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Home , Kauri gum, Pitch (resin)

114 SCIENTIFIC AMERICAN SUPPLEMENT No. 1677. F1

A FEW TECHNICAL SUGGESTIONS.

ROSI� is the cheapest and commonest (the heres to the and increases its thickness and tine, acetone, and benzol, but not in benzine, gasoline, all term resin is used to designate substances of this consequent ability to resist the solution used for etch­ or naphtha. is the best material for lining nature), and is obtained in the distillation of turpen­ ing. Asphalt is used for the same purpose, but the plating tanks or as a stopping-off varnish.-The Brass tine oil from crude . Three grades of dragon's blood is preferable, as it melts at a lower World. are known to commerce: Virgin, yellow dip, and temperature. hard. The first turpentine that exudes from the tree Gum guaiacum is obtain ell from a tree which grows THE PREPARATION OF GOLD TRI­ after it has been boxed, iil- "virgin rosin." It has a in the West Indies. The tree is cut in the same man­ CHLORIDE FOR PHOTOGRAPHIC light color. Yellow dip is the next best grade, ner that a tree is treated for obtaining turpentine and the hard is really the scrapings from the tree and the gum exudes. This gum is not extensively PURPOSES. after the turpentine refuses to run. It is very dark used. It is employed to a limited extent in medicine By RA�DOLPH BOLLL,\O. colored. White rosin contains water which renders for the treatment of rheumatism. It is also used in THE double chloride of gold and sodium and aqueous it opaque. If the water is driven off, the rosin be­ the etching of steel knives. Gum guaiacum is soluble solutions of gold trichloride find extensive applica­ comes yellow. in alcohol, and a varnish is produced. This is brushed tion in photography in connection with the toning of The chief uses of rosin are in the manufacture of over the knife and allowed to dry. A rubber stamp is silver prints, in order to reduce the harsh tints to a cheap , soaps, in the lining of beer kegs and stamped upon a pad of cotton cloth wet with a solu­ more pleasing color. With silver giving a visible casks to make waterproof, as a flux in soldering tin, tion of and then upon the surface of the steel image, the fixing bath alone gives a picture of an and in various mixtures of greases, belt dressings, and knife coated with the varnish. The rubber stamp has unattractive brick-red or salmon color; but an alkaline adulteration of oils. the design that is to be etched upon the steel. The solution of gold chloride, applied to the print before When rosin is distilled, "rosin oil" is produced. This potash dissolves the gum and leaves the steel bare. fixing, will be r'educed by the silver of the image, is used in the manufacture of printing inks. It is The etching is then done with nitric acid diluted with and the gold will be deposited upon it, changing its also used to adulterate . The hard rosin four parts of water. The gum guaiacum is quite solu­ color to a purple or a pleasing bluish black. The most that is dark colored is frequently called "turpentine ble in alkalies, which makes this etching process economical method of obtaining gold salts is to pre­ ." Rosin is soluble in turpentine and benzine, possible. pare them from the metal itself. Pure gold is worth but only slightly in alcohol. Gum is produced by the bite of insects upon $20.67 an ounce. It can be easily produced by solution - pitch is obtained in the distillation of the branches of certain East Indian trees. The shellac of some alloy of gold and copper in nitro-hydrochloric wood for making wood alcohol and acetic acid. It exudes in the form of drops which cover the insects. acid and the application to this solution of gold and should not be confused with turpentine pitch as it has These drops are collected and melted in muslin bags copper of some chemical reagent that will cause a pre­ more the nature of a , while turpentine pitch by means of hot water and the insects strained out. cipitation of metallic gold, To begin operations, all if rosin. The melted shellac is poured onto a hot plate, and the the old scrap jewelry that can be collected, such as Burgundy pitch closely resembles common rosin. scales as they occur in commerce are produced. It is settings, wire, pins, old watch cases, etc., which may It is obtained from the Norway and is lighter usually of a brownish-orange color. run from 9 to 18 karats (that is, 24 parts of the alloy in color. It has the peculiar property of combining The bleached shellac is formed by passing chlorine contain 9 to 18 karats of gold) are broken up into into a solid mass withjn a