Measurement methods nitric acid

Elemental composition Ni 64.68%, S 35.33%. The compound may be identified by x-ray crystallographic and physical properties. Nickel may be measured in nitric acid extract by AA or ICP methods (See Nickel). 

Potential interferences in the measurement of nitric acid using this method include removal of gaseous HN03 on the Teflon particle filter and/or volatilization of particle nitrate collected on this Teflon filter. As discussed in Chapter 7, NH4N03 is a common particle component, but exists in equilibrium with gas-phase NH3 and HN03 ... 

Buhr, S. M., M. P. Buhr, F. C. Fehsenfeld, J. S. Flolloway, U. Karst, R. B. Norton, D. D. Parrish, and R. E. Sievers, Development of a Semi-Continuous Method for the Measurement of Nitric Acid Vapor and Particulate Nitrate and Suflate, Atmos. Environ., 29, 2609-2624 (1995). 

Other Methods. Ion chromatography using conductance detection can be used to measure low (<1%) levels of nitrite, chloride, sulfate, and other ions in nitric acid. Techniques for ion chromatographic analysis are available (93). 

Nitrometer Method. The nitrometer method also is used to determine nitric acid or nitrates in mixed acid or oleum. It involves the measurement of the volume of NO gas that is Hberated when mercury is oxidized by nitric acid. The method is based on the following reaction ... 

An initial solution was prepared by dissolving metallic niobium powder in 40% hydrofluoric acid. The dissolution was performed at elevated temperature with the addition of a small amount of nitric acid, HN03, to accelerate the process. The completeness of niobium oxidation was verified by UV absorption spectroscopy [21]. The prepared solution was evaporated to obtain a small amount of precipitate, which was separated from the solution by filtration. A saturated solution, containing Nb - 7.01 mol/1, HF - 42.63 mol/1, and corresponding to a molar ratio F Nb = 6.08, was prepared by the above method. The density of the solution at ambient temperature was p = 2.0 g/cc. Concentrations needed for the measurements were obtained by diluting the saturated solution with water or hydrofluoric acid. 

The ionisation may be attributed to the great tendency of the free hydrogen ions H+ to combine with water molecules to form hydroxonium ions. Hydrochloric and nitric acids are almost completely dissociated in aqueous solution in accordance with the above equations this is readily demonstrated by freezing-point measurements and by other methods. 

Spectrophotometric methods may often be applied directly to the solvent extract utilising the absorption of the extracted species in the ultraviolet or visible region. A typical example is the extraction and determination of nickel as dimethylglyoximate in chloroform by measuring the absorption of the complex at 366 nm. Direct measurement of absorbance may also be made with appropriate ion association complexes, e.g. the ferroin anionic detergent system, but improved results can sometimes be obtained by developing a chelate complex after extraction. An example is the extraction of uranyl nitrate from nitric acid into tributyl phosphate and the subsequent addition of dibenzoylmethane to the solvent to form a soluble coloured chelate. 

Note on the gravimetric standardisation of hydrochloric acid. The gravimetric standardisation of hydrochloric acid by precipitation as silver chloride is a convenient and accurate method, which has the additional advantage of being independent of the purity of any primary standard (compare Section 10.38). Measure out from a burette 30-40mL of the, say, 0.1M hydrochloric acid which is to be standardised. Dilute to 150 mL, precipitate (but omit the addition of nitric acid), and weigh the silver chloride. From the weight of the precipitate, calculate the chloride concentration of the solution, and thence the concentration of the hydrochloric acid. 

After each series of experiments with beams of various intensity the section plate would be removed from the cell and disassembled, with radioactive silver washed out by nitric acid. Radioactivity of the solutions obtained was measured by a multichannel spectrometric scintillation y-counter with sensitivity of up to 10 G, i. e. around 10 of atoms which, according to calculations, is 10 times lower than sensitivity of ZnO sensor 10 G or 10 of Ag atoms respectively [28]. This difference in sensitivity lead to great inconveniences when exposing of targets was used in above methods. Only a few seconds were sufficient to expose the sensor compared to several hours of exposure of the scintillation counter in order to let it accumulate the overall radioactivity. It is quite evident that due to insufficient stability during a long period of exposure time an error piled up. 

John et al. [37] described a colorimetric method for the estimation of primaquine phosphate. Sample solutions of different dilutions (0.15-0.6 mL) of the drug (6-24 pg/mL) were treated with 5 mL of 1% cerric ammonium sulfate in dilute nitric acid and made up to 25 mL with water. The absorbance of the resulting light purple solution was measured at 480 nm after similar 30 min. Beer s law was obeyed from 5 30 pg/mL of primaquine phosphate. The method is applicable to bulk formulations in addition to tablets and capsule formulation. 

