Metal nitrates and nitrites

Nitrites generally decompose at lower temperatures than the corresponding nitrates. The formation of nitrites as intermediates during the decomposition of nitrates is doubtful (or difficult to demonstrate). However, with nitrites, the decomposition is supposed to take place according to the scheme 

Accumulation of gaseous products may result [814] in oxidation of the nitrite to the nitrate (if the latter is stable at the reaction temperature). 

Anhydrous nitrates and nitrites are often difficult to prepare and residual water can hydrolyze the reactant with the formation of basic 

Decomposition of the rare earth nitrates proceeded [821] through the intermediate formation of oxysalts of the form MON03 and E values were low Nd(N03)3, 33 kJ mole 1, 663-703 K Dy(N03)3, 23 kJ mole 1, 583—633 K Yb(N03)3, 46 kJ mole 1, 563—598 K. Thermogravimetric curves showed that the formation of anhydrous salts was possible, in contrast to observations by Wendlandt and Bear [826]. In a similar study [827] of the reaction of Pr(N03)3 at 558—758 K, the intermediate formation of a nitrite is postulated during decomposition to a non-stoichiometric residual oxide, Pr0li83 (the actual composition depends on temperature). 

Barium and lead nitrites [821] decompose to yield nitrates [828] 

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The initial study on the MeO-TEMPO / Mg(N03)2 / NBS triple catalyst system in the oxidation of 1 indicated the necessity of all three components the TEMPO based catalyst, the nitrate source (MNT) and the bromine source (NBS). A large number of metal nitrates and nitrites were screened initially and the highest activity and aldehyde selectivity under comparable reaction conditions were recorded using Mg(N03)2 as the nitrate component. A number of organic and inorganic bromides soluble in HOAc were also screened and high reaction rates were found when NBS was used as the bromide source. The effect of the concentration of the individual components of the new triple catalyst system on the reaction rate, on the conversion of 1 and on the selectivity to 2 over 60 min reaction time is shown in Figure 1. 

E.A. Bordushkova, Thermal Stability and Decomposition Kinetics of Alkali Metal Nitrates and Nitrites, PhD thesis (Rostov State University, Rostov, 1984). 

J. Greenberg and L. J. Hallgren, Infrared Absorption Spectra of Alkali Metal Nitrates and Nitrites Above and Below the Melting Point, J. Chem. Phys. 33, 900-902, 1960. 

Diverse and sometimes contrasting types of kinetic behaviour have been described for the decompositions of salts in this class, which includes the metal carbonates, sulphates, nitrates and nitrites, phosphates, oxyhalides, permanganates and chromates (Sects. 3.1—3.7, respectively). It is con-... 

Reduction of nitrate (and nitrite) occurs by interaction with the metal, for example, by metallic iron that has been widely studied for elaborating a technology to remove nitrate from water [66-70]. The very principle of this procedure that the anodic transformation (dissolution) corrosion of metallic iron Fe(0) leading to the formation of Fe(II) and Fe(III) species is coupled with the reduction process. The effect of pFi and the iron-to-nitrate ratio, temperature, and mass transport were studied under various conditions in order to elaborate a suitable technology. 

Many compounds have been tested as ignition quality improvers—additives which shorten the ignition delay to a desirable duration. An extensive review in 1944 (6, 43) listed 303 references, 92 dealing with alkyl nitrates and nitrites 61 with aldehydes, ketones, esters, and ethers 49 with peroxides 42 with aromatic nitro compounds 29, with metal derivatives 28 with oxidation and oxidation products 22 with polysulfides 16 with aromatic hydrocarbons nine with nitration and four with oximes and nitroso compounds. In 1950, tests at the U. S. Naval Engineering Experiment Station (48) showed that a concentration of 1.5% of certain peroxides, alkyl nitrates, nitroaikanes, and nitrocarbamates increased cetane number 20 or more units. 

In zinc phosphating. a small amount of iron phosphate is formed initially, bul ihe bath contains primary zinc phosphate. ZnlHiP04)>, which crystallizes on Ihe metal surface as secondary and tertiary zinc phosphates, ZnHP04 and Znt(P04 j. respectively, when the pH rises at the mclal/solulion interlace. The most frequently used baths contain accelerators, preferably nitrates and nitrites, which oxidize the hydrogen lormcd hy the pickling reactions. The fundamental zinc phosphate reactions occur in three steps, all in the same hath ... 

