We propose to speak of some silver bars ... and silver nitrate ... by Mark Twain

Discussion in 'Darkroom Developing and Printing' started by Lloyd Erlick, Jun 11, 2006.

  1. Lloyd Erlick

    Lloyd Erlick Guest

    Territorial Enterprise, February 17-22, 1863

    SILVER BARS - HOW ASSAYED

    We propose to speak of some silver bars which
    we have been looking at, and to talk science
    a little, also, in this article, if we find
    that what we learned in the latter line
    yesterday has not escaped our memory. The
    bars we allude to were at the banking house
    of Paxton Thornburgh, and were five in
    number; they were the concentrated result of
    portions of two eight-day runs of the Hoosier
    State Mill, on Potosi rock. The first of the
    bricks bore the following inscription, which
    is poetry stripped of flowers and flummery,
    and reduced to plain common sense: "No. 857;
    Potosi Gold and Silver Mining Company; Theall
    & Co., assayers; 688.48 ounces, gold, 020
    fine, silver, 962 fine; gold $572.13, silver
    $1,229.47." Bars No. 836 and No. 858 bore
    about the same inscription, save that their
    values differed, of course, the one being
    worth $1,800, and the other a fraction under
    $1,300. The two largest bars were still in
    the workshop, and had not yet been assayed;
    one of them weighed nearly a hundred pounds
    and 1 was worth about $3,000, and the other,
    which contained over 900 ounces, was worth in
    the neighborhood of $2,000. The weight of the
    whole five bars may be set down in round
    numbers at 300 pounds, and their value, at
    say, $10,000. Those are about the correct
    figures. We are very well pleased with the
    Hoosier State mill and the Potosi mine - we
    think of buying them. From the contemplation
    of this result of two weeks' mill and mining
    labor, we walked through the assaying rooms,
    in the rear of the banking house, with Mr.
    Theall, and examined the scientific
    operations there, with a critical eye. We
    absorbed much obtuse learning, and we propose
    to give to the ignorant the benefit of it.
    After the amalgam has been retorted at the
    mill, it is brought here and broken up and
    put into a crucible (along with a little
    borax,) of the capacity of an ordinary plug
    hat; this vessel is composed of some kind of
    pottery which stands heat like a salamander;
    the crucible is placed in a brick furnace; in
    the midst of a charcoal fire as hot as the
    one which the three Scriptural Hebrew
    children were assayed in; when the mass
    becomes melted, it is well stirred, in order
    to get the metals thoroughly mixed, after
    which it is poured into an iron brick mould;
    such of the base metals as were not burned
    up, remain in the crucible in the form of a
    "sing." The next operation is the assaying of
    the brick. A small chip is cut from each end
    of it and weighed; each of these is enveloped
    in lead and placed in a little shallow cup
    made of bone ashes, called a cupel, and put
    in a small stone-ware oven, enclosed in a
    sort of parlor stove furnace, where it is
    cooked like a lost sinner; the lead becomes
    oxydized and is entirely absorbed by the
    pores of the cupel - any other base metals
    that may still linger in the precious stew,
    meet the same fate, or go up the chimney. The
    gold and silver come from the cupel in the
    shape of a little button, and in a state of
    perfect purity; this is weighed once more,
    and what it has lost by the cooking process,
    determines the amount of base metal that was
    in it, and shows exactly what proportion of
    it the bar contains - the lost weight was
    base metal you understand, and was burned up
    or absorbed by the cupel. The scales used in
    this service are of such extremely delicate
    construction that they have to be shut up in
    a glass case, since a breath of air is
    sufficient to throw them off their balance -
    so sensitive are they, indeed, that they are
    even affected by the particles of dust which
    find their way through the joinings of the
    case and settle on them. They will figure the
    weight of a piece of metal down to the
    thousandth part of a grain, with stunning
    accuracy. You might weigh a musquito here,
    and then pull one of his legs off, and weigh
    him again, and the scales would detect the
    difference. The smallest weight used - the
    one which represents the thousandth part of a
    grain - is composed of aluminum, which is the
    metallic base of common clay, and is the
    lightest metal known to science. It looks
    like an imperceptible atom clipped from the
    invisible corner of a piece of paper whittled
    down to an impossible degree of sharpness -
    as it were - and they handle it with pincers
    like a hair pin. But with an excuse for this
    interesting digression, we will return to the
    silver button again. After the weighing,
    melting and re-weighing of it has shown the
    amount of base metal contained in the brick,
    the next thing to be done is to separate the
    silver and gold in it, in order to find out
    the exact proportions of these in the bar.
    The button is placed in a mattrass filled
    with nitric acid, (an elongated glass bottle
    or tube, shaped something like a bell
    clapper) which is half buried in a box of hot
    sand - they called it a sand bath - on top of
    the little cupel furnace, where all the
    silver is boiled out of said button and held
    in solution, (when in this condition it is
    chemically termed "nitrate of silver.") This
    process leaves a small pinch of gold dust in
    the bottom of the mattrass which is perfectly
    pure; its weight will show the proportion of
    pure gold in the bar, of course. The silver
    in solution is then precipitated with
    muriatic acid (or something of that kind - we
    are not able to swear that this was the drug
    mentioned to us, although we feel very
    certain that it was,) and restored to metal
    again. Its weight, by the musquito scales,
    will show the proportion of silver contained
    in the brick, you know. Now just here, our
    memory is altogether at fault. We cannot
    recollect what in the world it is they do
    with the "dry cups." We asked a good many
    questions about them - asking questions is
    our regular business - but we have forgotten
    the answers. It is all owing to lager beer.
    We are inclined to think, though, that after
    the silver has been precipitated, they cook
    it a while in those little chalky-looking
    "dry cups," in order to turn it from fine
    silver dust to a solid button again for the
    sake of convenient handling - but we cannot
    begin to recollect anything about it. We said
    they made a separate assay of the chips cut
    from each end of a bar; now if these chips do
    not agree - if they make different statements
    as to the proportions of the various metals
    contained in the bar, it is pretty good proof
    that the mixing was not thorough, and the
    brick has to be melted over again; this
    occurrence is rare, however. This is all the
    science we know. What we do not know is
    reserved for private conversation, and will
    be liberally inflicted upon any body who will
    come here to the office and submit to it.
    After the bar has been assayed, it is stamped
    as described in the beginning of this
    dissertation, and then it is ready for the
    mint. Science is a very pleasant subject to
    dilate upon, and we consider that we are as
    able to dilate upon it as any man that walks
    - but if we have been guilty of carelessness
    in any part of this article, so that our
    method of assaying as set forth herein may
    chance to differ from Mr. Theall's, we would
    advise that gentleman to stick to his own
    plan nevertheless, and not go to following
    ours - his is as good as any known to
    science. If we have struck anything new in
    our method, however, we shall be happy to
    hear of it, so that we can take steps to
    secure to ourself the benefits accruing
    therefrom.

    [reprinted in The Works of Mark Twain; Early
    Tales & Sketches, Vol. 1 1851-1864, (Univ. of
    California Press, 1979), pp. 211-14.]
    http://www.twainquotes.com/18630222t.html
     
    Lloyd Erlick, Jun 11, 2006
    #1
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