Nitrite standard

St CA 45, 6l56(1951)(Reverse Redox method) 9) M. Halse, MeddNotskFarm-Selskap 16, 166-9(1954) CA 49, 13024(1955) (Determination of NG in mixtures with PETN) (Saponification to nitrite at 20°, then reaction with sulfanilic acid and a-naphthyl amine for a colorimetric measurment against nitrite standards) 10) P. Lhoste, MP 37, 149-52(1955)... 

Dilute 0.5,1.0,2.0, 5.0, and 10.0 mL of the secondary standard to 100 mL, respectively. This would give a series of standards of strength 0.05, 0.1, 0.2, 0.5, and 1.0 mg N03-N/L, respectively. Check the efficiency of the column by comparing one of the reduced nitrate standards to a nitrite standard at the same concentration. If the reduction efficiency falls below 75%, use freshly prepared Cu-Cd granules. 

The ion chromatographic determination of weak acid anions is complicated by ion exclusion in the suppressor column, resulting in faster elution and sharper peaks, directly proportional to the degree of exhaustion of the suppressor column [7], A lOmg L 1 nitrite standard showed a 37% increase in peak height over an 8h period when monitored with the conductivity detector while on only a minor 2% increase in peak height was observed over the same time period by using the ultraviolet detector after the separator column. 

Lab 12, 553-4(1946) fit CA 41, 1954(1947)(De-termination of small quantities of NG in the air. in the presence of nitrogen oxides)(Involves saponification to nitrite which is determined colorimetrically) 8) P. Fainer, CanJChem. 29, 46-53(1951) CA 45, 6156(1951)(Reverse Redox method) 9) M. Halse, MeddNorskFarm-Selskap 16, 166-9(1954) CA 49, 13024(1955) (Determination of NG in mixtures with PETN) (Saponification to nitrite at 20°, then reaction with sulfanilic acid and a-naphthyl amine for a colorimetric measur ment against nitrite standards) 10) P. Lhoste, MP 37, 149-52(1955) fit CA 50, 17451 (I956)(Rapid analysis of NG tablets) (Dewarda method) 10a) G.C. Whitnack et al, AnalChem 27, 899—901 (1955)(Polaro-graphic detn of NG in double-base proplnts)... 

How would you prepare a nitrite standard containing approximately 2 ppm nitrite nitrogen from a concentrated standard containing 0.018 74 M NaN02 ... 

Intercalibration tests have demonstrated that impurity of the nitrite standard or partial decomposition of the standard solutions are the most likely sources for deviations between different laboratories Korolejfand Palmork, 1977). 

Nitrite standard solution Anhydrous sodium nitrite (NaN02) is dried at 100 °C for 1 h and 0.690 g is dissolved in IL of pure water. The solution contains lOmmol/L of nitrite and should be stored cool and dark (a refrigerator is not required but is preferable). 

Commercially available sodium nitrite, even analytical grade, may contain <100% NaN02- Aged solid reagents should, therefore, not be used for the preparation of the nitrite standard. 

Figure 4. Effects of rosemary phytochemicals on LPS-induced nitrite formation in RAW 264.7 cells. Cells were treated with or without indicated concentrations of tested compounds [carnosic acid (CA), carnosol (CL), rosmarinic acid (RA), ursolic acid (UC)] and LPS (1 pg/mL) for 24 h. Amounts of nitrite released to culture medium was determined by Griess reagent and read at OD 550 nm with a sodium nitrite standard curve. Data represent means SE of triplicate tests.

Nitroethane and 1-(3,4 methylenedioxy) 2- nitropropane This method of producing the above mentioned nitro compounds is by far the best Ritter has come across yet The problem with standard nitroethane synthesis is that the -NO2 source most commonly used is silver nitrite (a la Merck Index citing). Needless to say, this is going to be an expensive compound to make as it is not available commercially but must be synthesized from costly silver nitrate. The other methods mentioned in Vogels 5th masterpiece... 

Standard 1/10 N nitrite is used to titrate a solution prepared by dissolving 10—100 mg of sulfamic acid and about 6 mL of (1 + 1) H2SO4 in 300 mL of distilled water at 40—50°C. At the end point, the colorless external potassium iodide starch-paste indicator changes to blue. A 1-mL solution of 1/ION NaN02 is equivalent to 9.709 mg of sulfamic acid. The 1/10 N nitrite titrant solution is standardized using primary standard-grade sulfamic acid. For sulfamate assay determination, the same procedure is used as for sulfamic acid. 

