285 
1908-9.] Magnetic Properties of certain Copper Alloys. 
that its magnetism may be due in great measure to the free copper 
contained, and not to a manganese-copper constituent. Lastly, the tests 
given in the table indicate that pure aluminium (such as had been used in 
making the aluminium-bronzes and the Heusler alloys) is not susceptible of 
retaining any measurable trace of permanent magnetism. The result of the 
tests on the materials (4)-(10) is therefore to show that specimens containing 
free copper undergo a marked improvement in magnetic quality on cooling 
from 15° C. to — 190° C., and that quenching is likewise accompanied by an 
increase of residual magnetism — except, of course, in so far as these effects 
may be masked to a greater or less extent by those due to the presence of 
other magnetic materials. 
The Magnetism of the Heusler Alloy . — These results have an important 
bearing on the magnetism of the Heusler alloy. A characteristic feature 
of these bronzes is that their retentivity at the temperature of liquid air is 
greater than at room temperature. This holds even in the case of baked 
specimens of alloy B or D, where the cooling diminishes the saturation 
value of I. Such an effect is of the same kind as that given by free copper. 
It is also similar to that found in the 10 per cent, aluminium-bronze, but its 
great magnitude in such cases as the quenched castings D is more suggestive 
of the free copper than of the copper-aluminium compounds. Hitherto the 
magnetism of the Heusler alloy has been often ascribed to the manganese 
alone, whose transformation temperature it has been conjectured — though 
neither proof nor evidence can be adduced in support — is lowered by its 
solution in the other constituents. The one point always referred to in this 
connection is the list of several elements arranged by S. Meyer * in descend- 
ing order of atomic susceptibility (that quantity being defined as the mean 
susceptibility of a space containing one gram atom of the substance per 
litre). The series is as follows : — Ho, Er, Gd, Mn, Fe, Sa, Co, Yt, Nd, Ni, 
Pr. This list is of course based to a very large extent on the magnetic 
properties exhibited by salts of the elements. Manganese therefore comes 
before iron. For although in general the magnetism of pure iron is incom- 
parably greater than that of manganese, yet the susceptibility of many 
manganous salts exceeds that of the corresponding ferrous and ferric 
compounds, j* The experiments described in the present paper have, how- 
ever, a more immediate bearing on the subject. The authors do not claim 
that the investigations afford an explanation of the magnetic phenomena of 
the Heusler alloy, but they consider that the magnetic properties of the 
alloy show a suggestive similarity to those of Cu 3 A1, and that the presence 
* Ann. d. Phys., 1889, lxix., S. 236. 
t Per. d. Dentsch. Chem. Gesell 1900, xxxiii. S. 448. 
