Siphons.

The most simple and handy siphon in many cases, is a piece of lead pipe bent so as to have two unequal branches, the smaller of which plunges into the liquid to be drawn off. A section of India-rubber tube may be employed for

similar purposes.

But, as these materials may be chemically acted upon by various solutions, glass siphons are used with or without a suction tube (Figs. 188, 189).

For siphoning corrosive solutions which cannot be touched with the fingers, a siphon with a suction tube is used (Fig. 188). The shorter leg is plunged into the liquid, and the longer one closed with the finger or an India-rubber pad pressed against it. Then, with the mouth, suction should be carefully applied at the lateral suction tube until the liquid fills the longer leg.

If there be danger in inhaling a poisonous vapor, the action of the mouth may be replaced by an India-rubber ball, fastened to the suction tube. The longer branch of

the siphon is closed as before, and the ball compressed in order to remove the air. By its elasticity the ball resumes its former volume, thus producing a suction which starts the siphon in action.

The Thermometer

Is an instrument intended for ascertaining the temperature of fluids or liquids in which it is immersed. It acts by the dilatation or contraction of mercury or colored alcohol, contained in a bulb of thin glass, which is attached to a capillary tube deprived of air, and upon which the graduation is marked.

The scale employed in this work is that of Fahrenheit, which is commonly used in English speaking countries. In this, the 0 of the scale represents the temperature of a mixture of salt and ice; 32° is the point of melting ice, and 212° that of boiling water.

CHAPTER LXXI.

MIXTURES.

RED ORMOLU-YELLOW ORMOLU-DEAD LUSTRE FOR JEWELRY

—DEAD LUSTRE (HARD) FOR CLOCKS—DEAD LUSTRE (SOFT)

FOR SMOOTH SURFACES AND FIGURES-GREEN-FOR-RED LUSTRE GILDERS' WAX.

Mixtures.

AFTER having enumerated the principal chemical products, apparatus, and instruments employed in our art, it remains for us only to give the formula of certain mix. tures employed in gilding by fire, or by the wet processes.

Some of these have been given in the chapters on gilding, but their repetition may be serviceable.

We may add to it a small proportion of annotto, madder, cochineal, or other coloring matter, ground in water, or in weak vinegar.

The salts are fused together in their water of crystallization; and if the gilding be strong and durable, a small proportion of common salt may be added.

39

DEAD LUSTRE (soft) for SMOOTH SURFACES AND FIGURES.

The whole is melted, and stirred until cold.

100.

CHAPTER LXXII.

USEFUL NOTES AND COMMENTS.

ANTIDOTES AND HYGIENE OF THE WORKSHOP.

We have seen that the majority of the chemical products employed in our art are very poisonous, or at least unwholesome. It is therefore well, after having pointed out the dangerous properties of these substances, to furnish, in case the necessity therefor should occur, the means of neutralizing their effects, either entirely, or at least sufficiently to retard their poisonous action until professional aid can be summoned.

Poisoning by Acids.

All the powerful acids, with the exception of hydrocyanic (prussic) acid, operate nearly in the same manner. They are corrosive poisons, and the more concentrated they are, the more energetic is their action.

It should not be forgotten that, when very diluted, these substances lose their poisonous properties; WATER, therefore, in the greatest abundance will be the first thing to administer. Tepid water and distilled water will act as emetics, and should be preferred if they are at hand. Milk and the white of eggs, which coagulate with the acids and partly neutralize them, may be successfully employed; but no antidote excels CALCINED MAGNESIA, or the carbonate of this base, which may be introduced into the stomach without danger, and will completely neutralize the acids, forming with them purgative salts. In the