Monograph: |
Phosphoric Acid
Odourless, clear, colourless, corrosive, syrupy liquid.
Miscible with water or alcohol. When stored at a low temper-
ature it may solidify, forming a mass of colourless crystals
which do not melt until the temperature reaches 28Β°. Store in
airtight glass containers.
Dilute Phosphoric Acid
Dilute Phosphoric Acid (Ph. Eur.) contains 9.5 to 10.5% w/w
H,PO, and may be prepared by mixing phosphoric acid 115 g
with water 885 g. Diluted Phosphoric Acid (USNF) contains
9.5 to 10.5% w/w H3P04 and may be prepared by mixing
phosphoric acid 115 g with 885 g of water. Store in airtight
containers.
Adverse Effects and treatment
Phosphoric acid is highly irritant and corrosive and inges-
tion has proved fatal. The corrosive effect causes severe pain.
There may be violent vomiting, hematemesis. and circulato-
ry collapse; acids can also produce intravascular coagulation
and haemolysis. Ulceration may lead to perforation and pa-
tients can suffer strictures and pyloric stenosis. Asphyxiation
may result from laryngeal oedema. Inhalation of acid fumes
or aspiration of ingested acids may cause pneumonitis.
Treatment of Adverse Effects
Treatment following ingestion is mainly symptomatic. Care-
ful gastric lavage or aspiration may be performed but emetics
must not be used. The use of large amounts of water or milk
for dilution or neutralizing agents such as aluminium hydrox-
ide is controversial: carbonates and bicarbonates should not
be used as release of carbon dioxide distends the stomach.
Opioid analgesia may be required for pain. Endoscopy should
be performed and surgical intervention may be necessary.
There is little evidence to support the value of corticosteroids
in preventing stricture formation.
Acid burns of the skin should be flooded immediately with
water and the washing should be copious and prolonged. Any
affected clothing should be removed while flooding is being
earned out. For burns in the eye. the lids should be kept open
and the eye flushed with a steady stream of water. A few drops
of a local anaesthetic solution will relieve lid spasm and facil-
itate irrigation.
Uses and Administration
Phosphoric acid has industrial uses. Dilute phosphoric acid
has been used well diluted in preparations intended for the
management of nausea and vomiting . Phosphoric
acid 35% gel has been used in dentistry to etch tooth enamel.
In Great Britain, a technical grade of orthophosphoric acid I
in 330 of water is an approved disinfectant for foot-and-
mouth disease.
Phosphoric acid is used in homoeopathic medicine.
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