22 MICROSCOPIC TECHNIQUES 



3. To the sections washed with neutral distilled water add a 

 few drops of the hydroxyquinoline reagent, and after 5-15 min. drain 

 off the liquid. 



4. Add 1 drop of 25% ammonium hydroxide to form precipitate. 



5. Wash in neutral distilled water. No large crystals should re- 

 main. 



6. A lithium carmine nuclear stain may be applied. 



7. Dehydrate with terpinol and mount in petrolatum, or examine 

 directly in neutral water. 



Result. Iron appears as a greenish-black, calcium as a pale 

 yellow, magnesium as a straw-yellow, aluminum as a yellowish- 

 green, zinc and manganese as a yellow, and copper as a greenish- 

 yellow precipitate. 



NICKEL 



A method has been devised by Cretin and Pouyanne ( 1933) for 

 the histological demonstration of nickel in bone material by pre- 

 cipitation of nickel ammonium phosphate. 



Cretin and Pouyanne Method for Nickel 



SPECIAL REAGENTS 



Fixative. Add 30 ml. formalin and 5 drops ammonium hydrosulfide 



to 100 ml. physiological saline soln. 

 10% Ammonium Phosphate. 



PROCEDURE 



1. Fix tissue in the special fixative soln. 



2. Transfer to the ammonium phosphate soln. in order to pre- 

 cipitate the insoluble nickel ammonium phosphate. 



3. Decalcify and section. 



4. Stain the nickel compound with alcoholic hematoxylin. 



5. Wash, dehydrate, clear, and mount. 



Result. Nickel will appear as a lilac deposit, or blue if present 

 in abundance. 



LEAD AND COPPER 



For many years the chromate method has been used for the micro- 

 chemical detection of lead in tissues ( Frankenberger, 1921; Cretin, 



