QUESTIONS AND ANSWERS 27 



Mention a compound of each of the halogens. 



Sodium chloride, potassium iodide, sodium bromide and hydro- 

 fluoric acid. 



Describe the properties of bromine and give a method for its prepara- 

 tion. 



At ordinary temperature, bromine is a heavy, dark, reddish- 

 brown liquid, giving off yellowish-red fumes of an exceedingly 

 suffocating and irritating odor; it is very volatile and has a specific 

 gravity of 2.99. It is soluble in water, is a strong disinfecting and 

 bleaching agent and acts as a corrosive poison. 



Bromine is prepared by treating magnesium bromide with 

 chlorine. 



MgBr, -f 2C1= MgCl, -f 2Br. 



Give the properties and uses in medicine of bromine. 



Properties given above. Sodium and potassimn bromide are 

 used in medicine as antispasmodics, narcotics and ne.rve sedatives. 



GOLD 



Give a test for gold and gold compounds. 



Most reducing agents, as oxalic acid, ferrous sulphate, etc., 

 precipitate gold from its solutions as a dark-brown powder. 



SILVER 



Describe silver, giving names of its most important compounds used in 

 medicine. 

 Silver is a pure, white brilliant metal, a good conductor of heat 

 and electricity, and is malleable and ductile. It is univalent and 

 forms but one series of salts. It is not affected by the oxygen of the 

 air, but is readily affected by traces of hydrogen sulphide, which 

 forms a black film of sulphide upon the surface. Its atomic weight 

 is 107, its specific gravity is 10.5 and its symbol is Ag. Compounds 

 used in medicine are : silver nitrate, protargol, argyrol, collargol. 



What is lunar caustic? How is lunar caustic prepared and what is 



its medicinal use? 



Lunar caustic is nitrate of silver, fused into roixnd sticks, or 



pencils. It is prepared by adding 4 per cent, hydrochloric acid to 



sUver nitrate, fusing and pouring into suitable moulds. It is used 



for cauterizing inflamed surfaces, warts, etc. 



Give a chemical test for silver. 



Add to a solution of silver a solution of hydrogen sulphide 

 or ammonium sulphide, and a dark-brown precipitate of silver sul- 

 phide will be produced. 



