IQQ S. HADA; HOW MERCUROUS AND 



it had better be exposed for a time in a desiccator before storing it. It 

 has been found to keep quite unchanged, or, when a little effloresced 

 and faintly yellowish, to be still free from mercuric salt. Crystals, 

 after pressing in paper, have been left in a basin exposed to the air, but 

 covered from the entrance of dust, and after the lapse of a full year and 

 through wide ranges of temperature and moisture, have remained almost 

 unchanged ; some of the crystals had remained clear, some had be- 

 come opaque, while all had become very slightly brown owing 

 probably only to hydrogen sulphide, while even the opaque crystals 

 hardly showed the presence of any mercuric salt. Well cleansed and 

 effloresced mercurous nitrate kept in a bottle has always a peculiar 

 ozone-like odour, according to my experience. 



A solution of mercurous nitrate, free from nitrous acid and in a 

 closed vessel, appears to be quite «table while kept in the dark. 



Decomposition of mercurous nitrate by water. — When normal mer- 

 curous nitrate has been freed with care from its acid mother-liquor, it 

 is always decomposed by water and in such a way as to give an acid 

 solution and a precipitate of basic mercurous nitrate. I have been 

 unable to get the salt to dissolve completely in a little warm water, as 

 it is stated to do in Gmelin's Handbook and some later works, except 

 where the crystals had been little more than drained from their mother- 

 liquor. Even after the acid solution and the basic salt have been 

 kept for some hours in an open vessel at or about 100°, but not in a 

 strong light, the basic salt (of a dull yellow colour) still remains 

 essentially free from mercuric salt, although the solution now contains 

 it in consequence of dissociation, as will be presently described. Rose in 

 1841 (Annalen 39, 106) described such a basic precipitate as a mixture 

 of basic mercuric salt, mercury, and unchanged normal mercurous 

 nitrate, combatting the notion that any insoluble basic mercurous salts 

 exist. It would be difficult to prove the precipitate to be altogether 



