182 METALS AND THEIR COMBINATIONS. 



9. A piece of bright metallic copper, when placed in a 

 slightly acid mercury solution (which must not contain any free 

 nitric acid) becomes coated with a dark film of metallic mercury 

 in a fine state of division. The mercury may be separated by 

 placing the copper (after having been washed with water and 

 dried at a very gentle heat) in a narrow test-tube and heating 

 to redness, when the mercury is volatilized and deposited in the 

 cooler part of the tube. 



10. All compounds of mercury are completely volatilized by 

 heat, either with or without decomposition. 



QUESTIONS. 



281. How is silver obtained from the native ores, and how may it be 

 prepared from silver coin ? 



282. State of silver nitrate : its composition, mode of preparation, 

 properties, and names by which it is known. 



283. Give analytical reactions for silver. 



284. How is mercury found in nature ; how is it obtained from the 

 native ore ; what are its physical and chemical properties ? 



285. Mention the three oxides of mercury ; how are they made, what 

 is their composition, what is their color and solubility? 



286. State of the two chlorides of mercury : names, composition, mode 

 of preparation, solubility, color, and other properties. 



287. Mention the same of the two iodides, as above for the chlorides. 



288. State the difference between mercuric sulphate, basic mercuric 

 sulphate, and mercurous sulphate. 



289. What is formed when ammonium hydrate, calcium hydrate, 

 potassium or sodium hydrate are added to either mercurous or mercuric 

 chloride? 



290. Give tests answering for any mercury compound, and tests by 

 which mercuric compounds may be distinguished from mercurous com- 

 pounds. 



30. ARSENIC. 



As = 74.9. 



General remarks regarding the metals of the arsenic group. The 

 metals belonging to either of the five groups considered here- 

 tofore, show much resemblance to each other in their 

 chemical properties and consequently in their combinations. 

 This is much less the case among the six metals (As, Sb, Sn, Au, 



