Red fuming nitric acid

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Red fuming nitric acid
Fuming nitric acid 40ml.jpg
Names
IUPAC name
Nitric acid
Other names
Red fuming nitric acid
Identifiers
ChemSpider
  • None
Properties
HNO3 + NO2
AppearanceLiquid, red fumes
Density Increases as free NO2 content increases
Boiling point 83 °C (181 °F; 356 K)
Miscible in water
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
Skin and metal corrosion; serious eye damage; toxic (oral, dermal, pulmonary); severe burns
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Red fuming nitric acid (RFNA) is a storable oxidizer used as a rocket propellant. It consists of nitric acid ( H N O 3), dinitrogen tetroxide ( N 2 O 4) and a small amount of water. The color of red fuming nitric acid is due to the dinitrogen tetroxide, which breaks down partially to form nitrogen dioxide. The nitrogen dioxide dissolves until the liquid is saturated, and produces toxic fumes with a suffocating odor. RFNA increases the flammability of combustible materials and is highly exothermic when reacting with water. [1]

Contents

Since nitrogen dioxide is a product of decomposition of nitric acid, its addition stabilizes nitric acid in accordance with Le Chatelier's principle. Addition of dinitrogen tetroxide also increases oxidizing power and lowers the freezing point. [2]

It is usually used with an inhibitor (with various, sometimes secret, substances, including hydrogen fluoride; [3] :62 any such combination is called inhibited RFNA, IRFNA) because nitric acid attacks most container materials. Hydrogen fluoride for instance will passivate the container metal with a thin layer of metal fluoride, making it nearly impervious to the nitric acid.

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. This is inefficient and it is not normally used this way.

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 as an ignition catalyst [3] :115–9) and SV-Stoff (94% nitric acid with 6% dinitrogen tetroxide) and nicknamed Salbei (sage).

Inhibited RFNA was the oxidizer of the world's most-launched light orbital rocket, the Kosmos-3M. In former-Soviet countries inhibited RFNA is known as Mélange.

Other uses for RFNA include fertilizers, dye intermediates, explosives, and pharmaceutical acidifiers. It can also be used as a laboratory reagent in photoengraving and metal etching. [4]

Compositions

Corrosion

Hydrofluoric acid content of IRFNA [5] [6]
When RFNA is used as an oxidizer for rocket fuels, it usually has a HF content of about 0.6%. The purpose of the HF is to act as a corrosion inhibitor by forming a metal fluoride layer on the surface of the storage vessels.
Water content of RFNA [7]
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 0.1% 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 [5]
Stainless steel, aluminium alloys, iron alloys, chrome plates, tin, gold and tantalum were tested to see how RFNA affected the corrosion rates of each. Experiments were performed using 16% and 6.5% RFNA samples and the different substances listed above. Many different stainless steels showed resistance to corrosion. Aluminium alloys did not endure as well as stainless steels especially in high temperature, but the corrosion rates were not high enough to prohibit the use of this with RFNA. Tin, gold and tantalum showed high corrosion resistance similar to that of stainless steel. These materials are better though because at high temperatures the corrosion rates did not increase much. Corrosion rates at elevated temperatures increase in the presence of phosphoric acid. Sulfuric acid decreased corrosion rates.

See also

Related Research Articles

<span class="mw-page-title-main">Nitric acid</span> Highly corrosive mineral acid

Nitric acid is an inorganic compound with the formula HNO3. It is a highly corrosive mineral acid. The compound is colorless, but samples tend to acquire a yellow cast over time due to decomposition into oxides of nitrogen. Most commercially available nitric acid has a concentration of 68% in water. When the solution contains more than 86% HNO3, it is referred to as fuming nitric acid. Depending on the amount of nitrogen dioxide present, fuming nitric acid is further characterized as red fuming nitric acid at concentrations above 86%, or white fuming nitric acid at concentrations above 95%.

The Ostwald process is a chemical process used for making nitric acid (HNO3). The Ostwald process is a mainstay of the modern chemical industry, and it provides the main raw material for the most common type of fertilizer production. Historically and practically, the Ostwald process is closely associated with the Haber process, which provides the requisite raw material, ammonia (NH3). This method is preferred over other methods of nitric acid production, in that it is less expensive and more efficient.

