SILVER NITRATE. REDUCTION. 109 



of nitrate of silver of known strength, and adds ammonia to- 

 it until the precipitate that is formed just redissolves, then 

 dilutes the solution until it contains from 0*75 to O50 per 

 cent, of the salt. 



This ammonia-nitrate solution is intended principally for the 

 impregnation of the endothelium of vessels by injection, but 

 can also be used for the impregnation of membranes by pour- 

 ing on. It has the advantage of impregnating absolutely 

 nothing but endothelium or epithelium; connective tissue is 

 not affected by it. It is also said to give a sharper localisation 

 of the stain than the ordinary solutions. 



ALFEEOW (Arch, de PhysioL, 1874; Laboratoire d'histologie 

 du College de France, 1874, p. 258. DUVAL, Precis, p. 230) 

 recommends the soluble silver salts of organic acids, viz. the 

 picrate, lactate, acetate, and citrate, as giving better results 

 than the nitrate. He employs them in solutions of 1*800, and 

 adds to the solution employed for staining a small quantity of 

 the acid of the salt taken (10 to 15 drops of a concentrated 

 solution of the acid to 800 c.c. of the solution of the salt). 

 The object of the free acid is to decompose the precipitates 

 formed by the action of the silver salt on the chlorides, 

 carbonates, and other substances existing in the tissues, leaving 

 only the albuminate, which is a more resistant compound. 



200. Silver Nitrate. Reduction. Reduction may be effected 

 in other media than distilled water. 



V. RECKLINGHAUSEN washed his preparations in salt solution 

 before exposing them to the light in distilled water ( Arch. f. 

 path. Anat., xix, p. 451). Physiological salt solution (0*75 per 

 cent.) is commonly used for these washings. 



MULLEE (Arch. /.path. Anat., xxxi, p. 110), after impregna- 

 tion by immersion for two or three minutes in a 1 per cent, 

 solution of nitrate of silver, in the dark, adds to the solution 

 a small quantity of 1 per cent, solution of iodide of silver 

 (dissolved by the aid of a little iodide of potassium). After 

 being agitated in this mixture, the preparations are washed 

 with distilled water, and exposed to the light for two days in 

 a 1 per cent, solution of nitrate of silver (see also GIEEKE in 

 Zeit.f. wiss. Mik.,i, 1884, p. 396). 



ROUGET (Arch, de Physiol., 1873, p. 603) reduces in glycerin. 



SATTLEE (Arch.f. mik. Anat., xxi, p. 672) exposes to the light 



