VITAMIN A AND CAROTENE 



251 



slightly flattening the end for a distance of 10-15 mm., inserting 

 the nail in a small high-speed hand drill with the end projecting 

 about 20 mm., and mounting the drill vertically with the nail up. 

 The liquids are mixed by touching the side of the tube near the 

 bottom to the rapidly rotating nail. If this apparatus is not avail- 

 able mixing may be effected by adding a 1 cm. length of stainless 

 steel wire (0.041 in. diameter — may be obtained from Newark 

 Wire Cloth Co.) and shaking. For the extraction with the kero- 

 sene-xylol, the open ends of the tubes are sealed in a flame and 

 then shaken vigorously. Care is taken to prevent contamination 

 of the tops of the tubes by serum which would be charred when 

 the tubes are sealed. 



Fig. 81. Arrangement for ultra- 

 violet irradiation. Mercury lamp (A) 

 is held vertically in a clamp, base up, 

 with the other end extending 3 or 4 

 cm. into a hole 8 cm. in diameter, 

 B-B, in a large block of wood, C, 

 which serves as a base. Semicircular 

 racks {D, D') are provided for hold- 

 ing the glass tubes in a circle equi- 

 distant from the lamp (6 cm. from the 

 center of the lamp). These racks may 

 be made from pieces of quarter inch 

 plywood held about 2 cm. apart, with 

 the upper piece drilled to hold the 

 tubes. Twenty or thirty holes may be 

 drilled in each rack along a semicir- 

 cular line. From Bessey et al. (1946) 



B 



SPECIAL REAGENTS 



1 N Potassium Hydroxide in 90% Alcohol. Add 1 vol. 11 A^ potas- 

 sium hydroxide to 10 vol. absolute alcohol. Prepare on the day it 

 is used. If the color develops rapidly or if the reagent gives a blank, 

 reflux the alcohol with potassium hydroxide and distill. 



