Youngs Demonstrative Translation of Scientific Secrets | Page 5

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 give it a coat of No. 22 solder. This is done by laying a piece of cold solder on the iron, and spreading it over with a heated soldering iron, when by this means you get the iron nicely plated with solder, then lay on your silver-plate evenly, and gently rub it over with the heated soldering iron, and it will become firmly united with the