THE 

 LONDON, EDINBURGH, ind DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[FIFTH SERIES.] 

 DECEMBER 1884. 



LIV. On the Changes produced in the Molecular Condition of 

 Iron by Heating to Redness and Cooling. By Carl Fromme*. 



SOME years ago, upon the publication of some magnetic 

 experiments! , I made a short communication upon the 

 change in density which steel undergoes upon hardening, 

 and subsequently added to the fuller description J of the same 

 experiments, in these Annalen, a series of observations made 

 to determine the distribution of density in the interior of a 

 hardened steel bar. The general applicability of one of the 

 former results has recently been called in question by obser- 

 vations of H. Meyer§ . These observations show an increase 

 in density upon hardening for one (" drawn soft bright steel") 

 of three kinds of steel examined, whilst the other two kinds 

 ("best bright English cast steel" and "polished English steel") 

 showed the decrease which alone I had observed ||. I have 

 therefore made new experiments upon these phenomena of 

 change of density upon hardening, and endeavoured to obtain 

 a nearer insight into the reasons of these phenomena by ex- 

 tending the observations to the different modifications of iron, 

 from pure electrolytic iron free from carbon to the more highly 

 carbonaceous cast iron. 



The question of the distribution of density in a hardened 

 steel bar had been far from solved by the single series of obser- 



* Translated from Wiedemann's A?malen, No. 7 (1884). 



t GoU. Nachr. 1876, pp. 157-168. 



% Wied. Ann. viii. pp. 352-356 (1879) ; Phil. Mag. [5] viii. p. 421 

 (1879). 



§ H. Meyer, Wied. Ann, xviii. p. 233 (1883). 



|| There is an older observation of Binmann (in his Geschichte desEisens, 

 German translation by Karsten), according to which Styrian steel expe- 

 rienced an increase in density of from 7*782 to 7*822 upon hardening. 



Phil Mag. S. 5. Yol. 18. No. 115. Dec. 1884. 2 I 



