Part 234

GALVANIZED PAPER: See Paper, Metallic.

GAMBOGE STAIN: See Lacquers.

GAPES IN POULTRY: See Veterinary Formulas.

GARANCINE PROCESS: See Dyes.

«GARDENS, CHEMICAL:»

See also Sponges.

I.—Put some sand into a fish-globe or other suitable glass vessel to the depth of 2 or 3 inches; in this place a few pieces of sulphate of copper, aluminum, and iron; pour over the whole a solution of sodium silicate (water glass), 1 part, and water, 3 parts, care being taken not to disarrange the chemicals. Let this stand a week or so, when a dense growth of the silicates of the various bases used will be seen in various colors. Now displace {369} the solution of the sodium silicate with clear water, by conveying a stream of water through a very small rubber tube into the vessel. The water will gradually displace the sodium silicate solution. Care must be taken not to disarrange or break down the growth with the stream of water. A little experimenting, experience and expertness will enable the operator to produce a very pretty garden.

II.—This is a permanent chemical garden, which may be suspended by brass chains with a lamp behind.

Prepare a small beaker or jar full of cold saturated solution of Glauber’s salt, and into the solution suspend by means of threads a kidney bean and a non-porous body, such as a marble, stone, glass, etc. Cover the jar, and in a short time there will be seen radiating from the bean small crystals of sulphate of sodium which will increase and give the bean the aspect of a sea urchin, while the non-porous body remains untouched. The bean appears to have a special partiality for the crystals, which is due to the absorption of water by the bean, but not of the salt. In this way a supersaturated solution is formed in the immediate neighborhood of the bean, and the crystals, in forming, attach themselves to its surface.

III.—A popular form of ornamental crystallization is that obtained by immersing a zinc rod in a solution of a lead salt, thus obtaining the “lead tree.” To prepare this, dissolve lead acetate in water, add a few drops of nitric acid, and then suspend the zinc rod in the solution. The lead is precipitated in large and beautiful plates until the solution is exhausted or the zinc dissolved. In this case the action is electro-chemical, the first portions of the lead precipitated forming with the zinc a voltaic arrangement of sufficient power to decompose the salt.

It is said that by substituting chloride of tin for the lead salt a “tin tree” may be produced, while nitrate of silver under the same conditions would produce a “silver tree.” In the latter case distilled water should be used to prevent precipitation of the silver by possible impurities contained in ordinary water.

GAS FIXTURES: See Brass.

GAS FIXTURES, BRONZING OF: See Plating.

GAS SOLDERING: See Soldering.

GAS-STOVES, TO CLEAN: See Cleaning Preparations and Methods.

GAS TRICK: See Pyrotechnics.

GEAR LUBRICANT: See Lubricants.

«GELATIN:»

«French Gelatin.»—Gelatin is derived from two sources, the parings of skins, hides, etc., and from bones. The latter are submitted to the action of dilute hydrochloric acid for several days, which attacks the inorganic matters—carbonates, phosphates, etc., and leaves the ossein, which is, so to say, an isomer of the skin substance. The skin, parings of hide, etc., gathered from the shambles, butcher shops, etc., are brought into the factory, and if not ready for immediate use are thrown into quicklime, which preserves them for the time being. From the lime, after washing, they pass into dilute acid, which removes the last traces of lime, and are now ready for the treatment that is to furnish the pure gelatin. The ossein from bones goes through the same stages of treatment, into lime, washed and laid in dilute acid again. From the acid bath the material goes into baths of water maintained at a temperature not higher than from 175° to 195° F.

The gelatin manufacturer buys from the button-makers and manufacturers of knife handles and bone articles generally, those parts of the bone that they cannot use, some of which are pieces 8 inches long by a half inch thick.

Bones gathered by the ragpickers furnish the strongest glue. The parings of skin, hide, etc., are from those portions of bullock hides, calf skins, etc., that cannot be made use of by the tanner, the heads, legs, etc.

The gelatin made by Coignet for the Pharmacie Centrale de France is made from skins procured from the tawers of Paris, who get it directly from the abattoirs, which is as much as to say that the material is guaranteed fresh and healthy, since these institutions are under rigid inspection and surveillance of government inspectors and medical men.

There is a gelatin or glue, used exclusively for joiners, inside carpenters, and ceiling makers (plafonneurs), called rabbit vermicelli, and derived from rabbit skins. As the first treatment of these skins is to saturate them with mercury bichloride, it is needless to say the product is not employed in pharmacy. {370}

«To Clarify Solutions of Gelatin, Glues, etc.»—If 1 per cent of ammonium fluoride be added to turbid solutions of gelatin or common glue, or, in fact, of any gums, it quickly clarifies them. It causes a deposition of ligneous matter, and also very materially increases the adhesive power of such solutions.

«Air Bubbles in Gelatin.»—The presence of minute air bubbles in cakes of commercial gelatin often imparts to them an unpleasant cloudy appearance. These minute air bubbles are the result of the rapid, continuous process of drying the sheets of gelatin by a counter-current of hot air. Owing to the rapid drying a hard skin is formed on the outside of the cake, leaving a central layer from which the moisture escapes only with difficulty, and in which the air bubbles remain behind. Since the best qualities of gelatin dry most rapidly, the presence of these minute bubbles is, to a certain extent, an indication of superiority, and they rarely occur in the poorer qualities of gelatin. If dried slowly in the old way gelatin is liable to be damaged by fermentation; in such cases large bubbles of gas are formed in the sheets, and are a sign of bad quality.

«GEMS, ARTIFICIAL:»

See also Diamonds.

The raw materials for the production of artificial gems are the finest silica and, as a rule, finely ground rock crystals; white sand and quartz, which remain pure white even at a higher temperature, may also be used.