BRIDGMAN. 



ACTION OF MERCURY ON STEEL. 



333 



Figure 7. Form of the 

 fracture in a cylinder of 

 soft tool steel when the 

 fluid exerting the pressure 

 is mercury. 



distinctly visible, while Amagat states that he -could find no trace of 



the crack with a microscope. (See Figure 7.) 



In all these tests of the soft steel cylinders the punched out pieces 



were found more or less amalgamated around the sheared edges. In 



particular, when the cylinder of soft tool 



steel last mentioned was cut so that the 



fissure was exposed, it showed beautiful 



amalgamation over the entire surface of the 



rupture. This led to a short investigation 



of the possibility of amalgamating iron or 



steel. It has been known for some time that 



mercury is capable of dissolving a small 



quantity of iron, and that conversely an iron 



surface may be amalgamated by mercury.'* 



This amalgamation is a matter of some diffi- 

 culty, which may be made to take place by 



certain chemical or electrical reactions, but 



under ordinary conditions does not occur at 



all. It does not seem to have been noticed that under proper condi- 

 tions the amalgamation of iron is a matter of the greatest ease, the 



difficulty under ordinary conditions being 

 due apparently to a thin protecting layer of 

 oxide. The following experiment showed 

 strikingly how great the affinity between 

 clean iron and mercury is. A piece of iron 

 was broken underneath a mercury surfa.ce 

 so that the freshly ruptured surface came 

 directly in contact with the mercury. The 

 diagram illustrates the form of experiment. 

 (See Figure 8.) The test piece, in the shape 

 of a thin hollow cjdinder, is covered with 

 mercury in an iron receptacle, and broken 

 by forcing a wedge into the hole. In every 

 case the broken surface is brightly and com- 

 pletely amalgamated, the mercury wetting 

 it exactly as water wets a surface to which 

 it adheres. The same result was obtained 



with hard and soft nickel steel, hard and soft tool steel, bessemer steel 



Figure 8. Apparatus for 

 fracturing steel under the 

 surface of mercury. 



* See, for example, Richards, Wilson, and Garrod-Thomas, Pub. Carnegie 

 Inst. Wash., No. 118, 54, 1909; also Richards and Garrod-Thomas, ZS. Phys. 



Chem., 72, 181 (1910). 



