272 PHYSIOLOGICAL CHEMISTRY 



(c) Guaiac Test. Make this test on the aqueous extract according to the 

 directions given on page 265. The guaiac solution may also be applied directly 

 to the stain without previous extraction in the following manner : Moisten the 

 stain with water, and after allowing it to stand several minutes, add an alcoholic 

 solution of guaiac (strength about i : 60) and a little hydrogen peroxide or old 

 turpentine. The customary blue color will be observed in the presence of blood. 



(d) Benzidine Reaction. Make this test according to directions given on 

 page 267. 



(e) Acid Hematin. If the stain fails to dissolve in water extract with acid 

 alcohol and examine the spectrum for absorption bands of acid hematin (see 

 Absorption Spectra, Plate II). 



1 Hankin: Brit. Med. Jour., p. 1261, 1906. 

 Sutherland and Mitra: Biochemical Journal, 8, 128, 1914. 



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