422 SUMMARY OF CURRENT RESEARCHES RELATING TO 



It is suggested that the a constituent thus produced contained less than 

 62 p.c. copper. J. E. Stead describes a method for distinguishing the 

 a, /3, and y phases in brass. Polishing is finished on a very wet block. 

 The surface of the specimen is dried with a clean linen rag before the 

 water has evaporated at all. The specimen is heated to 80-100° C, 

 rubbed with chamois leather and floated on molten tin or lead. A 

 gaseous mixture made by blowing air through dilute ammonium sul- 

 phide solution is directed on the polished surface until the desired tints 

 appear. The a constituent passes through the range of colour, dark 

 yellow, brown, carmine, blue, to slate-grey. The y constituent when 

 associated with a remains unaltered, and appears white on the coloured 

 ground. The method may be used for detecting variations in distribu- 

 tion of copper in the a phase, since it is capable of developing the 

 primary dendritic structure. For distinguishing (3 and y when they 

 occur together, air containing traces of bromine instead of ammonium 

 sulphide may be used. 



Structure of Electro-deposited Copper-tin Alloys.* — In the course 

 of an investigation upon the electro-deposition of copper-tin bronzes, 

 E. Kremann, C. T. Suchy, J. Lorber, and R. Maas have studied the 

 micro-structure of the deposits. Alloys deposited from cyanide electro- 

 lytes were more uniform than those from a tartrate electrolyte. 



Annealing after Quenching of Copper-tin and Copper-zinc Alloys.f 

 A. Portevin has quenched and annealed a copper-tin alloy containing 

 80 p.c. copper and a copper-zinc alloy containing 58 p.c. copper. The 

 bronze was quenched at 700° C, the brass at 825° C. ; in each case 

 some of the a constituent was dissolved in the apparent $ upon heating, 

 and retained structurally in the (3 by quenching. On reheating to 

 temperatures which were raised in successive experiments, the a separated 

 from the (3 in the form of needles, or at the grain boundaries. The 

 needles produced the appearance of the Widmannstatten structure. The 

 first effect of reheating the quenched alloys was to increase the hardness 

 somewhat ; the hardness then fell off again as the annealing tempera- 

 ture was raised. The copper-aluminium alloys have been shown to 

 behave in a similar manner. 



System Silver-silver-sulphide. :{: — C. C. Bissett has made a thermal 

 investigation of the equilibrium of this system, and has examined 

 twenty alloys microscopically. Between 17 and 94 p.c. silver sulphide 

 the molten alloys separate into two liquids. Silver sulphide appears to 

 be slightly soluble in silver in the solid state. The eutectic contains 

 99 p.c. silver sulphide. No compounds in addition to the Ag 2 S were 

 found. Two etching reagents were used ; hot potassium cyanide solu- 

 tion etched the sulphide without attacking the silver, while freshly 

 prepared hot ferric sulphate solution etched the silver without attacking 

 the sulphide. 



* Monatsh. Chem., xxxv. (1914) pp. 219-88. 



t Comptes Rendus, clviii. (1914) pp. 1174-7 (4 figs.). 



% Journ. Chem. Soc, cv. (1914) pp. 1223-8 (7 figs ). 



