50 



Scientific Proceedings (117). 



water or ammonia solutions, they readily form the sheaf-like 

 bundles so characteristic of tyrosin. 



They are soluble in boiling water, N/10 ammonia, and dilute 

 mineral acids, slightly soluble in dilute acetic acid and relatively 

 insoluble in cold water, cold and hot absolute alcohol, ether, 

 toluene, acetone, benzine, carbon disulphide, glycerine and 

 chloroform. They are not decomposed in aqueous solution by 

 heating in the Arnold sterilizer at ioo° C. or in the autoclave at 

 15 lbs. pressure for 1 hour. 



They give Pirie's, Hoffmann's and Denige's tests. 1 

 The senior author is now engaged in perfecting the method of 

 extraction and in studying the crystal formation of other an- 

 aerobes. 



23 (1770) 



A method for the preparation of cystin. 



By CARL L. A. SCHMIDT. 



[From the Department of Biochemistry and Pharmacology of the 

 University of California, Berkeley, California.} 



A number of years ago Folin 2 described an improved method 

 for the preparation of cystin which has come into general use. It 

 is based on the fact that the solubility of cystin is a minimum 

 in solutions possessing an acidity between P H 4-5. To obtain 

 the optimum acidity for the precipitation of cystin, the HC1 used 

 to hydrolyze the protein is neutralized by the addition of sodium 

 acetate. Although good yields of the amino acid are obtained 

 by this method it nevertheless is not economical for the produc- 

 tion of cystin in quantity since large amounts of relatively ex- 

 pensive materials are required. Neutralization of HC1 with 

 sodium acetate results in the simultaneous precipitation of humin 

 which later necessitates the repeated use of large quantities of 

 charcoal to effect its removal. 



In the method described below the HC1 is in large part re- 

 covered by vacuum distillation. Use is then made of commercial 

 finishing lime to neutralize the remaining HC1, to precipitate 



1 Hammerstein-Mandel, "A Text-book of Physiological Chemistry," J. Wiley & 

 Sons, N. Y., 1912, p. 150. 



'Folin, O., J. Biol. Chem., 1910, viii, 9-10. 



