102 SCIENCE~ PROGRESS 
phenylalanine ester fraction is hydrolysed by evaporating with 
concentrated hydrochloric acid, when the hydrochloride is 
obtained. 
The ester method can be combined with the methods for 
obtaining tyrosine and the diamino acids. The protein is 
therefore hydrolysed by sulphuric acid, the tyrosine separated 
by crystallisation, and the diamino acids precipitated by 
phosphotungstic acid. The filtrate, after removal of phospho- 
tungstic acid, is treated as above described for the separation 
of the monoamino acids. 
From the above it is obvious that a mixture of amino acids 
is still present ; their final separation, as they result from the 
various fractions, has still to be carried out. The methods 
employed are best described by taking a particular protein as 
illustration, ¢.¢. crystallised oxyhamoglobin, which was hydro- 
lysed by Abderhalden by the above method, and gave five 
fractions of esters from which the appended weights of amino 
acids were isolated: 
Temperature. Pressuie. Wojent of Weights of Amino Acids. 
Fraction I. To 40° (vapour) Iomm.| 64°2 gm.| 14°2 gm. alanine. 
4 II. 40—60 ss 10 4 |107'0 ,, | 26:0 gm. alanine, oz 
leucine, I gm. protein. 
hn SAAR 100° (water bath)| 02, | 4034 ,, | 247°5 gm. leucine, 21.5 
| gm. protein, 
» LV. 100—130° (oil bath) | 0'2,, 81°7_ ,,_ | 19°5 gm. phenylalanine, 
II°3 gm. aspartic acid, 
4'2 gm. glutamic acid, 
I'7 gm. serine. 
3 V. 130—160° 53 O25, 93°0 ,, | 21°71 gm. phenylalanine, 
| 4't gm. glutamic acid, 
I1‘O gm. aspartic acid, 
I'O gm. serine. 
Oxyhzemoglobin contains no glycine, so that its separation 
was not necessary, but as ester hydrochloride four-fifths can 
be isolated when the protein contains 20 per cent. in its 
molecule; the remainder is distilled as ester, and passes into 
the first fraction with alanine ester, from which it is separated 
by conversion into its ester hydrochloride. The alanine is then 
separated by crystallisation, after removal of the hydrochloric 
acid, and is characterised by conversion into its benzoyl deriva- 
tive. Owing to partial racemisation occurring during the 
