348personal, clothing, and surface contamination is also required. In addition, due to
the high energy of the beta particles, shielding this radiation with the normally used
dense materials (e.g. lead), gives rise to secondary emission of X-rays via
Bremsstrahlung (braking radiation). Therefore shielding must be accomplished
with low density materials, e.g. Plexiglas (Lucite), other plastics, water, or (when
transparency is not required), even wood.
33 P, a beta-emitter (0.25 MeV) with a half-life of 25.4 days. It is used in life-science
laboratories in applications in which lower energy beta emissions are
advantageous such as DNA sequencing.Occurrence
In terms of stellar nucleosynthesis, stable forms of phosphorus are produced in large
(greater than 3 solar masses) stars by fusing two oxygen atoms together. This requires
temperatures above 1,000 megakelvins.
Phosphorus is not found free in nature, but it is widely distributed in many minerals, mainly
phosphates. Phosphate rock, which is partially made of apatite (an impure tri-calcium
phosphate mineral), is an important commercial source of this element. About 50 percent
of the global phosphorus reserves are in the Arab nations. Large deposits of apatite are
located in China, Russia, Morocco, Florida, Idaho, Tennessee, Utah, and elsewhere.
Albright and Wilson in the United Kingdom and their Niagara Falls plant, for instance, were
using phosphate rock in the 1890s and 1900s from the Îles du Connétable, Tennessee
and Florida; by 1950 they were using phosphate rock mainly from Tennessee and North
Africa. In the early 1990s Albright and Wilson's purified wet phosphoric acid business was
being adversely affected by phosphate rock sales by China and the entry of their long-
standing Moroccan phosphate suppliers into the purified wet phosphoric acid business.
Production
The majority of phosphorus-containing compounds are produced for use as fertilizers. For
this purpose, phosphate-containing minerals are converted to phosphoric acid. Two
distinct routes are employed, the main one being treatment of phosphate minerals with
sulfuric acid. The other process utilizes white phosphorus, which may be produced by
reaction and distillation from very low grade phosphate sources. The white phosphorus is
then oxidized to phosphoric acid and subsequently neutralized with base to give
phosphate salts. Phosphoric acid obtained via white phosphorus is relatively pure and is
the main source of phosphates used in detergents and other non-fertilizer applications.
Elemental Phosphorus
About 1,000,000 short tons (910,000 t) of elemental phosphorus is produced annually.
Calcium phosphate (phosphate rock), mostly mined in Florida and North Africa, can be
heated to 1,200–1,500 °C with sand, which is mostly SiO 2 , and coke (impure carbon) to
produce vaporized P 4.
The product is subsequently condensed into a white powder under water to prevent
oxidation by air.
Even under water, white phosphorus is slowly converted to the more stable red
phosphorus allotrope. The chemical equation for this process when starting with
fluoroapatite, a common phosphate mineral, is:
4 Ca 5 (PO 4 ) 3 F + 18 SiO 2 + 30 C → 3 P 4 + 30 CO + 18 CaSiO 3 + 2 CaF 2