18 Mr. E. G. Young. On the Optical Rotatory 



to dryness without obtaining any visible residue. Table II gives the results 

 of a series of crystallisations : — 



Table II. 



Crystallisation. 



Second. 



Third. 



Fourth. 



Fifth. 



Sixth. 



Average. 



Concentration (per cent.) 



Ph 



[«]» 



We 



7-31 

 5 3 



-8-87° 

 -10 -80 

 -30 "34 

 -36 -93 



5-43 

 4-9 



-6-70° 

 -8-16 

 -30 -82 

 -37*36 



11 -17 



4-9 

 -13 -80° 

 -16 -73 

 -30-87 

 -37 -74 



9 25 



5 -1 

 -11 -29° 

 -13 -77 

 -30 61 

 -37 34 



11 -09 

 4-9 

 -13 '72° 

 -16-73 

 -30-89 

 -37 -63 



-30 '81° 

 -37 53 



The values obtained for the specific rotation of successive recrystallisations 

 is thus in very good agreement with that observed by Hopkins previously 

 with similar material. 



On account of the difficulty of washing free from sulphate encountered in 

 the Devoto method, I have considered it of interest to compare this 

 procedure with the simpler one of coagulating the sample for analysis in a 

 buffer mixture at the isoelectric point. The most convenient buffer mixture 

 for this purpose is a solution of acetic acid and sodium acetate in equal 

 molecular proportions. Thus, 5 c.c. of a 1ST/1 CH3COOH solution were 

 mixed with 5 c.c. of a N/1 CHsCOONa solution, and the whole diluted 

 to 50 c.c. This solution has a Ph of 4-74. To this mixture was added the 

 volume of albumin solution, containing about half a gramme of protein 

 (5 to 10 c.c). The containing vessel was then heated for half an hour on a 

 boiling water bath, to coagulate the albumin completely. It was then 

 allowed to cool, filtered off on to hardened filter paper, and washed until 

 free from sulphate. The washing period is much briefer than when 

 {NH 4 ) 2 S0 4 is used as coagulating medium. But, even with this procedure, 

 sulphate ions are very slowly removed after the first day's washing at the 

 rate of about 1 mgrm. per 100 c.c. of filtrate. 



Table III represents the specific rotatory power observed in a series of 

 crystallisations by the use of both methods of coagulation simultaneously 

 carried out, and it also shows a beautiful agreement between the determina- 

 tions of the albumin concentration by the two methods used. The specific 

 rotations obtaiued are particularly interesting, in that they are constant in 

 magnitude after the second crystallisation, yet slightly lower than the series 

 reported in Table II. This suggests two possibilities. There might be slight 

 molecular differences in the albumin of two different lots of eggs hitherto 

 undetected by our crude methods of analysis, or, what is much more probable, 

 the crystals obtained in the first crystallisation might be a slightly different 



