Part 241

GLYCERINE AS A DETERGENT: See Cleaning Preparations and Methods.

GLYCERINE PROCESS: See Photography.

GLYCERINE SOAP: See Soap.

GLYCERINE DEVELOPER: See Photography.

«Gold»

(See also Jewelers’ Formulas.)

«Gold Printing on Oilcloth and Imitation Leather.»—Oilcloth can very easily be gilt if the right degree of heat is observed. After the engraving has been put in the press, the latter is heated slightly, so that it is still possible to lay the palm of the hand on the heated plate without any unpleasant sensation. Go over the oilcloth with a rag in which a drop of olive oil has been rubbed up, which gives a greasy film. No priming with white of egg or any other priming agent should be done, since the gold leaf would stick. Avoid sprinkling on gilding powder. The gold leaf is applied directly on the oilcloth; then place in the lukewarm press, squeezing it down with {380} a quick jerky motion and opening it at once. If the warm plate remains too long on the oilcloth, the gold leaf will stick. When the impression is done, the gold leaf is not swept off at once, but the oilcloth is first allowed to cool completely for several minutes, since there is a possibility that it has become slightly softened under the influence of the heat, especially at the borders of the pressed figures, and the gold would stick there if swept off immediately. The printing should be sharp and neat and the gold glossy. For bronze printing on oilcloth, a preliminary treatment of printing with varnish ground should be given. The bronze is dusted on this varnish.

Imitation leather is generally treated in the same manner. The tough paper substance is made to imitate leather perfectly as regards color and pressing, especially the various sorts of calf, but the treatment in press gilding differs entirely from that of genuine leather. The stuff does not possess the porous, spongy nature of leather, but on the contrary is very hard, and in the course of manufacture in stained-paper factories is given an almost waterproof coating of color and varnish. Hence the applied ground of white of egg penetrates but slightly into this substance, and a thin layer of white of egg remains on the surface. The consequence is that in gilding the gold leaf is prone to become attached, the ground of albumen being quickly dissolved under the action of the heat and put in a soft sticky state even in places where there is no engraving. In order to avoid this the ground is either printed only lukewarm, or this imitation leather is not primed at all, but the gold is applied immediately upon going over the surface with the oily rag. Print with a rather hot press, with about the same amount of heat as is employed for printing shagreen and title paper. A quick jerky printing, avoiding a long pressure of the plate, is necessary.

«Liquid Gold.»—Take an evaporating dish, put into it 880 parts, by weight, of pure gold; then 4,400 parts, by weight, of muriatic acid, and 3,520 parts, by weight, nitric acid; place over a gas flame until the gold is dissolved, and then add to it 22 parts, by weight, of pure tin; when the tin is dissolved add 42 parts, by weight, of butter of antimony. Let all remain over the gas until the mixture begins to thicken. Now put into a glass and test with the hydrometer, which should give about 1,800 specific gravity. Pour into a large glass and fill up with water until the hydrometer shows 1090; pour all the solution into a chemical pot and add to it 1,760 parts, by weight, balsam of sulphur, stirring well all the while, and put it over the gas again; in an hour it should give, on testing, 125° F.; gradually increase the heat up to 185° F., when it should be well stirred and then left to cool about 12 hours. Pour the watery fluid into a large vessel and wash the dark-looking mass 5 or 6 times with hot water; save each lot of water as it contains some portion of gold. Remove all moisture from the dark mass by rolling on a slab and warming before the fire occasionally so as to keep it soft. When quite dry add 2 1⁠/⁠4 times its weight of turpentine and put it over a small flame for about 2 hours; then slightly increase the heat for another hour and a half. Allow this to stand about 24 hours, and then take a glazed bowl and spread over the bottom of it 1,760 parts, by weight, of finely powdered bismuth; pour the prepared gold over it in several places. Now take a vessel containing water and place inside the other vessel containing the gold, and heat it so as to cause the water to boil for 3 hours; allow it to remain until settled and pour off the gold from the settlings of the bismuth, and try it; if not quite right continue the last process with bismuth until good; the bismuth causes the gold to adhere.

