Red fuming nitric acid
Encyclopedia
Red fuming nitric acid (RFNA) is a storable oxidizer used as a rocket propellant
. It consists mainly of nitric acid
, also containing 13% dinitrogen tetroxide
and 3% water
. The dissolved nitrogen dioxide is very concentrated and can be found at room temperature. The color of the resulting red fuming nitric acid is due to the dinitrogen tetroxide, which breaks down partially to form nitrogen dioxide
. White fuming nitric acid
does not contain free dinitrogen tetroxide. RFNA gives off a suffocating odor. It increases the flammability of combustible materials and is highly exothermic when reacted with water.
It is usually used with an inhibitor
(with various, sometimes secret, substances, including hydrogen fluoride
; any such combination is called "inhibited RFNA" IRFNA) because nitric acid attacks most container materials.
It can also be a component of a monopropellant
; with substances like amine nitrates dissolved in it, it can be used as the sole fuel in a rocket. It is not normally used this way however.
During World War II
, the German military used RFNA in some rockets. The mixtures used were called S-Stoff (96% nitric acid with 4% ferric chloride) and SV-Stoff (94% nitric acid with 6% dinitrogen tetroxide).
Inhibited RFNA, used in modified SS-1 Scud
missiles as an oxidizer by the Iraqi military during the 1991 Persian Gulf War
, was suggested as a possible factor causing Gulf War Syndrome
. However, this theory was later refuted.
Other uses for RFNA include fertilizers, dye intermediates, explosives, and pharmaceutic aid as acidifier. It can also be used as a laboratory reagent in photoengraving, metal etching.
Rocket propellant
Rocket propellant is mass that is stored in some form of propellant tank, prior to being used as the propulsive mass that is ejected from a rocket engine in the form of a fluid jet to produce thrust. A fuel propellant is often burned with an oxidizer propellant to produce large volumes of very hot...
. It consists mainly of nitric acid
Nitric acid
Nitric acid , also known as aqua fortis and spirit of nitre, is a highly corrosive and toxic strong acid.Colorless when pure, older samples tend to acquire a yellow cast due to the accumulation of oxides of nitrogen. If the solution contains more than 86% nitric acid, it is referred to as fuming...
, also containing 13% dinitrogen tetroxide
Dinitrogen tetroxide
Dinitrogen tetroxide is the chemical compound N2O4. It is a useful reagent in chemical synthesis. It forms an equilibrium mixture with nitrogen dioxide; some call this mixture dinitrogen tetroxide, while some call it nitrogen dioxide.Dinitrogen tetroxide is a powerful oxidizer, making it highly...
and 3% water
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...
. The dissolved nitrogen dioxide is very concentrated and can be found at room temperature. The color of the resulting red fuming nitric acid is due to the dinitrogen tetroxide, which breaks down partially to form nitrogen dioxide
Nitrogen dioxide
Nitrogen dioxide is the chemical compound with the formula it is one of several nitrogen oxides. is an intermediate in the industrial synthesis of nitric acid, millions of tons of which are produced each year. This reddish-brown toxic gas has a characteristic sharp, biting odor and is a prominent...
. White fuming nitric acid
White fuming nitric acid
White fuming nitric acid is a storable liquid oxidizer used with kerosene and hydrazine rocket fuel. It consists of nearly pure nitric acid . WFNA is commonly specified as containing no more than 2% water and less than 0.5% dissolved nitrogen dioxide or dinitrogen tetroxide.WFNA was sometimes...
does not contain free dinitrogen tetroxide. RFNA gives off a suffocating odor. It increases the flammability of combustible materials and is highly exothermic when reacted with water.
It is usually used with an inhibitor
Corrosion inhibitor
A corrosion inhibitor is a chemical compound that, when added to a liquid or gas, decreases the corrosion rate of a material, typically a metal or an alloy. The effectiveness of a corrosion inhibitor depends on fluid composition, quantity of water, and flow regime...
(with various, sometimes secret, substances, including hydrogen fluoride
Hydrogen fluoride
Hydrogen fluoride is a chemical compound with the formula HF. This colorless gas is the principal industrial source of fluorine, often in the aqueous form as hydrofluoric acid, and thus is the precursor to many important compounds including pharmaceuticals and polymers . HF is widely used in the...
; any such combination is called "inhibited RFNA" IRFNA) because nitric acid attacks most container materials.
It can also be a component of a monopropellant
Monopropellant
Monopropellants are propellants composed of chemicals or mixtures of chemicals which can be stored in a single container with some degree of safety. While stable under defined storage conditions, they react very rapidly under certain other conditions to produce a large volume of energetic gases...
; with substances like amine nitrates dissolved in it, it can be used as the sole fuel in a rocket. It is not normally used this way however.
During World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
, the German military used RFNA in some rockets. The mixtures used were called S-Stoff (96% nitric acid with 4% ferric chloride) and SV-Stoff (94% nitric acid with 6% dinitrogen tetroxide).
