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Potassium nitrate

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Potassium nitrate[1]
CAS number 7757-79-1 YesY
PubChem 24434
ChemSpider 22843 YesY
UN number 1486
KEGG D02051 N
RTECS number TT3700000
Jmol-3D images Image 1
Molecular formula KNO3
Molar mass 101.1032 g/mol
Appearance white solid
Odor odorless
Density 2.109 g/cm3 (16 °C)
Melting point

334 °C

Boiling point

400 °C decomp.

Solubility in water 133 g/L (0 °C)
360 g/L (25 °C)
2470 g/L (100 °C)
Solubility slightly soluble in ethanol
soluble in glycerol, ammonia
Crystal structure Orthorhombic, Aragonite
MSDS External MSDS
EU Index Not listed
EU classification Oxidant (O)
R-phrases R8 R22 R36 R37 R38
S-phrases S7 S16 S17 S26 S36 S41
NFPA 704
NFPA 704.svg
Flash point Non-flammable
LD50 3750 mg/kg
Related compounds
Other anions Potassium nitrite
Other cations Lithium nitrate
Sodium nitrate
Rubidium nitrate
Caesium nitrate
Related compounds Potassium sulfate
Potassium chloride
Supplementary data page
Structure and
n, εr, etc.
Phase behaviour
Solid, liquid, gas
Spectral data UV, IR, NMR, MS
 N(what is this?)  (verify)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Potassium nitrate is a chemical compound with the formula KNO3. It occurs as a mineral niter and is a natural solid source of nitrogen. Its common names include saltpetre (saltpeter in American English), from Medieval Latin sal petræ: "stone salt" or possibly "Salt of Petra" and nitrate of potash. The mineral nitratite also named Peru saltpetre or Chile saltpetre (American Peru saltpeter or Chile saltpeter) refers not to potassium nitrate but to the natural mineral form of a similar chemical sodium nitrate. Major uses of potassium nitrate are in fertilizers, rocket propellants and fireworks; it is one of the constituents of gunpowder. When used as a food additive in the European Union, the compound is referred to as E252.



[edit] History of production

The earliest known complete purification process for potassium nitrate was outlined in 1270 by the Arab 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'), where he first described the use of potassium carbonate (in the form of wood ashes).[2]

Into the 20th century, niter-beds were prepared by mixing manure with either mortar or wood ashes, common earth and organic materials such as straw to give porosity to a compost pile typically 1.5×2×5 meters in size.[3] The heap was usually under a cover from the rain, kept moist with urine, turned often to accelerate the decomposition and leached with water after approximately one year. Dung-heaps were a particularly common source: ammonia from the decomposition of urea and other nitrogenous materials would undergo bacterial oxidation to produce various nitrates, primarily calcium nitrate, which could be converted to potassium nitrate by the addition of potash from wood ashes.

A variation on this process, using only urine, straw and wood ash, is described by LeConte. Stale urine is placed in a container of straw hay and is allowed to sour for many months, after which water is used to wash the resulting chemical salts from the straw. The process is completed by filtering the liquid through wood ashes and air-drying in the sun.[3]

During this period, the major natural sources of potassium nitrate were the deposits crystallizing from cave walls and the accumulations of bat guano in caves. Traditionally guano was the source used in Laos for the manufacture of gunpowder for Bang Fai rockets.

Potassium nitrates not only supplied the oxidant and much of the energy for gunpowder in the 19th century, but after 1889 small arms and large artillery increasingly began to depend on cordite, a smokeless powder which required in manufacture large quantities of nitric acid derived from mineral nitrates (either potassium nitrate, or increasingly sodium nitrate), and the basic industrial chemical sulfuric acid. These propellants, like all nitrated explosives (nitroglycerine, TNT, etc.) use the energy available when organic nitrates burn or explode and are converted to nitrogen gas, a process that releases large amounts of energy.