Thus, it was observed that the first-order rate constants (/q) for nitrate reduction by untreated Fe° increase due to the pretreatment of iron metal with HC1 however, observed increases in the rate constant for nitrite reduction have been relatively small under similar acid pretreatment conditions. During the first 12 hr, the rate constant for nitrate reduction showed a gradual decline, and this decline seems to have been clearly influenced by the presence of chloride. The reaction rate constants for nitrate and nitrite reduction by untreated Fe° turnings are directly dependent on the concentration of Fe° used, ranging between 69.4 and 208.2 g/L thus /c, and k, increase linearly with increases in the surface area of the untreated iron. Table 13.8 demonstrates that acid-treated Fe° is more reactive than its untreated counterpart. 

Rahman, A. and Agrawal, A., Reduction of nitrate and nitrite by iron metal implications for ground water remediation. Abstract Paper. Am. Chem. Soc., Environ. Part 1, 213,175, April 13, 1997. 

Heavy metals, arsenic speciation, mercury speciation, organophosphates, organochlo-rine pesticides, VOCs, dichloroethane, trichloroethylene cotinine, nitrates and nitrites, creosote, PAHs (wood smoke), radionuclides, cyanide, dioxin-furan, disinfection byproducts, perchlorates, phthalate metabolites, thiodiglycol (mustard gas), sarin... 

Statutory legislation to control the levels of such substances in food has been introduced in the UK and elsewhere. In more recent years, other potentially toxic elements have come into focus. Lead, cadmium and mercury have been the subject of much monitoring of the food chain and other metals, in particular aluminium, are continuing to attract attention. Nitrate and nitrite in food from food additive use is regulated across the European Union, but its presence in food crops has raised concerns. 

Chemical contamination does not respect international borders. The contaminants are spread worldwide by air and water. Environmental organic contaminants and inorganic contaminants such as metals and metal compounds, nitrate and nitrite will be present in all foods, though sometimes in quantities below the limit of detection of the analytical methods of today. Moreover, foods as well as raw materials and ingredients for food production are to an increasing extent traded across borders. 

Water quality and components present in the solution matrix affect the catalytic reaction. Acids dissolve the Pd metal, while bases promote some reactions. Batch tests showed that oxygen, sulfate, nitrate, and nitrite slowed reaction somewhat sulfite slowed it significantly, and bisulfide deactivated the catalyst completely. Column tests of TCE reaction on a Pd/alumina catalyst with DI water caused no observable deactivation, but deactivation was seen with the reaction of TCA on Pd/C. In the Pd/alumina column, the addition of nitrate to DI water did slow the reaction phosphate, carbonate, and carbon dioxide caused some deactivation. Regeneration through evacuation and oxidation of the catalyst improved the activity. 

Synonyms nitrogen peroxide Formula N02 MW 46.01 CAS [10102-44-0] occurs in the exhausts of automobiles and in cigarette smoke produced by the reaction of nitric acid with metals and decomposition of nitrates or during fire reddish-brown fuming liquid or gas sharp pungent odor liquefies at 21°C solidifies at -9.3°C density of liquid 1.45 at 20°C vapor 1.58 (air= 1) reacts with water to form nitric acid and nitrogen oxide reacts with alkalies to form nitrates and nitrites highly toxic. 

Oxidising agents—diphenylamine test. Filter a portion of the sample md add 2 (hops of the filtrate to 1 ml of a 1% solution of diphenylamine in sulphuric acid. A deep blue colour, appearing immediately, indicates tiie presence of an oxidising agent. The test will detect hypochlorite (from domestic bleach), bromates, chlorates, iodates, nitrates, and nitrites. Tests to distinguish between certain anions will be foimd imder Metals and Anions (p.64). 

SAFETY PROFILE Moderately toxic by subcutaneous route. Incompatible with metal nitrates, sodium nitrite. When heated to decomposition it emits very toxic fumes of Na20 and SO. See also SODIUM THIOSULFATE and SODIUM THIOSULFATE, PENTAHYDRATE. 

Similarly, the anode potential can be controlled by adding a suitable reducing agent. For example, if deposition of metallic lead at the cathode is desired, the anodic deposition of lead dioxide can be prevented by use of hydroxylamine or hydrazine in dilute hydrochloric acid. Lingane and Jones found hydrazine to be superior in keeping the anode potential at a lower value and in forming simpler oxidation products (nitrogen instead of mixtures of nitrous oxide, nitrate, and nitrite). 

Nitric oxide is more active than free nitrogen. For example, nitric oxide combines with oxygen and water in the atmosphere to make nitric acid. When it rains, nitric acid is carried to the earth. There it combines with metals in Earth s crust. Compounds known as nitrates and nitrites are formed. 

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