Scientific American Supplement, No. 458, October 11, 1884 by Various
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Various >> Scientific American Supplement, No. 458, October 11, 1884
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The bevel gearing is revolved by shafting connected with pulley wheels and
belting, the wheels being 3 ft. and 11/2 ft. in diameter, and 6 in. broad.
The driving engine is placed at one end of the building. Each vat requires
from 21/2 to 3 horse-power, or in other words, an expenditure of 1
horse-power per ton of ore treated.
At the bottom of the vat, and in front of it, a large wooden stop-cock is
fitted, through which the liquid amalgam is drawn off at the end of the
process into another shallow-bottomed and smaller vat, Figs. 1 and 2.
Directly above this last vat there is a water hose, supplied with a
flexible spout, through which a strong stream of water is directed upon
the amalgam as it issues from the grinding vat, in order to wash off all
impurities.
The following is the mode of working usually employed. The grinding vat or
tina is first charged to about one-fifth of its depth with water and from
6 cwt. to 7 cwt. of common salt. The amount of salt required in the
process depends naturally on the character of the ore to be treated, as
ascertained by actual experiment, and averages from 150 lb. to 300 lb. per
ton of ore. Into this brine a jet of steam is then directed, and the
stirrer is set to work for about half an hour, until the liquid is in a
thoroughly boiling condition, in which state it must be kept until the end
of the process.
As soon as the liquid reaches boiling point, the stamped and roasted ore
is run into the vat, and at the end of another half-hour about 1 cwt. of
mercury is added, further quantities being added as required at different
stages of the process. The stirring is kept up continuously for eight to
twelve hours, according to the character and richness of the ores. At the
end of this time the amalgam is run out through the stop-cock at bottom of
the vat, is washed, and is put into hydraulic presses, by means of which
the mercury is squeezed out, leaving behind a thick, pulpy mass, composed
mainly of silver, and locally termed a "pina," from its resembling in
shape the cone of a pine tree. These pinas are then carefully weighed and
put into a subliming furnace, Figs. 5 and 6, in order to drive off the
rest of the mercury, the silver being subsequently run into bars. About
four ounces of mercury are lost for every pound of silver made.
The actual quantities of mercury to be added in the grinding vat, and the
times of its addition, are based entirely on practical experience of the
process. With ore assaying 150 oz. to 175 oz. of silver to the ton, 75
lb. of mercury are put in at the commencement, another 75 lb. at intervals
during the middle of the process, and finally another lot of 75 lb.
shortly before the termination. When treating "pacos," or earthy chlorides
of silver, assaying only 20 oz. to 30 oz. of silver to the ton, 36 lb. of
mercury is added to 21/2 tons of ore at three different stages of the
process as just described.
The _rationale_ of the process therefore appears to be that the
chlorination of the ores is only partially effected during the roasting,
so as to prevent the formation of injurious salts, and is completed in the
vats, in which the chloride of copper is formed progressively as required,
by the gradual grinding away of the copper by friction between the bottom
copper plates and the stirrer; and this chloride subsequently becoming
incorporated with the boiling brine is considered to quicken the action of
the mercury upon the silver.
_Subliming_.--The subliming furnace, shown in Figs. 5 and 6, is a plain
cylindrical chamber, A, about 4 ft. diameter inside and 41/2 ft. high, lined
with firebrick, in the center of which is fixed the upright cast-iron
cylinder or retort, C, of 1 ft. diameter, closed at top and open at
bottom. The furnace top is closed by a cast-iron lid, which is lifted off
for charging the fuel. Round the top of the furnace is a tier of radial
outlet holes for the fuel smoke to escape through; and round the bottom is
a corresponding tier of inlet air-holes, through which the fuel is
continually rabbled with poles by hand. The fuel used is llama dung,
costing 80 cents, or 2s. 6d., per 250 lb.; it makes a very excellent fuel
for smelting purposes, smouldering and maintaining steadily the low heat
required for subliming the mercury from the amalgam. Beneath the furnace
is a vault containing a wrought-iron water-tank, B, into which the open
mouth of the retort, C, projects downward and is submerged below the
water. For charging the retort, the water-tank is placed on a trolly; and
standing upright on a stool inside the tank is placed the pina, or conical
mass of silver amalgam, which is held together by being built up on a
core-bar fitted with a series of horizontal disks. The trolly is then run
into the vault, and the water-tank containing the pina is lifted by
screw-jacks, so as to raise the pina into the retort, in which position
the tank is then supported by a cross-beam. The sublimed mercury is
condensed and collected in the water; and on the completion of the process
the tank is lowered, and the spongy or porous cone of silver is withdrawn
from the retort. The subliming furnaces are ranged in a row, and
communicate by lines of rails with the weigh-house.