From 1903 until the World War I era, potassium nitrate for black powder and fertilizer was produced on an industrial scale from nitric acid produced via the Birkeland–Eyde process, which used an electric arc to oxidize nitrogen from the air. During World War I the newly industrialized Haber process (1913) was combined with the Ostwald process after 1915, allowing Germany to produce nitric acid for the war after being cut off from its supplies of mineral sodium nitrates from Chile (see nitratite). The Haber process catalyzes ammonia production from atmospheric nitrogen, and industrially-produced hydrogen. From the end of World War I until today, practically all organic nitrates have been produced from nitric acid from the oxidation of ammonia in this way. Some sodium nitrate is still mined industrially. Almost all potassium nitrate, now used only as a fine chemical, is produced from basic potassium salts and nitric acid.

[edit] Production

Potassium nitrate can be made by combining ammonium nitrate and potassium hydroxide.

NH4NO3 (aq) + KOH (aq) → NH3 (g) + KNO3 (aq) + H2O (l)

An alternative way of producing potassium nitrate without a by-product of ammonia is to combine ammonium nitrate and potassium chloride, easily obtained as a sodium-free salt substitute.

NH4NO3 (aq) + KCl (aq) → NH4Cl (aq) + KNO3 (aq)

Potassium nitrate can also be produced by neutralizing nitric acid with potassium hydroxide. This reaction is highly exothermic.

KOH (aq) + HNO3 → KNO3 (aq) + H2O (l)

[edit] Properties

Potassium nitrate has an orthorhombic crystal structure at room temperature, which transforms to a trigonal system at 129 °C. Upon heating to temperatures above 560 °C, it decomposes into potassium nitrite, generating oxygen:

2 KNO3 → 2 KNO2 + O2

Potassium nitrate is moderately soluble in water, but its solubility increases with temperature (see infobox). The aqueous solution is almost neutral, exhibiting pH 6.2 at 14 °C 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.[4]

[edit] Uses

Potassium nitrate is mainly used in fertilizers, as a source of nitrogen and potassium – two of the macro nutrients for plants. When used by itself, it has an NPK rating of 13-0-44. Potassium nitrate is also one of the three components of black powder, along with powdered charcoal (substantially carbon) and sulfur, where it acts as an oxidizer.

In the process of food preservation, potassium nitrate has been a common ingredient of salted meat since the Middle Ages,[5] but its use has been mostly discontinued due to inconsistent results compared to more modern nitrate and nitrite compounds. Even so, saltpetre is still used in some food applications, such as charcuterie and the brine used to make corned beef.[6] Sodium nitrate (and nitrite) have mostly supplanted potassium nitrate's culinary usage, as they are more reliable in preventing bacterial infection than saltpetre. All three give cured salami and corned beef their characteristic pink hue.

Potassium nitrate is an efficient oxidizer, which produces a lilac-colored flame upon burning due to the presence of potassium. It is therefore used in amateur rocket propellants and in several fireworks such as smoke bombs, made with a mixture of sucrose and potassium nitrate.[7] It is also added to pre-rolled cigarettes to maintain an even burn of the tobacco.[8]

Potassium nitrate is the main component (usually about 98%) of tree stump remover, as it accelerates the natural decomposition of the stump.[9] It is also commonly used in the heat treatment of metals as a solvent in the post-wash. The oxidizing, water solubility and low cost make it an ideal short-term rust inhibitor.

Potassium nitrate was used to ensure complete combustion of paper cartridges for cap and ball revolvers, as a treatment agent for the paper used to make the cartridges.[10]

[edit] Pharmacology

Potassium nitrate can be found in some toothpastes for sensitive teeth.[11] Recently, the use of potassium nitrate in toothpastes for treating sensitive teeth has increased and may be an effective treatment.[12][13]

Potassium nitrate in some toothpastes has shown to relieve asthmatic symptoms in some people. It was used in centuries past to treat asthma as well as arthritis.[citation needed]

Potassium nitrate successfully combats high blood pressure and was once used as a hypotensive. Other nitrates and nitrites such as glyceryl trinitrate (nitroglycerin), amyl nitrite and isosorbide derivatives are still used to relieve angina.

