286. Instances of Electrolysis.—(a) Medicines, especially those containing a mineral substance, are sometimes introduced into the human body by electrolysis. (b) Water and gas pipes are sometimes much weakened by the effects of electric currents in the earth, especially return currents from street railways. Such currents use the metal pipes as a conductor. At the place where the current leaves the metal and enters the ground, it removes metallic ions from the pipe. This process continuing, the pipe becomes weakened and at length breaks. (c) Copper is purified by the use of electric currents that remove the copper from ore or from other metals and deposit it upon electrodes. Electrolytic copper is the purest known. (d) Aluminum is obtained by the use of large currents of electricity that first heat the material used until it melts and then deposit the metal from the fluid material by electrolysis. These results are called chemical effects of the current since by the use of electric currents substances are changed chemically, that is, they are separated into different chemical substances.
Important Topics
1. Electrolysis, electroplating, anode, cathode, ion.
2. Theory of electrolysis—evidence: (a) electrolysis of water; (b) conductivity of acid and water.
3. Laws of electrolysis.
4. Practical use of electrolysis.
Exercises
1. A dynamo has an E.M.F. of 10 volts. What is the resistance in the circuit when 20 amperes are flowing?
2. How much silver will be deposited in an hour by this current?