DETECTION OF IMPUEITIES. , 235 



355. How can the presence of ferrous sulphate be demonstrated in 

 either ammonium chloride, calcium phosphate, magnesium carbonate, 

 aluminium sulphate, or cupric sulphate? 



356. State the various methods by which preparations of iron are 

 examined for metallic impurities, and how ferric chloride can also be 

 tested for ferrous chloride, nitric and sulphuric acids. 



357. By what methods can zinc oxide be tested for any other metal, 

 and for carbonic, sulphuric, or hydrochloric acid ? 



358. Give methods for detecting metallic impurities in compounds of 

 lead, copper, bismuth, and silver. 



359. What is the action of heat upon mercury compounds, and by 

 what solvents may the various officinal mercury preparations be dis- 

 solved ? 



360. How is mercuric chloride detected in mercurous chloride, and 

 how mercuric iodide in mercurous iodide ? 





