The Coagulation of Protein by Sunlight. 



237 



re fluxing absolute alcohol. After drying nitration was carried out as 

 recommended by Blitz and von Vegesack (8). The washed and dried cellulose 

 nitrate was dissolved in anhydrous alcohol-ether mixture (3 : 1) to form a 

 3 per cent, solution. This was applied by the Sorensen technique to a test- 

 tube of f- inch diameter. Six or seven applications were given with a drying 

 interval of 10 minutes between applications, and a fiual drying period of 

 5 to 7 hours before soaking in water. 



The Dialysing Apparatus. — The general arrangement of the various parts 

 was essentially that of Sorensen, although a smaller, slightly modified cell was 

 used. The latter had a capacity of 250 c.c, while the membrane sack held 

 40 c.c. By the insertion of an extra limb in the upper part of the cell, very 

 close to the neck, it was possible to remove the dialysate completely from the 

 lower opening by the admission of air through the extra limb before intro- 

 ducing fresh water. This, I have found, allows of more rapid removal of the 

 electrolytes present with a minimal use of distilled water, and also of the 

 ready withdrawal of samples of the dialysate for analysis. The dialysis was 

 carried out at room temperature, i.e., 10-15° C, and the negative pressure 

 found necessary varied from 5 to 20 cm. of mercury. The dialysate was 

 replaced with distilled water twice daily. The only satisfactory way of 

 determining whether the dialysing apparatus was in proper working order 

 was to carry out a series of analyses on the successive dialysates withdrawn. 

 Table I shows how efficiently the cell was functioning when it contained a 

 solution of ovalbumin of 1T09 per cent, strength. After the fifth day no 

 further positive test for the predominant impurity, (NH^SC^, could be 

 obtained. The solution contained l - 440 grm. (NH^SO^ at the start and the 

 first two days' dialysis served to remove more than 98 per cent, of the con- 

 taminating sulphate. 



Table I. — Dialysis of Ovalbumin Solution, 1T09 per cent. 









(NH 4 ) 2 S0 4 content. 



Day. 



S0 4 test. 



Protein test. 













Grm. 



Per cent, total. 



1 



+ + + + 





1 -2675 



88 -02 



2 



+ + 





-1473 



10 -23 



3 



+ 





-0187 



1 -30 



4 



+ 





-0023 



0-16 



5 







-0007 



0-05 





1 -4365 



99-76 



