GRAVITY AND CENTRIFUGAL FORCE 



331 



Bredig^ was the first to show that centrifugal force does 

 produce changes in pressure. By centrifuging gases in a tube 

 containing several chambers joined by capillary tubes, he 

 showed that the pressure in the outermost chamber was greatest. 



Lobry de Bruyn and van Calcar^ produced the same sort of 

 effect in solutions, showing that solute is driven away from the 

 axis of rotation. They were able by centrifuging to crystallize 

 out a third of the solute from a saturated solution of sodium 



TABLE II 

 Sedimentation Equilibrium in a Gold Sol 



sulfate. It was not possible however to get a quantitative 

 confirmation of the thermodynamic equation. 



A series of brilliant experiments of this sort has recently 

 been performed by The Svedberg and his associates in connec- 

 tion with the development of the ultra-centrifuge. While the 

 major part of the work has been concerned with diffusion rather 

 than equilibrium, certain aspects illustrate in a beautiful manner 

 the relations which we have been considering. 



In the first place it is very important to know the relative 

 distribution of the particles in equilibrium even if the study is 

 mainly concerned with diffusion which will not be continued 



