Metals volumetric methods

Principle. An organic compound which contains chlorine is mixed with sodium peroxide and ignited in a closed metal bomb. The chlorine is thus converted to sodium chloride, and after acidification the chloride is estimated by the Volhard volumetric method. Bromine and iodine, when constituents of organic compounds similarly treated, are converted largely into sodium bromate and iodate respectively these ions are therefore subsequently reduced by hydrazine to bromide and iodide ions, and estimated as before. 

Nickel also is deterrnined by a volumetric method employing ethylenediaminetetraacetic acid as a titrant. Inductively coupled plasma (ICP) is preferred to determine very low nickel values (see Trace AND RESIDUE ANALYSIS). The classical gravimetric method employing dimethylglyoxime to precipitate nickel as a red complex is used as a precise analytical technique (122). A colorimetric method employing dimethylglyoxime also is available. The classical method of electro deposition is a commonly employed technique to separate nickel in the presence of other metals, notably copper (qv). It is also used to estabhsh caUbration criteria for the spectrophotometric methods. X-ray diffraction often is used to identify nickel in crystalline form. 

Hydrogen uptake of reduced catalysts (X) was measured by volumetric method with an AUTOSORB-l-C analyzer (Quantachrome Instruments). Hydrogen adsorption was carried out at 373 K after in situ H2 reduction at 773 K for 6 h in the adsorption cell. The dispersion and particle size of metallic Co were calculated by the following equations, assuming that the stoichiometry for hydrogen adsorption on the metallic site is unity ... 

A range of different methods measures the solubility of hydrogen in metals and alloys. Manometric methods [98] and gas volumetric methods [99] have been used to determine pressure-composition isotherms at selected temperatures for a range of alloys [100-103],... 

Weld metal buildup shall be allowed when restoring the specified nominal thickness of pipe components or attachments. Weld metal buildup shall not be allowed to increase thickness or to alter alignment. Completed weld metal buildup shall be examined by a volumetric method. All weld buildup shall be as permitted by the engineering design. 

To determine PCT cnrve by volnmetric method at first we have to know mass of analyzed powder (hydride or pnre metal). The typical mass of powder used in volumetric method is in a range 50-500 mg and depends on (reactor volume with volume of connecting pipes, valves, and transdncer). After the mass measurement, the powder is loaded into specimen holder and then it is placed in the Sieverts apparatus reactor. To prevent any oxidation and for safety reason the system must be purged a few times by argon and then evacnated. However, one must be careful how much powder is appropriate for the absorption/desorption volume of a Sieverts-type apparatus. 

Volumetric Methods.—Nickel may be conveniently estimated volu-metrically in the absence of cobalt, copper, silver, gold, and the platinum metals by means of potassium cyanide.4 The solution containing the nickel is, if acid, neutralised with ammonia and some ammonium sulphate is added to render the indicator more sensitive. A little ammonia is now added, and a few drops of potassium iodide and silver nitrate. The solution becomes turbid in consequence of the precipitation of silver iodide. The liquid is now titrated with potassium cyanide solution until the turbidity just disappears. The reaction consists in converting the nickel salt into the double cyanide, Ni(CN)a.2KCN, after which any excess of potassium cyanide attacks the silver iodide, yielding the soluble double cyanide, AgCN.KCN. The disappearance of the turbidity therefore indicates the complete conversion of the nickel salt. A slight correction is necessary for the silver introduced. 

Transition metal ions, within the zeolite framework, may undergo a reductive carbonylation to give mononuclear monovalent carbonyl coumpounds M(I)(CO) and ultimatly to give zerovalent polynuclear carbonyl clusters. The rhodium(I)and iridium(i)carbonyIs were identified using spectroscopic and volumetric methods, the zerovalent rhodium and Iridium clusters M (CO)j were also synthetized in the zeolite matrix and their structure investigated using IR, NMR and spin labelling methods. 

Complexometric titrations in the clinical laboratory are limited to those substances that occur in fairly high concentrations since volumetric methods are generally not too sensitive. The most important complexometric titration is the determination of calcium in blood (see Ref. 8). Chelating agents such as. EDTA are used in the treatment of heavy-metal poisoning, for example, when children ingest chipped paint that contains lead. The calcium chelate (as Na2CaY) is administered to prevent complexation and removal of calcium in the bones. Heavy metals such as lead form more stable EDTA chelates than calcium does and will displace the calcium from the EDTA. The chelated lead is then excreted via the kidneys. 

