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926 copper with the iron containing-vessel in the presence of the fused electrolyte (Rawdon). Metallic sodium is formed in contact with the copper and appears to penetrate between the crystals of the metal. A case has also been described where molten solder (lead-tin) acted in a similar manner when in contact with a particular kind of brass, the so-called " manganese bronze " (Dickenson).

Copper Alloys. With regard to copper alloys, some progress has been made in regard to the difficult question of nomenclature. A committee appointed by the Institute of Metals has issued a first nomenclature Report which begins by defining the old terms " brass" and " bronze." The former is defined as any alloy of copper with zinc, containing more than 50% of copper; if other elements besides zinc and copper are present, they are to be named as a prefix to the term " brass." Thus an alloy containing 2% tin, 28% zinc, and re- mainder copper would be termed a " tin brass." Bronze on the other hand is defined as implying an alloy of copper with tin, containing more than 50% of copper, with the same convention in regard to additional elements. Thus an alloy containing 10% tin, 2% zinc, and remainder copper would be called a " zinc bronze." An attempt is also made to systematize nomenclature of more complex alloys. In the course of six or seven years this nomenclature, so far as brass and bronze are concerned, has made considerable headway, and these two terms are now rarely used except within the definitions named. On the other hand, the alloy formerly known as " German silver" and now generally, but quite misleadingly, named " nickel silver," should, under systematic nomenclature, be called " nickel brass," but there is some trade prejudice against the use of such a name.

An immense amount of experiment and research has been devoted to copper alloys, but the results cannot be adequately summarized in a few lines. A considerable number of special alloys are now known, each possessing valuable properties for various purposes. The alumi- nium manganese copper alloys have been very fully studied and described in the Ninth Report to the Alloys Research Committee of the Institution of Mechanical Engineers; these include alloys capable of attaining tensile strengths as high as 52 tons per sq. inch. Other alloys of special strength have been launched under various proprietary names, such as " Rubel bronze " and " Turbadium." For war purposes a most important part was played by the cupro- nickel alloys, containing either 15 or 20 % of nickel, remainder copper. The production of this alloy on the very large scale required for the war, revealed considerable difficulties in its production, aris- ing mainly from casting-defects in the slabs used for rolling. The remarkable power of this material to undergo extremely severe cold- working, without becoming excessively brittle, suggests that it is likely to have other useful applications beside bullet envelopes, but for industrial purposes these alloys have not yet been Widely ex- ploited. On the other hand, the much more expensive Monel metal has been widely pushed and has found considerable practical applica- tion, mainly on account of the valuable combination of great strength with great power of resisting corrosion which it possesses. This alloy is manufactured " direct " by the reduction of ores from the Sud- bury district in Canada, and special virtue is claimed on the ground that it is a " natural " alloy and has not been melted together in the foundry. It is more than doubtful whether such a claim can be in any way substantiated.

Corrosion. In connexion mainly with copper alloys, a very large amount of study has been devoted to the subject of corrosion, under the auspices of the Corrosion Research Committee of the Institute of Metals. The results have been embodied in five extensive Reports to that body, and serve to throw a large amount of new light on the corrosion, particularly, of marine condenser tubes. This is ascribed, essentially, to the formation on the surfaces of the tubes of an adherent, but by no means impervious, deposit of basic salts. By restricting the circulation of water in contact with the metal under these deposits, they lead to the formation of solutions containing a fairly high concentration of cupric chloride, and such a solution rapid- ly attacks brass, with the resulting formation of pits and ultimately of holes. It is considered that the brass as a whole is dissolved under these deposits, but that in certain conditions the cooper is redeposited as a spongy mass, thus leading to the apparent dezincification " of the brass at such points. The prevention of this, the most de- structive type of corrosion, thus becomes a question of preventing the formation of such adherent deposits, and several devices for this purpose have been suggested. The latest proposal is to coat the interior surfaces of the condenser tubes with a thin layer of metallic lead. Recently, the scope of the researches undertaken by the above- mentioned committee has been extended to include fresh-water (land) condenser plant, and a special sub-committee has been formed to study the whole question of the corrosion of aluminium alloys. Results of these inquiries and of a parallel investigation into atmos- pheric corrosion, undertaken by the Non-ferrous Metals Research Assn., are not yet available.

