592 



SUMMARY OF CURRENT RESEARCHES. 



New Reagent for Etching Mild Steel.* — W. Rosenhain and 

 J. L. Haughton, give an amplified account of this reagent.f The 

 formula recommended is : — ■ 



Ferric chloride (Fe„Cl 6 ) 30 grm. 



Hydrochloric acid (cone.) 100 c.cm. 



Cupric chloride (CuCl 2 ) 1-0 grm. 



Stannous chloride (SnCl,) 0*5 ,, 



Water 1 litre. 



The steel surface must be perfectly clean before etching ; this is 

 best secured by finishing the polishing on a very wet block, washing the 

 specimen immediately in a jet of alcohol, and immersing it completely 

 in the reagent. The structure of martensite is developed very clearly. 

 The principal value of the reagent, however, lies in its capacity for 

 indicating phosphorus segregation, as described previously. 



* Journ. Iron and Steel Inst., lxxxix. (1914, 1) pp. 515-27 (17 figs.). 

 t See this Journ., 1914, p. 222. 