Potassium nitrate was once thought to induce impotence, and is still falsely rumored to be in institutional food (such as military fare) as an anaphrodisiac; however, there is no scientific evidence for such properties.[14][15]

[edit] See also

The crystal structure of KNO3

[edit] References

  1. ^ Record of Potassium nitrate in the GESTIS Substance Database from the IFA, accessed on 2007-03-09.
  2. ^ Ahmad Y Hassan, Potassium Nitrate in Arabic and Latin Sources, History of Science and Technology in Islam.
  3. ^ a b LeConte, Joseph (1862). Instructions for the Manufacture of Saltpeter. Columbia, S.C.: South Carolina Military Department. p. 14. http://docsouth.unc.edu/imls/lecontesalt/leconte.html. Retrieved 2007-10-19. 
  4. ^ B. J. Kosanke, B. Sturman, K. Kosanke, I. von Maltitz, T. Shimizu, M. A. Wilson, N. Kubota, C. Jennings-White, D. Chapman (2004). "2". Pyrotechnic Chemistry. Journal of Pyrotechnics. pp. 5–6. ISBN 1889526150. http://books.google.com/books?id=Q1yJNr92-YcC&pg=PA9. 
  5. ^ "Meat Science", University of Wisconsin
  6. ^ Corned Beef, Food Network
  7. ^ Amthyst Galleries, Inc.
  8. ^ Inorganic Additives for the Improvement of Tobacco, TobaccoDocuments.org
  9. ^ Stump Remover MSDS
  10. ^ Kirst, W.J. (1983). Self Consuming Paper Cartridges for the Percussion Revolver. Minneapolis, Minnesota: Northwest Development Co.. 
  11. ^ "Sensodyne Toothpaste for Sensitive Teeth". 2008-08-03. http://us.sensodyne.com/products_freshmint.aspx. Retrieved 2008-08-03. 
  12. ^ "The Effect of Potassium Nitrate and Silica Dentifrice in the Surface of Dentin". http://sciencelinks.jp/j-east/article/200315/000020031503A0361500.php. Retrieved 2010-07-16. 
  13. ^ Managing dentin hypersensitivity, Robin Orchardson and David G. Gillam, J Am Dent Assoc, Vol 137, No 7, 990-998. 2006
  14. ^ "The Straight Dope: Does saltpeter suppress male ardor?". 1989-06-16. http://www.straightdope.com/classics/a3_221.html. Retrieved 2007-10-19. 
  15. ^ Jones, Richard E.; Kristin H. López (2006). Human Reproductive Biology, Third Edition. Elsevier/Academic Press. p. 225. ISBN 0120884658. http://books.google.com/books?id=pfiZfui2XLIC&pg=PA225. 

[edit] Bibliography

  • Dennis W. Barnum. (2003). "Some History of Nitrates." Journal of Chemical Education. v. 80, p. 1393-. link.
  • Alan Williams: The production of saltpeter in the Middle Ages, Ambix, 22 (1975), pp. 125–33. Maney Publishing, ISSN 0002-6980.

[edit] External links

MSDS Number: P5950 * * * * * Effective Date: 08/20/08 * * * * * Supercedes: 10/19/05 POTASSIUM NITRATE


1. Product Identification

Synonyms: Saltpeter; niter; Nitric acid, potassium salt
CAS No.: 7757-79-1
Molecular Weight: 101.1
Chemical Formula: KNO3
Product Codes:
J.T. Baker: 3190, 3192, 3193
Mallinckrodt: 3651, 6370, 6390, 6715, 7028

2. Composition/Information on Ingredients

  Ingredient                                CAS No         Percent        Hazardous                                  
  ---------------------------------------   ------------   ------------   ---------   
  Potassium Nitrate                         7757-79-1        99 - 100%       Yes                                                                    

