Potassium nitrate is a chemical compound with the chemical formula KNO3.
It is an ionic
salt of potassium ions K+ and nitrate ions NO3−, and is therefore an alkali metal nitrate.
Potassium nitrate[1]
Names
IUPAC name
Potassium nitrate
Other names
Saltpeter
Saltpetre
Nitrate of potash[2]
Identifiers
CAS Number 7757-79-1
3D model (JSmol) Interactive image
ChEMBL ChEMBL1644029
ChemSpider 22843
ECHA InfoCard 100.028.926
EC Number 231-818-8
E number E252 (preservatives)
KEGG D02051
PubChem CID 24434
RTECS number TT3700000
UNII RU45X2JN0Z
UN number 1486
CompTox DTXSID4029692
Dashboard (EPA)
InChI
InChI=1S/K.NO3/c;2-1(3)4/q+1;-1
Key: FGIUAXJPYTZDNR-UHFFFAOYSA-N
InChI=1/K.NO3/c;2-1(3)4/q+1;-1
Key: FGIUAXJPYTZDNR-UHFFFAOYAM
SMILES
[K+].[O-][N+]([O-])=O
Properties
Chemical formula KNO3
Molar mass 101.1032 g/mol
Appearance white solid
Odor odorless
Density 2.109 g/cm3 (16 °C)
Melting point 334 °C (633 °F; 607 K)
Boiling point 400 °C (752 °F; 673 K)
(decomposes)
Solubility in water 133 g/L (0 °C)
242 g/L (20 °C)
2439 g/L (100 °C)[3]
Solubility slightly soluble in ethanol
soluble in glycerol, ammonia
Basicity (pKb) 15.3[4]
Magnetic −33.7·10−6 cm3/mol
susceptibility (χ)
Refractive 1.335, 1.5056, 1.5604
index (nD)
Structure
Crystal structure Orthorhombic, Aragonite
Thermochemistry
Heat capacity (C) 95.06 J/mol K
Std enthalpy of -494.00 kJ/mol
formation (ΔfH⦵298)
Hazards
Main hazards Oxidant, harmful if
swallowed, inhaled, or
absorbed on skin. Causes
irritation to skin and eye
area.
Safety data sheet See: data page
ICSC 0184
GHS pictograms
GHS hazard H272, H315, H319, H335
statements
GHS precautionary P102, P210, P220, P221, P280
statements
NFPA 704
0
1
0
OX
Flash point non-flammable (oxidizer)
Lethal dose or concentration (LD, LC):
LD50 (median 1901 mg/kg (oral, rabbit)
dose) 3750 mg/kg (oral, rat)[5]
Related compounds
Other anions Potassium nitrite
Other cations Lithium nitrate
Sodium nitrate
Rubidium nitrate
Caesium nitrate
Related Potassium sulfate
compounds Potassium chloride
Supplementary data page
Structure and Refractive index (n),
properties Dielectric constant (εr), etc.
Thermodynamic Phase behaviour
data solid–liquid–gas
Spectral data UV, IR, NMR, MS
Except where otherwise noted, data are given for
materials in their standard state (at 25 °C [77 °F],
100 kPa).
verify (what is ?)
Infobox references
It occurs in nature as a mineral, niter. It is a source of nitrogen, from which it derives its
name. Potassium nitrate is one of several nitrogen-containing compounds collectively
referred to as saltpeter or saltpetre.
Major uses of potassium nitrate are in fertilizers, tree stump removal, rocket
propellants and fireworks. It is one of the major constituents of gunpowder (black
powder).[6] In processed meats, potassium nitrate reacts with hemoglobin and generates a
pink color.[7]
Contents
EtymologyEdit
Potassium nitrate, because of its early and global use and production, has many names.
Hebrew and Egyptian words for it had the consonants n-t-r, indicating likely cognation in
the Greek nitron, which was Latinised to nitrum or nitrium. Thence Old French
had niter and Middle English nitre. By the 15th century, Europeans referred to it
as saltpeter[8] and later as nitrate of potash, as the chemistry of the compound was more
fully understood.
The Arabs called it "Chinese snow" (Arabic: ثلج الصينthalj al-ṣīn). It was called "Chinese salt"
by the Iranians/Persians[9][10][11][12][13] or "salt from Chinese salt marshes" (Persian: نمک
شوره چينيnamak shūra chīnī).[14][15]
PropertiesEdit
Potassium nitrate has an orthorhombic crystal structure at room temperature, which
transforms to a trigonal system at 129 °C (264 °F).
Potassium nitrate is moderately soluble in water, but its solubility increases with
temperature. The aqueous solution is almost neutral, exhibiting pH 6.2 at 14 °C (57 °F) for a
10% solution of commercial powder. It is not very hygroscopic, absorbing about 0.03%
water in 80% relative humidity over 50 days. It is insoluble in alcohol and is not poisonous;
it can react explosively with reducing agents, but it is not explosive on its own.[3]
Thermal decompositionEdit
Between 550–790 °C (1,022–1,454 °F), potassium nitrate reaches a temperature
dependent equilibrium with potassium nitrite:[16]
2 KNO3 ⇌ 2 KNO2 + O2
History of productionEdit
From mineral sourcesEdit
The earliest known complete purification process for potassium nitrate was outlined in
1270 by the chemist and engineer Hasan al-Rammah of Syria in his book al-Furusiyya wa
al-Manasib al-Harbiyya (The Book of Military Horsemanship and Ingenious War Devices). In
this book, al-Rammah describes first the purification of barud (crude saltpeter mineral) by
boiling it with minimal water and using only the hot solution, then the use of potassium
carbonate (in the form of wood ashes) to remove calcium and magnesium by precipitation
of their carbonates from this solution, leaving a solution of purified potassium nitrate,
which could then be dried.[17] This was used for the manufacture of gunpowder and
explosive devices. The terminology used by al-Rammah indicated a Chinese origin for the
gunpowder weapons about which he wrote.[18]
At least as far back as 1845, Chilean saltpeter deposits were exploited in Chile and
California.
