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by Andrew Dalke.
Original Post: Molecular Formula - History of Chemical Nomenclature
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This has been a hard set of essays to write because I actually know
very little of the real history of chemical nomenclature and because
it's a complicated topic. I know how things work now, for computers,
but not how we got here.
John Bradshaw's talk
at MUG '01 (which I missed) and other MUGs, and Eugene Garfield's PhD thesis
An Algorithm for Translating Chemical Names to Molecular Formulas
were very helpful, as was an email exchange with Dave Weininger. I hope
to chat with Dave some more, to help fill in the missing parts. Perhaps
I'll even interview him. :)
Where do chemical names come from? If you ever read very old books
which mention chemistry you might have come across names like "spirit
of salt" (hydrochloric acid) or, since the early chemists were German,
names like äpfelsäuer (malic acid). Cool sounding names,
but not used any more. That tradition evolved out of the alchemy
tradition where you described things on the basis of where they came
from (along with a lot of obsfucation because you didn't want anyone
else to know your secrets). "Spirit of salt" was made by mixing
sulphuric acid ("spirit of vitriol", where "vitriol" is the glassy
metal sulphate) and salt. Malic acid is what makes the apple taste
sour, and is the source of the taste of many a hard candy. Here's
another fun one; formic acid was so named because the carboxylic acid
was originally distilled from ants (Latin: formicae).
I was looking for a good on-line reference to a story which used old
chemistry terms. I couldn't find one, but I did recall that Jules
Verne's Mysterious Island had some nice chemistry in it.
Chapter 17
describes making nitroglycerin ("dynamite was not yet known at the
time when the settlers worked on Lincoln Island") with phrases like:
Cyrus Harding could have manufactured this substance by treating the
carbonate of potash, which would be easily extracted from the
cinders of the vegetables, by azotic acid
The novel was writen in 1875, which when you compared it to the next
section gives some indication in the advances of chemistry during
sixty years.
Modern chemical nomenclature started with Berzeluis, one of the
so-called fathers of chemistry, back in the early 1800s. He said that
chemicals should be named by what they are, not by where they came
from. (After all, you can find malic acid elsewhere, like in cherries.)
He created the system of 1-letter and 2-letter atomic symbols taught
today in secondary school, with the letters taken from the Latin words
for the element (hence "Pb" for plumbum; lead).
He proposed that compounds be described by chemical formulas based
on their elemental composition.
His
paper on the topic, published in 1813, is a short and enjoyable
read. The purpose of a molecular formula is
to facilitate the expression of chemical proportions, and to enable
us to indicate, without long periphrases, the relative number of
volumes of the different constituents contained in each compound
body. By determining the weight of the elementary volumes, these
figures will enable us to express the numeric result of an analysis
as simply, and in a manner as easily remembered, as the algebraic
formulas in mechanical philosophy.
A formula was not meant as a way to replace the old symbols developed
by "fellow-laborers in the antiphlogistic revolution" which were used
to mark the sides of the jars in the lab. (Am I also a laborer in the
antiphlogistic revolution? It sounds exciting!)
Analytic chemistry gives "the relative number of volumes of the
different constituents contained in each compound body." That is, the
number of each element in the molecule. Sort this list of elements
alphabetically and you've got a description of the molecule which is
invariant; it won't change no matter the source of the sample nor the
person doing the analysis.