89 



Free iron may also be demonstrated by the use of a pure aque- 

 ous solution of hematoxylin (dark-blue color); other metals, how- 

 ever, also unite with hematoxylin (e. g., calcium). 



237. Masked Iron does not give the reaction with pure aqueous 

 hematoxylin [31, 34]. Macallum applies the ammonium sulphide at 

 higher temperature (60 C.) and for several days. 



238. Phosphorus. See Macallums methods [31]. 



239. Potassium. See Macallum's method [33]. 



240. Chlorides. See Macallum's method [32]. Cautions! 



241. Calcium stains strongly with aqueous hematoxylin and 

 may often be so demonstrated. To identify the calcium and dis- 

 tinguish from iron, usual chemical tests may be applied [31, 28]. 



