I have observed, with great interest, the developments of modern chemistry that your
journal has shed light upon. However, as a philosopher I feel that these opposing
theories have sometimes spent too much time trying to displace each other, rather than
concentration on the greater goal shared between all realms of science, and even
humanity – uncovering its very nature and truth. I enclose some thoughts on the work
published in the past two volumes of your journal, that I wish for you to consider for
your next publication.
Regards
Gregory Fitzgerald
Chemistry is a science that is, most definitely, still in its infancy. The later half
of the eighteen-century has seen the science climb off its knees and onto its feet with
the ideas surrounding the phlogiston theory, championed by Mr Cavendish and Mr
Priestley. However, the foundations behind the said theory have been shaken severely
by the groundbreaking French scientist, Antoine-Laurent Lavoisier, and his theory
that water is composed of two simple substances, Hydrogen and Oxygen, rather than
being a simple substance itself. However, as shall be discussed throughout this article,
I fear that both doctrines, in fighting for recognition within the scientific community,
have failed to accept their fallibilities. But in order to explain this, I feel it necessary
to summarise some aspects of the doctrines of phlogiston and that of oxygen.
The recent argument to spill from the opposing camps of the two doctrines has been
over the composition of metals. To summarise his argument in a particularly brief
manner, Mr. Priestly has suggested that a metal consists of phlogiston, combined to a
peculiar calx, or “metal base”. Hence, on liberating phlogiston from the base, we are
left with the calx in its pure form.
M. Lavoisier believes that metals are simple substances, and that in the
calcinations of a metal, the metal absorbs oxygen in order to form an oxide, removing
the metallic properties of the metal itself, to be brief. In his treatise on the Elements of
Chemistry, Lavoisier discusses how the union between the metal and oxygen is
achieved – when the attraction the metal has towards the oxygen overpowers
oxygen’s attraction towards caloric, the metal joins with oxygen to form the oxide.
As the Rev. Cedric Grimes has pointed out in a recent edition of the Nicholson
Journal, Mr. Lavoisier’s ideas were founded on the behaviour of mercury, which
when gently heated in oxygen forms precipitate per se, or red mercury. Lavoisier
noticed that as red mercury is heated further, the mercury is returned to its original
state and oxygen is evolved. Mr. Priestly has pointed out that Lavoisier’s extension of
this theory to all metals and calxs is incorrect, as many calxs will not be restored to
their original metal as heat is applied. Rev. Grimes comments on how precipitate per
se and minium (red lead) must contain dephlogisticated air (oxygen), suggesting that
the calx can only be revived when heated in a phlogiston-bearing substance, for
example, inflammable air (hydrogen). He continues to suggest, “When the calx is
heated in inflammable air, the oxygen combines with it to form water”. If Water does
consist of hydrogen and oxygen, surely this is proof that inflammable air is indeed
hydrogen gas?
With our present scientific knowledge, it seems that we are unable to
conclusively decide why phlogiston, or hydrogen, must be present. Phlogiston theory
is suggestive that a compound rich in phlogiston must be present in order to restore
the original state of the metal.
My suggestion, of a solution to the problem of reducing a calx to its metal
(without the presence of a so-called phlogiston-baring substance), is to be found
within the method undertaken to achieve the process. I believe that, quite simply, the
amount of heat required to separate the metal base from the oxygen is far greater than
we are able to produce with our current methods. If we could produce a greater
amount of heat, we would be able to remove the oxygen from the calx, leaving the
pure metal. Current scientific method does not have the ability to break down the
force that combines the oxygen and metal simply by heating.
It seems that debating, within the chemical world, over the nature of
Phlogiston and Caloric, is a sign that modern chemistry is in a currently irresolvable
situation.
As a philosopher, I fear that the search for the proof of the existence of either
of the two substances is perhaps a waste of time. The doctrines of phlogiston and
caloric have both suffered from vast criticism – but it seems that neither can offset its
rival. It seems that the time has come for chemistry to attempt to solve its problems,
without looking for solutions in a weightless, imponderable substance, or a substance
that compounds require a deficiency of in order to exist.
Whilst I agree that water consists of oxygen and hydrogen, I feel that the
nature of Lavoisier’s imponderable substance, caloric, is dubious and that its
existence should be confirmed before the scientific community considers its
theoretical applications. The nature of an imponderable substance allows us,
potentially, to explain the chemical, or even physical, nature of any situation and this
is type of thinking could draw chemistry back into the ideas of its predecessors in
“science”. The nature of what separates a gaseous compound from its solid or liquid
counterparts is an area of chemistry and physics that requires a much greater
understanding before suggesting reasons for how and why, for example, a liquid can
be decomposed into gases.
In The Elements of Chemistry, Mr. Lavoisier also describes four experiments
in the paper, the third of which involved passing steam (100 grs. of water, heated to
boiling) over red-hot iron with a tube. The results, characterised with Lavoisier’s
impressive weights of the experiments reactants and products, show that 15 grs. of
hydrogen gas are evolved and that the iron has gained 85 grs. of additional weight.
