234 ANALYTICAL CHEMISTKY. 



Mercuric iodide should be dissolved by 25 parts of boiling 1 

 alcohol, or by digesting it with potassium iodide and water. 



Mercurous iodide should be tested for mercuric iodide by 

 digesting it with alcohol, which, upon evaporation, should leave 

 no residue. 



Ammoniated mercury should be wholly soluble without effer- 

 vescence in warm hydrochloric, nitric,, or acetic acid; when 

 digested with diluted alcohol, the filtrate should not be acted 

 upon by hydrosulphuric acid or potassium iodide (absence of 

 mercuric chloride). 



The basic mercuric sulphate is almost insoluble in cold water, 

 but soluble in diluted hydrochloric or nitric acid. 



Examination of compounds of arsenic. Arsenious and arsenic 

 oxides, arsenious bromide and iodide are completely volatilized by 

 heating (a residue indicating non-volatile impurities). The 

 four compounds are also soluble in water, the bromide and 

 iodide with decomposition. 



Examination of compounds of antimony. Antimonious oxide 

 should be completely soluble in tartaric acid; the solution 

 should be tested for chlorides and sulphates by means of silver 

 nitrate and barium chloride ; also for iron, by potassium ferro- 

 cyanide. 



Antimonious and antimonic sulphides are soluble in concentrated 

 hydrochloric acid, with liberation of hydrosulphuric acid and 

 formation of the trichloride. 



Antimonic oxide, as well as antimonious oxychloride, is dissolved 

 by boiling with sodium or potassium hydrate. 



QUESTIONS. 



351. Give some general methods by which the mineral acids may be 

 examined for metallic impurities and their strength determined. 



352. How is sulphuric acid to be tested for sulphurous and nitric acids, 

 and how is nitric acid tested for sulphuric and hydrochloric acids ? 



353. What impurities are sometimes present in phosphoric acid? 

 How is their presence demonstrated ? 



354. By what tests is sodium carbonate detected in sodium bicar- 

 bonate, and potassium iodate in potassium iodide? 