3. Hazards Identification

Emergency Overview

SAF-T-DATA(tm) Ratings (Provided here for your convenience)
Health Rating: 2 - Moderate
Flammability Rating: 0 - None
Reactivity Rating: 3 - Severe (Oxidizer)
Contact Rating: 2 - Moderate (Life)
Storage Color Code: Yellow (Reactive)

Potential Health Effects

Causes irritation to the respiratory tract. Symptoms may include coughing, shortness of breath.
Causes irritation to the gastrointestinal tract. Symptoms may include nausea, vomiting and diarrhea. May cause gastroenteritis and abdominal pains. Purging and diuresis can be expected. Rare cases of nitrates being converted to the more toxic nitrites have been reported, mostly with infants.
Skin Contact:
Causes irritation to skin. Symptoms include redness, itching, and pain.
Eye Contact:
Causes irritation, redness, and pain.
Chronic Exposure:
Under some circumstances methemoglobinemia occurs in individuals when the nitrate is converted by bacteria in the stomach to nitrite. Nausea, vomiting, dizziness, rapid heart beat, irregular breathing, convulsions, coma, and death can occur should this conversion take place. Chronic exposure to nitrites may cause anemia and adverse effects to kidney.
Aggravation of Pre-existing Conditions:
No information found.

4. First Aid Measures

Remove to fresh air. If not breathing, give artificial respiration. If breathing is difficult, give oxygen. Get medical attention.
Induce vomiting immediately as directed by medical personnel. Never give anything by mouth to an unconscious person. Get medical attention.
Skin Contact:
Immediately flush skin with plenty of water for at least 15 minutes while removing contaminated clothing and shoes. Get medical attention. Wash clothing before reuse. Thoroughly clean shoes before reuse.
Eye Contact:
Immediately flush eyes with plenty of water for at least 15 minutes, lifting lower and upper eyelids occasionally. Get medical attention immediately.

5. Fire Fighting Measures

Not combustible, but substance is a strong oxidizer and its heat of reaction with reducing agents or combustibles may cause ignition.
Some nitrates may explode when shocked, exposed to heat or flame, or by spontaneous chemical reaction. Sealed containers may rupture when heated. Sensitive to mechanical impact.
Fire Extinguishing Media:
Dry chemical, carbon dioxide, Halon, water spray, or fog. If water is used, apply from as far a distance as possible. Water spray may be used to keep fire exposed containers cool. Do not allow water runoff to enter sewers or waterways.
Special Information:
Wear full protective clothing and breathing equipment for high-intensity fire or potential explosion conditions. This oxidizing material can increase the flammability of adjacent combustible materials.

6. Accidental Release Measures

Remove all sources of ignition. Ventilate area of leak or spill. Wear appropriate personal protective equipment as specified in Section 8. Spills: Clean up spills in a manner that does not disperse dust into the air. Use non-sparking tools and equipment. Reduce airborne dust and prevent scattering by moistening with water. Pick up spill for recovery or disposal and place in a closed container.

7. Handling and Storage

Keep in a tightly closed container, stored in a cool, dry, ventilated area. Protect against physical damage and moisture. Isolate from any source of heat or ignition. Avoid storage on wood floors. Separate from incompatibles, combustibles, organic or other readily oxidizable materials. Containers of this material may be hazardous when empty since they retain product residues (dust, solids); observe all warnings and precautions listed for the product.

8. Exposure Controls/Personal Protection

Airborne Exposure Limits:
None established.
Ventilation System:
A system of local and/or general exhaust is recommended to keep employee exposures as low as possible. Local exhaust ventilation is generally preferred because it can control the emissions of the contaminant at its source, preventing dispersion of it into the general work area. Please refer to the ACGIH document, Industrial Ventilation, A Manual of Recommended Practices, most recent edition, for details.
Personal Respirators (NIOSH Approved):
For conditions of use where exposure to dust or mist is apparent and engineering controls are not feasible, a particulate respirator (NIOSH type N95 or better filters) may be worn. If oil particles (e.g. lubricants, cutting fluids, glycerine, etc.) are present, use a NIOSH type R or P filter. For emergencies or instances where the exposure levels are not known, use a full-face positive-pressure, air-supplied respirator. WARNING: Air-purifying respirators do not protect workers in oxygen-deficient atmospheres.
Skin Protection:
Wear impervious protective clothing, including boots, gloves, lab coat, apron or coveralls, as appropriate, to prevent skin contact.
Eye Protection:
Use chemical safety goggles and/or full face shield where dusting or splashing of solutions is possible. Maintain eye wash fountain and quick-drench facilities in work area.

