CHAPTER I.

Silver.

Pure silver is, next to gold, the finest metal, but of a smoother and more polished nature. It may be said to be almost infinitely malleable, but it will not so easily yield or extend under the hammer as fine gold. As a malleable metal, however, it stands next to it in this respect. It is characterized by its perfectly white colour, being the whitest of all the metals. It is harder than gold, yet in a pure state it is so soft that it can easily be cut with a knife. On account of its extreme softness, when in a pure state, it is employed for filigree work, being utterly devoid of that elastic power which is found in the metal when alloyed. It is for this reason that the Indian filigree workers, who are the finest in the world, are so very particular about the absolute purity of the metal before commencing the manufacture of their artistic work; all of which is exceedingly beautiful.

It is reported that fine silver is capable of being beaten into leaves of less than one-hundred-thousandth part of an inch in thickness. For the accuracy of this statement we cannot vouch, never having had occasion to try the experiment; its employment in that form being unknown in the ordinary industrial pursuits. Fine silver is extremely ductile, and may be drawn into the very finest wire without breaking, and almost without annealing. Its purity can be partly ascertained by the latter process; for perfectly fine silver never changes colour by heat, whereas when it contains alloy it blackens if heated in contact with a current of air, and soon hardens in wire-drawing.

Silver was a metallic element known to the ancients, and it is repeatedly mentioned in the Holy Scriptures. In the time of the patriarchs we read of it as having been constantly employed in the transactions of nations, and that it was in use as a standard of value; thus forming a circulating medium for the purpose of exchange. This function it has always continued to fulfil down to the present day, except that since the year 1816 it has not been so employed in the English currency. However, as token money, it is everywhere recognised as a circulating medium of trade. The Egyptian symbol for silver was represented by Fig. 1, relating to the moon; in modern chemistry it is understood by _ag._ from the Latin name _argentum_, denoting silver.

Fine silver is capable of receiving a polish scarcely inferior in lustre to that of highly polished steel, and in this state it reflects more light and heat than any other metal, without any perceptible change of colour for some considerable time. It is chiefly on this account, as well as its resistance to oxidation in air and water, that it is used for such a variety of purposes, not only of ornament and luxury, but also in a domestic way. Silver, unlike gold, cannot resist the influence of sulphuretted hydrogen, from the action of which it very soon becomes much tarnished if left exposed in damp rooms, &c.

Silver ranks next to gold in point of ductility and malleability. When pure, its density, or specific gravity, lies between 10.47 and 10.50, taking water as 1, according to the degree of compression it has received by rolling and hammering. It is fusible at a full red heat, or about 1873° Fahr. It is a metal having a very low radiating power for heat; hence silver wire of given dimensions retains and conducts heat better than a similar piece of another metal; for the same reason, a liquid contained in a silver vessel retains its heat much longer than if placed in one made of some other substance. Silver volatilises when subjected to a very great temperature in the fire, emitting rather greenish fumes. It loses between 2/21sts and 3/25ths, in proportion to its impurity, of its absolute weight in air when weighed in water. In point of tenacity it occupies the fifth position among the useful metals. In hardness it lies between copper and gold; and a small addition of the former substance considerably increases this quality, in which state it is largely employed in the arts. Nitric acid is the proper solvent for silver, as it dissolves it with the greatest ease and rapidity, forming _nitrate_ of silver, which is much used for medical purposes, and in art. Sulphuric and hydrochloric acids act upon it but slowly in the cold. Silver resists partially the best aqua-regia, probably on account of the dense chloride which forms on the surface of the metal, from the action of the hydrochloric acid in the mixture of aqua-regia.

Fine silver is largely used in the industrial and commercial arts, in the manufacture of silver lace and fine filigree work; the latter branch being more commonly practised in India, Sweden, Norway, and some parts of Germany, where labour is cheap, than in England. This class of silversmith's work takes a long time to produce, and as labour forms the chief item of its cost, this, not unnaturally, acts as a great drawback in the extension of the art of very fine filigree working, in all its intricate variety, in countries where labour is dear. To this subject we shall subsequently refer again in detail. Fine silver, with a small proportion of alloy, is largely used by all nations for purposes of coinage. It amalgamates with nearly all the metals, but is principally used in alloys suitable to the watchmaker's and silversmith's art. The purchasable price of fine silver for manufacturing purposes, which in 1884 was 4_s._ 8_d._ is now, 1921, 3_s._ per ounce, troy weight, varying however in value according to the total amounts purchased; for which see refiners' and assayers' charge lists, to be procured at the offices of any bullion dealer. The silver ores of commerce have generally an intermixture of a small quantity of gold, and sometimes instances have occurred in which it has been employed in manufactures without a proper chemical investigation; and in such cases the loss resulting from the omission would have amply paid the expenses of the process.

Exposed to the action of hot and concentrated sulphuric acid, silver dissolves, setting free sulphurous acid. By the application of this process--which is one of the most advantageous methods--silver may readily be separated from gold, sulphuric acid having no action upon the latter metal. With the exception of gold, silver perhaps more perfectly resists the action of the _caustic alkalies_ and the powerful effects of _nitre_ (saltpetre) than any other metal, if we omit platinum from the list of elements at present known to metallurgical chemistry. For reasons such as these its superiority for the manufacture of utensils for culinary and other domestic purposes is at once apparent, and because it is a metal upon which _vegetable acids_ produce no effect.