590 



SCIENCE PROGRESS 



perature of the latter corresponding to the fusion-point of 

 the organic compound. (See figs, ia and ib.) 



As the result of these determinations, it appears that the 

 diamagnetic property is complex and very similar to the 

 magnetic property possessed by ferro-magnetic substances 

 above and below their critical temperatures. 



The essential difference between the two types of phenomena 



/-1 l/>V>eotxS oy Supercooled Itcju'td jg 



* ■' * ■ 



-<*>' 



Crystal/me. 



(tat 



-*-/* 



to xo *3o 4.0 5"o Co 7° 

 Je>nper-a.tu.re (°C)-> 



Fig. ia. 



Substance, benzophenone. abc shows susceptibility on cooling from liquid to vitreous mass. 

 Crystallisation started at c and was complete at d. de, susceptibility curve for crystals on 

 warming to room temperature. fg and Hi, two independent curves, the latter showing the 

 rise of susceptibility at the melting-point b. 



M«3<}7ie rising Force, OS' , 



. vw? 



A2L.A' 



ig I 1— . 1- r -rt 1 1 ■ ' — r ' ' 



,K 35*0 4jOO k&> too SSO 600 (,S0 7°0 7*0 900 



^Te-m^r-dfure (°C) 



Fig. ib. 



Substance, nickel steel (4*7 per cent., Ni). a'b'c' shows very small induction on cooling from 

 above 8oo° C., through magnetic critical temperature b', to about 6oo° C. Molecular change 

 started at c', and was complete at d'. d'e', induction curve on heating to critical temperature, 

 e'b' showing the fall of induction at the magnetic change-point. 



lies in the nature of magnetic moment associated with an indi- 

 vidual molecule, i.e. with the arrangement of the electron 

 orbits on Langevin's theory. If the substance is diamagnetic, 

 the molecule, taken as a whole, has a zero resultant moment ; 

 if the substance is paramagnetic or ferro-magnetic, the mole- 

 cule has a definite resultant magnetic moment, and conse- 

 quently the magnetic property varies in the latter case with 

 temperature. 



