264 SUMMAKY OF CURRENT RESEARCHES RELATING TO 



microstructure. High tensile strength appeared to be associated with a 

 comparatively fine state of division of the graphite, and a net-like 

 formation of the phosphorus eutectic. 



Magnetic Properties of Alloys of Ferro-magnetic Metals.* — G. 

 Tammann deduces some general rules from the experimental data pre- 

 viously published by himself and others, relating to the magnetic 

 properties of alloys containing iron, cobalt, and nickel. A solid solu- 

 tion of a non-magnetic in a ferro-magnetic metal is magnetic, while a 

 solid solution of a ferro-magnetic in a non -magnetic metal is non- 

 magnetic. Chemical compounds are practically non-magnetic. The 

 depression of the temperature at which magnetic properties disappear on 

 heating, by the presence of other elements, is discussed. 



Magnetic Character of Compounds of Non-magnetic Elements.f 

 E. Wedekind has studied the magnetic properties of the compounds 

 MnB, MnSb, Mn 2 Sb, and MnP. The greatest temporary magnetism 

 was shown by MnSb, the least by MnP. 



Metallographic Observations at High Temperatures. J— P. Ober- 

 hoffer has attacked the problem of direct microscopic examination of 

 easily oxidised metals at temperatures up to 1000° C. The le Chatelier 

 stand with horizontal stage above the Microscope tube is used. The 

 section is held, polished face down, at the lower end of a vertical quartz 

 tube on which a heating coil of platinum wire is wound. The quartz 

 tube is contained within a glass vessel with flat bottom, through which 

 the specimen is observed, surrounded by a brass cooling vessel, through 

 which water circulates. A vacuum is maintained in the glass vessel by 

 means of an air-pump. Gases can be introduced for etching the hot 

 specimen ; chlorine and hydrogen were tried. A diaphragm of sheet 

 platinum resting on the flat bottom of the glass vessel, reflects upwards 

 heat which would otherwise be radiated downwards to the Microscope 

 objective, but permits observation through a central opening. A thermo- 

 couple in contact with the specimen enables its temperature to be followed. 

 During the heating the specimen was observed, usually with a 16 mm. 

 objective and Zeiss No. 18 compensating eye-piece, till the beginning of 

 a change was noted. The heating current was cut off, and the specimen, 

 when cool, was photographed without being disturbed. Heating was 

 then resumed, and when the change had proceeded further, the specimen 

 was cooled and photographed again. These operations were repeated as 

 required. In this way the transformation from austenite to pearlite was 

 followed, but more definite results were secured in the observation of 

 the formation of temper carbon in cast iron. The results obtained are 

 of value chiefly as indicating the possibilities of the method. 



Determination of Melting-points.§ — W. P. White discusses methods 

 of determining melting and freezing points, and the sources of error in 

 the results obtained. The prime cause of obliquity in melting curves is 

 the presence of impurities, which cause the melting to occupy a certain 

 temperature interval. 



* Zeitschr. Phys. Chem., lxv. (1908) pp. 73-83. 

 t Op. cit., lxvi. (1909) pp. 614-32 (4 figs.). 

 % Metallurgie, vi. (1909) pp. 554-67 (41 figs.). 



§ Amer. Journ. Sci., xxviii. (1909) pp. 453-73, 474-89, through Journ. Chem. 

 Soc, xcvi. (1909) pp. 970-1. 



