganic world, and the ac- 
tions of ferments in the organic world. 
As, in the case of my colloidal catalyzers, 
we are dealing with reactions in which 
enormously developed surfaces are involved, 
so is it probable that the same condition 
obtains in the actions of ferments, enzymes, 
