Background current (density):
See residual current (density).
Base: A compound
that dissociates to produce hydroxyl (OH-) anions when dissolved in water (also
called "caustic" or "alkali"). See also pH.
electroplating solution is often called "bath."
An assembly of two or more cells electrically connected to form a unit. For
example, a 12V SLI battery is made up of six 2V cells in series. However, the
term is also often used to indicate a single cell. A device that stores electrical
energy using electrochemical cells. Chemical reactions occur spontaneously at
the electrodes when they are connected trough an external circuit, producing
an electrical current. The physical construction of the battery is such that
it does not permit the intermixing and consequent direct reaction of the chemicals
stored in it. Strictly speaking, a battery should consist of several, internally
connected, electrochemical cells. (The individual cells in a battery can be
series or parallel coupled, or a combination of both.) However, in present usage
all storage devices (single cell and multiple cell) are called batteries.
The regulation of charging and discharging conditions (eg control of temperature,
cut-off voltages, current).
polymeric material added to the active mass to increase its mechanical strength.
Electrochemistry of biological systems and biological compounds.
An electrode that is shared by two series-coupled electrochemical cells in such
a way that one side of the (usually planar) electrode acts as an anode in one
cell and the other side acts as a cathode in the other cell. In storage batteries
and fuel cell stacks many cells are usually connected internally, and it is
a very efficient design feature to use a single planar structure for electrodes
in two neighboring cells and also as the electrical interconnection between
them. An electrode assembly which functions as the anode of one cell on one
side, and as the cathode of the next cell on the other side. Also known as a
'duplex' electrode, especially in Leclanché batteries.
A potentiostat that controls the potential of two working electrodes independently
in the same cell. Typically used in conjunction with a rotating-ring-disk electrode.
See brine electrolysis.
See trickle charging.
See hydrodynamic boundary layer.
Brightening agent, brightener:
Small amounts of (usually organic) compounds added to an electroplating solution
that changes the mechanism of the plating to produce "bright" (mirror like)
Electrolysis of an aqueous solution of common table salt (sodium chloride),
also called "brine," results in the production of chlorine gas at the anode
and hydrogen gas at the cathode. Since the hydrogen is produced by breaking
up water molecules, the solution is becoming basic around the cathode and a
solution of sodium hydroxide (also called "caustic" or "alkali") is produced.
If the electrolysis is carried out in a divided cell, the products are chlorine,
caustic, and hydrogen. If the electrolysis is carried out in an undivided cell
and the chlorine gas and the caustic are allowed to mix and react with each
other, sodium hypochlorite (bleach) is produced if the cell operates close to
room temperature, and sodium chlorate is produced if the cell is operated near
the boiling point of water. Electrolysis is the only large-scale industrial
process for the production of chlorine gas and these chlorine chemicals. Smaller
scale cells are also used to produce chlorine-based disinfectants in municipal
water-treatment plants and for swimming pools. The overall cell reaction is:
2NaCl + 2H2O = Cl2 + H2 +2NaOH Chlorine gas and sodium hydroxide react to form
sodium hypochlorite and sodium chloride: Cl2 + 2NaOH = NaOCl + NaCl + H2O Sodium
hypochlorite will react further at high temperature to form sodium chlorate
and sodium chloride: 3NaOCl = NaClO3 + 2NaCl (although, sodium chlorate can
also form by direct electrochemical oxidation).
A solution with a constant, specified pH. The pH of the solution "resists" any
change: addition of small amounts of solvent or even acid or base will not appreciable
change the pH. This is called "buffer capacity."
A typically not insulated (not covered with insulation) conductor used to carry
a large current or to make a common connection between several circuits. A rigid
metallic conductor which connects different elements of a battery; also, the
conductor for an electrical system to which a battery terminal is attached.
Miniature cylindrical cell having a characteristic disc shape. See coin cell.
See current leakage.