Platinum, Etc. The metallurgy of the noble metals has not under- gone any very striking development during the period under review, either in regard to extraction or uses. The cyaniding process has undergone a series of more or less minor improvements, and it was at one time thought that aluminium dust would replace zinc -dust as the precipitant for pregnant solutions. Although aluminium is used to some extent, zinc-dust still predominates and the same re- mark applies to the proposed method of precipitating the metal

electrolytically. In regard to platinum, there has been an ever- increasing scarcity, enhanced by the complete upheaval in Russia. The great rise in the price of platinum has naturally led to the study of possible substitutes for various purposes, and a number o( such materials have been put forward. Thus for the " breaks " used in the magnetos of internal combustion engines, tungsten spark- ing points have been substituted for platinum with great success. For chemical purposes various alloys, some containing gold and pal- ladium, have been tried, but only with partial success, since none of them really possess the combination of properties chemical resis- tance and very high melting point which renders platinum so valuable. A number of special alloys, in which tungsten and chro- mium generally play an important part, also exhibit great chemical resistance, but in these cases the hardness and brittleness of the material are generally a serious difficulty. For use in chemical work on a large scale, however, a considerable number of alloys have been produced which attain a fair measure of success. Silicon itself h; many advantages for some of these purposes, but in the impure forn generally met with, it is relatively weak and brittle.

Zinc. The metallurgy of zinc received much anxious attentio during the war period. Reference has been made above to the genera questions relating to zinc extraction, but the use of the metal and it: alloys also received attention. On the Allied side there was at one time considerable shortage of zinc, and substitute alloys were studied for all purposes which should avoid the use of zinc. The shortage then disappeared, and at a later stage alloys consisting mainly o" zinc were tried as substitutes for brass and for certain aluminiur alloys. Some of these zinc alloys proved to possess remarkable properties, tensile strength exceeding 20 tons per square inch bein obtained in cast alloys containing about 3 % of copper and 7 % ( aluminium, remainder zinc. It was further found that these alloy could be extruded and, under certain conditions, rolled. In tn severely rolled state they show remarkable ductility when slowlv loaded, but are entirely brittle if the stress ft applied rapidly; annealed even by quite moderate warming they revert to tli strength and entire non-ductility of the cast material. Unfortunately it has been found that alloys of this type, when they contain both aluminium and copper, are unstable and undergo serious changes c' volume, accompanied by great loss of strength, even at the ordinar temperature if kept for any considerable time, such as a year. Non the less, a considerable number of shell-fuses were successfully mad of such an alloy, but they were used before dangerous deterioratior had set in. It is interesting to note that on the German side, while there was never any shortage of zinc, this metal and its alloys wer extensively employed as substitutes for other metals. Pure zinc was widely used in place of copper for electrical purposes, while zinc alloys with copper and aluminium were also largely used. Appar- ently, cases of failure due to the instability of these materials passed unnoticed under the stress of war; at all events, German metal- lurgists have described these " war bronzes," without mention of such deterioration with time, except as the result of corrosion. It may be mentioned, however, that alloys rich in zinc, which contain either copper alone or aluminium alone, appear to be free from the trouble in question (Rpsenhain, Haughton and Bingham).

Aluminium. Aluminium and its alloys have played a particu- larly conspicuous part and have undergone remarkable developments during recent years. Prior to the outbreak of war, aluminium itself had become relatively very cheap (below 100 per ton), and this fact stimulated interest in its use. During the war, on the other hand, while the metal itself became scarce and very dear, its applications for military purposes grew enormously in importance and raise its alloys for the first time to the rank of important materials < engineering construction. Its uses arose mainly in connection with air-craft and became increasingly important in the closing years of the war. It must, of course, be recognized that this rapid develop- ment of aluminium alloys under war conditions was to a consider- able extent the result of progress which had been made prior to 1914. One step in this progress was marked by the section on light alloy contained in the Ninth Report to the Alloys Research Committe (Rosenhain and Lantsberry), published in 1909; but the discovery, by Wilm of Berlin, of the possibility of hardening aluminium and its alloys, when a small percentage of magnesium had been added to them, led to the next and very important forward step. The appli- cation of this discovery to the best of the alloys, described in th above-named Report, led to the production of the now widely know and used alloy " duralumin." This contains from 3 to 5% of copp about I % of manganese and about 0^5 % of magnesium. As rolli this material has a tensile strength of about 1 8 tons per square inch but if heated to a temperature of 480 C. to 500 C. and quenche ' it gradually acquires much greater strength rising to about : tons per square inch; the ductility remaining the same at about 16 to 18% elongation on 2 inches. There can be no doubt that such i material, possessing the strength of a very mild steel combined with ; density as low as 2-8, constituted a remarkable advance in wrought aluminium alloys. At quite an early stage in its history this alloy wa employed for the construction of Zeppelin airships. The manufactur of the alloys was taken up in England under licence from the German patentee, and the alloy has been extensively used in the constructior of British rigid airships. Its use has, however, not been free fron difficulties and disadvantages, and great efforts have been made i