«Preparation of Balsam of Sulphur.»—Take 16 parts oil of turpentine; 2 1⁠/⁠2 parts spirits of turpentine; 8 parts flour of sulphur.

Place all in a chemical pot and heat until it boils; continue the boiling until no sulphur can be seen in it; now remove from the heat and thin it with turpentine until about the thickness of treacle, then warm it again, stirring well; allow it to cool until it reaches 45° F., then test it with the hydrometer, and if specific gravity is not 995 continue the addition of turpentine and warming until correct, let it thoroughly cool, then bottle, keeping it air-tight.

«To Purify Bismuth.»—Take 6 parts bismuth metal, 3⁠/⁠4 part saltpeter. Melt together in a biscuit cup, pour out on to a slab, and take away all dirt, then grind into a fine powder.

«To Recover the Gold from the Remains of the Foregoing Process.»—Put all the “watery” solutions into a large vessel and mix with a filtered saturated solution of copperas; this will cause {381} a precipitate of pure metallic gold to gradually subside; wash it with cold water and dry in an evaporating dish.

All rags and settlings that are thick should be burnt in a crucible until a yellow mass is seen; then take this and dissolve it in 2 parts muriatic acid and 1 part nitric acid. Let it remain in a porcelain dish until it begins to thicken, and crystals form on the sides. Add a little nitric acid, and heat until crystals again form. Now take this and mix with cold water, add a solution of copperas to it and allow it to settle; pour off the water, and with fresh water wash till quite free from acid. The gold may then be used again, and if great care is exercised almost one-half the original quantity may be recovered.

The quantities given in the recipe should produce about 13 to 15 parts of the liquid gold. It does not in use require any burnishing, and should be fired at rose-color heat. If desired it can be fluxed with Venice turpentine, oil of lavender, or almonds.

«Treatment of Brittle Gold.»—I.—Add to every 100 parts, by weight, 5 to 8 parts, by weight, of cupric chloride and melt until the oily layer which forms has disappeared. Then pour out, and in most cases a perfectly pliable gold will have been obtained. If this should not be the case after the first fusion, repeat the operation with the same quantity of cupric chloride. The cupric chloride must be kept in a well-closed bottle, made tight with paraffine, and in a dry place.

II.—Pass chlorine gas through the molten gold, by which treatment most of the gold which has otherwise been set aside as unfit for certain kinds of work may be redeemed.

«Assaying of Gold.»—To determine the presence of gold in ores, etc., mix a small quantity of the finely powdered ore in a flask with an equal volume of tincture of iodine, shake repeatedly and well, and leave in contact about 1 hour, with repeated shaking. Next allow the mixture to deposit and dip a narrow strip of filtering paper into the solution. Allow the paper to absorb, next to dry; then dip it again into the solution, repeating this 5 to 6 times, so that the filtering paper is well saturated and impregnated. The strip is now calcined, as it were, and the ashes, if gold is present, show a purple color. The coloring disappears immediately if the ashes are moistened with bromine water. The same test may also be modified as follows: Cover the finely pulverized ore with bromine water, shake well and repeatedly during about 1 hour of the contact, and filter. Now add to the solution stannic protochloride in solution, whereby, in case gold is present, a purple color (gold purple of Cassius) will at once appear. In case the ore to be assayed contains sulphides, it is well to roast the ore previously, and should it contain lime carbonate, it is advisable to calcine the ore before in the presence of ammonium carbonate.

«Gold Welding.»—Gold may be welded together with any metal, if the right methods are employed, but best with copper. Some recipes for welding agents are here given.

I.—Two parts by weight (16 ounces equal 1 pound) of green vitriol; 1 part by weight (16 ounces equal 1 pound) of saltpeter; 6 parts by weight (16 ounces equal 1 pound) of common salt; 1 part by weight (16 ounces equal 1 pound) of black manganic oxide or pulverized, and mixed with 48 parts by weight (16 ounces equal 1 pound) of good welding sand.

