22 VETERINARY STATE BOARD 



Describe a simple test for carbon dioxide and write the reaction. 



Pass the gas through lime water and the solution becomea 

 turbid. 



Ca(OH), + CO, = CaC03 + H,0. 



Compare as to weight, carbon dioxide with air. 



Carbon dioxide is one and one-half times heavier than air. 



Describe the manufacture of some carbide and mention its common use. 

 C'alciTmi carbide (CaC,) is manufactured on a commercial scale 

 by heating, in an electric furnace, a mixture of lime and coal, or 

 coal tar (CaO -f 30 = CaCj + CO). It is used for generating 

 acetylene gas, which is formed by the action of calcium carbide and 

 water (CaC, + H^O = C^H^ + CaO). 



What is marsh gas? Give its formula and chemical importance with 

 a method of preparation. 



Marsh gas (CH^) is a colorless gas which burns readily with a 

 bluish-yellow flame, emitting much heat but little light. In nature 

 it is produced by the decay of dead leaves in the bottom of stagnant 

 pools. It also accumulates in coal mines as the dreaded ' ' fire damp ' ' 

 and mixing with the oxygen of the air forms deadly explosions. In 

 impure form it is obtained from wells in some localities and is used 

 for lighting and heating. It can be prepared by mixing aluminum 

 carbide and water [Al.Cg + I2H2O = 3CH, + 4A1(0H)3]. 



Find the weight of each of the products formed by the complete com- 

 bustion of 20 grammes of marsh gas (CH^). [Atomic 

 weight of C = 12, of O = 16.] 



CH, + 2O2 = CO, + 2H,0. 



16 : 44 = 29 : X, X = 55 grammes of CO,. 



16 : 36 = 20 : X, X = 45 grammes of H,0. 



Describe the manufacture of illuminating gas. 



Bitxuninous or cannel coal is heated in clay or brick retorts and 

 the products of distillation pass out into a series of pipes in which 

 water, coal-tar, ammonia, etc., are deposited. The gas still con- 

 tains impurities, which are removed by passing it over some absorb- 

 ent substance, such as slaked lime. 



Describe the construction and operation of the Bunsen burner. 



In a gas flame, if the air is excluded, soot and smoke will form 

 copiously. But if the combustion is rendered more perfect, no car- 

 bon is deposited and the flame becomes hotter, but less brilliant. In 

 the Bunsen burner, this is arranged for by allowing air to enter at 

 the bottom of the burner and become thoroughly mixed with the 

 gas before the latter is ignited. If the openings through which 



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