<span class="mw-page-title-main">Aqua regia</span> Mixture of nitric acid and hydrochloric acid in a 1:3 molar ratio

Aqua regia is a mixture of nitric acid and hydrochloric acid, optimally in a molar ratio of 1:3. Aqua regia is a fuming liquid. Freshly prepared aqua regia is colorless, but it turns yellow, orange or red within seconds from the formation of nitrosyl chloride and nitrogen dioxide. It was so named by alchemists because it can dissolve noble metals like gold and platinum, though not all metals.

<span class="mw-page-title-main">Hypergolic propellant</span> Type of rocket engine fuel

A hypergolic propellant is a rocket propellant combination used in a rocket engine, whose components spontaneously ignite when they come into contact with each other.

Unsymmetrical dimethylhydrazine (abbreviated as UDMH; also known as 1,1-dimethylhydrazine, heptyl or Geptil) is a chemical compound with the formula H2NN(CH3)2 that is primarily used as a rocket propellant. At room temperature, UDMH is a colorless liquid, with a sharp, fishy, ammonia-like smell typical of organic amines. Samples turn yellowish on exposure to air and absorb oxygen and carbon dioxide. It is miscible with water, ethanol, and kerosene. At concentrations between 2.5% and 95% in air, its vapors are flammable. It is not sensitive to shock.

<span class="mw-page-title-main">Oxidizing agent</span> Chemical compound used to oxidize another substance in a chemical reaction

An oxidizing agent is a substance in a redox chemical reaction that gains or "accepts"/"receives" an electron from a reducing agent. In other words, an oxidizer is any substance that oxidizes another substance. The oxidation state, which describes the degree of loss of electrons, of the oxidizer decreases while that of the reductant increases; this is expressed by saying that oxidizers "undergo reduction" and "are reduced" while reducers "undergo oxidation" and "are oxidized". Common oxidizing agents are oxygen, hydrogen peroxide, and the halogens.

<span class="mw-page-title-main">Dinitrogen tetroxide</span> Chemical compound

Dinitrogen tetroxide, commonly referred to as nitrogen tetroxide (NTO), and occasionally (usually among ex-USSR/Russian rocket engineers) as amyl, is the chemical compound N2O4. It is a useful reagent in chemical synthesis. It forms an equilibrium mixture with nitrogen dioxide. Its molar mass is 92.011 g/mol.

<span class="mw-page-title-main">Nitric oxide</span> Colorless gas with the formula NO

Nitric oxide is a colorless gas with the formula NO. It is one of the principal oxides of nitrogen. Nitric oxide is a free radical: it has an unpaired electron, which is sometimes denoted by a dot in its chemical formula. Nitric oxide is also a heteronuclear diatomic molecule, a class of molecules whose study spawned early modern theories of chemical bonding.

<span class="mw-page-title-main">Nitrogen dioxide</span> Chemical compound with formula NO₂

Nitrogen dioxide is a chemical compound with the formula NO2. One of several nitrogen oxides, nitrogen dioxide is a reddish-brown gas. It is a paramagnetic, bent molecule with C2v point group symmetry. Industrially, NO2 is an intermediate in the synthesis of nitric acid, millions of tons of which are produced each year, primarily for the production of fertilizers.

Nitrogen oxide may refer to a binary compound of oxygen and nitrogen, or a mixture of such compounds:

<span class="mw-page-title-main">Nitrous acid</span> Chemical compound

Nitrous acid is a weak and monoprotic acid known only in solution, in the gas phase, and in the form of nitrite salts. It was discovered by Carl Wilhelm Scheele, who called it "phlogisticated acid of niter". Nitrous acid is used to make diazonium salts from amines. The resulting diazonium salts are reagents in azo coupling reactions to give azo dyes.

<span class="mw-page-title-main">Dinitrogen pentoxide</span> Chemical compound

Dinitrogen pentoxide is the chemical compound with the formula N2O5. It is one of the binary nitrogen oxides, a family of compounds that contain only nitrogen and oxygen. It exists as colourless crystals that sublime slightly above room temperature, yielding a colorless gas.