short time after it has gas into a solution of shellac dissolved in borax. The small bits and placed in a pint beaker. About two been broken up. Although quite brittle, it is plastic, shellac is precipitated and then melted and pulled ounces of scrap is a convenient weight to operate on. particularly in summer, and it is impossible to pre­ under water in the same manner that candy is treated. This is covered with a mixture of one ounce of strong serve it for over a few hours in the pulverized condi­ This renders it white and fibrous and removes the ' hydrochloric acid hnd three ounces of strong nitric tion. It soon melts, so to speak, into a solid mass. borax. acid, and the acids allowed to act over night on Gum sandarac is called "gum jupiter," and is ob­ Shellac is soluble in alcohol, and forms a hard, the scrap in a warm place. Solution of the alloy tained from a tree growing in the northern part of quick-drying varnish, extensively used for patterns, takes place without difficulty, and the beaker and its Africa. Its principal use is in the manufacture of var­ varnishing and similar work. It is also used in the contents are now allowed to stand on a water bath nishes. French polishing of wood. The wood is given a large or hot plate heated to about boiling point and thus Gum resembles gum sandarac in appearance number of coats of thin shellac varnish, and each evaporated - fo a thick syrup, very nearly to dryness. and its properties, and is obtained from shrubs which coat is polished or rubbed down before the other is To the contents of the beaker containing chlorides 9f grow along the shores of the Mediterranean Sea. Both applied. In this manner the last coat is very smooth, gold and copper is added hot water, diluting to about gum mastic and gum sandarac are soluble in acetone, although not highly polished ltl,e some other forms of four ounces. Now dissolve about three ounces of fer­ turpentine, and alcohol. Gum mastic is used in var­ varnish. rous sulphate (copperas crystals) in suffi.�ient water to nish maldng. Shellac is soluble in borax, and this solution may make a saturated solution, and add this to the con­ Gum dammar is found in the Moluccas and exudes be used as a varnish or . At one time it was tonts of the beaker containing the gold and copper from a treo similar to the pine. It is a very light extensively used as a cheap lacquer, but at the�Jresent solution. Metallic gold, having its characteristic lus­ colored gum, and is used for the manufacture of the time it has been entirely replaced by the gun-cotton trous appearance, is precipitated, a ferric salt remain­ lightest colored or transparent varnishes. . Lacquer made by dissolving shellac in al­ ing in solution. Copper remains in solution. A funnel Amber is not a true gum, as it is not produced by cohol is now used to a limited extent, and is gradually i,; now fitted with a filter paper, and the precipitated any tree or plant at the present time. It is a "fossil being replaced by the gun-cotton lacquers. At one gold collected on it, and washed with hot water until resin," as it was formed in primeval times, probably time it was the only lacquer used, It must be applied it is entirely free of copper and iron salts. The pre­ in the same manner that other gums are now produced. while the work is warm, in order to prevent the ab­ cipitated gold, which has been retained on the filter, Germany produces nearly all of the amber, and it is sorption of moisture by the alcohol and the produc­ is now removed by taking the filter paper out of the cast up on the shores of the Baltic in storms. The tion of a turbidity on the surface. funnel and placing the precipitate in another pint fact that it frequently contains insects indicates that Gum elemi is 9btained from a tree growing in the beaker, adding nitri� and hydrochloric acids, as it was of vegetable origin. The insects became en­ Philippine Islands. It has a white or gray color, and directed in the first treatment, and thus dissolving the tangled in the gum as they are to-day in those which is soft and tough. It is soluble in alcohol. It is used gold again, evaporating to syrup or to such a degree are now found. Amber is very hard and takes a in the manufacture of varnishes to toughen them of concentration that no odor of acid fumes is notice­ high polish. It is not soluble in any of the solv­ when hard gums are used. able. The gold trichloride is next dissolved in water, ents. When heated above its melting point, how­ Gutta percha is the gum obtained from an East and is now ready'for "toning" baths. It is chemically ever, it is partially decomposed and then may be dis­ Indian tree. The crude product is purified by grind­ pure, and is entirely free from copper salts. The final solved by turpentine or al.cohol. 