Hafnium produced by the van Arkel and de Boer process. Thomas
The process developed by van Arkel and de Boer; used for refining
zirconium and hafnium by the decomposition of iodide on a hot wire.
Syn:van Arkel and de Boer process
Thomas
iodide process for producing titanium
Process involving the reaction of impure titanium metal with iodine to
form the volatile tetraiodide, which is then decomposed on a hot wire at
temperatures between 2,000 degrees F and 2,730 degrees F (1,093 degrees C
and 1,500 degrees C) to form high-purity titanium and iodine.
Volumetric analysis involving either titration with a standardized
solution of iodine, or the release by a substance under examination of
iodine in soluble form, so that its concentration can be determined by
titration, using starch as an indicator. The method is used with
substances that can oxidize potassium iodide to release free iodine, or
conversely with substances which combine with free iodine. The basis of
reaction is I2 +2Na2 S2 O3 --> 2NaI+Na2
S4 O6 . Also called iodometry. Pryor, 3
A nonmetallic, bluish-black, lustrous solid element, volatilizing at
ordinary temperatures into a blue-violet gas with an irritating odor.
Symbol, I. Occurs sparingly in sea water, in saltpeter and nitrate-bearing
earth (known as caliche), in brines, and in brackish waters from oil and
salt wells. Its compounds are used in medicines, photography, and organic
chemistry. Handbook of Chemistry and Physics, 3
Accurate determinations of very low concentrations of carbon monoxide are
required of samples from pits troubled with spontaneous combustion and
those in which diesel locomotives are operating. This method involves the
passage of a known volume of the sample first through a train of reagents
for purifying and drying and then through a heated tube of iodine
pentoxide; if carbon monoxide is present, proportional amounts of iodine
and carbon dioxide are formed, either of which may be determined.
Sinclair, 1
An iodine pentoxide (Hoolamite) test consists of a glass tube filled with
a reagent mixed with fuming sulfuric acid and carried by crushed pumice
through which a known volume of the air to be sampled is discharged from a
rubber bulb after preliminary drying. The bulb is squeezed 10 times; the
carbon monoxide present changes the color of the reagent from grey to
green, and the concentration is obtained by reference to a color chart
supplied with the instrument. The instrument reads down to about 0.07%
carbon monoxide. Sinclair, 1
See:iodembolite
See:iodargyrite
See:cordierite
An atom or a group of atoms combined in a radical or molecule that carries
a positive or a negative electric charge as a result of having lost or
gained one or more electrons. It may exist in solution, usually in
combination with molecules of the solvent, or out of solution; it may be
formed during electrolysis and migrate to the electrode of opposite
charge, or it may be formed in a gas and be capable of carrying an
electric current through the gas. Webster 3rd
Reversible exchange of ions contained in a crystal for different ions in
solution without destruction of crystal structure or disturbance of
electrical neutrality. The process is accomplished by diffusion and occurs
typically in crystals possessing one- or two-dimensional channelways where
ions are relatively weakly bonded. Also occurs in resins consisting of
three-dimensional hydrocarbon networks to which many ionizable groups are
attached. Syn:base exchange
A tube packed with particles or beads of resin chosen for their ability to
capture specific ions from an aqueous solution as it passes through the
column.
Use of an electrode reversible to the ion under test to form a half cell.
This is connected by a salt bridge to a reference electrode, and the
resulting electromotive force is measured. Pryor, 3
a. Electrostatic force holding ions together in a crystal. Hurlbut
b. A chemical bond between atoms, one of which is an electron donor and
the other is an electron acceptor. Gaudin, 2
The situation when, for a prescribed temperature, pressure, concentration
of reactants, and pH, the rate of dissociation of molecules into ions is
approx. in balance with that of their recombination. Pryor, 3
Movement of a charged particle through an electrolyte toward an electrode
of opposite charge sign. The losses in a neutral salt around two
electrodes during the passage of electric current are in ratio to
velocities of ions migrating from these electrodes. Ionic velocities are
stated in centimeters per second for a potential gradient of 1 V/cm.
Pryor, 3
Velocity in a dilute solution of an ion where the potential difference
across this is 1 V/cm. For hydrogen ions, the velocity is 0.00326 cm/s.
Pryor, 3
Fraction of total current carried by one ion during electrolysis (ion
migration). Pryor, 3
A term referring to two different materials found in the Ione Valley of
northern California: (1) a clay mineral, possibly a variety of kaolinite,
found as scales in the Ione sandstone formation, and (2) an impure fossil
hydrocarbon found in lignite, which is brownish-yellow, dissolved by
chloroform, and yields a brown, tarry oil on destructive distillation.
The process of adding electrons to, or knocking electrons from, atoms or
molecules, thereby creating ions. High temperatures, electrical
discharges, and nuclear radiation can cause ionization. Lyman