|OddMix ELECTRONICS - VOLTAIC CELLS|
Primary Voltaic Electrolytic Galvanic Chemical Cells General Information
|Fig 1. Voltaic Primary Cell|
Voltaic or galvanic cell - Fig. 1. - result when two primary conductors are immersed into an electrolyte. All voltaic cells utilize one or more electrolyte and one or more different primary conductors, metals. All electrolytic cells generate electricity by chemical action. Chemical action results in the change of substances from their original form to a new substance with new properties. Voltaic cells produce electrical energy by direct conversion that is a result of a redox chemical reaction.
At the beginning of our current electronics age, primary cells were the only source of useable electricity. After a slow evolution voltaic cells are a form of often used convenient source of portable electric energy. Voltaic cells are usually the most expensive form of electric energy.
The open circuit voltage of a galvanic cell is independent of the size of the electrodes, their distance or the volume of electrolyte and it only dependent on the electrode materials and the type of electrolyte. Electrode polarization opposes current flow. The most difficult part to develop a primary cell is to find suitable depolarizer materials. That is why some cells use a single electrolyte and others use two or more.
The rapid development for the postal, rail and transportation sectors required a large number of primary cells. The Daniel type cells with their depolarizer were immensely popular from their introduction in 1850 in the Morse telegraph service. In some special service they are still in use to this very day. The chromium acid Bunsen cells were widely used in 1910 for laboratory experiments. They often charged the newly invented first lead acid cells until steam powered dynamos became available. The Lalande type copper cells also in 1910 were often powered small electric motors, and the rail services for signaling were used some of them until recently.
Single Fluid Primary cell types: Cell Name Pos. Pole Neg. Pole Electrolyte V Comments Air C Amal. Zn 20% NaOH 1.45 Air depolarized Bichromate C Zn 120g CrSO4+H2SO4 2 Medium current Clark Std Hg+Hg2SO4&ZnSO4 Amal. Zn 100% ZnSO4 1.43 Cupron CuO Zn 20-22 Be° NaOH 0.8 Strong current 1A long time Fery C Amal. Zn 100% NH4Cl 1.4 Air depolarized Gassner dry C Zn ZNO+NH4Cl+ZnCl2 1.4 MnO2 depolarizer Law C Zn 15% NH4Cl 1.4 Air depolarized Lalande-Edison CuO Amal. Zn 20% NaOH 1.1 Leclanché C Zn NH4Cl 1.5 Strong current short time Leclanché dry C Amal. Zn NH4Cl+ZnCl2 1.6 MnO2+C depolarizer Main PBO2 Amal. Zn H2SO4 - density 1.1 2.5 Meidinger Cu Zn ZnCl2 - 170g/L 1 Weak current for long time Mercury Hg Zn HgO_ZnO 1.2 Med current for long time Poggendorf C Amal. Zn K2Cr2O7+H2SO4+H2O 2.0 MnO2+C depolarizer Regnault Cd Amal. Zn H2SO4+CaSO4+H2O 0.34 Strong current Silver Chloride Ag+AgCl Zn 23% NH4Cl 1.0 Volta couple Cu Zn NaCl solution 1.0 First cell made Weston normal Hg+HgSO4+CdSO4 Cdam 100% CdSO4 1.02 Lab standard
Double Fluid Primary cell types: Cell Name +Pole Catholyte Neg. Pole Anolyte V Comments Bunsen C 100% HNO3 Amal. Zn 10% H2SO4 1.9 Strong current galv. Lab Daniel Cu CuSO4 Zn 25% ZnSO4 1.1 Weak current for long time Fuller C K2Cr2O7+H2SO4 Amal. Zn 8% H2SO4 2.0 Grove Pt 100% HNO3 Zn 8% H2SO4 1.93 Strong current short time Marie Davy C Hg2SO4 Amal. Zn 12% H2SO4 2 Partz C K2Cr2O7+H2SO4 Amal. Zn MgSO4 2 Modified Bunsen
The Leclanché type cell survived relatively unchanged since its invention in 1868. All dry cells are descendents to the original wet cell. Dry cells are not dry. Instead of the liquid electrolyte, dry cells have their electrolyte in a gel or paste form. It increases the cell resistance, but makes it possible to have portable cells for flashlights, radios, and other items.
Special thanks to Mr. Logue whose persistent, generous support and book donations helped substantially to compound some of this and other long forgetten technical data.