'When amber is dis­ ing in hot water, when all the dirt and foreign matter reaction is expressed thus: Au, + 2HNO" + 6HCl := tilled, ('1 of amber is produced. If this oil is treated are removed. The mass is then formed into balls. 2AuCI" + 2NO + 4H,O. A compound of gold and sodi­ with nitric acid, an artificial musk is produced. A Gutta percha is soluble in bisulphide of carbon, chloro­ um chlorides, in mcHecular proportions, crystalliz()s fine varnish is made from amber. form, and benzol. It is used for taking impressions of readily and is more stuble. This is the double chloride is also called Australian dammar. It objects, as it becomes plastic when heated to about of gold and sodium of the photographic dealers, and is obtained in and is the fossil remains 140 deg. Fah. Up,on cooling, it again becomes a solid. can be prepared by evaporating the solution of gold of some kind, as it is dug from the earth. Insects are It is also used in the manufacture of a large number trichloride to dryness as directed, weighing the resi­ found in this gum as they are in amber. Kauri gum of tire cements, tapes, and in the making of insulated due, and adding an equal weight of sodium chloride is darker in color than the true gum dammar. wire. (common salt), then adding sufficient water to dis­ Gum copai, with the exception of amber, is the hard­ Asphalt is one of the most valuable . It Is solve both salts, and slowly evaporating to dryness est gum. It also has a light color and is used in the supposed to be the oxidized residue obtained in nature l again. This salt is a deep yellow color, and keeps very manufacture of the best grades of varnish. In order by the evaporation of . The crude asphalt well. It is also of use in vreparing certain toning to dissolve it, however, it must first be melted and contains two substances: petrolene and aspha.ltene. Pe­ solutions calling for a definite weight of the salt. To turpentine and oil added to it. This fact accounts for trolene is soluble in naphtha, benzine, or gasoline. tone prints with the trichloride solution, add bicarbon­ the frequent clouds of smoke that exude from the while the asphaItene is not. The asphaltene, however, ate of soda to the gold solution until it is alkaline to chimney of a varnish factory. The turpentine and oil is dissolved by benzol. litmus paper, and then immerse the silver prints in often catch fire under these circumstances. The island of Trinidad supplies large quantities of this solution until they acquire the requisite shade. The hardest copal is a fossil gum and is found in asphalt, where the "pitch lake" is situated. Other The bath may be used until completely exhausted. tropical countries, buried in the earth like amber and countries also furnish it. kauri gum. The purest asphalt is found in Utah, and is called Dragon's blood is a red colored gum that is obtained "gilsonite." This variety is extensively used in the Balloon chases by automobiles are becoming popular from the fruit of a palm tree found in the East Indies. manufacture of asphalt varnish. It is also used in in Europe. In a recent chase of this kind, M. Pierre It exudes from the fruit and is collected by the na­ the manufacture of the so-caUed "hard-rubber" elec­ Garnier, in the:-balloon "Eole IlL," went up with the tives, melted and cast into _sticks which are rolled in trical goods. object of alighting after having traveled 25 miles. the hands to make into long rods. These rods are Asphalt is extensively used in the manufacture of Automobiles followed as best they could, four prizes wrapped in fiber and thus are found in the market. It pavements. The Trinidad asphalt occurs in two being offered for the first four arrivals. The aeronaut is soluble in alcohol, and is now and then used in the forms: "lake pitch" and "land pitch." The latter �s did everything possible to render the chase difficult manufacture of colored varnishes. Its principal use is the harder of the two and melts at a higher tempera­ for automobiles, simulating descent, maneuvering with in etching and photo-engraving. It is employed for ture. Asphalt may be toughened by mixing it with the guide rope and then rising again to an altitude dusting on the plate to be etched when a design has heavy paraffine oil while melted. of a mile. Several of the pursuers contrived to be in been transferred to the metal. The dragon's blood ad- Asphalt is soluble in bisulphide of carbon, turpen- "at the death."

© 1908 SCIENTIFIC AMERICAN, INC