28 MICROSCOPIC TECHNIQUES 



citric acid. Shake the mixture for 30 sec. immediately after prepar- 

 ing it. 



4. Transfer sections rapidly to a 5% sodium hyposulfite soln. and 

 after a few min. wash thoroughly in water. 



5. Dehydrate, clear, and mount. 



Result. Granules of gold appear black due to a surface deposit 

 of silver. 



Elftman and Elftman Method for Gold 



SPECIAL REAGENTS 



3 % Hydrogen Peroxide. 



PROCEDURE 



1. Fix tissue in neutral formalin, prepare paraffin sections, mount 

 with the aid of egg albumin, and then expose to formaldehyde vapor 

 for 1 hr. to increase the affixation. 



2. After removing the paraffin and running down to water, place 

 in 3% hydrogen peroxide at 37° for at least 24 hr.; in most cases 3 

 days or longer gives the best results. 



3. Do not stain the sections since staining may mask the gold 

 deposit. If staining is required, however, the interference is only 

 slight with light green SF (yellowish) or hematoxylin, and eosin 

 can be used when the gold is present as a sufficiently dense deposit. 



4. Wash the sections in distilled water and dehydrate in the 

 usual manner. 



5. Mount the sections in damar. 



Result. Gold is made apparent by its presence in colloidal form. 

 The color of the deposit depends on the particle size, and accordingly 

 shades from rose to purple to blue and black are obtained. Usually 

 rose predominates. 



Okamoto et al. Method for Gold 



The procedure is the same as that in the Okamoto et al. method 

 for silver using precipitation reagent II (page 26). The gold ap- 

 pears as a reddish-violet or brownish-red precipitate. The removal 