* * * * *
INTERESTING FACTS ABOUT PLATINUM.
After an excellent day of weakfishing on Barnegat Bay and an exceptionable
supper of the good, old fashioned, country tavern kind, a social party of
anglers sat about on Uncle Jo Parker's broad porch at Forked River,
smoking and enjoying the cool, fragrant breath of the cedar swamp, when
somehow the chat drifted to the subject of assaying and refining the
precious metals. That was just where one of the party, Mr. D.W. Baker, of
Newark, was at home, and in the course of an impromptu lecture he told the
party more about the topic under discussion, and especially the platinum
branch of it, than they ever knew before.
"Our firm," he said, "practically does all the platinum business of this
country, and the demand for the material is so great that we never can get
more than we want of it. The principal portion, or, in fact, nearly all of
it, comes from the famous mines of the Demidoff family, who have the
monopoly of the production in Russia. It is all refined and made into
sheets of various thicknesses, and into wire of certain commercial sizes,
before it comes to us; but we have frequently to cut, roll, and redraw it
to new forms and sizes to meet the demands upon us. At one time it was
coined in Russia, but it is no longer applied to that use. We have
obtained some very good crude platinum ore from South America and have
refined it successfully, but the supply from that source is, as yet, very
small. I am not aware that it has been found anywhere else than in
Colombia, on that continent, but the explorations thus far made into the
mineral resources of South America have been very meager, and it is by no
means improbable that platinum may yet be discovered there in quantities
rivaling the supply of Russia.
"A popular error respecting platinum is that its intrinsic value is the
same as that of gold. At one time it did approximate to gold in value, but
never quite reached it, and is now worth only $8 to $12 an ounce,
according to the work expended upon it in getting it into required forms
and the amount of alloy it contains. The alloy used for it is iridium,
which hardens it, and the more iridium it contains the more difficult it
is to work, and consequently the more expensive. When pure, platinum is as
soft as silver, but by the addition of iridium it becomes the hardest of
metals. The great difficulty in manipulating platinum is its excessive
resistance to heat. A temperature that will make steel run like water and
melt down fireclay has absolutely no effect upon it. You may put a piece
of platinum wire no thicker than human hair into a blast furnace where
ingots of steel are melting down all around it, and the bit of wire will
come out as absolutely unchanged as if it had been in an ice box all the
time.
"No means has been discovered for accurately determining the melting
temperature of platinum, but it must be enormous. And yet, if you put a
bit of lead into the crucible with the platinum, both metals will melt
down together at the low temperature that fuses the lead, and if you try
to melt lead in a platinum crucible, you will find that as soon as the
lead melts the platinum with which it comes into contact also melts and
your crucible is destroyed.
"A distinguishing characteristic of platinum is its extreme ductility. A
wire can be made from it finer than from any other metal. I have a sample
in my pocket, the gauge of which is only one two-thousandth of an inch,
and it is practicable to make it thinner. It has even been affirmed that
platinum wire has been made so fine as to be invisible to the naked eye,
but that I do not state as of my own knowledge. This wire my son made."
Mr. Baker exhibited the sample spoken of. It looked like a tress of silky
hair, and had it not been shown upon a piece of black paper could hardly
have been seen. He went on:
"The draw plates, by means of which these fine wires are made, are
sapphires and rubies. You may fancy for yourselves how extremely delicate
must be the work of making holes of such exceeding smallness to accurate
gauge, too, in those very hard stones. I get all my draw plates from an
old Swiss lady in New York, who makes them herself to order. But, delicate
as is the work of boring the holes, there is something still more delicate
in the processes that produce such fine wire as this. That something is
the filing of a long point on the wire to enable the poking of the end of
it through the draw plate so that it can be caught by the nippers. Imagine
yourself filing a long, tapering point on the end of a wire only one
eighteen-hundredths of an inch in diameter, in order to get it through a
draw plate that will bring it down to one two-thousandths. My son does
that without using a magnifying glass. I cannot say positively what uses
this very thin wire is put to, but something in surgery, I believe, either
for fastening together portions of bone or for operations. A newly
invented instrument has been described to me, which, if it does what has
been affirmed, is one of the greatest and most wonderful discoveries of
modern science. A very thin platinum wire loop, brought to incandescence
by the current from a battery--which, though of great power, is so small
that it hangs from the lapel of the operator's coat--is used instead of a
knife for excisions and certain amputations. It sears as it cuts, prevents
the loss of blood, and is absolutely painless, which is the most
astonishing thing about it.
