Youngs Demonstrative Translation of Scientific Secrets | Page 5

used to dissolve the precipitate is dilute, it will be necessary
to condense the liquor by evaporation to obtain the yellow prussiate in
crystals. The remaining solution is the coppering solution; should it not
be convenient to separate the yellow prussiate by crystallization, the
presence of that salt in the solution does not deteriorate it nor interfere
with its power of depositing copper.
19. PECULIARITIES IN WORKING CYANIDE OF COPPER
SOLUTION
The true composition of the salts thus formed by copper and cyanide of
potassium has not yet been determined, but their relations to the battery
and electrolyzation are peculiar. The solution must be worked at a heat
not less than from 150 to 200 degrees Farenheit (that is not quite as hot
a boiling water, which is 212 degrees Farenheit.) All other solutions we
have tried follow the laws, that if the electricity is so strong as to cause
gas to be evolved at the electrode, the metal will be deposited in a
sandy or powdered state, but the solution of cyanide of copper and
potassium is an exception to these laws, as there is no reguline deposit
obtained unless gas is freely evolved from the surface of the article
upon which the deposit is taking place. As this solution is used hot, a
considerable evaporation takes place, which requires that additions be
made to the solution from time to time. If water alone be used for this
purpose it will precipitate a great quantity of the copper as a white
powder, but this is prevented by dissolving a little cyanide of potassium
in the water at the rate of 4 ounces to the gallon. The vessels used in
factories for this solution are generally of copper, which are heated

over a flue or in a sand-bath, the vessel itself serving as the positive
electrode of the battery; but any vessel will suit if a copper electrode is
employed when the vessel is not of copper.
20. PREPARATION OF IRON FOR COATING WITH COPPER
When it is required to cover an iron article with copper, it is first
steeped in hot caustic potash or soda to remove any grease or oil. Being
washed from that it is placed for a short time in diluted sulphuric acid,
consisting of about one part acid to 16 parts of water, which removes
any oxide that may exist. It is then washed in water and scoured with
sand till the surface is perfectly clean, and finally attached to the battery
and immersed in the cyanide solution. All this must be done with
despatch so as to prevent the iron combining with oxygen. An
immersion of five minutes duration in the cyanide solution is sufficient
to deposit upon the iron a film of copper, but it is necessary to the
complete protection of the iron that it should have a considerably thick
coating, and as the cyanide process is expensive, it is preferable when
the iron has received a film of copper by the cyanide solution, to take it
out, wash it in water, and attach to it a simple cell or weak battery, and
put it into a solution of sulphate of copper. If there is any part not
sufficiently covered with copper by the cyanide solution, the sulphate
will make these parts of a dark colour, which a touch of the finger will
remove. When such is the case, the article must be taken out, scoured,
and put again into the cyanide solution till perfectly covered. A little
practice will render this very easy. The sulphate solution for covering
iron should be prepared by adding it by degrees a little caustic potash,
so long as the precipitate formed is re-dissolved. This neutralizes a
great portion of the sulphuric acid, and thus the iron is not so readily
acted upon. When the iron is thus coppered, proceed to silver it in the
manner recommended for silvering according to receipt No. 9; or if you
want to put a very heavy coating of silver on it, make use of a strong
battery.
21. SOLDERING FLUID
For mending articles of tin, iron, zinc, copper, and almost all other
metals. Take 2 fl. ounces of muriatic acid, add zinc till bubbles cease to
rise, add 1/2 a teaspoonful of sal-ammoniac and 2 ounces of water.
Damp the part you wish to solder with this fluid, lay on a small piece of
lead, and with a piece of hot iron or soldering iron solder the part.

22. SOLDER FOR TIN
Take of pewter 4 parts, tin 1 part, bismuth 1 part; melt them together.
Resin is used with this solder.
23. COLD METHOD OF SILVERING IRON WITH SILVER-PLATE
Polish the iron toy wish to silver, then damp it over with soldering fluid
(receipt No. 21) When this is done