GENERAL SCIENCE 



in the conducting wire to be noticeable, too, and at times the wire may 

 become incandescent. 



In the process of electroplating we have a good illustration of elec- 

 trolysis. When the terminals of a broken circuit are immersed in the 

 plating solution as an electrolyte, and a current of electricity is sent 

 through it, the positively charged metallic ions in the liquid pass to 

 the cathode. Here, upon losing their electrification, they are deposited 

 as a metallic coating upon whatever serves as cathode. 



On the other hand the negatively charged ions pass to the anode, 

 lose their electrification, and unite with the anode when it is of suitable 

 material. At other times they unite with the water surrounding the 

 anode, and again at other times escape as gaseous products into the 

 atmosphere. 



It must be remembered that in this theory of the dissociation of 

 electrolytes in solution into ions there is the most satisfactory explana- 

 tion of what actually occurs a phenomenon that otherwise remains 

 complex and not understood. 



LIMESTONE, AND OTHER CARBONATES 



One of the chief chemical industries is the manufacture of 

 sodium carbonate from common salt (NaCl). The impor- 

 tance of it, and of its related and dependent industries, 

 requires that every well-informed person have some knowl- 

 edge of it, at least as much as may be gained from a high 

 school text in Chemistry. The extent of industries such as 

 this is in no small degree an index of the industrial activities 

 of a nation. 



In the Solvay process of manufacture saturated solutions of 

 common salt are treated with ammonia (NH 3 ). This with 

 water forms ammonium hydroxide or "ammonia water" 

 (NH 4 OH). Carbon dioxide (CO 2 ) passed into the solution 

 may be supposed to form carbonic acid (H 2 CO 3 ) with the 

 water. As a final result of chemical changes that occur, 

 sodium bicarbonate (HNaCO 3 ) or " baking soda" separates 

 out as a finely divided solid. These chemical changes for 



