ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 115 



copper-zinc alloys is discussed. The author suggests that the effect 

 of high casting temperature on copper-tin and other alloys is due to 

 dower rate of solidification caused by the greater heating of the mould. 



Mechanism of Annealing.* — G. D. Bengough and 0. V. Hudson 

 discuss the annealing process in copper alloys. In the case of single 

 phase alloys or pure metals the effect of annealing seems to be essen- 

 tially the conversion of Beilby's hard A phase into the C or crystalline 

 phase. In more complex alloys, such as Muntz metal, annealing may 

 produce a change of constitution. The annealing temperature of 

 cartridge brass may be between 550° and 730° C, preferably 600°-650° C. 

 The Microscope affords a ready means of controlling the annealing 

 process. 



Phosphor Bronze.f — A. Philip has collected a large number of 

 chemical analyses and mechanical tests of phosphor bronze, and from 

 them deduces the following as a suitable specification : — copper 90-92, 

 tin 7 "4-9 "7, phosphorus - 3-0"6 p.c. The author prefers to examine 

 micro-sections polished but not etched. A grey network is probably 

 €u 3 P. The presence of this network of hard copper phosphide in a 

 matrix of softer copper-tin alloy renders the metal suitable for bearings. 



Metallographic Investigation of Alloys. f—W. Rosenhain discusses 

 inetallographic methods, dealing chiefly with those in which there is con- 

 siderable divergence in the practice of different investigators. The 

 necessity for using pure materials, for checking by actual analysis the 

 composition of each alloy prepared, for using reasonably large quantities 

 of metal in the thermal investigations, for accuracy of temperature 

 measurement (by a potentiometer method when thermocouples are used), 

 and for employing slow rates of cooling, is emphasized. The paper con- 

 tains much criticism of the methods employed in Tammann's laboratory 

 at Gottingen. 



Intermetallic Compounds.§ — C. H. Desch gives an account of 

 criteria for the existence of compounds. In binary metallic systems 

 the methods available for the establishment of the existence and formula? 

 of compounds are,: — 1. Thermal analysis. 2. Microscopic examination. 

 3. Determination of electromotive force between an alloy and one of 

 its component metals. 4. Chemical examination of residues (apt to give 

 misleading results). 5. Measurements of (a) hardness, (b) density, 

 (c) electrical conductivity. 6. Determination of heat of formation (an 

 untrustworthy method). The combination of thermal and microscopic il 

 examination offers the most certain means of detecting compounds, 

 electrical conductivity probably ranking next in importance. The author 

 gives a list of well established compounds. 



Structure of a Brittle Steel Sheet.||— A. Sauveur has examined a 

 steel sheet, carbon ■ 05 p.c, exhibiting brittleness of the kind described by 



* Ironmonger's Chronicle, lxi. (1908) pp. 5-20. 



f Tom. cit., pp. 25-30. { Tom. cib., pp. 30-40 (5 figs.). 



§ Tom. cit., pp. 40-3 (5 figs.). 



)| Electrochem. and Met. Industry, vi. (1903) p. 271 (3 figs.). 



I -1 