"Our greatest consumers of platinum are the electricians, particularly the
incandescent light companies. I supply the platinum wire for both the
Edison and the Maxim companies, and the quantity they require so
constantly increases that the demand threatens to exceed the supply of the
metal. Sheets of platinum are bought by chemists, who have them converted
into crucibles and other forms."
The reporter's curiosity was awakened by Mr. Baker's mention of the old
lady who made those very fine draw plates, and on his return to the city
he hunted her up. Mrs. Francis A. Jeannot, the lady in question, was found
in neat apartments in a handsome flat in West Fifty-first street. Age has
silvered her hair, but her eyes are still bright, and her movements
indicate elasticity and strength. She is a native of Neufchatel,
Switzerland, and speaks English with a little difficulty, but whenever the
reporter's English was a little hard for her a very pretty girl with
brilliant eyes and crinkly jet-black hair, who subsequently proved to be a
daughter of Mrs. Jeannot, came to the rescue. With the girl's occasional
aid, the old lady's story was as follows:
"I have been in this business for thirty years. I learned it when I was a
girl in Switzerland. Very few in this country know anything correctly
about it. Numbers of people endeavor to find it out, and they experiment
to learn it, especially to do it by machinery, but without success. But,
ah, me! It is no longer a business that is anything worth. Thirty years
ago many stone draw plates were wanted, for then there was a great deal
done in filigree gold jewelry. Then the plates were worth from $2.50 up to
as high as $15, according to the magnitude of the stones and the size of
the holes I bored in them. Now, however, all that good time is past.
Nobody wants filigree gold jewelry any more, and there is so little demand
for fine wire of the precious metals that few draw plates are desired. The
prices now are no more than from $1.25 up to say $8, but it is very rare
that one is required the cost of which is more than $4. And of that a very
large part must go to the lapidary to pay for the stone and for his work
in cutting it to an even round disk. Then, what I get for the long and
hard work of boring the stone by hand is very little. 'By hand?' Oh, yes.
That must always be the only good way. The work of the machine is not
perfect. It never produces such good plates as are made by the hand and
eye of the trained artisan. 'How are they bored?' Ah, sir, you must excuse
me that I do not tell you that. It is simple, but there is just a little
of it that is a secret, and that little makes a vast difference between
producing work which is good and that which is not. It has cost me no
little to learn it, and while it is worth very little just now, perhaps
fashion may change, and plates may be wanted to make gold wire again to an
extent that may be profitable. I do not wish to tell everybody that which
will deprive me of the little advantage my knowledge gives me. 'The
stones?' Oh, we of course do not use finely colored ones. They are too
valuable. But those that we employ must be genuine sapphires and rubies,
sound and without flaws. Here are some. You see they look like only
irregular lumps of muddy-tinted broken glass. Here is a finished one."
The old lady exhibited a piece of solid brass about an inch long,
three-quarters of an inch in width, and one-sixteenth in thickness. In its
center was a small disk of stone with a hole through it, a hole that was
very smooth, wide on one side and hardly perceptible on the other. The
stone was sunk deep into the brass and bedded firmly in it. She went on:
"You will find, if you try, that you can with difficulty push through that
hole a hair from your beard. But, small as it is, it must be perfectly
smooth, and of an accurate gauge. I do not any longer myself set the
stones in the brass, as I am not so strong as I once was. My son does that
for me. But neither he nor my daughter, nor anybody else in this country,
I believe, can bore the holes so well as I can even yet. 'How long does a
draw plate last?' Ah! Practically forever. Except by clumsy handling or
accident, it does not need to be replaced, at least in one lifetime. And
there is another reason why I sell so few now. Those who require them are
supplied. 'Watch jewels?' Yes, I used to make them, but do so no longer.
