PLATINUM, PALLADIUM, AND URANIUM 29 



of the colored silver precipitate from the sections, if silver was pres- 

 ent, can be carried out by treating with a saturated soln. of potas- 

 sium bromide for 1 hr. or more. If the sections are then washed in 

 distilled water and placed in 1% potassium nitrite for 24 hr. or 

 longer at 36° (or heated in the nitrite soln. for 1 min.) the gold 

 precipitate will dissolve leaving those of platinum or palladium, 

 should either of these be present. 



PLATINUM 



The Okamoto et al. method for silver may be employed unchanged 

 for the detection of platinum in tissues (see page 26). 



PALLADIUM 



The method of Okamoto, Mikami, and Nishida (1939) for the 

 visualization of palladium in sections of tissue follows the Okamoto 

 et al. silver method (p. 26) with 1 difference. Between steps 1 and 

 2 in the procedure, the following is introduced: treat the dry sections 

 with chlorine gas until the black palladium granules are made 

 colorless. 



URANIUM 



Two chemical tests have been presented for the localization of 

 uranium in tissue sections. Both are founded on the precipitation of 

 dark brown uranium ferrocyanide. Schneider ( 1903) was the first 

 to use this technique on the tissues of animals that had been in- 

 jected with uranium salts. Gerard and Cordier (1932) followed the 

 Prussian blue method for iron and reported good results. The latter 

 employed Bouin-Hollande or Carnoy fixatives and their coloring 

 reagent was 2% potassium ferrocyanide containing 2% hydrochlo- 

 ride acid. For details of the test, see the Prussian blue procedure for 

 iron, page 20. 



The fluorescent properties of uranium salts subjected to ultra- 

 violet radiation can be utilized for the detection of these salts in in- 

 cinerated sections of tissue as indicated by Policard and Okkels 

 ( 1930) ; see page 145. 



ft. 



