512 SUMMARY OF CURRENT RESEARCHES. 



tion of the two metals was stable. Microscopic examination of cross 

 sections of the specimens after heating indicated that diffusion had taken 

 place in every case, frequently to a marked degree. 



Pair of Metals. Time of Heating, and Temperature. 



Iron-aluminium 50 hours at 635° C. 



Iron-copper .. . . 5 ,, 1000" 



Copper-nickel 10 „ 1000° 



Copper-bronze (20 p.c. tin) 50 „ 750° 



Copper-zinc 50 „ 400° 



Copper-tin .. 50 „ 218 c 



Copper-brass (42 p.c. zinc) 50 ,, 800" 



i 



Micro-actions of Acids and Metals.* — J. Scott describes the 

 microscopic appearance of the salts obtained when small fragments of 

 metals were dissolved in a few drops of nitric acid on glass slips and 

 the solutions allowed to evaporate. The preparations were photographed 

 with oblique illumination. 



Structure of Fire-brick. J — G. Rigg describes the microstructure of 

 a number of specimens of fire-brick, examined in the form of thiu slices. 

 The more compact and close-textured bricks possess good resisting power 

 against the penetrating action of corrosive slags and gases. 



National Physical Laboratory 4 — Among the subjects of metal- 

 lurgical investigation to which microscopic methods have been applied 

 were the aluminium-zinc and aluminium-zinc-copper alloys, the effects 

 of strain in metals at high temperatures, brittleness in steel, structure of 

 steel at high temperatures, and intercrystalline cohesion in metals. In 

 the study of cases of failure of rails, tyres and similar articles, the micro- 

 scopic examination of complete cross sections proved useful, since local 

 defects do not readily escape detection when this method is used. 



* Foundry Trade Journ., xvi. (1914) pp. 523-5 (6 figs.). 



t Journ. Ind. and Eng. Chem., v. (1913) pp. 549-54 (7 figs.). 



% Nat. Pbys. Lab. Ann. Report, 1912. 



