284 DAVID R. BRIGGS 



The supporting frame used for mounting the Abramson cell on the micro- 

 scopic stage is shown along with the cell itself in Figure 1. A simple frame 

 for supporting the second cell can be made from two 1" X 7" X H" brass 

 strips arranged parallel to the length of the cell and spaced and held 13^2" 

 apart by Bakelite blocks (1" X H" X 33^"). The latter are attached to the 

 brass strips near their ends with screws and in such a position that these 

 blocks can be shaped to fit, as saddles, the bends in the glass tubing of the 

 cell (F, Fig. 2) on either side of the flat portion. These saddles are shaped 

 to such a height that the flat cell portion is held in a horizontal position at the 

 level of the bottom of the brass strips and the cell is anchored with thin metal 

 straps to the support at the points of contact with the saddles. The whole 

 assembly will set flat on the microscope stage with the flat part of the cell 

 flush with the stage. Pins, put through one of the brass strips in such posi- 

 tions that they will fit into the holes in the microscope stage (usually occupied 

 by sHde clamps), will aid in keeping the cell and mount always in the same 

 position on the stage and prevent accidental shifting from position after 

 the proper depth in the cell has been attained for correct electrophoresis 

 measurements. {Note:\" = 1 inch = 2.54 cm.) 



The Abramson cell as described has the advantage that somewhat 

 higher degrees of magnification can be employed than is possible with 

 the other cell because of the greater optical distance from the top of 

 the upper glass plate to the bottom of the cell lumen in the latter. 

 Each cell has some advantages over the other in ease of manipulation. 

 Each will, in most circumstances, prove itself to be free of fnany tech- 

 nical disadvantages associated with most other cells described in the 

 literature. 



4. Measurements and Calculations 



The mechanics of measurement of the electrophoretic mobility of 

 particles by this method involves the observation of the motion of the 

 particle at the proper depth in the cell, the measurement of the time 

 required (using a stopwatch) for the particle to move a chosen dis- 

 tance, as indicated on a calibrated eyepiece micrometer, and a deter- 

 mination of the field strength acting upon the particle. The latter 

 is best obtained from a measurement of the specific conductivity (X) 

 of the solution containing the particles, a measurement of the cross- 

 sectional area (A) of the fiat cell at the point of observation and a 

 measurement of the current (7) passing through the cell at the time 

 of measurement. The current is usually measured with a micro- or 

 milliammeter placed in series with the electrophoresis cell in the circuit 



