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Proceedings of the Royal Society of Edinburgh. [Sess. 
group, rather than to study fully the variation of magnetic properties with 
composition. Only a few castings were therefore necessary. In arriving 
at a decision as to what castings should be attempted, the authors were 
influenced by the following considerations. As the melting-points of the 
three constituent elements were spread over a wide range of temperature,* 
the simplest procedure was to prepare a manganese-copper alloy and add 
the tin to it. An alloy of 70 per cent, by weight of copper and 30 per cent, 
manganese was the most suitable for this purpose, as it has the lowest melt- 
ing point (viz. about 870° C.) of the copper-manganese system.f An alloy 
richer in manganese would have been less satisfactory, as such material is 
apt to be far from homogeneous on casting.^; Moreover, with increasing 
manganese-content there is an increasing tendency for the heated metal to 
absorb carbon, for which element manganese has a strong affinity .§ With 
the 30 per cent, manganese bronze this tendency is little marked and may 
be effectively guarded against by suitable precautions when casting. The 
amount of tin to be added was provisionally fixed from Heusler’s observa- 
tions. || From these it appeared that the interesting alloys would be those 
with 15 or 18 per cent, of tin. It was found, however, that alloys much 
richer in tin were more magnetic, and hence the series finally prepared con- 
tained alloys with from 14 to 50 per cent. 
Materials Employed . — The materials employed were the purest specimens 
obtainable. The copper was a high-grade electrolytic copper, and any traces 
of impurities must have been extremely small, and of negligible influence. 
The tin, obtained from Kahlbaum, was of a similar high degree of purity. 
The manganese metal contained about 98 - 5 per cent, of pure manganese, the 
remainder consisting chiefly of silicon, iron, and aluminium in diminishing 
proportions. 
Preparation of the SO per cent. Manganese Bronze . — The preparation of 
the 30 per cent, manganese copper alloy was carried out in the following 
manner:— The copper was first melted in a “Salamander” crucible under a 
layer of barium chloride. The proper amount of manganese was then added, 
and the heating continued until the metal was completely dissolved. The 
crucible was now removed from the furnace, the contents carefully stirred, 
and, while the metal cooled to the desired casting temperature, the surface 
was skimmed. The alloy was poured into a series of dry sand moulds which 
* Melting points : — Manganese 1260°, copper 1084°, tin 227° C. 
t S. Schemtschiischny, G. Urasow, and A. Rykowski, Jour. Russ. Phys. Ghem. Soc ., 
xxxviii., 1050 (1906) ; Zeit. f. anorg. Ghem ., lvii., 253 (1908). 
I R. Sahinen, Zeit.f. anorg. Ghem., lvii., 1 (1908). 
§ K. Bornemann, Metallurgie, vi., 329 (1909). 
|| F. Heusler, Schriften Naturf. Ges. Marburg , xiii. [5], 266 (1904 
