252 



Mr. W. Boseiihaiii. 



[May 1,. 



The authors hope that these experiments may prove of use in afford- 

 ing an indication of the comparative behaviour of this " apio-ro-KpoLTioL "' 

 or noblest metal platinum, with the behaviour of the constructive 

 metals, copper, nickel, iron and steel, when under the influence of 

 stress ; and the experiments have also shown that the microscopic in- 

 fluences of stress in the heavy metal platinum are analogous to those 

 which have been observed in metals of lower specific gravity. 



DESCRIPTION OF PLATE. 



Fig. 1. — Microscopic Effects of Compression Stress on Platinum, showing Crystal- 

 line Slip, as seen in Section. Magnification 120 diameters. Vertical- 

 illumination. Metal compressed 10 per cent. Arrow indicates direc- 

 tion of compressive force. 



Fig. 2. — Microscopic Effects of Compression Stress on Platinum, showing Crystal- 

 line Slip, as seen in Section. Magnification 120 diameters. YerticaL 

 illumination. Metal compressed 10 per cent. Arrow indicates direc- 

 tion of compressive force. 



Fig. 3. — Same as fig. 2, but magnified 250 diameters. 



"A Note on the Eecrystallisation of Platinum." By Walter 

 Eosexhaix, B.A. (Cantab.), B.C.E. (Melbourne). Communi- 

 cated by Professor Ewixg, F.E.S. Eeceived May 1, — Bead. 

 May 15, 1902. 



In a recent paper* Professor Ewing and the present author have 

 described phenomena of recrystallisation in a number of metals, such 

 as lead, tin, zinc, and cadmium, at temperatures well below the melting 

 points of those metals. I have recently observed phenomena which 

 appear to me to be of a very similar nature in the case of platinum. 



It is a well-known fact that a prolonged exposure to a high tempera- 

 ture renders platinum brittle, and that the surface of such platinum,, 

 when it has been exposed to flame, shows markings " resembling the 

 appearance of galvanised iron." f This phenomenon has generally been 

 ascribed to the action of carbon, and by one author specifically to the 

 action of acetylene. f Having studied the phenomena closely with the 

 aid of the microscope, I do not find this view entirely confirmed. 



In the first place, on examining the surface of the "changed" 

 platinum with the microscope, it is seen to show a pattern which is 



* " On the Crystalline Structure of Metals," second paper, ' Phil. Trans.,' A,. 



1900, Vol. 195, pp. 279—301. 



f "The Action of the Acetylene Flame on Platinum," J. J. Eedwood, 'Soc. 

 Chem. Industry Journ.,' vol. 17, p. 1107; also ' Zeitschrift fur Analjt. Chem./ 



1901, heft 6, p. 411. 



