528 SUMMARY OF CURRENT RESEARCHES RELATING TO 



(5) carbon crucibles for melting ; (6) stirrers for keeping molten metal 

 in motion while a cooling curve is taken. 



Invariant Systems and the Composition of Eutecties.* — A. Gorboff 

 discusses the application of the phase rule to the composition of eutecties, 

 and from an examination of the results obtained bv numerous investiga- 

 tors, concludes that eutecties follow the law of multiple proportions. 

 Thus the composition of a eutectic may be expressed, like that of a com- 

 pound, by a chemical formula with rational indices. Some further 

 general rules governing the composition of eutecties are given. 



Microscopy and Macroscopy in Workshop Practice.! — J. E. Stead 

 has collected from many manufacturers and investigators opinions as to 

 the value of microscopical study of metals, and quotes a number of 

 typical opinions. He then describes cases in which metallographic 

 methods have proved of great use. A steel casting, before annealing, 

 usually has a skin of somewhat higher carbon content than the interior. 

 This surface layer is decarburised by annealing. Microscopic examina- 

 tion will reveal whether a casting has been annealed or not, and if so, 

 will indicate if a suitable temperature has been employed. Etching the 

 surface of a casting with 20 p.c. nitric acid after rough polishing will 

 show if electric welding has been practised, and whether electrically 

 welded steel has been subsequently annealed or not. The heating by 

 friction of wire ropes sometimes leads to the formation of a dangerously 

 brittle and hard skin in the subsequent rapid cooling. Such a brittle 

 skin can be detected by the Microscope. Many other instances are 

 given. 



Formation of Alloys by Pressure. :£ — W. Spring agrees with 

 Tammann that the formation of alloys under pressure is a result of 

 diffusion, which is not accelerated by the pressure. 



Specific Heat of Metallic Alloys.§ — A. Y. Saposhnikoff has deter- 

 mined the specific heats at 15° to 100° G. of a number of binary alloys 

 belonging to four typical systems : (1) bismuth-cadmium ; (2) lead-tin ; 

 (3) bismuth-antimony ; (4) zinc-antimony. Regnault's law, which re- 

 quires that the specific heat of an alloy should be equal to the mean 

 arithmetical specific heat of its components, is confirmed. 



Mounting of Metal Sections. || — E. Preuss describes the following 

 as a new method. The section, which may be quite irregular in shape, 

 is placed on a level surface with the polished face down. A brass ring 

 with parallel ends is placed over it and the spaces between section and 

 ring filled up with plasticine. The ring with the section thus fixed in 

 it is mounted on a slide with the polished face up. 



* Journ. lluss. Phys. Chem. Soc, xli. (1909) pp. 1241-1300, through Journ. 

 Chern. Soc. xcviii. (1910) p. 111. 



t Proc. Int. Assoc, for Testing Materials, No. 15 (1910) pp. 205-10 (26 figs.). 



X Zeitschr. Elektrochem., xv. (1909) p. 984, through Journ. Chem. Soc. xcviii. 

 (1910) p. 126. 



§ Journ. Russ. Phvs. Chem. Soc, xli. (1909) pp. 1708-11, through Journ. Chem. 

 Soc, xcviii. (1910) p. 182. 



|| Stahl und Eisen, xxix. (1909) p. 239 (2 figs.). 