They can be imported from Europe at the price of $1 a dozen, and at such a
figure one could not earn bread in making them here."--_Manuf. Gazette._
* * * * *
BAYLE'S LAMP CHIMNEY.
The different types of lamps used in domestic lighting present several
imperfections, and daily experience shows too often how difficult it is,
even with the most careful and best studied models, to have a perfect
combustion of the usual liquids--oil, kerosene, etc.
[Illustration: BAYLE'S NEW LAMP CHIMNEY.]
Mr. P. Bayle has endeavored to remedy this state of things by experiments
upon the chimney, inasmuch as he could not think of modifying the
arrangements of the lamps of commerce "without injury to man" interests,
and encountering material difficulties.
The chimney is not only an apparatus designed to carry off the smoke and
gases due to combustion, for its principal role is to break the
equilibrium of the atmospheric air, which is the great reservoir of
oxygen, and to suck into the flame, through the difference of densities,
this indispensable agent to combustion. The lamps which we now use are
provided with cylindrical chimneys either with or without a shoulder at
the base. The shouldered chimney would be sufficient to suck in the
quantity of air necessary for a good combustion if we could at will
increase its dimensions in the direction of the diameter or height. But,
on account of the fragile nature of the material of which it consists, as
also because of the arrangement of the lighting apparatus, we are forced
lo give the chimney limited dimensions. The result is an insufficient
draught, and consequently an imperfect combustion. It became a question,
then, of finding a chimney which, with small dimensions, should have great
suctional power. Mr. Bayle has taken advantage of the properties of
convergent-divergent ajutages, and of the discovery of Mr. Romilly that a
current of gas directed into the axis and toward the small base of a
truncated cone, at a definite distance therefrom, has the property of
drawing along with it a quantity of air nearly double that which this same
current could carry along if it were directed toward a cylinder. In
getting up his new chimney, Mr. Bayle has utilized these principles as
follows: Round-burner lamps have, as well known, two currents of air--an
internal current which traverses the small tube that carries the wick, and
an external one which passes under the chimney-holder externally to the
wick. In giving the upper part of the chimney, properly so called, the
form of a truncated cone whose smaller base is turned toward the internal
current of air, that is to say, in directing this current toward the
contracted part of the upper cone, at the point where the depression is
greatest, a strong suction is brought about, which has the effect of
carrying along the air between the wick and glass, and giving it its own
velocity. The draught of the two currents having been effected through the
conical form of the upper part of the chimney, it remained to regulate the
entrance of the external current into the flame. If this current should
enter the latter at too sharp an angle, it would carry it toward the mouth
of the chimney before the chemical combustion of the carbon and oxygen was
finished; and if, on the contrary, it should traverse it at too obtuse an
angle, it would depress and contract it. Experience has shown that in the
majority of cases the most favorable angle at which the external current
of air can be led into the flame varies between 35 deg. and 45 deg.. We say in the
majority of cases, for there are exceptions; this depends upon the
combustive materials and upon the conditions under which they enter the
flame. The annexed figure shows the form adopted by the inventor for oil
and kerosene lamps. As may be seen, the chimney consists of two cones, A
and B, connected end to end by their small bases. The upper one, A, or
divergent cone, is constructed according to a variable angle, but one
which, in order to produce its maximum effect, ought not to differ much
from 5 deg.. This cone rests upon the convergent one, B, whose angle, as we
have said, varies between 35 deg. and 45 deg.. To the large base of this cone
there is soldered a cylindrical part, c, designed for fixing the chimney
to the holder. The height given the divergent cone is likewise variable,
but a very beautiful light is obtained, when it is equal to six times the
diameter of the contracted part. When the lamp is designed to be used in a
still atmosphere, free from abrupt currents of air, the height may be
reduced to four times the diameter of the base, without the light being
thereby rendered any the less bright. As for the height to be given the
convergent cone, B, that is determined by the opening of the angle
according to which it has been constructed. Finally, as a general thing,
the diameter of the small base should be equal to half the large base of
the convergent cone, B.
