at the Royal Institution, 1 900-1 907. 387 



recorded. Sulphur, seleuium, red phosphorus and arsenic are all 

 violently acted upon but tellurium and antimony are not affected. 

 Sodium is slowly attacked, potassium violently after an interval; 

 lime is decomposed with violence and the hydrocarbon anthracene is 

 at once acted upon. It has been argued that these observations 

 indicate the persistence of a high degree of affinity at low tempera- 

 tures but it may be questioned whether such is the case : the least 

 change would cause the temperature to rise locally and once started 

 might take place under " spheroidal state " conditions. 



Modifications in the Properties of Mattkr at 

 Low Temperatures. 



Effect of extreme Refrigeration on Alloys of Iron. — In continua- 

 tion of previous work on the strength of metals at the temperature 

 of liquid air, Sir James Dewar and Mr. (now Sir) R. A. Hadfield 

 have carried out a long series of observations with iron and allied 

 metals. The results corroborate the inference previously drawn 

 that all common metals and alloys increase in tenacity at low tem- 

 peratures whetlier their ductility increase or decrease, the change 

 persisting only during the period of cooling. 



In the case of Swedish charcoal-iron, the tenacity rose from 20 to 

 ;)8 tons per square inch, there being substantially no elongation. 

 Steels behaved similarly. 



Nickel was improved not only in tenacity (its tensile strength 

 being increased from 29 to 46 tons) but also in ductility (from 43 to 

 51 per cent.). Moreover, the ductility of all the nickel-iron alloys 

 examined was diminished to oidy a moderate extent by cooling. 



Era manganese steel (containing C 1*23, Mn 12*64 per cent.), 

 which is remarkable as being non-magnetic and on account of its 

 tenacity (56 tons) and ductility (30 per cent, elongation), when 

 cooled to - 185°, although but sliglitly more tenacious was almost 

 entirely detoughened, being elongated only to the extent of 2J 

 per cent. 



The most remarkable are the iron-manganese-nickel alloys con- 

 taining about 6 per cent, of manganese and from 14 to 24 per cent, 

 of nickel. These alloys are non-magnetic and possess the highest 

 electric resistance of any known alloys ; they are also the most 

 ductile alloys yet made. The ductility of an alloy containing about 

 14 per cent, of nickel was reduced by cooling from 75 to 25 per 

 cent. ; one containing about 18 per cent, decreased in ductility 

 only from 57 to 42 per cent., whilst a third containing 24 per cent, 

 actually rose in ductility from 60 to 67 per cent. — this being the 

 first alloy met with which increased in ductility on cooling. 



Such results are very remarkable. The magnetic properties of 

 iron are probably not, as was at one time supposed, inherent in the 



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