Analytical and Laboratory Operations. Sulfamic acid has been recommended as a reference standard in acidimetry (55). It can be purified by recrystaUization to give a stable product that is 99.95 wt % pure. The reaction with nitrite as used in the sulfamic acid analytical method has also been adapted for determination of nitrites with the acid as the reagent. This reaction is used commercially in other systems for removal of nitrous acid impurities, eg, in sulfuric and hydrochloric acid purification operations. 

If a solution of a nitrite is titrated in the ordinary way with potassium permanganate, poor results are obtained, because the nitrite solution has first to be acidified with dilute sulphuric acid. Nitrous acid is liberated, which being volatile and unstable, is partially lost. If, however, a measured volume of standard potassium permanganate solution, acidified with dilute sulphuric acid, is treated with the nitrite solution, added from a burette, until the permanganate is just decolorised, results accurate to 0.5-1 per cent may be obtained. This is due to the fact that nitrous acid does not react instantaneously with the permanganate. This method may be used to determine the purity of commercial potassium nitrite. 

Discussion. Satisfactory results are obtained by adding the nitrite solution to excess of standard 0.1 M cerium(IV) sulphate, and determining the excess of cerium(IV) sulphate with a standard iron(II) solution (compare Section 10.96). 

Procedure. Weigh out accurately about 1.5 g of sodium nitrite and dissolve it in 500 mL of boiled-out water in a graduated flask. Shake thoroughly. Place 50 mL of standard 0.1 M cerium(IV) sulphate in a conical flask, and add 10 mL of 2M sulphuric acid. Transfer 25 mL of the nitrite solution to this flask by means of a pipette, and keep the tip of the pipette below the surface of the liquid during the addition. Allow to stand for 5 minutes, and titrate the excess of cerium(IV) sulphate with standard 0.1 M ammonium iron(II) sulphate, using... 

Determine the volume of the standard cerium(IV) sulphate solution which has reacted with the nitrite solution, and therefrom calculate the purity of the sodium nitrite employed. 

Procedure. To 100 mL of the neutral sample solution (containing not more than 0.4 mg nitrite) add 2.0 mL of solution A and, after 5 minutes, 2.0 mL of solution B. The pH at this point should be about 1.5. Measure the absorbance after 10 minutes in the wavelength region of 550 nm (yellow-green filter), in a spectrophotometer against a blank solution prepared in the same manner. Calculate the concentration of the nitrite from a calibration plot prepared from a series of standard nitrite solutions. 

Dual-temperature and simple LPHW heating systems typically require 1,000 to 1,300 ppm as N02 (1,500-2,000 ppm as NaN02) when a standard nitrite/borate/TTA formulation is employed. (This is about twice the level required for cold and chilled water closed loop systems.)... 

The PVD process by means of electric arc evaporation has attained a high degree of importance in deposition of hard layers on an industrial scale. The hardness achieved is a minimum of 2100 HV. Compare this to the standard nitriting process which provides a hardness of about 900 HV or the stelliting process which offers about 500-600 HV. Extmsion screws treaded with this special process in the tire industry have seen a much improved wear life when processing highly filled silica compounds or very hard apex compounds. 

The reaction gives better yield with dienes, styrenes, or alkenes substituted with EWGs than with simple alkenes. These groups increase the rate of capture of the aryl radical. The standard conditions for the Meerwein arylation employ aqueous solutions of diazonium ions. Conditions for in situ diazotization by f-butyl nitrite in the presence of CuCl2 and acrylonitrile or styrene are also effective.115... 

Twenty weakly acidic drugs, including niclosamide, were determined by a nonaqueous catalytic thermometric titration method. Catalysis of the anionic polymerization of acetonitrile was used for endpoint indication. The solvent used was a mixture of acetonitrile and dimethylformamide or pyridine, and the titrant was sodium methoxide, potassium hydroxide, tertiary butanol, or tertiary butanol-sodium nitrite. Recoveries, limits of detection and relative standard deviations were tabulated [31]. 

Van den Berg [131] used this technique to determine nanomolar levels of nitrate in seawater. Samples of seawater from the Menai Straits were filtered and nitrite present reacted with sulfanilamide and naphthyl-amine at pH 2.5. The pH was then adjusted to 8.4 with borate buffer, the solution de-aerated, and then subjected to absorptive cathodic stripping voltammetry. The concentration of dye was linearly related to the height of the reduction peak in the range 0.3-200 nM nitrate. The optimal concentrations of sulfanilamide and naphthyl-amine were 2 mM and 0.1 mM, respectively, at pH 2.5. The standard deviation of a determination of 4 nM nitrite was 2%. The detection was 0.3 nM for an adsorption time of 60 sec. The sensitivity of the method in seawater was the same as in fresh water. 

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