Elements of Chemistry

Monday 8 February 2016

A rich source for the Nature of Science

Imagine teaching or studying chemistry knowing nothing about the periodic table, sub-atomic particles, ionic dissociation, equilibrium, etc. and where the formula for water is H.O. I’ve just been given a wonderful leather bound first edition of Elements of Chemistry by Robert Kane published in 1841. Robert Kane (1809 - 1890) was Professor of Chemistry at the Apothecaries' Hall, Dublin.

For those who wonder how to teach the Nature of Science a book like this offers some fantastic food for thought. [1] For example, Mendeleyev first devised the periodic table in 1869 and yet in 1841, when this book was written, Kane talks about ‘the chlorine family’ so it was already well known that elements such as chlorine, bromine and iodine possess similar chemical properties. Kane also talks about the fluoride of calcium. This provides evidence that although fluorine the element was not isolated until 1886 (by Henri Moissan) some of its compounds were already known decades earlier and named fluorides. In the 1840s the Lavoisier definition of an acid being the oxide of a non-metal and water still seems to have held sway as Kane writes, ”The chlorides and iodides of hydrogen, although popularly called acids (muriatic and hydriodic acid), are thus really salts. …… as they do not unite with metallic oxides to form salts, but they decompose them, water being evolved”.

This is supported by the written equation:

“Cl.H and K.O produce Cl.K and H.O”


Note that at that time water was considered to be H.O as although Avogadro had postulated the idea of molecules in 1816 it was not properly recognised by the scientific community until Cannizzaro’s work in1858, 17 years after Kane’s book was first written.

Remember too, that this was written some forty three years before Arrhenius published his Ph.D thesis on the dissociation of electrolytes in solution, which is the basis of the ionic theory of acids – a thesis which was widely ridiculed by his professors at Uppsala university at the time even though Arrhenius went on to win the Nobel Prize for this work in 1903.

I’ve just given a few extracts from the book that show the state of chemistry knowledge at the time. It is easy to underestimate how much was known even if it lacked a modern explanation and it helps to understand Isaac Newton’s famous quote of 1676 ("If I have seen further, it is by standing on the shoulders of giants.") that new theories often depend upon the earlier work of others.


Footnotes



Comments


To post comments you need to log in. If it is your first time you will need to subscribe.