The new chimney should be placed upon the holder in such a way that the
upper part of the wick tube, D, is a few millimeters beneath the base of
the convergent cone. The height to be given the wick varies according to
the lamp used. It is regulated so as to obtain a steady and regular
combustion. In oil lamps it must project about 11/2 centimeters. If two
lamps of the same size be observed, one of which is fitted with the new
chimney and the other with the old style, we shall be struck with the
difference that exists in the color of the flame as well as in its
intensity. While in the case of the cylindrical glass the flame is red and
dull, in that of the circuit it is white and very bright. This, however,
is not surprising when we reflect upon the theoretical conditions upon
which the construction of the new chimney is based--the strong influx of
air having the result of causing a more active combustion of the liquid,
and consequently of raising to white heat the particles of carbon
disseminated through the flame. As it was of interest to ascertain what
the increase of illuminating power was in a given lamp provided with the
new chimney, Mr. Felix le Blanc undertook some photometric experiments.
The trials were made with a Gagneau lamp provided with a chimney of the
ordinary shape, and then with one of Mr. Bayle's. The measurements were
made after each had been burned half an hour. The light of the standard
Carcel lamp being 1, there was obtained with the Gagneau lamp with the
ordinary chimney 1.113 carcels, and with the Bayle chimney 1.404 carcels.
Thus 1.113:1.404 represents the ratio of the same lamp with the ordinary
chimney and with that of Bayle. Whence it follows that the light of the
lamp with the old chimney being 1, that with the new one is 1.26, say an
increase of about 25 per cent. There is nothing absolute about this
figure, however. On kerosene lamps the new chimney, compared with the
contracted Prussian one, gives an increase of 40 per cent. in illuminating
power, and the oil is burned without odor or smoke.
As it was of interest to see whether this increase in intensity was not
due to a greater consumption of oil, a determination was made of the
quantity of the latter consumed per hour. The Gagneau lamp, with the old
chimney, burned 62.25 grammes per hour, and with the Bayle 63 grammes in
the same length of time.
It may be concluded, then, that the increase in light is due to the
special form given the chimney. This new burner is applicable to gas lamps
as well as to oil and petroleum ones.
The effects obtained by the new chimney may be summed up as follows:
increase in illuminating power, as a natural result of a better
combustion; suppression of smoke; and a more active combustion, which
dries the carbon of the wick and thus facilitates the ascent of the oil.
The velocity of the current of air likewise facilitates the action of
capillarity by carrying the oil to the top of the wick. Moreover, the
great influx of air under the flame continually cools the base of the
chimney as well as the wick tube, and the result is that the excess of oil
falls limpid and unaltered into the reservoir, and produces none of those
gummy deposits that soil the external movements and clog up the conduits
through which the oil ascends. Finally, the influx of air produced by this
chimney permits of burning, without smoke and without charring the wick,
those oils of poor quality that are unfortunately too often met with in
commerce.--_La Nature._
* * * * *
MODERN LOCOMOTIVE PRACTICE.
[Footnote: Paper read before the Civil and Mechanical Engineers' Society,
April 2, 1884.]
By H. MICHELL WHITLEY, Assoc. M.I.C.E., F.G.S.
A little more than half a century ago, but yet at a period not so far
distant as to be beyond the remembrance of many still living, a
clear-headed North-countryman, on the banks of the Tyne, was working out,
in spite of all opposition, the great problem of adapting the steam engine
to railway locomotion. Buoyed up by an almost prophetic confidence in his
ultimate triumph over all obstacles, he continued to labor to complete an
invention which promised the grandest benefits to mankind. What was
thought of Stephenson and his schemes may be judged by the following
extracts from the _Quarterly Review_ of 1825, in which the introduction of
locomotive traction is condemned in the most pointed manner:
"As to those persons who speculate on making railways general throughout
the kingdom, and superseding every other mode of conveyance by land and
water, we deem them and their visionary schemes unworthy of notice.... The
gross exaggeration of the locomotive steam engine may delude for a time,
but must end in the mortification of all concerned.... It is certainly
some consolation to those who are to be whirled, at the rate of 18 or 20
miles per hour, by means of a high-pressure engine, to be told that they
are in no danger of being sea-sick while on shore, that they are not to be
scalded to death or drowned by the bursting of a boiler, and that they
need not mind being shot by the shattered fragments, or dashed in pieces
by the flying off or breaking of a wheel. But with all these assurances,
we would as soon expect the people of Woolwich to suffer themselves to be
fired off upon one of Congreve's ricochet rockets, as trust themselves to
the mercy of such a machine going at such a rate."
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