BY DR. LAUDER BRUNTON. 441 



water, dissolve them in ammonia, and allow the solution to 

 evaporate, until the tyrosine crystallizes. 



It forms fine colorless microscopic needles, with a silky 

 lustre, and without taste or smell. 



Or digest fibrin with pancreas, see Itl. 



Characters. Let a drop of a solution of tyrosine in hot 

 water evaporate on an object-glass, and examine it under the 

 microscope. Long needle-like crystals will be seen which are 

 often united in single tufts, or in radiating groups of tufts. 



Solubility. I. Cold water dissolves it with difficulty. 2. 

 Boiling water dissolves it easily. Almost all the tyrosine 

 crystallizes out on cooling. It is insoluble in, 3. Absolute 

 alcohol, 4. Ether. It is easy soluble in, 5. Ammonia, 6. Liq- 

 uor potassne, 7. Concentrated solution of potassium or sodium 

 carbonate, 8. Alcoholic solution of caustic potash, 9. Concen- 

 trated hydrochloric or sulphuric acid, and, 10. Dilute mineral 

 acid. 11. Acetic acid dissolves it with difficulty. 12. Nitric 

 acid dissolves it. Let the solution stand a while. A yellow 

 crystalline powder of nitro-tyrosine will separate. Pour oil' the 

 liquid and add liquor potasste 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 boil- 

 ing water or ammonia, and let it crystallize out. 



41. Tests for Tyrosine. It is distinguished b}^ 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 lew 

 drops of mercuric nitrate solution. Boil it for a little while. 

 If tyrosine is present, the liquid will become rose-colored, and 

 will afterwards deposit a red precipitate. 



2. Piria's Test. Pour a few drops of concentrated sulphu- 

 ric 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 carbonate 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 ty'rosine, 

 with a drop or tw/ of nitric acid, on a piece of platinum foil, 

 and evaporate ge/tly. If it is really tyrosine, it will quickly 

 become of a bri<pt yellow color, and will leave a deep yellow 

 shining residue. Add ;i l\ i w drops of liquor potassae to it, and 

 it will form a yellowish-red solution. Evaporate, and it will 

 leave a brown residue. 



