This form of notation was quite extensively employed for a time,
especially by mineralogists, but it was entirely abandoned later.
It is interesting to notice that Dalton, who lived until 1844, to reach
the age of 78, differed from other chemists in refusing to accept the
letter-symbols of Berzelius. In a letter written to Graham in 1837 he
said: “Berzelius’s symbols are horrifying. A young student in chemistry
might as soon learn Hebrew as to make himself acquainted with them. They
appear like a chaos of atoms ... and to equally perplex the adepts of
science, to discourage the learner, as well as to cloud the beauty and
simplicity of the atomic theory.”
This forcibly expressed opinion was apparently tinged with self-esteem,
but there is no doubt that Dalton was sincere in believing that the
atoms were best represented by his circular symbols, because, as is well
known, he thought that all the atoms were spherical in form, and it is
evident that circles give the proper picture of spherical objects. At
the present time some insight as to the structure of atoms is being
gained, and it appears possible that the time may come when pictures of
their external appearance that are not wholly imaginary may be made.
_Changes in Formulas._—Even before the year 1826, Berzelius displayed
great skill in arriving at many formulas that agree with our present
ones, for example, H_{2}O for water, ZnCl_{2} for zinc chloride,
N_{2}O_{5} for nitric acid (anhydride), CaO for calcium oxide, CO and
CO_{2} for the oxides of carbon, and many others. But at the same period
other authorities, especially Gay-Lussac in France and Gmelin in
Germany, on account of a lack of appreciation for Avogadro’s principle
and for other reasons, such as the use of symbols to represent combining
weights rather than atoms, were using different formulas for some of
these compounds, such as HO, ZnCl and NO_{5}, so that their formulas for
many of the compounds of hydrogen, chlorine, nitrogen and several other
elements differed from those of Berzelius. The employment of different
formulas involved the use of different atomic or combining weights. For
example, with the formula H_{2}O for water the composition by weight
requires the ratio 1 to 16 for the weights of the hydrogen and oxygen
atoms, while with HO the ratio is 1 to 8.
Berzelius attempted to bring about greater uniformity in formulas and
atomic weights by making changes in his table of atomic weights
published in 1826. He practically doubled the relative atomic weights of
hydrogen, chlorine, nitrogen, and of the other elements that gave twice
as many atoms in his formulas as in those of others, and at the same
time he wrote the symbols of these elements with a bar across them to
indicate that they represented double atoms. For example, he wrote:
H̶O ZnC̶l N̶O_{5},
instead of