The properties of the iron metal were found to have changed and Mr. Lavoisier
concluded that the iron had been converted “into a black oxyd, precisely similar to
that which has been burnt in oxygen gas”. There has been some mention that
Lavoisier has not clearly shown that the weight gained by the iron is due to the
imbibing of oxygen gas. I feel that Mr. Lavoisier’s results explicitly show this. The
precise weight gain of 85 grs and the production of 15 grs of hydrogen are too
coincidental to not be due to the decomposition of water.
Mr. Priestley’s response to the experiment has been that the oxide of iron, or
finery cinder, is in fact not the same as the rust of iron, a compound produced when
iron is exposed to air. Rust of iron is typically red in colour and Mr. Priestley suggests
that Lavoisier’s iron oxide is in partially oxygenated, and should undergo further
oxygenation to produced rust of iron.
It is in this writer’s view that Mr. Priestley has forgotten, in this instance, the
true nature of chemistry. That is chemistry, as we know it, is still questionable, and I
suggest that not all chemical compounds will react as we predict them to. It is this
lack of understanding that I fear the world’s top chemists struggle to admit is present
within chemistry.
I would like to cast my own options on the theory behind the results of Mr.
Lavoisier’s experiment. Firstly, it seems that the oxide of iron, or finery cinder, is a
different compound to that of the rust of iron. The oxide of iron contains iron and
oxygen, but the rust of iron, formed by exposure to our common air, could consist of
iron, oxygen and hydrogen. Therefore, further oxygenation to iron oxide shall not
produce the rust of iron.
Another logical explanation to the problem can be suggested by considering
the very nature of the red-hot iron. Perhaps, on heating, the iron undertakes different
reaction properties that are unobtainable when at room temperature.
Lavoisier also discusses the intermediate nature of the metals combined with
oxygen, including four degrees of oxygenation with nomenclature to describe each.
Compounds within the first, and lowest, degree are known as oxyds. If an oxyd is to
undergo further oxygenation, if may reach the second degree of oxygenation, where
the name of the compound is specific in relating the name of the base to this degree of
oxygenation. For instance, if the base of sulphur is oxygenated to this degree, it shall
be know as sulphurous acid. The third degree of oxygenation of the same base would
give it the name of Sulphuric acid, and if oxygenated to the fourth degree, it shall be
known as oxygenated sulphuric acid. The various colours of the oxygenated
compounds can distinguish the different states of oxygenation of the metals.
As a philosopher with limited scientific knowledge, I feel Lavoisier’s
development of new language in order to best describe that of chemistry shall, as we
may observe in years to come, perhaps preserve the longevity of oxygen theory. The
lack of developments with the same effective within Phlogiston theory has, at times,
made the theory incredibly confusing within describing itself. Often, Mr. Priestley, in
his writings, will talk about the actions of his inflammable air, or dephlogisticated
airs, but often fails to specify which inflammable or dephlogisticated airs he is
concerned with in the particular instance. Critics have often claimed that Mr. Priestley
has failed to be definitive on which airs fall into which group, and this lack in
attention to the small details in the theory can confuse readers.
The development and use of the electric pile to produce a spark, and the
splitting of water using an electric current, has drawn an entire new spectrum of
possibilities to the field of chemistry. Whilst I personally believe we do not
understand enough about the nature of the spark, I would briefly like to comment on
an experiment performed by Mr Priestley. On addition of dephlogisticated air to a
volume of inflammable air twice greater than that of the former, Priestely found that
the use of a spark produced what he called phlogisticated nitrous acid. Mr Priestley
also found that the strength of the acid could be improved with use of purer air. This
suggests that the nature of the spark must have some relation to that of the acid, and
that the use of purer air cause the product compound to more acid present. Priestly
also comments that phlogisticated air can be used in place of inflammable to produce
the same acid, and therefore the same thing must be present in both – phlogiston. It
could easily be argued that hydrogen is in fact present in both of these airs.
Finally, I would like to mention that despite which of the two scientific
theories over the composition of water and the nature of air are found to be true, we
must not forget the great research and discoveries of Mr Priestley, and before him,
Henry Cavendish and Joseph Black. The work on air of these three scientists deserve
to be remembered as some of the most important work of the 18th century, as the
progression of chemistry is largely due to such work. I feel that I must mention that
modern scientific method and understanding is extremely limited, and jumping to
rapid conclusions over scientific truths will harm the development of chemistry.
Recent work in the infantile, new field of electrochemistry will without a doubt
unravel more discoveries about our science, but theories must be well thought out and
their creators must stand back and accept when flaws are pointed out in these said
theories – rather than attempting to cover the holes with weak hypotheses. If we were
at the truth, all non-truths and fallibilities would be exposed. I feel that the great
chemists of this, 19th century, shall be those that bear these ideas in mind.