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and attach itself to the surfaces to be united. M. Christofle and M. Charrière made, in 1855, during the Exposition, solderings with zinc or tin. But this is a weak solder and does not make a firm seam. MM. Tissier, after some experiments made in my laboratory, proposed alloys of aluminium and zinc, which did not succeed any better. However, M. Denis, of Nancy, has remarked that whenever the aluminium and the solder melted on its surface are touched by a piece of zinc, the adhesion becomes manifest very rapidly, as if a particular electrical state was determined at the moment of contact. But even this produces only weak solderings, insufficient in most cases.

"A long time ago, M. Hulot proposed to avoid the difficulty by previously covering the piece with copper, then soldering the copper surfaces. To effect this, plunge the article, or at least the part to be soldered, into a bath of acid sulphate of copper. Put the positive pole of a battery in communication with the bath, and with the negative pole touch the places to be covered, and the copper is deposited very regularly. M. Mourey has succeeded in soldering aluminium by processes yet unknown to me; samples which I have seen looked excellent. I hope, then, that this problem has found, thanks to his ingenuity, a solution; a very important step in enlarging the employment of aluminium."

Mierzinski gives the following statements about M. Mourey's solder ::

"Mourey, who first made a practicable solder for aluminium, used two kinds of solder, soft and hard. The first was used for the usual soldering up of flasks or pieces of metal. He made solders of five different alloys, the composition of which were as given in the table below:

Al
Zn

I. II. III. IV. V.
20 15 12 8
80 85 88 92

6

94

These solders have varying melting points, and thus there results the hard and soft solders. One can take a soft solder, as IV., for brazing, and one like II. for ordinary soldering."*

Schwarzt improved these solders by adding copper to the alloy. His solders have the following composition :

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Mourey recommends improved solders of some

what similar composition. They are:

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* It is usual to employ hard solder for brazing, and No. II.

would be harder than No. IV.-J. W. R.

+ Dingler, 157, 445.

Dingler, 166, 205.

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Col. Frishmuth† states that the solder just given is used for fine ornamental work, while for lowergrade work he uses the following:

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Frishmuth recommends for a flux, in all cases, either paraffin, stearin, vaselin, copaiva balsam, or benzine. In the solder for fine work, if aluminium is used in larger quantity than recommended, the solder becomes brittle.

Kerl and Stohman give the following practical observations on this subject:

"At first, the soldering of aluminium appeared impossible. But Ph. Mourey, a gold and silver worker in Paris, invented a new method by which he could solder any kind of object of this metal. The following are his receipts:

"There are needed, according to the objects to be soldered, five different solders, which are composed of aluminium, copper, and zinc, in different proportions :

* Techniker, vi. 249.

Wagner's Jahresb., 1884.

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"To make the solder, first put the copper in the crucible. When it is melted, then add the aluminium in three or four portions, thereby somewhat cooling the melted mass. When both metals are melted, the mass is stirred with a small iron rod, and then the required quantity of zinc added, free from iron, and as clean as possible. It melts very rapidly. The alloy is then stirred briskly with an iron rod for a time, some fat or benzine being meanwhile put in the crucible to prevent contact of the metal with air and oxidation of the zinc. Finally the whole is poured out into an ingot mould previously rubbed with benzine. After the addition of zinc, the operation must be finished very rapidly, because the latter will volatilize and burn out. As soon as the zinc is melted, the cru-. cible is taken out of the fire.

"The separate pieces of metal to be soldered together are first well cleaned, then made somewhat rough with a file at the place of juncture, and the appropriate solder put on it in pieces about the size of millet grains. The objects are laid on some hot charcoal, and the melting of the solder effected by a blast lamp or a Rochemont turpentineoil lamp. During the melting of the solder, it is rubbed with a little soldering iron of pure alumin

ium. The soldering iron of pure aluminium is essentially a necessity for the success of the operation, since an iron of any other metal will alloy with the metals composing the solder, while the melted solder does not stick to the iron made of aluminium.

"The method just described differs from the one described by Mourey in so far that he used, at first, alloys of aluminium and zinc only, with no copper. He used one of the more fusible alloys to first unite the pieces, and then used a less fusible one to finish with. In order to avoid the oxidation of the solder he added while using the hard solder, which must be worked with a hotter iron, a quantity of copaiva balsam and turpentine, which acts just as borax in working silver. With these new solders of aluminium, copper, and zinc the process is much simpler, the work is done with one solder and the moistening with balsam is unnecessary. The solderings may be done so perfectly that plates soldered together never break at the joint when bent back and forth, but always give way in other places; which is a result not always possible in the best soldering of plates of silver."

Bell Bros. used to operate the works at Newcastle-on-Tyne, and their description may contain a few points not yet brought forward :-*

"In order to unite pieces of aluminium, small

*Chem. News, iv. 81.

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