272 SUMMARY OF CURRENT RESEARCHES RELATING TO 



unaffected. A scheme for the metallographies! identification of the 

 coin pounds occurring in slags found in iron and steel, is outlined, the 

 appropriate reagents being given in tabular form. 



Action of Mercury on Steel at High Pressures.* — In the course 

 of an investigation of the thermal properties of mercury and water 

 under high pressure, P. W. Bridgman found that hollow cylinders of 

 hardened steel burst at very much lower than the natural bursting 

 pressure when the fluid exerting the pressure was mercury. That this 

 rupture was due to the amalgamation of the steel was evident from the 

 appearance of the fracture. It was found that the fractured surface of 

 steel broken under mercury was amalgamated. Any exposure to air 

 before contact with mercury completely prevents amalgamation. The 

 explanation advanced to explain the bursting of the pressure cylinders, 

 involves the initial amalgamation of the steel permitted by its state of 

 elastic strain. The rapidity with which the amalgamation spreads is 

 greatly increased by the action of hydrostatic pressure. 



Influence of Silicon on Cast Iron.f — A. Hague and T. Turner have 

 studied seventeen alloys containing 2*3 to 2*9 p.c. total carbon, the 

 silicon content increasing from 0* 03 to 4 ■ 83 p.c. The molten alloy was 

 cast in a mould giving a bar of circular section, and simultaneous 

 observations were made of time, temperature, and change in length. 

 Sections of the bars were examined microscopically, and mechanical tests 

 were made. The pearlite arrest-point was gradually raised from 

 700° to 800° C. by the silicon additions, which also raised to a smaller 

 extent the temperature of final solidification, from 1130° to 1160° C. The 

 temperature of commencing solidification appears to be lowered by 

 increasing silicon. 



Manganese in Cast Iron.} — H. I. Coe has measured the changes in 

 length which occur in cast bars of iron-manganese-carbon alloys during 

 cooling from the molten state. Simultaneously with these measure- 

 ments, time-temperature cooling curves were taken. Hardness measure- 

 ments were made on the cast bars, which were also microscopically 

 examined. The forty-eight alloys studied are divided into two series, 

 the first being prepared from pure white cast iron, the second from grey 

 cast iron containing 2*45 p.c. silicon. Manganese increased from to 

 nearly 40 p.c. In the white iron series the temperature of commencing 

 solidification was lowered by manganese, but the eutectic freezing point 

 was not affected up to 20 p.c. manganese. An alloy containing 4 p.c. 

 carbon, 26 to 28 p.c. manganese, 68 p.c. iron, appeared to be a pure 

 eutectic, with its freezing point 15° C. below that of the eutectic of the 

 pure iron-carbon system. The Arl temperature was lowered by about 

 20° C. for each 1 p.c. of manganese ; this arrest gradually diminished 

 in intensity, disappearing at about 10 p.c. manganese. In the grey iron 



* Proc. Amer. Acad. Arts and Sciences, xlvi. (1911) pp. 325-41 (9 figs.). 

 t Journ. Iron and Steel Inst., lxxxii. (1910) pp. 72-104 (25 figs.). 

 X Tom. cit., pp. 105-46 (25 figs.). 



