ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 785 



Carbon-iron Diagram.* — H. M. Howe explains and supports at 

 considerable length the double diagram of the iron-carbon system, 

 indicating metastable equilibrium between iron and cementite, and stable 

 equilibrium between iron and graphite. The evidence for and against 

 this diagram is fully considered. The constituents austenite, cementite 

 and ferrite are subdivided, and new terms are defined and employed 

 by the author to indicate the genesis of each subdivision. For instance, 

 cementite is classed as primary, eutectic, pro-eutectoid, or eutectoid cemen- 

 tite. Though graphite usually results from the decomposition of ce- 

 mentite, the author considers that eutectic graphite is sometimes formed 

 directly from the molten state. In solidification the habitual order is 

 through the metastable to the stable system. While cementite often 

 changes directly into graphite and iron, graphite can only change into 

 cementite through an intermediate state of solution in iron as austenite. 



Vanadium-iron Alloys.f — R. Vogel and G-. Tammann found that 

 alloys with more than 30 p.c. vanadium could not be prepared by 

 melting the metals together. High vanadium alloys were accordingly 

 made by reduction of mixtures of the oxides with aluminium. Silicon 

 was also reduced in the reaction from the crucible. A diagram is 

 therefore given for a series of vanadium-iron alloys containing 7 " 5 p.c. 

 silicon. By using magnesia-lined crucibles for the alumino-thermic 

 reduction, the authors obtained alloys nearly free from silicon. Iron 

 and vanadium form a continuous series of mixed crystals. The solidi- 

 fication point of the vanadium used was found by the Wanner pyrometer 

 to be 1750 ± 30° C. ; probably pure vanadium solidifies at a some- 

 what higher temperature. 



Siiicon-aluminium Alloys. — W. Fraenkel has determined the 

 equilibrium diagram. No compounds are formed. Silicon and 

 aluminium are completely miscible in the liquid state ; in the solid 

 the limits of solubility appear to be not greater than ■ 5 p.c. silicon in 

 aluminium and 2 p.c. aluminium in silicon. The eutectic contains 

 10 p.c. Si, and melts at 57<s° 0. Microscopic verification of the 

 composition of the mixed crystals was difficult. 



Composition of Saturated Mixed Crystals.§ — W. v. Lepkowski 

 has investigated, in two series of alloys, the production of super- 

 saturated mixed crystals by rapid cooling. The microstructure of 

 samples cooled in the furnace was compared with that of samples 

 east in iron moulds standing in ice. While in the tin-bismuth series 

 the concentration of tin in solid solution in bismuth could be raised 

 from to between l'l and 1*5 p.c. by rapid cooling, no effect of this 

 kind could be produced at either end of the copper-silver series. The 

 equilibrium diagram of the tin-bismuth series was re-determined. 



* Bull. Amer. Lust. Mining Engineers, xxii. (1908) pp. 461-529 (10 figs.). 



t Zeitschr. Anorg. Ckern., lviii. (1908) pp. 73-82 (2 figs.). 



% Tom. cit., pp. 154-8 (1 fig.). 



§ Op. cit., lix. (1908) pp. 285-92 (8 figs.). 



