286 DAVID R. BRIGGS 



have been made), which the experimenter is able to obtain, a freshly 

 made dilute suspension of human erythrocytes in 0.067 M phosphate 

 buffer of pH 7.4 can be observed in the cell. At 25°C. the observed 

 mobility for these cells should agree very closely with the value 1.3 X 

 10 ~^ cm. 2 per volt second. 



Since the microelectrophoresis cells are not readily constructed in 

 a form susceptible to thermostatic control, it is always necessary to 

 keep the wattage dissipation within the fiat part of the cell at such a 

 low value that convection currents are not generated. This is not 

 difficult to attain when the electrical conductivity of the solution is 

 very low but, as the ionic strength approaches 0.1, disturbances from 

 this source will be encountered and measurement may become impos- 

 sible. Heating of the contents of the cell from the microscope lamp 

 must be avoided for the same reasons. Such heating can usually be 

 avoided by placing a cell filled with water in front of the lamp so that 

 heat rays will be absorbed before reaching the microscope system. 



While a mixture of visible particles of varying mobilities can be 

 recognized and, perhaps, statistically analyzed as to mobility distri- 

 bution, this method cannot give any information as to the number or 

 relative amounts of components in a nonmicroscopically visible mix- 

 ture of disperse components (such as blood serum). It is in this re- 

 gard, particularly, that the microscopic method loses preference to 

 the moving-boundary method. 



5. Some Recent Accomplishments 



The microelectrophoresis method of measuring the mobility prop- 

 erties of microscopically visible particles has been applied to a wide 

 variety of substances ranging from inorganic suspensions and emul- 

 sions to living cellular materials. Only a few examples need be re- 

 ferred to in order to illustrate the diversity of systems upon which such 

 studies can yield important information. Red blood cells of humans 

 are found to be remarkably constant in mobility (independent of sex 

 or race) and to present surfaces not affected by other soluble proteins 

 in the blood {14)- Soaps are shown to impart mobilities (and surface 

 charges) to dirt particles that are proportional to the detergent power 

 of the soap (15). Latex particles are shown to be covered by proteins 

 in some species and by Hpides in others (16). Isoelectric points of 

 soluble proteins and their change in charge with pH can be studied 

 by this method (17). The nature of the surface membranes of micro- 



