Bauhaus-Universität Weimar

Handbook for the Physiological Laboratory. Text
Burdon-Sanderson, John Scott E. Klein Michael Foster T. Lauder Brunton
11. Acetic acid dissolves it with difficulty. 12. Nitric acid 
dissolves it. Let the solution stand a while. A yellow crystal¬ 
line powder of nitro-tyrosine will separate. Pour off the liquid 
and add liquor potassæ to the powder. It will dissolve and form 
a red solution. 
40. Detection of Tyrosine.—Treat the organ exactly as 
described in the process for the detection of leucine. The dried 
residue, after it has been extracted with boiling alcohol to remove 
the leucine, consists of tyrosine. Dissolve it in boiling water or 
ammonia, and let it crystallize out. 
41. Tests for Tyrosine—It is distinguished by its micro¬ 
scopic appearance, and by the following reactions. 
1. Hoffmann’s Test.—Put a little of the solution supposed to 
contain tyrosine in a test-tube ; add some water, and a few drops 
of mercuric nitrate solution. Boil it for a little while. If 
tyrosine is present, the liquid will become rose-coloured, and will 
afterwards deposit a red precipitate. 
2. Piria’s Test.—Pour a few drops of concentrated sulphuric 
acid on two or three pieces of tyrosine the size of a pin’s head 
in a watch-glass. Gently warm it for a little. Let the solution 
cool. Mix it with a little water, and add chalk or barium car¬ 
bonate till all effervescence has ceased. Filter. Evaporate, if 
necessary, to a small bulk at a gentle heat, and add a few drops 
of a neutral solution of ferric chloride. The fluid will become, of 
a beautiful violet. 
3. Scherer’s Test.—Put a little of the supposed tyrosine, with 
a drop or two of nitric acid, on a piece of platinum foil, and 
evaporate gently. If it is really tyrosine, it will quickly become 
of a bright yellow colour, and will leave a deep yellow shining i 
residue. Add a few drops of liquor potassæ to it, and it will j 
form a yellowish-red solution. Evaporate, and it will leave a 1 
brown residue.


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