Stein et al. [673] have described a simplified, sensitive, and rapid method for determining low concentrations of cadmium, lead, and chromium in estuarine waters. To minimise matrix interferences, nitric acid and ammonium nitrate are added for cadmium and lead only nitric acid is added for chromium. Then 10,20, or 50 pi of the sample or standard (the amount depending on the sensitivity required) is injected into a heated graphite atomiser, and specific atomic absorbance is measured. Analyte concentrations are calculated from calibration curves for standard solutions in demineralised water for chromium, or an artificial seawater medium for lead and cadmium. 

A number of workers have described methods for the determination of mercury in which the mercury is first reduced to the element or collected as the sulfide on a cadmium sulfide pad. It is then volatilized into a chamber for measurement. These techniques are extremely sensitive. Thillez108) recently described a procedure for urinary mercury in which the mercury is collected on platinum and then volatilized into an air stream. Rathje109) treated 2 ml of urine with 5 ml of nitric acid for 3 min, diluted to 50 ml, and added stannuous chloride to reduce the mercury to the element. A drop of Antifoam 60 was added and nitrogen was blown through the solution to carry the mercury vapor into a quartz end cell where it is measured. Six nanograms of mercury can be detected. Willis 93) employed more conventional methods to determine 0.04 ppm of mercury in urine by extracting it with APDC into methyl-n-amyl ketone. Berman n°) extracted mercury with APDC into MIBK to determine 0.01 ppm. 

Lynch et al. [21] have described a method for the determination of organic carbon in silty lake sediments. In this method the air-dried and sifted (-250 mesh) sample is leached with 4M nitric acid-0.1M hydrochloric acid for 1.5h at 90-95°C, and the extinction of the cooled, clean solution is measured at 500nm. The extinction correlates well with weight loss (%) on heating the sample between 120 and 800°C. The precision is 26%. The same leach solution can be used for trace-metal determinations. 

Adipic acid is of considerable importance since it is a precursor to nylon and polyester, which are extensively used in many products. Between two and three million tonnes are produced worldwide each year. Currently, its main method of manufacture is a costly, multistep process involving concentrated nitric acid. Nitrous oxide is produced as a by-product in such quantities that they measurably contribute to global warming and ozone depletion [24], A cleaner alternative to this process is clearly highly desirable. 

For the rapid determination of Tc in a mixture of uranium fission products. Love and Greendale have used the method of amalgam polarography. It consists in a selective reduction of technetium at a dropping mercury electrode at a potential of —1.55 V vs. SCE in a medium of 1 M sodium citrate and 0.1 M NaOH. Under these conditions, technetium is reduced to an oxidation state which is soluble in mercury. The amalgam is removed from the solution of fission fragments and the amount of Tc determined in nitric acid solution of the amalgam by a y count. For Tc the measurement accuracy is within 1 %, and the decontamination factor from other fission products 10 . 

The metal may he analyzed hy atomic absorption or emission spectrophotometry (at trace levels). Other techniques include X-ray diffraction, neutron activation analysis, and various colorimetric methods. Aluminum digested with nitric acid reacts with pyrocatechol violet or Eriochrome cyanide R dye to form a colored complex, the absorbance of which may be measured by a spectrophotometer at 535 nm. 

Cadmium in acidified aqueous solution may be analyzed at trace levels by various instrumental techniques such as flame and furnace atomic absorption, and ICP emission spectrophotometry. Cadmium in solid matrices is extracted into aqueous phase by digestion with nitric acid prior to analysis. A much lower detection level may be obtained by ICP-mass spectrometry. Other instrumental techniques to analyze this metal include neutron activation analysis and anodic stripping voltammetry. Cadmium also may be measured in aqueous matrices by colorimetry. Cadmium ions react with dithizone to form a pink-red color that can be extracted with chloroform. The absorbance of the solution is measured by a spectrophotometer and the concentration is determined from a standard calibration curve (APHA, AWWA and WEF. 1999. Standard Methods for the Examination of Water and Wastewater, 20th ed. Washington, DC American Public Health Association). The metal in the solid phase may be determined nondestructively by x-ray fluorescence or diffraction techniques. 

Elemental composition Ca 95.41% H 4.79%. A measured amount of the solid is carefully treated with water and the volume of evolved hydrogen is measured using a manometer (Ig liberates 1.16 L H2 at NTP). The solution is then acidified with nitric acid and diluted for the measurement of calcium by AA or ICP spectrophotometry, or by a wet method (see Calcium). The hberat-ed hydrogen gas may be analyzed by GC using a TCD. Many packed and capillary GC columns are commercially available. 

Elemental composition Ga 69.24%, P 30.76%. Gallium phosphide may be characterized hy its physical and electronic properties. It may also he analyzed hy various x-ray methods. Gallium may he measured hy AA and ICP spectrophotometry following digestion with nitric acid or aqua regia and appropriate dilution (See Gallium). 

Elemental composition Pb 64.11%, Cr 16.09%, O 19.80%. Lead chromate may be identified from its physical properties and x-ray crystallography. Lead and chromium can be measured in a nitric acid solution of the compound by AA, ICP, and other instrumental methods. (See Lead.)... 

