2 PC. Ray — On Mercurous Nitrite. [No. 1, 



S(!horlernmer in tlieir well-known treatise do not so much as mention 

 this compound, nor is there any refei-ence to it to be found in the latest 

 edition of Watt's Bictionarij of Chemistry. 



Method of Preparation. 



Yellow nitric acid, sp. gr. I*4d0, is diluted with water in the pro- 

 portion of 1 to 3 in a flask or beaker. A large excess of mercury is at 

 once poured into the liquid. The heat of solution of the acid in 

 water helps to start the reaction. A gentle effer\^escence of gases at 

 once takes place, and in the course of about an hour yellow needles, 

 resembling prismatic sulphur, begin to appear on the surface of mercury. 

 After a few hours the liquid together with the niercilry is carefully 

 decanted off, and the salt shaken out of the vessel over porous tiles to 

 remove the adhering mother-liquor. 



For purposes of analysis, etc., it is preferable to collect the first 

 day's or at most the second day's crops only, partly because minute 

 globules of mercury get entangled among the mass of the crystalline 

 deposit, which it is tedious to get rid of, and partly because the com- 

 position of the salt varies on standing in the liquid. Thus it is found 

 that if the salt instead of being removed is allowed to remain in con- 

 tact with the mercury and the mother-liquor, it gradually disappears 

 and in its place transparent, perfectly colourless, crystals are formed, 

 which grow in size witli time. These latter will be described under 

 the name of " Marignac's salt/' which is a basic mercurous nitrate. 



Qualitative tests. 

 The new compound among others answers to the following tests : — 



1. Dilute sulphuric acid slowly evolves nitrous fumes : more readily 

 on heating. 



2. On warming with a large excess of water, globules of mercury 

 separate out. Tn the cold the decomposition is only partial. 



The ferfectly clear mother-liquor, decanted off the mercury, gives 

 the following reactions : — 



(a) Boiled with an excess of pure caustic soda solution, it yields 

 a black dense precipitate, the filtrate from which, after acidification 

 with dilute sulphuric acid, rapidly decolorizes potassium permanganate 

 solution and instantly sets free iodine from potassium iodide. 



(6) Sodium cliloride throws down a copious white precipitate ; 

 after removal of the calomel, the filtrate is now divided into several 

 portions; to one is added caustic soda and a yellow precipitate is the 

 result, another portion treated with potassium iodide gives an orange 

 precipitate ; whilst a third portion on addition of hydrochloric and 

 phosphorous acids yields a further quantity of mercurous chloride. 



