. Dental electro-therapeutics. esence of some oxi-dizing agent which unites with the hydrogen as fast as itappears on the surface of the plates. In the Leclanchecell, manganese peroxide is the depolarizer; in bichromateof potash cell, chromic acid; in the persulphate of mercury,persulphate of mercury. Poles.—In all chemical cells the flow of current is fromthe positive ( + ) element to the negative ( —) xcithin thecell; that is, from the greater potential to the lesser, but it 42 ELECTRO-PHYSICS must not be forgotten that there is also a weaker currentwhich flows in the opposite direction from
. Dental electro-therapeutics. esence of some oxi-dizing agent which unites with the hydrogen as fast as itappears on the surface of the plates. In the Leclanchecell, manganese peroxide is the depolarizer; in bichromateof potash cell, chromic acid; in the persulphate of mercury,persulphate of mercury. Poles.—In all chemical cells the flow of current is fromthe positive ( + ) element to the negative ( —) xcithin thecell; that is, from the greater potential to the lesser, but it 42 ELECTRO-PHYSICS must not be forgotten that there is also a weaker currentwhich flows in the opposite direction from ( —) to ( + ).When the current of higher potential (+) passing throughthe electrolyte reaches the negative ( —) element it isconducted by it outside the cell to the end which is calledthe terminal; therefore the negative element without the cellbecomes the positive pole, because it conveys the currentof higher potential, and the positive element becomes thenegative pole. A study of the accompanying illustration Fig. 5. Direction of current inside and outside cell. will serve to explain how the current flowing in a closedcircuit from a cell has the + pole at the terminal of thenegative element. Testing the Poles.—The chemical action at the +pole in a circuit is acid and at the — pole alkaline; that is,when current flows through a liquid separating the terminalsin the circuit. Many simple tests which are useful in deter-mining the poles are based on the acidity and alkalinity ofthe respective poles. To find the poles: 1. Moisten a slip of blue litmusand place it on a glass slab, apply the electrodes conveying TESTING THE POLES 43 current from two poles of a battery or whatever source ofelectricity, about 3 cm. apart, the paper will turn red atthe + pole. 2. A few drops of phenol-phthalein (a clear, colorlessliquid) in a glass of water and two metal electrodes placed3 or 4 cm. apart in the water, with a current in circuit, willgive a bright purple coloring to the wate
Size: 1376px × 1815px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1910, bookpublisherphiladelphialeafeb
