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Subject: Tin pest

Tin pest

From: Thor Minnick <roniofhi>
Date: Thursday, October 15, 1998
In Instance 12:35, Jessica Johnson asks about Tin Pest.

At room and higher temperatures the most stable modification is
white tin--a malleable metal. At a temperature below 13 degrees C
the crystalline lattice of tin becomes rearranged, so that more
space is left between its atoms. A new modification--gray tin--is
formed. It loses the properties of metal and becomes a
semiconductor. The internal stresses that emerge in places of
contact between the different crystalline lattices cause the
material to crack and disintegrate into powder. One modification
turns into the other the faster, the lower the temperature of the
medium. The process has the fastest rate at minus 33 degrees C.

As mentioned by Barry Knight in another recent post, bismuth or lead
are alloyed w/ tin to stabilize these lattice "dislocations"

Excerpts below have been taken from Tales About Metals by S.Venetsky
(Mir Publishers, Moscow, English translation 1981), as it may help
in the understanding of some otherwise unexplainable phenomena
(interesting too!).

    In 1910 Captain Robert Scott, the famous British polar explorer,
    fitted out an expedition to the South Pole, at that time still
    in a terra incognita. For many weary a month had the expedition
    be been making its painful progress through the lifeless ice
    deserts of the Antarctic, leaving behind small caches of food
    and kerosene to take care of their needs on the way back. At the
    beginning of 1912 the expedition had finally reached its
    destination  but to the men's great disappointment they found a
    note there which made it clear that they had been preceded by
    the Norwegian explorer Roald Amundsen one month earlier.
    However, Captain Scott's worst misfortune was yet to come. On
    the way back it was discovered at the very first cache that the
    expedition was left without kerosene: the cans that had been
    stored up there were empty. The people, exhausted, freezing and
    hungry, could not warm themselves up nor prepare anything to
    eat. It was with the greatest difficulty that they managed to
    get to the next cache, but there too the cans were empty--the
    kerosene had leaked out. Powerless in the polar cold which was
    made worse by terrible blizzards that had begun by then, Captain
    Scott and his friends soon died.

    What was the reason for the mysterious disappearance of the
    kerosene? Why did the expedition so carefully planned end so
    tragically? What was Captain Scott's mistake?

    It was quite simple: the kerosene cans had been soldered with
    tin. The explorers must have been ignorant of the fact that at
    freezing temperatures tin "catches a cold", first losing its
    lustre and becoming dull gray and then disintegrating into
    powder.  This phenomenon--"tin plague"--was what sealed the fate
    of the expedition.

    Meanwhile it is a fact that tin's predisposition to "disease"
    had been known long before those sad events. It was noticed as
    early as the Middle Ages that tinware "developed" ulcers when
    exposed to frost, and that the "ulcers" gradually became larger
    and spread, finally reducing the metal to powder. It was known
    besides, that once a "sick" tin plate came into contact with a
    "healthy" one the latter would soon cover with gray spots and
    also "perish".

    At the end of the last century a train carrying bars of tin was
    sent from Holland to Russia. When the cars were unsealed in
    Moscow they appeared to contain some gray and useless powder--it
    was Russian winter playing a wicked trick on the buyers of tin.

    At about the same period a well-equipped expedition set out for
    Siberia. It seemed everything had been taken care of to ensure
    its success, except one thing: tin dishes had been taken. The
    result was that after a while spoons and bowls had to be carved
    from wood if the expedition was to go any further.

    At the very beginning of this century a shocking incident
    occurred at an army depot in St. Petersburg: an audit there
    discovered, to the horror of the quartermaster, that all tin
    buttons had vanished from the soldier's uniforms and the boxes
    that were supposed to contain such buttons were full of a gray
    powder. The quartermaster was desperate, expecting that he would
    be accused of theft and sent to a hard labour camp. But the poor
    fellow was saved by the report sent in from the chemical
    laboratory to which the contents of the boxes had been sent to
    be analyzed. It said: "The substance sent by you is doubtlessly
    tin. Apparently we are dealing here with the chemical phenomenon
    known as 'tin plague'."

Thor Minnick
Minnick Associates
Honolulu, Hawaii

                  Conservation DistList Instance 12:37
                 Distributed: Friday, October 16, 1998
                       Message Id: cdl-12-37-001
Received on Thursday, 15 October, 1998

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