COPPER, ZINC, LEAD, ETC. 



153 



tains soluble arsenic. In case of accidental poisoning 

 with Paris green, hydroxid of iron is usually employed 

 as an antidote. 



203. Occurrence of flercury. Mercury is found in 

 nature mainly in the form of the sulfid, HgS, commonly 

 called vermilion which, when roasted, yields SO 2 and Hg. 

 Mercury is extensively used in the preparation of alloys 

 and amalgams. 



204. Compounds of fiercury. Like copper, tin and 

 many other elements, mercury forms two series of salts, 

 the mercurous and mercuric compounds. Mercurous and 

 mercuric oxids, Hg 2 O and HgO, mercurous and mercuric 

 chlorids, HgCl and HgCl 2 , and the nitrates and sulfids 

 are among the more important compounds of mercury. 

 Mercuric chlorid is employed as an insecticide and also 

 as a germicide. It is very poisonous and is very destruc- 

 tive to all forms of animal and plant life ; it is frequently 

 used for the treatment of fungus diseases of plants. 



Experiment 35. Replacement of metals. Place, in separate 

 test-tubes, (i) 5 cc. of silver nitrate, (2) a piece of copper, and (3) 

 5 cc. of lead nitrate. To 

 the first test-tube, add a 

 piece of copper foil, to the 

 second a small piece of 

 lead, and to the third, 

 a piece of ziuc. After 

 a few minutes, examine 

 the contents of the vari- 

 ous test-tubes and observe 

 the results. Copper has 

 the power of replacing silver in solution, lead has the power of re- 

 placing copper, and zinc has the power of replacing lead. 



Fig. 61. 



