CAPILLARY DIVER TECHNIQUE 385 



the water cylinder and blow out the water from the pipette while 

 retaining the diver in the pipette. 



4. In a similar fashion, flush the diver with alcohol, toluol, 

 alcohol, and glass-distilled water in the order given. 



5. Transfer the diver into the tube in which it is to be stored, 

 draw off excess water, and dry in an oven at 110-120°. 



6. Never touch the cleaned diver with the fingers. 



(2) THE FLOTATION VESSEL 



The flotation vessel (Fig. 134) has been so designed that the diver 

 floats in medium enclosed between two air spaces, and the distance 

 between the upper and lower surfaces of the medium is such that 

 the ends of the diver are only about 0.5 mm. from the nearest air 

 space. With this design it has been found that the seals (Mi and Mo) 

 are effective in minimizing the exchange of air between the gas phase 

 of the diver and the medium, for the reasons discussed by Zeuthen 

 (1943, page 483). 



(3) PIPETTES 



Braking Pipette. The form of braking pipette required for 

 filling the capillary diver is shown in A, Figure 135. The capillary 

 (I) has an outer diameter of about 0.5 mm., and an inner diameter 

 a good deal less than 0.1-0.2 mm., and a length of about 3 cm. One 

 end of it is drawn out in a micro flame to an exceedingly fine bore, 

 which allows water to rise in the capillary at a rate of about 0.5 cm. 

 per sec. when the wide end is dipped into water to test it. The tube 

 (II), which is 1.5 mm. wide, holds I by means of a bit of DeKhotin- 

 sky cement. A thin-walled rubber tube is connected to II. A block of 

 soft transparent crude rubber (III) (a piece of red rubber labora- 

 tory tubing may be used) about 2X3X5 mm. is cut from a larger 

 piece after the rubber has been pierced with a needle and attached 

 to the wide end of I as shown. At the end away from I, the block is 

 cut at a slant to aid in finding the hole under the microscope. The 

 capillary diver is fitted into this hole using a binocular microscope 

 with good lighting to lessen the danger of breaking the diver during 

 the operation. The procedure to be used is as follows: 



1. Pick up the diver by means of two watchmaker's forceps* 

 which have their points covered with cork. 



2. Push the diver into the rubber block (III) until it almost 

 touches the glass of I. 



