180 



Furthermore, since we naturally prefer, when we carry out a 

 reaction either on a small scale in the laboratory or on a large 

 scale in chemical industry, to have it under our control as much 

 as possible, we contrive to perform most chemical changes with 

 our reacting materials in solution. By this means we are enabled, 

 in general, to forecast the course of the reaction accurately, to 

 arrange the conditions so that the reaction will be sure to proceed 

 smoothly, and to isolate without much difficulty those products 

 which we desire to obtain in a pure state. In the absence of a 

 solvent a reaction is much more liable to get out of hand, perhaps 

 explosively, with the result that the proper conditions of the 

 process are not maintained, and we obtain either a poor yield or 

 an impure product. 



Exercises. 1. By what experiments should you determine 

 which were the radicals in substances of the following composition : 



Cu(NO,) 2 , CaC0 3 , NH 4 Br, NHJ, KC10 4 and KMnO 4 . 

 There are always two ways, and usually three, of determining 

 the radicals what are they (pp. 171-2)? 



2. How should you determine whether a given substance were 

 an acid, base, or salt (electrolyte), or not? 



3. Make equations showing the interactions of solutions of 

 aluminium chloride A1C1 3 and of cupric sulphate CuSO 4 with 

 sodium hydroxide (p. 168). Name the products. 



4. Make equations showing the interactions of solutions of 

 zinc chloride ZnCl2 and of ferric chloride FeCla with silver sulphate 

 Ag 2 S0 4 . Name the products. 



5. What is the action of metallic zinc on solutions of sodium 

 chloride, lead nitrate Pb(N0 3 )2, silver sulphate Ag 2 SO 4 , mag- 

 nesium sulphate MgS0 4 , mercuric chloride HgCl2? 