II.—Filings of the metal to be used in welding are mixed with melted borax in the usual proportion. To be applied in the thickness desired.

III.—A mixture of 338 parts of sodium phosphate and 124 parts of boracic acid is used when the metal is at dark-red heat. The metal is then to be brought to a bright-red heat, and hammered at the same time. The metal easily softens at a high temperature, and a wooden mallet is best. All substances containing carbon should be removed from the surface, as success depends upon the formation of a fusible copper phosphate, which dissolves a thin layer of oxide on the surface, and keeps the latter in good condition for welding.

«To Recover Gold-Leaf Waste.»—To recover the gold from color waste, gold brushes, rags, etc., they are burned up to ashes. The ashes are leached with boiling water containing hydrochloric acid. The auriferous residuum is then boiled with aqua regia (1 part nitric acid and 3 parts hydrochloric acid), whereby the gold is dissolved and gold chloride results. After filtration and evaporation to dryness the product is dissolved in water and precipitated with sulphate of protoxide of iron. The precipitated gold powder is purified with hydrochloric acid.

«Gold from Acid Coloring Baths.»—I.—Different lots are to be poured together {382} and the gold in them recovered. The following method is recommended: Dissolve a handful of phosphate of iron in boiling water, to which liquor add the coloring baths, whereby small particles of gold are precipitated. Then draw off the water, being careful not to dissolve the auriferous sediment at the bottom. Free this from all traces of acid by washing with plenty of boiling water; it will require 3 or 4 separate washings, with sufficient time between each to allow the water to cool and the sediment to settle before pouring off the water. Then dry in an iron vessel by the fire and fuse in a covered skittlepot with a flux.

II.—The collected old coloring baths are poured into a sufficiently large pot, an optional quantity of nitro-muriatic acid is added, and the pot is placed over the fire, during which time the fluid is stirred with a wooden stick. It is taken from the fire after a while, diluted largely with rain water and filtered through coarse paper. The gold is recovered from the filtered solution with a solution of green vitriol which is stored in air-tight bottles, then freshened with hot water, and finally smelted with borax and a little saltpeter.

«Parting with Concentrated Sulphuric Acid.»—It is not necessary scrupulously to observe the exact proportion of the gold to the silver. After having prepared the auriferous silver, place it in a quantity of concentrated sulphuric acid contained in a porcelain vessel, and let it come to a violent boil. When the acid has either become saturated and will dissolve no more, or when solution is complete, remove the dissolving vessel from the fire, let it cool, and, for the purpose of clarifying, pour dilute sulphuric acid into the solution. The dissolved silver is next carefully decanted from the gold sediment upon the bottom, another portion of concentrated acid is poured in, and the gold is well boiled again, as it will still contain traces of silver; this operation may be repeated as often as is deemed necessary. The solution, poured into the glass jars, is well diluted with water, and the silver is then precipitated by placing a sheet of copper in the solution. The precipitate is then freshened with hot water, which may also be done by washing upon the filter; the granulated silver (sulphate of silver) is pressed out in linen, dried and smelted. The freshened gold, after drying, is first smelted with bisulphate of soda, in order to convert the last traces of silver into sulphate, and then smelted with borax and a little saltpeter.

«To Remove Gold from Silver.»—I.—Gold is taken from the surface of silver by spreading over it a paste, made of powdered sal ammoniac with aqua fortis and heating it till the matter smokes and is nearly dry, when the gold may be separated by rubbing it with the scratch brush.

II.—The alloy is to be melted and poured from a height into a vessel of cold water, to which a rotary motion is imparted, or else it is to be poured through a broom. By this means the metal is reduced to a fine granular condition. The metallic substance is then treated with nitric acid, and gently heated. Nitrate of silver is produced, which can be reduced by any of the ordinary methods; while metallic gold remains as a black sediment, which must be washed and melted.