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CATALYSIS. 33
Cw = 0, the velocity of the ester formation is expressed by the formula
Vi = ki-CA -Cs \ afterward it is expressed by the difference v\ — V2 or
ki’CA ’Cs —k2-CE -Cw. Of the two reaction velocities V\ and V2 at the
begining vi always diminishes while V2 increases. When k\-CA -Cs =
A*2"Ce-CV is attained, then the velocity of both reactions is the same;
no measurable decomposition occurs and the system is in equilibrium.
The equilibrium condition is the same irrespective of whether we start
from alcohol +acetic acid or from the corresponding quantity of acetic
ether +water. On equilibrium it is
h.CA .Cs = h.CE.Cw or ^^-J^= K.
t
Le-^w m
K is called the equilibrium constant; as is apparent it can be determined
in two ways—either from the concentration of the reacting bodies when
equilibrium is present or from the velocity coefficient k\ and fo as deter-
mined in a manner given below.
In the above-mentioned transformation of alcohol and acetic acid
these two bodies are simultaneously used up. The reaction is therefore
called bimolecular, and a reaction is called mono-, bi-, tri-, etc., molecular
according to the number of the kinds of molecules which diminish their
concentration thereby. 1
Berzelius 2
found that certain bodies by their mere presence, and
not by their affinity, have the power of awakening the dormant affinity
at a certain temperature, i.e., the power of starting a reaction. These
phenomena were called catalytic by Berzelius.
According to Ostwald 3
catalysis is the acceleration (or retardation)
of a slow-proceeding chemical change by the presence of a foreign body.
That body which influences a reaction in this manner is called a catalyst.
It does not itself undergo any appreciable change by the reaction.
Catalytic reactions have been studied, especially by Wilhelmy.4
van’t Hoff,5 Ostwald,6
Arrhenius 7
and Bredig.8 Of all other sub-
stances the acids and alkalies seem to act most catalytic. A well-known
1
It is assumed here that of every kind of molecule one molecule of each takea
part in the reaction.
o
2
Berzelius, Arsberattelse om framstegen i Fysik och Kemi., 13, p. 245 (1836).
3
Lehrb. d. aUg. chem. 2. Aufl. II., 1, 515.
4
Poggendorff’s Ann., 81, 413 (1850).
5
Etudes de dynam. chim. (1884).
’ 6
Lehrb. d. aUg. Chem., 2. Auf. II, 2, 199.
7
Zeitschr. f. physik. Chem., 4, 226 (1889).
8
Anorganische Fermente (1901); Bioch. Zeitschr., 6, 283 (1907).
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