The consumables to be tested are used to deposit a single weld bead which is rapidly quenched. Both the welding and quenching processes are carefully controlled. The specimen so produced is maintained at room temperature for a sufficient time to release its content of diffusible hydrogen, which is measured by volumetric methods and reported on unit mass of either deposited or fused metal (Note 2]. 

The volumetric method has very often been used with platinum catalysts for which quite satisfactory results are generally obtained it is usual to assume that the monolayer volume or amount, obtained as just described or by extrapolation corresponds to an H Ms (hydrogen atom to metal surface atom) ratio of 1 1. Some justification for this assumption is to be found, at least for particles of moderate size, in the adsorption stoichiometry shown by films and single crystals, but for very small particles and at high pressures the H/Mj ratio can exceed unity quite substantially this is especially so with rhodium" and iridium (see below). Care is however needed with palladium " " because of the risk of forming the hydride however, monolayer coverage is obtained at pressures below which dissolution starts. The base metals iron, cobalt and nickel have been... 

Bunsen worked out a method for the separation of platinum metals (preparation of pure rhodium). He determined the composition, NIg,NH3, of nitrogen iodide, developed a volumetric method of iodimetry, using a solution of sulphurous acid, and worked on water analysis. Bunsen and L. Schischkoff investigated the chemical reactions in the explosion of gunpowder. Bunsen discovered arsenic pentasulphide, and measured the adsorption of carbon dioxide on glass. ... 

Hie use of X-ylenol orange as an Indicator In acid solution Is one of the mpst sensitive of the volumetric methods, allowing microgram quantities to he determined (W5). Care must be taken, however, due to avoid the presence of other heavy metals which may Intefere. Indirect methods of titration using EDTA have been proposed (Cl) but these normally lack the sensitivity of the direct method. 

The overall reaction is characterized by product analyses and coulombic efficiency determinations. Carbon dioxide, which is the primary product in most organic reactions at noble-metal anodes, can be removed from acidic solutions in the anode compartment of the electrolytic cell by passing an inert gas through the cell, and then reacting quantitatively, e.g., with Ba(OH)2 or Ascarite. Carbon dioxide is not as easily determined in alkaline electrolyte, which must be analyzed, e.g., by volumetric methods or chromatography. Nonvolatile products from the oxidation are determined by analysis of the electrolyte, e.g., by gas chromatography, preferably with a flame ionization detector, or mass spectroscopy. Organic products can be extracted from the electrolyte... 

Ethoxylates with six or more ethylene oxide units form pseudocationic complexes with many metals, and the tetraphenylborates of these are insoluble or sparingly soluble in water. Several volumetric methods for the determination of ethoxylates are based on this. Some of them are two-phase procedures. 

In chemical gas adsorption (or chemisorption), the adsorbate molecules attach to the adsorbent surface by forming a chemical bond. For example, a reactive gas as hydrogen or carbon monoxide is used to obtain information on the active properties of the metal phase of a metal supported catalyst. The sample is first reduced in hydrogen and then evacuated to retrieve the active metal phase. In the volumetric method, known amounts of hydrogen (Pt, Ni, Rh, Ru) or CO (Pd, Pt) are dosed and subsequently adsorbed at different partial pressures, resulting in a chemisorption isotherm. This isotherm measurement is repeated... 

The metal is oxidized by CIO3 CIO4 B1O3" or IO3". An exeellent volumetric method uses selective oxidation (to avoid interference from Cr, etc.) by B1O3" with 804 " and a definite concentration of HCl. In this medium, V is oxidized to V, and, after removal of excess Br03", titrated with Fe T The endpoint may be determined electrometrically. 

The chemisorption of carbon monoxide is an established method for determining the surface area of dispersal metals, particularly in supported catalysts. The average area occupied by each molecule depends on whether attachment is on one or two sites, a state that can vary from metal to metal and with surface coverage [85]. The quantity of chemisorbed gases is commonly measured by volumetric methods with apparatus similar to that used for static BET gas adsorption measurements. 

The tin content of ores, concentrates, ingot metal, and other products is determined by fire assay, fusion method, and volumetric wet analysis. 

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