THE MOLECULAR WEIGHT OF HEMOGLOBIN 



89 



(4) The partial specific volume of the solute (F). 



(5) The density of the solvent (p). 



The rate of centrifugaUsation is in the region of 10,000 revolutions 

 per minute, which is responsible for a force of about 6000 times that 

 of gravity. The critical measurement is of course that of the concentra- 

 tion of the haemoglobin at different portions of the tube. In order 

 to understand how this is carried out the reader must first appreciate 

 the nature of the tube and of the centrifuge. The centrifuge con- 

 sists of a whirling disc of ebonite. In this disc are cut eight circular 

 holes. Pig. 18 shows the arrangement. Four of the holes in the disc 



Fig. 18. Diagrams of Svedberg centrifuge. 



contain what I have so far called "tubes," but what should be called 

 cells because they present flat surfaces when looked at from above 

 and from below. The actual cavity in each cell which holds the 

 haemoglobin solution is only a little over 1 cm. in length. The whole 

 is arranged so that the disc and its contents, with the exception 

 of the haemoglobin solution, is opaque, and thus a camera placed 

 above the cell will photograph the extent to which the solution has 

 sedimented. 



The photographs are taken while the disc is rotating. The 

 experiment lasts six hours. Experiments of this character have been 

 carried out on carboxyhaemoglobin and on methaemoglobin in dilute 

 solutions. 



