560 SUMMARY OF CURRENT RESEARCHES RELATING TO 



coarse structure, the coarse laminae of ferrite disappeared. Small pieces 

 were heated to temperatures ranging from 715° to 900° C, cooled in air, 

 and microscopically examined. Complete refining, involving the dis- 

 appearance of all ferrite lamination except that caused by re-precipitation 

 on lines of slag or manganese sulphide, took place on the completion of 

 the Ac 2-3 change, at 8*2 5°C. 



Thermo-electric Forces of Solid Solutions.*— A. L. Bernoulli has 

 made thermo-electric measurements for solutions of thallium and tin in 

 silver, of mercury in cadmium, and of tin, zinc, and nickel in copper. 

 Schenck's law was found to hold for sufficiently dilute solutions, but not 

 so well with higher concentrations. For the copper-zinc alloys the 

 potential differences are much greater than those calculated by Schenck's 

 formula ; this is ascribed to the formation of the compound Cu 2 Zn 3 . 



Defects in Alloys.f — 0. H. Desch discusses the character and origin 

 of defects commonly found in non-ferrous alloys. Sponginess is caused 

 by gases, dissolved in the molten alloy, being released during solidification. 

 The solubility of gases in molten metals appears to increase with rising 

 temperature. Brittleness may be due to the presence of oxide or inter- 

 crystalline eutectic. It is suggested that the " burning " temperature, in 

 brass, is that at which the zinc has a certain appreciable vapour pressure. 

 Of the numerous other defects described, many may be detected micro- 

 scopically. 



Solid Colloid Systems in Metallography.^ — 0. Benedicks develops 

 the view that troostite is a solid colloidal solution of cementite in iron. 

 Troostite, formed by reheating martensite, may by further reheating be 

 coagulated into pearlite. Sorbite is regarded as an intermediate stage in 

 which this coagulation is incomplete. Colloidal solutions probably exist 

 in the iron-nickel, iron-manganese, and other alloys. 



A. Lottermoser § compares iron-carbon alloys with gold glasses in 

 their capacity for forming solid colloidal solutions. 



Electrical Conductivity of Molten Alloys. — P. Muller describes in 

 detail the apparatus and method he has used for the determination of 

 electrical conductivity of alloys in the liquid state. Numerous results 

 are given for the systems potassium-sodium, lead-tin, potassium-mercury, 

 sodium-mercury, lead-cadmium, lead-antimony, lead-bismuth and lead- 

 zinc. The relation of the electrical conductivity and the temperature 

 coefficient to the constitution of the alloy is discussed. 



Equilibrium Diagrams. If — K. Bornemann enters upon a theoretical 

 discussion of some general properties of binary equilibrium diagrams, 

 these properties being illustrated by the complex transformations occur- 

 ring in the nickel-sulphur system. 



* Ann. Physik., xxxiii. (1910) pp. G90-706, through Journ. Chem. Soc. xcvir. 

 (1910) p. 1030. 



t Journ. Inst. Metals, iv. (1910) pp. 235-47, 257-64. 



% Zeitschr. Lhera. Ind. Kolloide, vii. (1910) pp. 290-9 (5 figs.). 



§ Op. tit., viii. (1911) pp. 95-6. 



Metallurgie, vii. (1910) pp. 730-40, 755-71 (35 fig<0. 

 1 Metallurgie, vii. (1910) pp. 740-7 (13 figs.). 



