1910-11.] On Magnetism of Copper-Manganese-Tin Alloys. 97 
the process. Little difference was found between the susceptibility corre- 
sponding to a given field for any temperature during the heating and that 
for the same temperature during the cooling, provided the interval between 
the two determinations was small. If, however, the specimen had been 
kept heated for some considerable time, a deterioration in quality was 
observed. Its amount was small, but increased with the time which had 
elapsed and the temperature employed. A remarkable effect was, however, 
noted in the case of the 38 per cent, tin alloy which exhibited such 
constancy of magnetic properties over the wide range from — 190° to 180° C. 
If heated up to 225° C. the alloy becomes non-magnetic, and if the heating 
be continued up to about 330° C. the magnetic quality is not regained on 
cooling. 
Quenching . — The effects of quenching the alloys were next investigated. 
Two temperatures of quenching were employed, one about 350° and the 
other about 580° C. The specimens to be experimented upon were raised 
to the desired temperature in the furnace, and then dropped vertically into 
cold water. Table IX. gives the results of the tests carried out on the 
quenched material at 15° and —190° C. with the corresponding values for 
the normalised condition for the sake of comparison. The effects of 
quenching are somewhat complex, but in all cases the coercive force is less 
in the quenched than in the unquenched materials, and there is generally 
a much greater increase in susceptibility on cooling to — 190° C. In the 
case of the quenching at 580° C. the resulting material is in all cases 
less magnetic than before. Quenching at 350° slightly improves the alloy 
with least tin, but the others undergo a deterioration which is larger the 
greater the tin content. In the 14 and 16 per cent, alloys the material is the 
less magnetic the higher the temperature of quenching. On the other hand, 
the 18 and 38 per cent, alloys are more magnetic after quenching at 580° C. 
than after quenching at 350°. This is similar to the effect observed in a 
copper-manganese-aluminium alloy which was rendered feebly magnetic 
by quenching at 610°, but which acquired greater permeability upon 
subsequent quenching about 700° C.* 
Instability of the Quenched Alloy . — In the case of a specimen of the 
16 per cent, tin alloy which was quenched at about 580° the value of I 200 
was reduced to about 44 per cent, of its initial value. In the course of two 
months it was found that this had increased from 44 to nearly 46 per cent., 
thereby showing that the quenched material undergoes slow transformation 
even at ordinary room temperature. 
VOL. XXXI. 
* A. D. Ross, Proc. Roy. Soc. Edin ., xxvii., 88 (1907). 
7 
