Radicals, Reactions, Realism - Philosophy of Chemistry - page 187

Another example of an empiricist 29 and operationalist approach to chemistry is
the theory of the Bohemian Chemist Franti ˇ ek Wald (1861-1930). In his article
“ Was ist ein chemisches Individuum ?”, Wald said:
Chemical individuals are phases that occur in a phase system with at least one independent
variation, and retain evidently consistent for all variations associated with the conditions of
the phase system. 30

Phases are characterized by Wald, for example, as follows: “In brief, with the
word phase we denote any part in a mixture in equilibrium that is perceived by the
senses, and that is a homogeneous part, distinguishable from another part.” 31 As to
triphenylmethyl, the preparation and comparison of different aggregate states is
extremely restricted. The dissolving, for example, leads to higher extinctions in
calorimetric measurements if no shielding gas is applied because the reaction with
oxygen is very quick. That means, because triphenylmethyl cannot be obtained
consistently for all variations of the observed phase system (that is the variations
through the states of aggregation) and because it (what?) cannot be perceived easily
by the senses and because for Gomberg it was not clear whether or not the obtained
substance was in equilibrium, it cannot be considered a chemical individual proper
according to Wald. Most radicals - if we take into account the current chemical
knowledge - are short-lived intermediates and cannot be prepared and handled like
common stuff samples and therefore can hardly be described in terms of a phase
conception or a macroscopic approach to stuff. Nevertheless Gomberg s radical and

all the other examples are chemical species, which is supported by the view of Jaap
van Brakel (unless the latter does not refer to the Gomberg story):
Chemical species which cannot be put into bottles, cannot be subjected to any
reversible phase transition, occur only in solutions or other special environments, have an
extremely short half-life, only “exist” in excited stages, etc., may have a full claim to being
a chemical species and may even claim to be a separate phase, but may or may not claim to
be substances. If the species only exist in equilibrium with other species “inside” pure
substances or solutions, it seems plausible to admit them as species, but not as substances.
This includes radicals, reactive fragments, activated complexes, ligand-receptor com-
plexes, etc. Whether (different kinds of) tautomers should be classified as separate
substances or species is less obvious. (van Brakel 2012 , 222)
Obviously the classical macroscopic approaches - at least in the versions of
Wald and Ostwald - do show disadvantages because of the unnecessary restrictions
to phases and stable preparations. In the following we shall try to find other
approaches which might throw some more light on the epistemological status of
the radical concept.

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29 Cf. van Brakel 2013 .
30 Ruthenberg 2009 , 75-76.
31 Ruthenberg 2008a , 59 (emphases original).