ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 119 



Metallography, etc. 



Phosphorus in Cast-iron.* — F. Wiist and E,. Stotz have examined 

 seven series of cast-irons, the phosphorus content in each series ranging 

 from small amounts to 2 p.c, and the percentage of other elements 

 remaining constant. The seven series differed from each other in 

 percentage of carbon, silicon, or manganese. The amount and form of 

 the graphite, which are most readily observed in polished unetched 

 sections, are of primary importance in their effect on mechanical 

 properties ; large graphite flukes reduce the strength of cast-iron. A 

 regular constituent of grey cast-iron containing more than • 1 p.c. 

 phosphorus is the ternary eutectic with a phosphorus content of about 

 6 p.c. Pearlite containing phosphorus frequently shows dark sorbitic 

 fields, which may be rich in phosphorus. Ferrite or cementite may be 

 present, according to the content of combined carbon. Phosphorus in 

 small amounts has no effect on the graphite, but when it increases 

 beyond • G p.c. the graphite masses collect into groups. 



Hypereutectic Iron-carbon Alloys. j—O. Ruff further discusses 

 the structure of alloys saturated with carbon at high temperatures and 

 quenched. 



Carbides of Molybdenum. | — J. 0. Arnold and A. A. Read have 

 examined five steels containing about • 8 p.c. carbon, with a molyb- 

 denum content ranging from 2-4 to 20-7 p.c. At about 18-25 p.c. 

 molybdenum, free carbide of iron disappeared, and a compound FesMogC 

 was obtained. Structures in which this double carbide occurred are 

 described. 



Heterogeneity of Steels. § — H. Le Chatelier and J. Lemoine 

 recommend the following modification of the Stead reagent for indi- 

 cating phosphorus segregation in steel : —Methyl alcohol, 100 c.cm. ; water, 

 18 c.cm. ; cone, hydrochloric acid, 2 c.cm. ; cupric chloride, crystal- 

 lized, 1 grm. ; magnesium chloride, crystallized, 4 grm. The difference, 

 in rate of deposition of copper, between the high and the low phosphorus 

 areas may be intensified by electrolytic action, the specimen being 

 wholly immersed in the reagent, and connected to the positive pole of 

 an accumulator ; a copper wire dipping into the reagent is connected to 

 the negative. Greater contrast is thus obtained between the areas 

 which differ in phosphorus content. The proportion of water in the 

 reagent is important. If this is too small, no copper is deposited ; if too 

 large, a rapid and uniform deposit of copper is formed. Photomicro- 

 graphs of transverse sections of a steel plate, etched with different 



* Ferrum, xii. (1915) pp. 89-96, 105-19 (19 figs.). 



t Zeitschr. Anorg. Chem., Ixxxix. (1914) pp. 39-47 (11 figs.). 



J Journ. Inst. Mech. Eng., 1915, pp. 629-51 (5 figs.). 



§ Comptes Rendus, clxi. (1915) pp. 373-8 (9 figs.). 



