Besides the copper series, the alloys containing 25 to 30 per cent zinc, and 75 to 70 per cent copper are especially suitable for rollers. Even so small a content of lead as 5 per cent exerts an injurious influence, and the samples containing lead showed blow-holes. Messrs. Dépierre and Spiral are of opinion that rolls of copper containing 1 to 2

per cent of phosphorus would yield excellent results as regards resisting chemical influences, as well as giving hardness, fineness of grain, homogeneousness, and durability. An addition of 1 per cent phosphorus might also be recommended for varieties of brass containing 30 to 35 per cent of zinc.

§ 190. Alloys said to be Non-oxidisable.-Lemarquand's alloy is said to consist of: copper 75, nickel 14, cobalt 15, tin 18, and zinc 72 parts. The metals must be pure. Marlie's alloy consists of: iron 10, nickel 35, brass 25, tin 20, zinc 10. Articles prepared from this alloy are made white hot, and dipped into a mixture of sulphuric acid 60 parts, nitric acid 10, hydrochloric acid 5, and water 25.

An alloy used as a substitute for gold and said to be non-oxidisable was found by the author to contain: copper 94.8, zinc 2.8, lead 67, and iron 1.34 per cent. The inventor recommends to dip the articles in dilute nitric acid, then to swill and dry, then to polish; and claims that they will keep their colour for a long time.

A new alloy has been prepared by Herr Reith of Bockenheim, Germany, and is said to practically resist the attack of most acid and alkaline solutions. It consists of: copper 74.5, tin 11.6, lead 9, antimony 4.9 parts. This alloy is therefore a bronze with the addition of lead and antimony. The inventor claims that it can be very advantageously used in the laboratory to replace vessels or fittings of ebonite, vulcanite, or porcelain.

§ 191. Amalgams for silvering Glass Globes.

Lead. Tin. Bismuth. Mercury.

1

2

The lead and tin are melted first, after which the bismuth

is added. The dross is scraped off, and the mercury added, when the whole mixture is well stirred. Leaves of Dutchmetal are sometimes added, according to the colour which it is desired to impart to the globes.

§ 192. Gersnein's Alloy, for making a soft mastic for uniting glass, earthenware, etc. It becomes so hard after a time that it may be polished like silver. 25 to 35 parts of precipitated copper are ground with strong sulphuric acid in a porcelain mortar, and then 65 to 70 parts by weight of mercury are gradually added. When the copper is amalgamated it is well washed in boiling water. Whenever it is desired to employ it as a mastic, it is made soft and plastic by heating to about 375° C. and well grinding in a mortar until it is soft. It is insoluble in weak acids, alcohol, ether, or boiling water. dentists for filling teeth.

It has been also employed by

§ 193. Sideraphite.-A new alloy, which resembles silver, and is very ductile and malleable, is composed of 63 parts of iron, 23 of nickel, 4 of tungsten, 5 of aluminium, and 5 of copper. The iron and the tungsten are melted together and then granulated, and the water into which the mixture is poured for this purpose must contain 1 lb. of slaked lime, and the same quantity of potash, to every gallon. The product formed by the fusion of the nickel, copper, and aluminium is also granulated in water containing the same proportion of lime and potash; and, during the melting the metals in the two crucibles must be kept covered with a flux made of two parts of borax and two of saltpetre. A piece of soda or alkali, weighing about the 2500 part of the whole mass, is to be put into the crucible containing the copper, nickel, and aluminium, in order to prevent the oxidation of the last-named metal; and, to prevent the same action taking place with the copper, a small piece of charcoal is added. It is advisable before the operation of granulation to well stir the contents of the two crucibles. The granulated metals are dried, melted in the

proportion given above, well shaken, and then run into bars. The new alloy, to which the name of sideraphite, or changeless iron, has been given, is said to have the appearance of silver or platinum, and not to be dearer than ordinary white metal. It will resist the action of sulphuric acid, is not attacked by the organic acids, and very slightly so by the inorganic acids.

§ 194. Alloy for Horology.-The following alloy, suited for the sockets of pivots of watches, was invented by Mr. Bennett. It consists of gold 31 parts, silver 19, copper 39, and palladium 11. He states that this alloy melts at a lower temperature than gold, and is harder than hammered iron. It has a reddish-brown colour, is as fine-grained as steel, and works as easily as brass, but its friction is much slighter than on ordinary pivots. Its most valuable property is that the oil it absorbs is not decomposed, but remains pure, in a fluid state. It has still greater advantages over sockets of fine stone, as it is not apt to break, is susceptible of a high polish, and is less costly than hard stone.

For other miscellaneous alloys see also p. 338.