Inorganic Substances 37 



Quincke's^^ iron sulfide test (A. Mayer, 1850). It is based 

 on the formation of green-black ferrous sulfide by the action 

 of ammonium sulfide. 



Method 



Dilute ammonium sulfide ( colorless or light yellow; darker 

 samples do not work well) with 5-10 volumes of distilled 

 water. Immerse sections for 20-30 minutes. Wash briefly 

 under the tap; counterstain with a red nuclear stain (safra- 

 nine, neutral red, lithium carmine); wash once more, dehy- 

 drate, and mount. Sites of hemosiderin iron show up in a very 

 dense green-black shade. 



This method is incompatible with the use of mercury-con- 

 taining fixatives. Even after treatment with iodine, enough 

 mercury may be left in the tissue to give a blackish precipi- 

 tate with the reagent. Ferrous sulfide is quite sensitive to 

 acids; even dilute hydrochloric acid will remove it in a mat- 

 ter of minutes; this property will differentiate it from the 

 acid-resistant sulfides of other metals ( lead, bismuth, etc. ) . 

 Even an acidic dye solution used for counterstaining, such as 

 alum carmine, may bleach the finest granules. 



It has been asserted that the ferrous sulfide method is more 

 sensitive than the Prussian blue method (the description of 

 which will follow) because it unmasks certain iron com- 

 pounds which do not react with the latter. However, on care- 

 ful comparison of consecutive serial sections stained accord- 

 ing to the two techniques, it becomes clear that the efficiency 

 of the two methods is the same, except for the fact that fer- 

 rous sulfide is quite opaque, while Prussian blue is somewhat 

 transparent. 



The most reliable reagent for the hemosiderin type of iron 

 is an acidified solution of potassium ferrocyanide ( Perls ).^* 

 Ferric ions, released by the action of the acid, are trapped by 



23. Quincke, H.: Arch. f. klin. Med., 25:567, 1880, and Arch. f. exper. 

 Path. u. Pharmakol, 37:183, 1896. 



24. Perls, M.: Virchows Arch. f. path. Anat., 39:42, 1867. 



