History on the Human Side
1. Fluorine (L. fluo, flow) was not prepared as an element until 1886, even
though the fluorine-containing mineral fluorspar or fluorite was described
in 1529 by Georg Bauer, the German physician and mineralogist better
known as Agricola. It appears likely that crude hydrofluoric acid was first
prepared in the early 18th century by an unknown English glassworker and
used to etch glass. Subsequently, in 1771, Swedish chemist Carl Wilhelm
Scheele obtained impure hydrofluoric acid—over a hundred years before
French chemist Henri Moissan isolated the element in 1886. The delay was
largely due to the reactivity and toxicity of fluorine. After the nearly
anhydrous hydrofluoric acid was prepared in 1809, French scientist Andre´-Marie
Ampe`re suggested (1811) that it was a compound of hydrogen with an
unknown element, analogous to chlorine, for which he suggested the name
fluorine. Fluorspar was then recognized to be calcium fluoride.

Fluorine’s toxicity caused serious health problems for several chemists. Sir
Humphry Davy tried to prepare the element by electrolytic decomposition of
various fluorides, but succeeded only in ruining his health. French chemist
Edmond Fre´my, as well as George and Thomas Knox of the Irish Academy,
Gay-Lussac, and The´nard all suffered loss of health due to their efforts to
make fluorine. At least two chemists—Paulin Louget and Jerome Nickles—
died as a direct result of attempts to isolate fluorine. Even Moissan, who finally
prepared the gas by electrolysis of anhydrous hydrofluoric acid containing KHF2
as an electrolyte, had earlier completed many unsuccessful experiments,
resulting in damage to his health. He received the Nobel prize in 1906, when
he was 54, but died the following year. Prior to World War II, fluorine remained
a laboratory curiosity. The use of uranium(VI) fluoride in the separation of
uranium isotopes and development of organic fluorine compounds and
polymers has made fluorine an important and much more familiar element.

2. Chlorine (Gr. chlorous, greenish-yellow) was discovered in 1772 by Scheele,
who thought it was an oxygen-containing substance. By 1810, Humphry Davy
had completed a careful search for the oxygen, but, failing to find any, changed
its name from oxymuriatic acid (muriatic acid is HCl and chlorine is an oxidation
product of HCl) to chlorine, since he was convinced this was an element. He had
some difficulty convincing the French of this, but his views eventually prevailed.
Chlorine has been directly or indirectly involved in human history for centuries.
At one time salt (NaCl) was more valuable than gold—wars were fought over the
control of its sources. Chlorine gas was used as a weapon in World War I, but by
contrast, in 1988 it became a federally required water disinfectant in all U.S.
public drinking water supplies. Chlorine and other halogen-containing
hydrocarbons show a similar apparent dichotomy in their use in a wide variety
of consumer, agricultural, and industrial products, while also being banned
because of environmental and health concerns. Even so, halogen-containing
polymeric hydrocarbon derivatives continue to ease our everyday lifestyle.

3. Bromine (Gr. bromos, stench) This element’s discovery is credited to French
chemist Antoine Je´rome Balard, who, in 1826, noted that bromine could be
liberated from a solution of residues remaining after sodium chloride had been
removed from sea water by bubbling chlorine through the solution. He deduced
that this was a new element similar to chlorine because the distillation of these
residues (containing MgBr2 ) with manganese dioxide and sulfuric acid also
produces bromine and is analogous to a known procedure for producing chlorine.
German chemist Justus von Liebig had actually isolated bromine prior to its
discovery by Balard, but he interpreted its properties (between those of
chlorine and iodine) as indicative of iodine chloride.

4. Iodine(Gr. iodes, violet) The discovery of iodine is credited to French chemist
Bernard Courtois. In 1811, from the ashes of burnt seaweed, he observed a
violet vapor that attacked his copper vessels. He called the condensed black
crystalline product “substance X.” In 1813, Davy, who was passing through
Paris, recognized substance X as an element analogous to chlorine and
suggested the name iodine. Historically, iodine has been prepared by a number
of methods and sources ranging from extraction from sea kelp and sea animals
to various methods of I oxidation and IO3reduction.

5. Astatine First prepared in 1940 by bombardment of bismuth with alpha particles.

Humor on the Fun Side





Donald asked his teacher if,
The jar of chlorine he could sniff:
Teacher queried, as he rose,
“How do we waft a gas to nose?”
Donny grinned and waved a hand;
In the jar his nose he slammed,
Donny crumpled in a fall;
The teacher ran for ethanol.
First aid was rendered on the spot
But Don said he felt “not so hot.”
And since he surely was not well
They sent him to the hospital.
From his bed he soon arose
And was putting on his clothes
When nursie caught him in the act;
She hid his clothes without much tact.
Now in bed, no pen or ink,
He had the time to think and think.
He understood the reason why
The teacher used to cry, and try
To get his students to take care
And mix a gas with lots of air,
And breathe in tiny little sniffs;
Not gulp down gas in great big whiffs.

(CHEM 13 NEWS, February 1979, p. 2)

Words about the concepts in this module can be obtained from the clues
given. Find these words in the block of letters:

1. Name of the anion ClO .
2. Most electonegative halogen.
3. Halide used to prevent tooth decay.
4. Halogen that is a yellow-green gas.
5. Largest halide anion.
6. General name of XO ion.
7. Number of electrons in outer energy level (any halogen).
8. Salt former.
9. Halogen that is a deep red liquid.
10. Name of the acid HIO2 .
12. Halogens Crossword Puzzle (see Appendix)
13. See relevant cartoons at end of module.

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