Synthetic Inorganic Chemistry

MERCURIC NITRATE 233

2. The cold dilute nitric acid in Question 1 does not oxidize
   the mercurous salt. Now add cold dilute hydrochloric acid, drop
   by drop, until all the mercurous salt is precipitated as white
   mercurous chloride, HgCl. Look up the solubility of mercurous
   and mercuric chlorides.


3. Filter off the precipitate obtained in Question 2. The
   solution will contain any mercuric salt which was present in the
   sample originally taken. What reagent could you use to test for
   mercuric salt in this solution? Make the test and report the result.


4. Addition of hydrochloric acid to the solution containing
   nitric acid gives the strongly oxidizing mixture known as aqua
   regia. What is the chief reason why, if the solution is cold and
   dilute, the mercurous salt escapes oxidation?

PREPARATION 33

MERCURIC NITRATE, Hg(NOs)2

When mercury is heated with an excess of nitric acid, mercuric

nitrate is produced. This salt is exceedingly soluble in water, and

it can be crystallized only with a good deal of difficulty. When

a solution of it containing an excess of nitric acid is evaporated,

it becomes a thick, heavy sirup, which by further driving off of

nitric acid and water becomes a pasty mass, due to formation of

small crystals of basic nitrate, Hg < _ *. If the materials taken

for the preparation of this salt are pure, the product can contain
no other foreign matter than an excess of nitric acid; consequently,
in view of the difficulty of obtaining good crystals, it is convenient
to preserve the salt in this pasty condition.

Materials: mercury, Hg, 25 grams = 0.125 F.W.
6.ZVHNO3, 60 cc.
Apparatus: 300-cc. flask.
125-cc. casserole.
2-ounce glass-stoppered bottle,
iron ring and ring stand.
Bunsen burner.
Procedure: Heat 25 grams of mercury in a flask in the hood with
60 cc. 6N HNO3 until it is all dissolved. Test a drop of the solu-
tion by adding to it in a test tube 1 cc. of cold water and a drop of