The highest specific impulse chemical rockets use liquid propellants. They can consist of a single chemical or a mix of two chemicals, called bipropellants. Bipropellants can further be divided into two categories; hypergolic propellants, which ignite when the fuel and oxidizer make contact, and non-hypergolic propellants which require an ignition source.

Nitrosyl fluoride (NOF) is a covalently bonded nitrosyl compound.

The chemical element nitrogen is one of the most abundant elements in the universe and can form many compounds. It can take several oxidation states; but the most common oxidation states are -3 and +3. Nitrogen can form nitride and nitrate ions. It also forms a part of nitric acid and nitrate salts. Nitrogen compounds also have an important role in organic chemistry, as nitrogen is part of proteins, amino acids and adenosine triphosphate.

Mixed oxides of nitrogen (MON) are solutions of dinitrogen trioxide (N2O3) in dinitrogen tetroxide/nitrogen dioxide (N2O4 and NO2). It may be used as an oxidizing agent in rocket propulsion systems.

<span class="mw-page-title-main">XLR81</span> American Agena rocket motor (1963–1984)

The Bell Aerosystems Company XLR81 was an American liquid-propellant rocket engine, which was used on the Agena upper stage. It burned UDMH and RFNA fed by a turbopump in a fuel rich gas generator cycle. The turbopump had a single turbine with a gearbox to transmit power to the oxidizer and fuel pumps. The thrust chamber was all-aluminum, and regeneratively cooled by oxidizer flowing through gun-drilled passages in the combustion chamber and throat walls. The nozzle was a titanium radiatively cooled extension. The engine was mounted on a hydraulic actuated gimbal which enabled thrust vectoring to control pitch and yaw. Engine thrust and mixture ratio were controlled by cavitating flow venturis on the gas generator flow circuit. Engine start was achieved by solid propellant start cartridge.

Mélange is a liquid oxidant rocket propellant component that was "used during the Soviet era as one of two components to propel small and medium range missiles." It is highly toxic and aggressive mixture of nitric acid and dinitrogen tetroxide (18-27%) and other additives and impurities with very limited amount of water. As the mixture is an extremely strong oxidant, it can ignite combustibles upon contact. Upon decomposition it produce red fumes of nitrogen tetroxide and nitric acid.

<span class="mw-page-title-main">Transition metal nitrate complex</span> Compound of nitrate ligands

A transition metal nitrate complex is a coordination compound containing one or more nitrate ligands. Such complexes are common starting reagents for the preparation of other compounds.

References

  1. Sugur, V. S.; Manwani, G. L. (October 1983). "Problems in Storage and Handling of Red Fuming Nitric Acid". Defence Science Journal. 33 (4): 331–337. doi: 10.14429/dsj.33.6188 .
  2. Schmidt, Eckart W. (2022). "Red Fuming Nitric Acid". Encyclopedia of Oxidizers. De Gruyter. pp. 3881–3962. doi:10.1515/9783110750294-029. ISBN   978-3-11-075029-4.
  3. 1 2 Clark, John Drury (23 May 2018). Ignition!: An Informal History of Liquid Rocket Propellants. Rutgers University Press. p. 302. ISBN   978-0-8135-9918-2. OCLC   281664.
  4. O'Neil, Maryadele J. (2006). The Merck index: an encyclopedia of chemicals, drugs, and biologicals. Merck. p. 6576. ISBN   978-0-911910-00-1.
  5. 1 2 Karplan, Nathan; Andrus, Rodney J. (October 1948). "Corrosion of Metals in Red Fuming Nitric Acid and in Mixed Acid". Industrial and Engineering Chemistry. 40 (10): 1946–1947. doi:10.1021/ie50466a021.
  6. Phelps, Edson H.; Lee, Fredrick S.; Robinson, Raymond B. (October 1955). Corrosion Studies in Fuming Nitric Acid (PDF) (Technical report). Wright Air Development Center. 55-109. Archived (PDF) from the original on July 27, 2018. Retrieved 2024-01-02.
  7. Burns, E. A.; Muraca, R. F. (1963). "Determination of Water in Red Fuming Nitric Acid by Karl Fischer Titration". Analytical Chemistry. 35 (12): 1967–1970. doi:10.1021/ac60205a055.

Further reading