Inorganic Substances 47 



Active chlorine ( CI2 ) can be demonstrated with the meth- 

 od of Ferguson and Silver. ^^ 



Method 



Fix small tissue fragments by dipping them in boiling for- 

 malin for a few seconds. Cut frozen sections 25 ^ thick. Im- 

 merse sections in the following reagent for 15-25 seconds: 

 dissolve 0.1 g. of o-tolidine and 1 g. of citric acid in 20 ml. 

 of water; fill up to 100 ml. Mount in glycerol. Greenish color 

 indicates small amounts; yellow and orange, larger amounts 

 of free CI2. 



Iodine —There are no good methods available either for 

 the iodide ion (see Gersh and Stieglitz)^^ or for occult iodine 

 ( e.g., in thyroxine ) . 



Phosphorus.— The demonstration of the phosphate ion was 

 described in the section on calcium. It should be added here 

 that, whereas the usual heavy-metal techniques do not differ- 

 entiate between phosphate and carbonate, there is a theo- 

 retical possibility of distinguishing between the two by the 

 use of uranyl salts. These will give a precipitate with phos- 

 phates but not with carbonates (uranyl carbonate being fair- 

 ly soluble). Insoluble uranyl phosphate is convertible into 

 reddish-brown uranyl ferrocyanide. 



Lihenfeld and Monti^^ have proposed the demonstration 

 of organic phosphates by hydrolyzing them with nitric acid 

 in the presence of ammonium molybdate and then reducing 

 the phosphomolybdate precipitate in a second step to molyb- 

 denum blue. This method is worthless histochemically. Even 

 if inorganic phosphate were the first soluble phosphorus-con- 

 taining compound liberated (and this is not in the least 

 likely), the method could not possibly localize it. First of 

 all, ammonium phosphomolybdate is not insoluble enough; 



58. Ferguson, R. L., and Silver, S. D.: Am. J. Clin. Patli., 17:35, 1947. 



59. Gersh, I., and Stieglitz, E. J.: Anat. Rec, 56:185, 1933. 



60. Lilienfeld, L., and Monti, A.: Ztschr. f. wissensch. Mikr., 9:332, 1892. 



