80 



CENTRIFUGES 



1600 



1200 



o 



q: 800 



400 



- I EC sw. buck, head 



Clinical electrifuge 55B, ser. no.i20 



4-15 ml polyethylene tubes • 



of water 



RCF, bottom of tube 

 II Jon 1961 



/ 



/ 



/• 





/ 



J \ L 



1 



J \ \ I 



3 4 5 6 7 

 Dial setting 



8 9 10 



Fig, 7-1. Typical calibration curve for a laboratory centri- 

 fuge; student data. 



across the tube and then slide down the wall against less resistance. The 

 effect on the settHng of particles is the same as increasing the relative 

 centrifugal force. The initial settling is faster and more thorough. The 

 final result of a long centrifugation, of course, must be the same as in 

 the horizontal tube. The chief advantage is the reduction in time re- 

 quired for adequate separation. The apparent RCF can be calculated 

 from a complex equation, but usually it is easier to take the manufac- 

 turer's word for it. 



Sedimentation 



The rate at which particles will settle or sediment in a centrifugal 

 field can be calculated. The information thus gained can be extremely 

 useful in two different ways. The length of time required to separate 

 a given-sized particle from its suspending liquid can be computed, per- 

 haps saving a good deal of trial-and-error work. In other cases, measure- 

 ment of the rate of sedimentation provides information about the size, 

 shape, density, or molecular weights of the particles. The molecular 

 weights of many proteins, for example, have been determined in the 

 analytical centrifuge. 



