The sun., 1900-12-30

has recently found that the tube may be
equally well constructed Of copper and
this may soon lead to the industrial appli-
cation Of the process. The difficulty OF
isolatng fiuorine ia due TO its extraordinary
chemical energy: for there are few sub
stances. elementary or compound. which
resist the action OF this pale. yellow. sufIo-
eating gas. In 1911 iodine. separated by
Courtois from the ashes OF sea plants. was
shown by Davy to be an element analogous
To chlorine Gay-Lussac subsequently in
vestigated it and prepared many of its COM
pounds: and in 1929 the last Of these ele-
ments. bromine. was discovered in the
mother liquor Of sea salt by Ballard. The
elements OF this group have been termed
-halogens." or salt producers"
JOHN pALToN's THEORY.
While Davy was pouring his researches
into the astonished ears Of the scientific
and dilettante world John Dalton. Man
chester schoolmaster. conceived theory
which has proved Of the utmost service
to the science Of chemistry and which
bids fair to outlast our day. IT had been
noticed by Wenzel. by Richter, by Wollas-
ton and by Cavendish. toward the end OF
the last century. that the same compounds
contain the same constituents In the same
proportions, or. as the phrase runs. pos
sess constant composition" Wollaston,
indeed. had gone one step further. and had
shown that when the vegetable acid. oxalic
acid. IL combined with potash. 1t forms
two compounds. in one of which the acid
il contained in twice as great an amount
relatively TO the potash a. in the other. The
names monordidte and binordldte Of potash
were applied TO these compounds. to in
dcate the respective proportions OF the
ingredients. Dalton conceived the happy
idea that by applying the ancient Greek
conception of atoms to such facts the rela-
tive weights OF the atoms could be deter
mined. Illustrating his views with the
two compounds Of carbon with hydrogen.
marsh gas and defiant cas, and wit the
two acids Of carbon. carbonic oxide. car
bonic "acid,' he regarded the former IA
compound Of one atom of carbon and one
Of hydrogen and the second as compound
of one atom of carbon and two of hydrogen.
and similarly for the two oxides Of carbon.
knowing the relative weights in which
these elements enter into combination. We
can deduce the relative weights of the
atoms. Placing the relative weight Of an
atom Of hydrogen equal to unity, we have
Gas Gas Oriif. Acif.
rIIsnn mydISsen N. 8 GoaiSsa oayssn. 10
Thus the first compound marsh gas. was
regarded by Dalton as composed of an atom
of carbon in union with an atom OF hydrogen:
or. 10 reproduce his symbols. as q Q;
willie the second. oletilnt gas. on this hy-
pothesis. was a compound Of two atoms Of
hydrogen with one of carbon. or O @ O.
Similarly the symbols . Q, and 9 o O
We're given 20 the two compounds Of carbon
with oxygen. SO water was assigned the
symbol O 0. for Dalton imagined it to be
n compound of one atom of hydrogen with
one Of oxygen Compounds containing only
two atoms were termed by him binary"
those containing three. "ternary;" four.
"quatsrnary," and so on. The weight Of
an atom of oxygen was eight times that Of
an atom of hydrogen, while that Of an atom
of carbon was six times as great as the unit.
BY assigning symbols to the elements.
consisting Of the initial letters Of their
names or Of the first two letters. formula
were developed. indicating the composition
Of the compound, the atomic weights Of
the elements being assured. Thus, Mao
signfed a compound of an atom of sodium
natrium) weighing twenty-three times IA
much as a similar atom of hydrogen, with an
atom OF oxygen. possessing eight times the
weight Of an atom Of hydrogen Therefore
81 pounds of soda should consist OF % pounds
Of sodium. in combination with : pounds
of oxygen. for. according to Dalton. each
smallest particle of soda contains an atom
OF each element and the proportion is not
changed. however many particles may be
considered.
II has been pointed ont by Judge Stallo
Of Philadelphia in his Concepts OF Physics"
that such "A hypothesis a. that OF Dalton
1, no explanation: that a fact Of nature, a.,
for example, the fact Of simple and multiple
is not explained by being mimi
hel Allowing the general truth OF this
statement, 1t Ia nevertheless undoubted that
chemistry owes much to Dalton's hypothe-
rlNs Il'hN iN III ~, II Ollt pI
the sunda Aental truths of nature. although
its form must be somewhat modified from
that in which Dalton conceived IL. Dalton's
work was first expounied by Thomas Thom-
son. professor at Glasgow. in his system
OF Chemistry" published in 1906; and subse-
qiently in Dalton's own New System OF
Chemical Philosophy" the three volumes OF
which were published in 1913. in 1910. and in
1921.
atomic WEIGHTS"
The determination of these Constants OF
Nature" was at once followed out hy many
chemists. Thomson among the first But
chief among the chemists who have pursued
this branch of work was Jacob Berzelius, a
Swede. who devoted his long life l77a-ls4sl
TO the manufacture of compounds and to the
Of their composition. or, a. it
is still termed, the determination of the
atomic weghts"-more correctly, "equiva-
lents"-of the elements OF which they are
1t Is to him that we owe most
of our analytical methods. for, prior to his
time. there were few, if any. accurate analy-