9. Physical and Chemical Properties

White crystals.
36 gm/l00 ml water
Specific Gravity:
ca. 7
% Volatiles by volume @ 21C (70F):
Boiling Point:
400C (752F)
Melting Point:
333C (631F)
Vapor Density (Air=1):
Vapor Pressure (mm Hg):
Negligible @ 20C
Evaporation Rate (BuAc=1):
No information found.

10. Stability and Reactivity

Stable under ordinary conditions of use and storage.
Hazardous Decomposition Products:
Oxides of nitrogen and toxic metal fumes may form when heated to decomposition.
Hazardous Polymerization:
Will not occur.
Heavy metals, phosphites, organic compounds, carbonaceous materials, strong acids, and many other substances.
Conditions to Avoid:
Heat, flames, ignition sources and incompatibles.

11. Toxicological Information

Oral rat LD50: 3750 mg/kg. Investigated as a mutagen, reproductive effector.
  --------\Cancer Lists\------------------------------------------------------
                                         ---NTP Carcinogen---
  Ingredient                             Known    Anticipated    IARC Category
  ------------------------------------   -----    -----------    -------------
  Potassium Nitrate (7757-79-1)           No          No            None

12. Ecological Information

Environmental Fate:
No information found.
Environmental Toxicity:
No information found.

13. Disposal Considerations

Whatever cannot be saved for recovery or recycling should be handled as hazardous waste and sent to a RCRA approved waste facility. Processing, use or contamination of this product may change the waste management options. State and local disposal regulations may differ from federal disposal regulations. Dispose of container and unused contents in accordance with federal, state and local requirements.

14. Transport Information

Domestic (Land, D.O.T.)
Proper Shipping Name: POTASSIUM NITRATE
Hazard Class: 5.1
UN/NA: UN1486
Packing Group: III
Information reported for product/size: 50KG

International (Water, I.M.O.)
Proper Shipping Name: POTASSIUM NITRATE
Hazard Class: 5.1
UN/NA: UN1486
Packing Group: III
Information reported for product/size: 50KG

International (Air, I.C.A.O.)
Proper Shipping Name: POTASSIUM NITRATE
Hazard Class: 5.1
UN/NA: UN1486
Packing Group: III
Information reported for product/size: 50KG

15. Regulatory Information

  --------\Chemical Inventory Status - Part 1\---------------------------------
  Ingredient                                       TSCA  EC   Japan  Australia
  -----------------------------------------------  ----  ---  -----  ---------
  Potassium Nitrate (7757-79-1)                     Yes  Yes   Yes      Yes                                      
  --------\Chemical Inventory Status - Part 2\---------------------------------
  Ingredient                                       Korea  DSL   NDSL  Phil.
  -----------------------------------------------  -----  ---   ----  -----
  Potassium Nitrate (7757-79-1)                     Yes   Yes   No     Yes          
  --------\Federal, State & International Regulations - Part 1\----------------
                                             -SARA 302-    ------SARA 313------
  Ingredient                                 RQ    TPQ     List  Chemical Catg.
  -----------------------------------------  ---   -----   ----  --------------
  Potassium Nitrate (7757-79-1)              No    No      No    Nitrate Cmpd
  --------\Federal, State & International Regulations - Part 2\----------------
                                                        -RCRA-    -TSCA-
  Ingredient                                 CERCLA     261.33     8(d) 
  -----------------------------------------  ------     ------    ------
  Potassium Nitrate (7757-79-1)              No         No         No        
Chemical Weapons Convention:  No     TSCA 12(b):  No     CDTA:  No
SARA 311/312:  Acute: Yes      Chronic: Yes  Fire: Yes Pressure: No
Reactivity: No          (Pure / Solid) 

Australian Hazchem Code: 1[T]
Poison Schedule: None allocated.
This MSDS has been prepared according to the hazard criteria of the Controlled Products Regulations (CPR) and the MSDS contains all of the information required by the CPR.

