1910-11.] On Magnetism of Copper-Manganese-Tin Alloys. 87 
had been lined with whiting. The castings were in the form of cylindrical 
rods about one inch in diameter, and when cold were removed from the 
moulds and sawn up into short lengths for use in the subsequent castings. 
Preparation of the Ternary Alloys. — A similar procedure was adopted 
in the preparation of the ternary alloys. The cupro-manganese was first 
melted and the tin added to it. Some difficulty was experienced in getting 
satisfactory castings. 
If the alloys are allowed to stand before casting there is risk of segregation 
commencing. On the other hand, if the stirring is continued up to the time 
of casting, a porous structure may result. When the appearance of the alloy 
or the chemical tests described below indicated any deviation from homo- 
geneity, the material was again melted up and recast. In view of the 
apparatus to be employed for the magnetic measurements, the castings were 
made in the form of rods about nine inches long and a little under half an 
inch in diameter. The preparation of these alloys was carried out by 
the authors at the works of Messrs Gray & Caldwell, brassfounders. 
Paisley. 
Chemical Analysis. — While it was found that there was very little loss 
in the castings, full chemical analysis was made of each alloy. This was 
considered advisable, as it gave the strongest proof of the homogeneity of the 
material. The analyses were made on portions of the actual specimens used 
in the principal tests. Two small portions were selected from different parts 
of the rod and examined gravimetrically. The tin was estimated in the 
form of stannic oxide and the copper as copper sulphide. The filtrate from 
which the tin and copper had been removed was made alkaline with 
ammonia, and the hydrated peroxide of manganese precipitated by the 
addition of bromine water. The precipitate was afterwards converted into 
Mn 3 0 4 and the manganese estimated as tetroxide. 
Programme of the Magnetic Tests. — The scheme of tests was as 
follows : — 
1. To determine the magnetic quality of the alloys in the condition 
as cast. 
2. To find the simplest and most efficient heat treatment for bringing 
the alloys into a stable condition with the highest possible magnetic quality. 
3. To investigate the changes produced in the magnetic properties by 
exposure of the alloys to different temperatures, and incidentally to deter- 
mine the critical temperature and investigate the reversibility of the effects 
due to the thermal treatment. 
4. To examine the effects produced by quenching, re-annealing, and 
baking the alloys. 
