ZOOLOGY AND BOTANY, MK'llOSCOPY, ETC. 219 



heating in an oxidizing atmosphere, were observed to contain, in addition 

 to the two constituents normally present, a third which formed a net- 

 work upon the Fe-FeS eutectic. This appearance is due to the entry of 

 oxygen into the binary eutectic, and it is suggested that the red-short- 

 ness in iron containing sulphur is due to oxidation of the Fe-FeS 

 eutectic. 



Chemical Method for Investigation of Alloys.* — A. Portevin 

 points out two possible sources of error, in addition to those which have 

 been indicated previously, in the determination of the composition of 

 compounds by analysis of the residues obtained when alloys are chemi- 

 cally acted upon by reagents. A single crystal, of a definite compound, 

 may in its growth completely enclose within itself a portion of the still 

 liquid alloy, differing considerably in composition from the crystal. 

 Photomicrographs of a crystal of CusSn in a bearing metal, and a crystal 

 of antimony in a copper-antimony alloy, are given : in each case the 

 crystal contains a kernel of eutectic. If, during the solidification of an 

 alloy, primary crystals A react with the liquid L giving a compound C, 

 the compound C may form a complete envelope round A, preventing 

 further reaction of A with L. Thus in the solid alloy, the C crystals 

 contain a kernel of A. 



Copper-zinc Alloys : the jS Constituent.! — H. C. H. Carpenter 

 has made further attempts to cause a visible separation of the f3 struc- 

 ture of the pure a and y eutectoid alloy, into a and y. No annealing, 

 however prolonged, will effect this separation. A section of pure 

 apparent ^ alloy was heated at 420° C, with its polished face in contact 

 with the polished face of a section of a eutectoid alloy containing 

 0*95 p.c. vanadium, which contained its a and y in a coarse crystalline 

 form. Incipient resolution of the pure eutectoid resulted from this 

 inoculation, and a further prolonged annealing of the pure eutectoid 

 alone caused the formation of coarse segregations of a and y. A lamellar 

 resolution of pure /3 was never observed. 



The structure of alloys of /3 composition, to which different percent- 

 ages of various common metals had been added, was investigated. The 

 effect upon the structural stability of the apparent (3 constituent was 

 slight when the added metal was bismuth, lead, chromium, manganese, 

 or iron, while aluminium, antimony, tin, silicon, and vanadium aid the 

 precipitation of visible a and y from apparent /3, In general, the struc- 

 tural stability of apparent ^ is at a maximum when no impurities are 

 present. 



Annealing of Quenched Aluminium Bronze.| — An alloy of 90 p.c. 

 copper and 10 p.c. aluminium consists of a eutectoid, together with 

 excess of the a constituent. Quenching from a temperature above the 

 critical point causes the replacement of the eutectoid by a " martensitic " 



* Rev. MetaUurgie, ix. (1912) pp. S84-90 (6 figs.). 



t Journ. Inst. Metals, viii. (1912, 2) pp. 51-85 (24 figs.). 



X Comptes Rendus, cliv. (1912) pp. 510-14(2 figs.). 



Q 2 



