196 Hydrolysis of the Soluble Protein of Swede Tuniips 



A determination of the amino nitrogen present was now made by 

 means of Van Slyke's apparatus. 10 c.c. of the solution were evaporated 

 to dryness and the residue dissolved in water. 



This gave 14-6 c.c. of N at 16-8° C. and 764 mm. 



= 0-01659 grm. N. 



Half of this comes from the amino groups 



= 0-00829 grm. N in amino form. ' 



The total weight of amino nitrogen is 0-415 grm. 

 The prohne nitrogen is 1-876 — 0-415 grm. 



= 1-461 grms. 



Proline contains 12-17 per cent, of nitrogen. 



1*461 grms. nitrogen = 12-02 grms. of proline. 



This is equal to a percentage of 4-17 of proline in the protein. 



Phenylalanine. 



The esters of Fraction 3 were diluted with three times their volume 

 of water and extracted three times with ether. The ethereal extract 

 was washed three times with water^ the washings being poured back 

 to the aqueous solution. The ether was distilled off and the phenyl- 

 alanine ester poured out into an evaporating basin. This was placed 

 on a water bath and concentrated hydrochloric acid added. (A serious 

 loss of ester took place here owing to some violent spurting caused by 

 adding the acid too suddenly.) The liquid was now evaporated down 

 to dryness^ a nearly white residue of phenylalanine hydrochloride being 

 left. Fraction 3 of the second distillation was treated similarly for 

 phenylalanine ester, but one extraction with ether was considered 

 sufficient. The saponification with hydrochloric acid was conducted 

 in a flask so as to avoid any risk of loss. The two yields were united. 



The weight of the hydrochlorides after standing over sulphuric acid 

 and caustic soda in a vacuum desiccator was 40-7 grms. (The ether 

 extract from the distillation residue (first distillation) was saponified 

 with hydrochloric acid, and gave a black residue which was not treated 

 further.) 



The crude hydrochlorides were recrystallised from concentrated 

 hydrochloric acid. The first crop of crystals obtained weighing 9-4 grms. 

 was pure phenylalanine hydrochloride containing 7-02 per cent, nitrogen 

 (theoretical 6-94 per cent.). A second fraction weighing 3-9 grms. 

 contained too high a percentage of nitrogen and had to be recrystaUised. 



