Part 245

GUM DROPS: See Confectionery.

GUM-LAC: See Oil.

GUMS USED IN MAKING VARNISH: See Varnishes.

GUN BARRELS, TO BLUE: See Steel.

GUN BRONZE: See Alloys, under Phosphor Bronze.

GUN COTTON: See Explosives.

GUN LUBRICANTS: See Lubricants.

GUNPOWDER: See Explosives.

«GUNPOWDER STAINS.»

A stain produced by the embedding of grains of gunpowder in the skin is practically the same thing as a tattoo mark. The charcoal of the gunpowder remains unaffected by the fluids of the tissues, and no way is known of bringing it into solution there. The only method of obliterating such marks is to take away with them the skin in which they are embedded. This has been accomplished by the application of an electric current, and by the use of caustics. When the destruction of the true skin has been accomplished, it becomes a foreign body, and if the destruction has extended to a sufficient depth, the other foreign body, the coloring matter which has been tattooed in, may be expected to be cast off with it.

Recently pepsin and papain have been proposed as applications to remove the cuticle. A glycerole of either is tattooed into the skin over the disfigured part; and it is said that the operation has proved successful.

It is scarcely necessary to say that suppuration is likely to follow such treatment, and that there is risk of scarring. In view of this it becomes apparent that any such operation should be undertaken only by a surgeon skilled in dermatological practice. An amateur might not only cause the patient suffering without success in removal, but add another disfigurement to the tattooing.

Carbolic acid has been applied to small portions of the affected area at a time, with the result that the powder and skin were removed simultaneously and, according to the physician reporting the case, with little discomfort to the patient.

Rubbing the affected part with moistened ammonium chloride once or twice a day has been reported as a slow but sure cure.

«GUTTA-PERCHA.»

«Gutta-Percha Substitute.»—I.—A decoction of birch bark is first prepared, the external bark by preference, being evaporated. The thick, black residue hardens on exposure to the air, and is said to possess the properties of gutta-percha without developing any cracks. It can be mixed with 50 per cent of India rubber or gutta-percha. The compound is said to be cheap, and a good non-conductor of electricity. Whether it possesses all the good qualities of gutta-percha is not known.

II.—A new method of making gutta-percha consists of caoutchouc and a rosin soap, the latter compounded of 100 parts of rosin, 100 parts of Carnauba wax, and 40 parts of gas-tar, melted together and passed through a sieve. They are heated to about 355° to 340° F., and slowly saponified by stirring with 75 parts of limewater of specific gravity 1.06. The product is next put into a kneading machine along with an equal quantity of caoutchouc cuttings, and worked in this machine at a temperature of 195° F. or over. When sufficiently kneaded, the mass can be rolled to render it more uniform.

GUTTER CEMENT: See Cement and Putty.

«GYPSUM:»

See also Plaster.

«Method of Hardening Gypsum and Rendering it Weather-Proof.»—Gypsum possesses only a moderate degree of strength even after complete hardening, {388} and pieces are very liable to be broken off. Various methods have been tried, with a view to removing this defect and increasing the hardness of gypsum. Of these methods, that of Wachsmuth, for hardening articles made of gypsum and rendering them weather-proof, deserves special notice. All methods of hardening articles made of gypsum have this in common: the gypsum is first deprived of its moisture, and then immersed in a solution of certain salts, such as alum, green vitriol, etc. Articles treated by the methods hitherto in vogue certainly acquire considerable hardness, but are no more capable of resistance to the effects of water than crude gypsum. The object of Wachsmuth’s process is not merely to harden the gypsum, but to transform it on the surface into insoluble combinations. The process is as follows: The article is first put into the required shape by mechanical means, and then deprived of its moisture by heating to 212° to 302° F. It is then plunged into a heated solution of barium hydrate, in which it is allowed to remain for a longer or shorter time, according to its strength. When this part of the process is complete, the article is smoothed by grinding, etc., and then placed in a solution of about 10 per cent of oxalic acid in water. In a few hours it is taken out, dried, and polished. It then possesses a hardness surpassing that of marble, and is impervious to the action of water. Nor does the polish sustain any injury from contact with water, whereas gypsum articles hardened by the usual methods lose their polish after a few minutes’ immersion in water. Articles treated by the method described have the natural color of gypsum, but it is possible to add a color to the gypsum during the hardening process. This is done by plunging the gypsum, after it has been deprived of its moisture, and before the treatment with the barium solution, into a solution of a colored metallic sulphate, such as iron, copper, or chrome sulphate, or into a solution of some coloring matter. Pigments soluble in the barium or oxalic-acid solutions may also be added to the latter.

Gypsum may be hardened and rendered insoluble by ammonium borate as follows: Dissolve boric acid in hot water and add sufficient ammonia water to the solution that the borate at first separated is redissolved. The gypsum to be cast is stirred in with this liquid, and the mass treated in the ordinary way. Articles already cast are simply washed with the liquid, which is quickly absorbed. The articles withstand the weather as well as though they were of stone.

GYPSUM FLOWERS: See Flowers.

GYPSUM, PAINT FOR: See Paint.

«HAIR FOR MOUNTING.»

The microscopist or amateur, who shaves himself, need never resort to the trouble of embedding and cutting hairs in the microtome in order to secure very thin sections of the hair of the face. If he will first shave himself closely “with the hair,” as the barbers say (i. e., in the direction of the natural growth of the hair), and afterwards lightly “against the hair” (in the opposite direction to above), he will find in the “scrapings” a multitude of exceedingly thin sections. The technique is very simple. The lather and “scrapings” are put into a saucer or large watch-glass and carefully washed with clean water. This breaks down and dissolves the lather, leaving the hair sections lying on the bottom of the glass. The after-treatment is that usually employed in mounting similar objects.

«Hair Preparations»

«DANDRUFF CURES.»