ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 677 



founded are not stated. The sections for microscopical examination 

 were finally polished with Globe polish, by hand. The best etching 

 reagent for these, as for the majority of copper alloys, is a 10 p.c. 

 aqueous solution of ammonium persulphate. This reagent dissolves 

 copper and certain other metals without the evolution of gas, or the 

 formation of a surface film. The surface, previous to etching, should 

 be perfectly freed from grease. The most satisfactory photomicrographs 

 are secured by using colour plates. 



Zinc Bronzes.* — L. Guillet and L. Revillon give the first results of 

 an investigation of the effect of other metals on the copper-tin alloys. 

 In cases in which zinc was the third metal, it was observed that the 

 8-phase existed when the tin content was below the percentage expres- 

 sing the solubility of tin in copper. The microscopical appearance 

 resembled that of an alloy containing somewhat more tin than the 

 amount present. The effect of the zinc may be expressed by a " coeffi- 

 cient of equivalence," in the same way as the effect of a third metal on 

 the copper-zinc alloys has been expressed. The examination of six alloys 

 containing 13' 7 to 4' 6 p.c. tin, 1*7 to 10 "2 p.c. zinc, and about 85 p.c. 

 copper, has shown that the " coefficient of equivalence " of zinc in bronzes 

 is very nearly 0, the zinc going into solution in the a-phase without 

 seriously altering the limit of solubility of tin. Results of mechanical 

 tests of twenty-one copper-tin-zinc alloys, are given. 



Ternary System Iron-copper-nickel, f — R. Vogel has employed prin- 

 cipally microscopical methods for the determination of the limits of 

 saturation of the ternary mixed crystals occurring in this system. Speci- 

 mens were submitted to long annealing to obtain equilibrium. Cooling 

 curves of some twenty-five alloys were taken. In the triangular diagram, 

 alloys of compositions lying outside a continuous curve passing through 

 the limits of saturation are, if sufficiently annealed, homogeneous solid 

 solutions. 



Light Alloys. $ — W. Rosenhain reviews the progress made in the 

 production of alloys combining great strength with a low specific gravity. 

 Aluminium, which in the pure state is weak, may be strengthened by the 

 addition of copper, alone or with manganese, or of zinc, or of other 

 metals. The effect of such additions upon corrosion is discussed. Alloys 

 of magnesium are beginning to find practical application. 



Thermo-electricity of Alloys.§— E. Rudolfi has investigated the 

 relation between constitution and thermo-electric properties of alloys. 

 Ten representative binary systems were examined, the E.M.F. developed 

 by each alloy against copper and against nickel being measured. One 

 junction was kept in molten ice, the other was heated in a paraffin bath. 

 Binary systems are classified in four groups : (1) neither compounds 

 nor solid solutions are formed, the concentration-E.M.F. curve is a 

 straight line ; (2) the components form a continuous series of solid 



* Rev. Metallurgie. vii. (1910) pp. 429-32 (2 figs.). 



t Zeitschr. Anorg. Chem., lxvii. (1910) pp. 1-16 (14 figs.). 



j Nature, lxxxiii. (1910) pp. 461-2. 



§ Zeitschr. Aiiorg. Chem., lxvii. (1910) pp. 65-96 (12 figs.). 



