432 AMOUNT OF A BIOLOGICAL SAMPLE 



ured and the dye is emptied into a known volume of water. The con- 

 centration of dye is determined colorimetrically in a microcuvette 

 and from it the volume of dye that was in the capillary is obtained. 

 This volume is subtracted from the volume of the dye plus object to 

 give the volume of the object. In the range 0.01 to 0.1 /A., objects 

 were measured with a probable error of about ±5% in single meas- 

 urements. 



Holler Method for Measurement of Volume 



SPECIAL APPARATUS 



Capillaries. Choose capillaries which have a cylindrical constant 

 bore for at least 10 mm. from one end and which have an inside 

 diameter suitable for the object to be measured (0.3 mm. for Chaos 

 chaos). Draw out the uncalibrated end of the capillary to a fine 

 tip and mount as a braking pipette (Fig. 123). Fire-polish the wide 

 end of the capillary but do not constrict the mouth. Place a mark 

 about 5 mm. from the mouth; a thread of DeKhotinsky cement 

 may be used. Dry the capillary with alcohol and air between 

 measurements. 



Moist Chamber. To prevent evaporation of the small volumes of 

 solution used, manipulations must be carried out in a moist 

 chamber (page 181). 



SPECIAL REAGENTS 



Dye Solution. Dialyze a soln. of acid violet (sodium tetraethyl-di- 

 p-sulfobenzyl-p^p'-diaminofuchsonimonium) in glass-distilled 

 water, and bring to a concentration of 1 % . Add sodium taurocho- 

 late to 0.01% and filter through a fiber-free material. Store in a 

 refrigerator, and about once every two weeks refilter to remove 

 dust and dye crystals which may have formed. 



PROCEDURE 



1. Transfer the object into a moist chamber by means of a brak- 

 ing pipette (page 359) . 



2. Place the object in a flat drop of the dye soln. contained in a 

 dish. 



3. Wash the object with the dye soln. by drawing it up into the 

 pipette a few times. 



