Light scattered by Spherical Metal Particles. 



477 



The curve I. indicates the kind of suspension that would be 

 obtained by centrifuging once for 30 mins. and once for 

 20 mins. The most numerous particles are those having 

 diameters of about 100 //-/z. If the suspension were centri- 

 six times for 30 mins. and then once for 20 mins., the 



fuged 



Fisr. 4. 



t>u 





i i — r i 







'a 









■^40 

 .0 







~ 









iJ 









u 









!l 





i/~N 





'•'-30 





/ \ 



_ 



O 





/ A 





O 





/ E A 





•1 





/ /'N / \ 





§20 



__ 



/ / \/ \ 



mm , 



If 





/ in/ V \ 





1 





/ / h \ 





IC 





/ / / \ \ 





o 4-o so 120 ieo 200 



Diameter of particles in fj/j. 

 Results of centrifuging. 



distribution shown by the curve II. would be obtained. The 

 maximum is now for those particles of diameter about 

 125/z/z, and is much sharper. The result of centrifuging 

 the suspension six times for 30 mins. and six times for 

 20 mins. is shown by the curve III., where the ordinates have 

 been multiplied by 100. The most numerous particles now 

 have diameters less than 100 fi/ju, and the maximum is not so 

 sharp. Moreover, the suspension has been much impoverished, 

 there being less than 0*25 per cent, of the original particles 

 left even at the maximum. 



It is therefore important to centrifuge the suspension a 

 large number of times for the longer period in order to free 

 it effectively from small particles, and then to centrifuge it 

 just a few times for the shorter period in order to remove 

 large particles. 



The suspensions used for the observations on the polariza- 

 tion of the scattered light were centrifuged from five to a 

 dozen times for the longer period. 