Elemental composition Pb 90.40%, H 0.29%, O 9.30%. The hydroxide is digested with nitric acid, diluted and analyzed for lead by AA, ICP or other instrumental technique (See Lead). A weighed amount of the salt is heated in an oven at 145°C and water lost is measured by gravimetry. The residue lead monoxide also may be analyzed by x-ray, or its lead content can be measured by various instrumental methods. 

Manganese in aqueous solution may be analyzed by several instrumental techniques including flame and furnace AA, ICP, ICP-MS, x-ray fluorescence and neutron activation. For atomic absorption and emission spectrometric determination the measurement may be done at the wavelengths 279.5, 257.61 or 294.92 nm respectively. The metal or its insoluble compounds must be digested with nitric acid alone or in combination with another acid. Soluble salts may be dissolved in water and the aqueous solution analyzed. X-ray methods may be applied for non-destructive determination of the metal. The detection limits in these methods are higher than those obtained by the AA or ICP methods. ICP-MS is the most sensitive technique. Several colorimetric methods also are known, but such measurements require that the manganese salts be aqueous. These methods are susceptible to interference. 

Mercury is most accurately determined by the cold vapor atomic absorption spectroscopic method. The instrument is set at the wavelength 253.7 nm. The metal, its salts and organic derivatives in aqueous solution can be measured by this method. The solution or the solid compounds are digested with nitric acid to convert into water-soluble mercury(ll) nitrate, followed by treatment with potassium permanganate and potassium persulfate under careful heating. The excess oxidants in the solution are reduced with NaCl-hydroxylamine sulfate. The solution is treated with stannous chloride and aerated. The cold Hg vapor volatdizes into the absorption cell where absorbance is measured. 

Elemental composition Hg 92.61%, 0 7.39%. The compound is digested in nitric acid and mercury in an appropriately diluted acid extract and then is measured by cold-vapor AA or by ICP. The compound may be characterized nondestructively by x-ray methods. 

Elemental composition Ni 63.32%, H 2.17%, O 34.51%. The hydroxide may be digested with nitric acid, diluted appropriately, and analyzed for nickel by various instrumental methods (See Nickel). Also, water content may be measured by TGA or DTA method after decomposing the hydroxide at 230°C. The residue NiO may be characterized by x-ray and other methods (See Nickel Oxide). 

Rhenium can be analyzed by various instrumental techniques that include flame-AA, ICP-AES, ICP-MS, as well as x-ray and neutron activation methods. For flame-AA analysis the metal, its oxide, or other insoluble salts are dissolved in nitric acid or nitric-sulfuric acids, diluted, and aspirated directly into nitrous oxide-acetylene flame. Alternatively, rhenium is chelated with 8-hydroxy quinoline, extracted with methylisobutyl ketone and measured by flame-AA using nitrous oxide-acetylene flame. 

Silver metal and its contents in silver alloys and salts can be measured at trace levels by various instrumental techniques such as flame- and furnace-AA, ICP-AES, ICP/MS and x-ray fluorescence methods. It is solubilized by digestion with nitric acid prior to analysis. The AA measurement may be carried out at the wavelength 328.1 nm and ICP analysis at 328.07 nm. ICP/MS is the most sensitive technique while x-ray fluorescence is relatively less sen-... 

Elemental composition Ag 65.03%, Cr 15.68%, 0 19.29%. The salt is dissolved in nitric acid, diluted, and analyzed for silver and chromium by flame-and furnace-AA, ICP-AES or other instrumental method to measure the contents of these metals. 

Elemental composition Ag 87.08%, O 12.92%. When dissolved in dilute nitric acid, oxygen is liberated immediately, which can be measured by GC or GC/ MS (m/z 32). Acid solution may be analyzed for silver by AA, ICP, or other methods. When treated with ammonia solution, nitrogen is evolved which can be measured by GC or GC/MS (m/z 28). 

Elemental composition Ti 59.95%, O 40.05%. The oxide may be identified by its physical properties and by x-ray methods. Titanium content may be measured by AA or ICP. The compound is digested in nitric acid or aqua regia, solubdized, and diluted sufficiently for metal analysis. 

Radioactivity of uranium can be measured by alpha counters. The metal is digested in nitric acid. Alpha activity is measured by a counting instrument, such as an alpha scintillation counter or gas-flow proportional counter. Uranium may be separated from the other radioactive substances by radiochemical methods. The metal or its compound(s) is first dissolved. Uranium is coprecipitated with ferric hydroxide. Precipitate is dissolved in an acid and the solution passed through an anion exchange column. Uranium is eluted with dilute hydrochloric acid. The solution is evaporated to near dryness. Uranium is converted to its nitrate and alpha activity is counted. Alternatively, uranium is separated and electrodeposited onto a stainless steel disk and alpha particles counted by alpha pulse height analysis using a silicon surface barrier detector, a semiconductor particle-type detector. 

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