SILVER AND GOLD 27 



3. Rinse sections in distilled water and counterstain with hema- 

 toxylin. 



4. Dehydrate, clear, and mount in balsam. 



Result. Silver in the tissue is colored reddish-violet. The other 

 metals will produce shades of the same color. 



Monovalent copper may be eliminated from visualization by 

 substituting precipitation reagent II for I, and mercury may be 

 similarly eliminated by employing reagent III. The silver precipitate 

 could be removed from the others by treating the colored sections 

 with 1% potassium bromide. 



GOLD 



Several methods have been used for the localization of gold in 

 tissues and Lison (1936. page 100) has discussed those of Christeller, 

 of Borchardt, and of Okkels. The first depends on treatment with 

 stannous chloride; the second employs silver nitrate followed by 

 nitric acid, and the last merely involves exposure to ultraviolet light 

 to obtain blackening of the gold granules. The more recent methods 

 of Roberts (1935), Okamoto, Akagi, and Mikami (1939), and Elft- 

 man and Elftman ( 1945) follow. The last-named method is probably 

 the best since it avoids the use of ions that might give rise to arti- 

 facts, and effects the bleaching of interfering pigments. 



Roberts Method for Gold 



SPECIAL REAGENTS 



Sliver Nitrate Reagent. Just before using dissolve 2 g. pure silver 

 nitrate in 100 ml. 10% gum arabic soln. in the dark. 



Hydroquinone Reagent. The day before using dissolve 1 g. pure 

 hydroquinone in 100 ml. 10% gum arabic soln. 



5% Citric Acid. 



5% Sodium Hyposulfite. 



PROCEDURE 



1. Fix tissue in Bouin fluid or 20% neutral formalin and wash 

 well with water. 



2. Prepare paraffin or frozen sections. 



3. Place sections for 5-10 min. in a fresh mixture of 2 ml. silver 

 nitrate reagent, 2 ml. hydroquinone reagent, and 1-3 drops of 5% 