Inhibited RFNA, used in modified SS-1 Scud
Al Hussein (missile)
Al Hussein or al-Husayn is the designation of an Iraqi ballistic missile. The missile was the result of upgrading the Soviet made Scud in order to achieve a longer range...
missiles as an oxidizer by the Iraqi military during the 1991 Persian Gulf War
Gulf War
The Persian Gulf War , commonly referred to as simply the Gulf War, was a war waged by a U.N.-authorized coalition force from 34 nations led by the United States, against Iraq in response to Iraq's invasion and annexation of Kuwait.The war is also known under other names, such as the First Gulf...
, was suggested as a possible factor causing Gulf War Syndrome
Gulf War syndrome
Gulf War syndrome or Gulf War illness describes a medical condition that affected veterans and civilians who were near conflicts during or downwind of chemical weapons depot demolition, after the 1991 Gulf War. A wide range of acute and chronic symptoms have included fatigue, musculoskeletal...
. However, this theory was later refuted.
Other uses for RFNA include fertilizers, dye intermediates, explosives, and pharmaceutic aid as acidifier. It can also be used as a laboratory reagent in photoengraving, metal etching.
Compositions
- IRFNA IIIa: 83.4% HNO3Nitric acidNitric acid , also known as aqua fortis and spirit of nitre, is a highly corrosive and toxic strong acid.Colorless when pure, older samples tend to acquire a yellow cast due to the accumulation of oxides of nitrogen. If the solution contains more than 86% nitric acid, it is referred to as fuming...
, 14% NO2Nitrogen dioxideNitrogen dioxide is the chemical compound with the formula it is one of several nitrogen oxides. is an intermediate in the industrial synthesis of nitric acid, millions of tons of which are produced each year. This reddish-brown toxic gas has a characteristic sharp, biting odor and is a prominent...
, 2% H2O, 0.6% HFHydrogen fluorideHydrogen fluoride is a chemical compound with the formula HF. This colorless gas is the principal industrial source of fluorine, often in the aqueous form as hydrofluoric acid, and thus is the precursor to many important compounds including pharmaceuticals and polymers . HF is widely used in the... - IRFNA IV HDA: 54.3% HNO3, 44% NO2, 1% H2O, 0.7% HF
- S-Stoff: 96% HNO3, 4% FeCl3
- SV-Stoff: 94% HNO3, 6% N2O4Dinitrogen tetroxideDinitrogen tetroxide is the chemical compound N2O4. It is a useful reagent in chemical synthesis. It forms an equilibrium mixture with nitrogen dioxide; some call this mixture dinitrogen tetroxide, while some call it nitrogen dioxide.Dinitrogen tetroxide is a powerful oxidizer, making it highly...
- AK20: 80% HNO3, 20% N2O4
- AK20F: 80% HNO3, 20% N2O4, fluorine-based inhibitor
- AK20I: 80% HNO3, 20% N2O4, iodine-based inhibitor
- AK20K: 80% HNO3, 20% N2O4, unknown inhibitor
- AK27I: 73% HNO3, 27% N2O4, iodine-based inhibitor
- AK27P: 73% HNO3, 27% N2O4, unknown inhibitor
Experiments
- Hydrofluoric AcidHydrofluoric acidHydrofluoric acid is a solution of hydrogen fluoride in water. It is a valued source of fluorine and is the precursor to numerous pharmaceuticals such as fluoxetine and diverse materials such as PTFE ....
Content of RFNA
- When RFNA is used as an oxidizer for rocket fuels, it usually has a HFHydrogen fluorideHydrogen fluoride is a chemical compound with the formula HF. This colorless gas is the principal industrial source of fluorine, often in the aqueous form as hydrofluoric acid, and thus is the precursor to many important compounds including pharmaceuticals and polymers . HF is widely used in the...
content of about .6%. The purpose of the HF is to act as a corrosion inhibitor. RFNA was tested for HF with a standard solution containing 12% of NO2 and a density of 1.57. These experiments were performed using an electrometric method. It was determined that the hydrofluoric acid content was about .5% by weight. This is very close to the usually .6% in rocket fuels.- WaterWaterWater is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...
content of RFNA
- Water
- To test the water content, a sample of 80% HNO3, 8-20% NO2, and the rest H2O depending on the varied amount of NO2 in the sample. When the RFNA contained HF, there was an average H2O% between 2.4% and 4.2%. When the RFNA did not contain HF, there was an average H2O% between .1% and 5.0%. When the metal impurities from corrosion were taken into account, the H2O% increased, and the H2O% was between 2.2% and 8.8%
- Corrosion of metals in RFNA
- Stainless steel, aluminum alloys, iron alloys, chrome plates, tin, gold and tantalum were tested to see how RFNA affected the corrosion rates of each. This is important to understand because the containers that RFNA is kept in will affect the RFNA. Experiments were performed using 16% and 6.5% RFNA samples and the different substances listed above. Many different stainless steels showed resistance to corrosion. Aluminum alloys did not hold up as well as stainless steels especially in high temperatures but the corrosion rates were not high enough to prohibit the use of this with RFNA. Tin, gold and tantalum showed high resistance such like that of stainless steel. These are better though because at high temperatures, the corrosion rates were still kept low. It is important to note that at higher temperatures and the presence of phosphoric acid, the corrosion rates increase while sulfuric acid helped the corrosion rates and kept the substances from corrosion.
External links
- National Pollutant Inventory - Nitric Acid Fact Sheet
- http://www.astronautix.com/props/nitidjpx.htm