3550. Dentists' Amalgam, or Gold Stopping

3550.    Dentists' Amalgam, or Gold Stopping. The dentists, in preparing and using this, commonly proceed as follows: A little pure grain-gold is heated in a bright iron ladle (or capsule), and enough pure mercury added to render it of a doughy consistence at the temperature of hot water. When it has become cold, the excess of mercury, if any, is removed by pressure in a piece of chamois leather. In using it, a little of the amalgam, as hot as can be borne, is kneaded in the hand, and at once pressed into the cavity of the tooth, where it gradually hardens. It is an excellent and durable stopping, and is, perhaps, preferable to all others, except the diamond tooth cement (see Index) for filling up cracks and cavities in the enamel, particularly of the front teeth, on account of its color and the ease of its application.

3551. Dentists' Amalgam of Silver

3551.    Dentists' Amalgam of Silver is used in the same way as the last; but its color is less natural, and is apt to be blackened by the sulphur in the secretions of the mouth and the food. (Sec No. 3535.)

3552. Dentists' Amalgams of Tin and Zinc

3552.      Dentists' Amalgams of Tin and Zinc are also employed as tooth cement, but are inferior in color to, darken sooner, and possess less durability, than that of silver.

3553. Alloy for Filling Teeth

3553.     Alloy for Filling Teeth. An alloy, which is sold in commerce in the shape of large, almost white filings, shows upon analysis the following composition: Tin, 611; silver, 388; copper, 1. The alloy is to bo amalgamated before use by warming it in a spoon with a little mercury. The combination takes place rapidly, and the amalgam, while still warm, is pressed in a piece of soft leather, whereby the excess of mercury is removed. It is now far preferable to the celebrated copper amalgam, as it retains its white color in the mouth, while the other turns dark. The hardness is a little less than that of the copper amalgam. (See No. 3542 (Tin Amalgam).)

3554. To Recover the Silver Alloy from Dentists' Amalgam

3554.    To Recover the Silver Alloy from Dentists' Amalgam. The silver alloy may be easily obtained from scraps of dentists' amalgam in the following manner: Provide 2 crucibles of different sizes, so that the smaller one, inverted, will rest a little way within the larger. Make a hole, about 1/4 inch in diameter, in the bottom of the smaller to provide a vent for the mercurial vapors. Place the pieces of amalgam in the larger crucible, invert the smaller one into it, lute them, and fasten them firmly together with steel wire. Place the whole, as soon as the luting is dry, into a blast furnace, and in a short time the mercury will all have passed off in vapor, when the crucible may be set aside to cool, and the alloy will be found in a button at the bottom. As some portion of the tin in the alloy has been lost in the operation, the button should be remelted in a clean open crucible, with the addition of a little pure tin. This will now be ready to make again into amalgam as occasion requires.

3555. Ruhmkorf's Amalgamating Fluid

3555. Ruhmkorf's Amalgamating Fluid. Dissolve by heat 2 parts by weight of mercury in 1 part aqua regia; when dissolved, add 10 parts hydrochloric acid. A worn-out zinc will be amalgamated in a few seconds by immersion in this fluid.