30 VETEEINARY STATE BOARD 



Describe the process of preparing lime water from lime stone. Write 

 the reactions. 



By heating lime stone, CO, is driven off and calcium oxide 

 obtained. One part of calcium oxide is slaked and agitated occasion- 

 ally during half an hour with 30 parts of water. The mixture is 

 then allowed to settle and the liquid, containing, besides calcium 

 hydroxide, the salts of the alkaU metals which may have been pres- 

 ent in the lime, is decanted and thrown away. To the calcium 

 hydroxide left, and thus purified, 300 parts of water are added 

 and oecasionaUy shaken in a well-stoppered bottle, from which the 

 clear liquid may be poured off for use. 



CaCOa + heat = CaO -f CO,, etc. 



CaO + H,0 = Ca(OH),. 



Ca(0H)2 + 3OOH2O = lime water. 



Describe with explanation the manufacture of plaster of Paris. 



Plaster of Paris is made by heating native calcium sulphate 

 (gypsum) and depriving it of part of its water. 



2(CaSO„2H,0)-f-heat = 2CaSO^.H20 (plaster of Paris) and 

 3HjO. 



What is gypsum? 



It is native calcium sulphate, CaS04,2H20, and occurs abund- 

 antly in nature in white translucent masses. 



Describe magnesium. Name its principal compounds used in medicine 

 and write the chemical formula of each compound named. 



Magnesium is a brilliant, almost silver-white alkaline metal with 

 a specific gravity of 1.74. It is tenacious and ductile; dissolves 

 readily in dilute acids, forming salts. It is easily combustible and 

 bums with an intensely brilliant light, and is used in photography 

 for flashlight purposes. 



Compounds used in medicine : oxide, MgO, known as magnesia ; 

 carbonate, MgCOg; sulphate (Epsom salts), MgSO^jTHaO. 



Describe the method of preparing Epom salts. Write the formula of 



Epsom salts. 



Prepared by treating magnesimn carbonate with sulphuric acid 



and evaporating the solution to the crystallizing point. MgCOa + 



H,SO, = MgSO, + H,0 + CO,. Formula of Epsom salts, MgSO,,- 



7H,0. 



Name and give the formula of a compound of barium used in medicine. 

 Barium chloride, BaCl,. 



