3208. Test Solution for Assaying Silver

3208.    Test Solution for Assaying Silver. Dissolve 541/4 grains pure sea-salt (see No. 3209 (Pure Sea-Salt)) in 22 ounces 3203/4 grains (avoirdupois) distilled water. Filter and keep in a stoppered bottle for use.

3209. Pure Sea-Salt

3209.     Pure Sea-Salt. Boil together for a few minutes, in a glass vessel, a solution of salt with a little pure bicarbonate of soda; filter; add muriatic acid until the liquor be neutral to litmus and turmeric paper; then evaporate and crystallize.

3210. To Extract Silver from Lead

3210.    To Extract Silver from Lead. This is easily done in a small way by melting the mixed metals by a strong heat in the open air.. The lead will be converted into litharge, and the silver will sink to the bottom of the crucible. On a large scale, the silver is extracted from the lead by the oxidation of the lead into a reverberatory furnace of a particu-lar construction. A shallow vessel, called a cupel, is filled with ashes, well packed and pounded down, and a cavity cut out for the reception of the nozzle of a bellows, through which air is forcibly driven. When the fire is lighted and the lead is in a state of fusion from the reverberation of the flame, the blast from the bellows is made to play forcibly on the surface, and in a short time a crust of oxide of lead or litharge is formed and driven off to the side of the cupel opposite to the mouth of the bellows, where a shallow aperture is made for it to pass over; another crust of litharge is formed and driven off, and this is repeated until nearly all the lead has been scorified and blown aside. The complete separation of the lead is indicated by the appearance of a brilliant lustre on the convex surface of the melted mass in the cupel, which is occasioned by the removal of the last crust of litharge which covered the silver. If the silver thus abstracted is not sufficiently pure, it is further refined in a reverberatory furnace, being placed in a cupel lined with bone ashes and exposed to an intense heat, so that the lead which escaped oxidation by the first process is converted into litharge, and is absorbed by the ashes of the cupel.

3211. Test for Metallic Silver

3211.    Test for Metallic Silver. The compounds of silver, mixed with carbonate of soda, and exposed on charcoal to the inner flame of a blow-pipe, afford white, brilliant, and ductile metallic globules, without any incrustation of the charcoal. (See also Assaying. )

3212. To Obtain Pure Silver

3212. To Obtain Pure Silver. Pure silver is obtained by placing a copper rod in a solution of nitrate of silver, digesting the precipitate in caustic ammonia, and washing with water; or by boiling recently precipitated and still moist chloride of silver in a bright iron vessel along with water. (See No. 3536 (To Obtain Pure Silver in Powder).)

3213. Solvent for Silver

3213. Solvent for Silver. Nitro-sulphuric acid. Dissolve 1 part nitre in 10 parts oil of vitriol. Used for dissolving the silver from plated goods, etc.. It dissolves silver at a temperature below 200°, and scarcely acts upon copper, lead, and iron, unless diluted. (See Nos. 3716 (Taking Silver from Copper, Etc), 3720, and 3721.) The silver is precipitated from the solution, after moderately diluting it, by common salt, and the chloride reduced as directed in Nos. 3214 and 3215.