16. Other Information

NFPA Ratings: Health: 1 Flammability: 0 Reactivity: 0 Other: Oxidizer
Label Hazard Warning:
Label Precautions:
Keep from contact with clothing and other combustible materials.
Store in a tightly closed container.
Do not store near combustible materials.
Remove and wash contaminated clothing promptly.
Avoid contact with eyes, skin and clothing.
Avoid breathing dust.
Keep container closed.
Use only with adequate ventilation.
Wash thoroughly after handling.
Label First Aid:
If swallowed, induce vomiting immediately as directed by medical personnel. Never give anything by mouth to an unconscious person. If inhaled, remove to fresh air. If not breathing, give artificial respiration. If breathing is difficult, give oxygen. In case of contact, immediately flush eyes or skin with plenty of water for at least 15 minutes while removing contaminated clothing and shoes. Wash clothing before reuse. In all cases, get medical attention.
Product Use:
Laboratory Reagent.
Revision Information:
No Changes.
Mallinckrodt Baker, Inc. provides the information contained herein in good faith but makes no representation as to its comprehensiveness or accuracy. This document is intended only as a guide to the appropriate precautionary handling of the material by a properly trained person using this product. Individuals receiving the information must exercise their independent judgment in determining its appropriateness for a particular purpose. MALLINCKRODT BAKER, INC. MAKES NO REPRESENTATIONS OR WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION ANY WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE WITH RESPECT TO THE INFORMATION SET FORTH HEREIN OR THE PRODUCT TO WHICH THE INFORMATION REFERS. ACCORDINGLY, MALLINCKRODT BAKER, INC. WILL NOT BE RESPONSIBLE FOR DAMAGES RESULTING FROM USE OF OR RELIANCE UPON THIS INFORMATION.
Prepared by: Environmental Health & Safety
Make potassium nitrate (saltpeter) from common household ingredients. Potassium chloride from lite salt and ammonium nitrate from a cold pack are reacted to yield potassium nitrate and ammonium chloride. This is an easy way to make your own potassium chloride if you can't find it in a store or just want to try a fun chemistry experiment. Potassium Nitrate Ingredients

* 40 g ammonium nitrate (from an instant cold pack which has ammonium nitrate listed as its ingredient)

* 37 g potassium chloride (sold as a salt substitute, with potassium chloride listed as the ingredient)

* 100 ml water

The Chemical Reaction

Aqueous solutions of ammonium nitrate and potassium chloride are reacted to exchange the ions and form potassium nitrate and ammonium chloride. The ammonium chloride is much more soluble in water than the potassium nitrate, so you will get potassium nitrate crystals, which can be separated from the ammonium chloride solution.

NH4NO3 + KCl → KNO3 + NH4Cl

Make Potassium Nitrate

1. Dissolve 40 g of ammonium nitrate into 100 ml of water.

2. Filter the solution through a coffee filter to remove any undissolved material.

3. Heat the solution with 37 g potassium chloride to dissolve the lite salt. Do not boil the solution.

4. Filter the solution and either set it in the freezer to chill or else put it in an ice bath so you can observe the crystallization of the potassium nitrate.

5. Pour off the ammonium chloride solution, leaving the potassium nitrate crystals. You can recover the ammonium chloride, too, if you like.

6. Once the potassium nitrate crystals are dry, you can use them for chemistry experiments. The resulting potassium nitrate does contain impurities, but it will work fine for pyrotechnics projects and other experiments described on this site.