274 SUMMARY OF CURRENT RESEARCHES RELATING TO 



An alcoholic solution may be used, but is slower in action. The action 

 of the reagent appears to be essentially the formation of films of sulphide 

 of iron, and as different constituents are acted upon with varying rapidity, 

 they become coated with sulphide films of different thickness. Photo- 

 micrographs of steel, in which the authors claim to have developed the 

 structure better with their new reagent than with any other, are given. 

 Sulphurous acid is not suitable for steels composed of ferrite and pearlite, 

 but is an excellent reagent for all other steels and pig irons. 



Fatigue of Metals.* — J. H. Smith describes a method for deter- 

 mining a series of yield ranges by experiment on a single specimen. 

 Numerous results obtained on different classes of steels, lead him to con- 

 clude that if a material be subjected to stress alternations of high period- 

 icity and of fixed range, and compressive or tensile mean stress be gradually 

 applied, a yielding condition will be found at a definite value of the applied 

 mean stress. 



Measurement of Hardness.f— G. Baume describes a dynamic method 

 of applying the Brinell test. The apparatus consists of a weighted rod, 

 suitably guided, holding at its lower end a hardened steel ball. The 

 impression made by a known weight of rod and height of fall on a 

 polished specimen is measured. 



Viscous Flow in Metals. J — E. N. da C. Andrade has devised a 

 method of loading a wire in tension in such a manner that the stress 

 remains constant however the wire may contract laterally on stretching. 

 By loading wires of lead, a lead-tin alloy, and copper in this way, the 

 author has demonstrated that, beyond the elastic limit, the extension 

 after some time becomes proportional to the time, or the flow becomes 

 viscous in character. The flow is purely viscous right up to breaking. 



Electrical Conductivity of Molten Alloys.§ — K. Bornemann and 

 P. Miiller have determined the electrical conductivity, at different tem- 

 peratures, of numerous alloys belonging to the binary systems sodium- 

 potassium, tin-lead, mercury-sodium, mercury-potassium, and others. It 

 is shown that indications of the presence of compounds in molten alloys, 

 and of the degree of dissociation of such compounds, may be obtained 

 from concentration-conductivity curves. The temperature at which the 

 separation of a homogeneous liquid alloy into two phases takes place is 

 characterized by a change in direction of the conductivity-temperature 

 curve, and may accordingly be determined by measurements of con- 

 ductivity at different temperatures. 



Temperature Co-efficients of Electrical Resistance. || — A. A. Somer- 

 ville gives curves showing the variation of resistance of nickel, tungsten, 

 molybdenum, and an alloy named nichrome, in the range of temperature 

 0°-1060° C. 



* Journ. Iron and Steel Inst., lxxxii. (1910) pp. 246-318 (37 figs.). 



t Archives des Sciences Physiques et ISaturelles (Geneva) xxx. (1910) pp. 

 418-20. 



X Proc. Roy. Soc, Series A, lxxxiv. (1910) pp. 1-12 (7 figs.). ] 



§ Metallurgie, vii. (1910) pp. 396-402 (5 figs.). 



|| Physical Review, xxx. (1910) pp. 532^i, through Science Abstracts, Sect. A, 

 xiii. (1910) pp. 448-9. 



