198 METALS AND THEIR COMBINATIONS. 



forms an acid which combines with metals, forming a series of 

 salts termed molybdates. Of interest is ammonium molybdate, 

 a solution of which in nitric acid is an excellent reagent for 

 phosphoric acid, with which it forms a yellow precipitate, in- 

 soluble in acids, soluble in ammonium hydrate. 



QUESTIONS. 



301. How is antimony found in nature, and what are the properties 

 of this metal ? 



302. State the composition of antimonious sulphide, and its color 

 when crystallized and amorphous. 



303. How do hydrochloric acid and alkaline hydrates act upon anti- 

 monious sulphide? 



304. What is the sulphurated antimony of the U. S. P. ? 



305. Mention the two chlorides of antimony, and state their prop- 

 erties. 



306. How is antimonious oxide made, and what is it used for ? 



307. Give tests for antimony. 



308. State the use made of tin in the metallic state ; mention the two 

 chlorides of tin, and what stannous chloride is used for. 



309. How are gold and platinum found in nature; by what acid may 

 they be dissolved, and what is the composition of the compounds 

 formed ? 



310. Which is the most important compound of molybdenum, and 

 what is it used for? 



