CAPILLARY DIVER TECHNIQUE 383 



specific gravity of 1.325 (page 347j ; however, it contains 0.5% 

 sodium taurocholate and has been made 0.1 N vi^ith respect to 

 sodium hydroxide by adding the calculated amount of 7.35 N sodium 

 hydroxide (29.4 g. sodium hydroxide in 100 g. soln.), which also 

 has a specific gravity of 1.325. 



The length of the various columns in the diver is shown in Figure 

 134. In general, the lengths of the various components in the charged 

 diver should fall in the range (given in mm.) : 



Seals of medium {Mi and M2) 0.7 to 1.0 



Air Space (Ln) ca. 0.5 



Solid paraffin seal (P) + paraffin oil seal (POi) 0.7 to 1.0 



Water drop (W) containing respiring cell 0.2 to 0.3 



Air space (L2) 1.5 to 2 times the diameter of the diver capillary 



Oil seal (PO2), between menisci 0.02 to 0.03 



Air space (L3) 2 to 3 



The paraffin oil seals prevent loss of water from W. The solid paraf- 

 fin fixes the positions of the various colimms. The oil seal (POo) is 

 made short so that the carbon dioxide formed by the respiration can 

 diffuse from W to il/o becoming absorbed due to the alkalinity of 

 the latter. 



Preparation of the Diver. The divers were first made in the 

 Carlsberg Laboratory from Thuringer glass, different samples of 

 which proved to be rather variable in property. Later Jena glass 

 was used and it was found that the glass drawn in an ordinary 

 flame (600-700°) was too brittle but that glass drawn at 1200- 

 1400° was suitable. The final test of the suitability of a glass is the 

 preparation and testing of control divers made from it. No informa- 

 tion is available at the moment concerning the properties of 

 American-made glass for divers. 



The tubing from which the diver capillaries are drawn should be 

 thin-walled (outer diameter/inner diameter = about 1.25). Only 

 capillaries should be selected which have constant outer diameters, 

 as tested by a gauge such as the Zeiss cover slip gauge. For those 

 selected, the ratio of the weight of the glass to the weight of mercury 

 required to completely fill each tube is determined. With Jena glass 

 (sp.gr. ca. 2.40) Zeuthen reported that the following requirement 

 must be met for the weight of the mercury and glass: 9.2 > 

 mercury/ glass > 7.7, and with Thuringer glass: 10.0 > mercury/ 

 glass > 8.3. Variations of the inner diameter must be checked by 

 moving a 5—10 mm. column of mercury along the capillary and 



