Gravimetric determination

In a weak nitric acid solution chloride ions react with silver ions. Spar- 

Any sulphite ions or sulphide ions present are oxidized with hydrogen peroxide (about 3 to 5 %). 

Rinsing liquid distilled water acidified with nitric acid. 

Acidify a measured volume of water between 100 ml and 1000 ml with nitric 

Keep the precipitate over night in the dark (on exposure to light part of 

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Amino-4-methylthiazole also gives a complex with Hg(II) that has been used in a gravimetric determination of this metal (366). 

This table includes the more common reagents used in gravimetric determinations. The lists of elements precip-... 

Harris, T. M. Revitalizing the Gravimetric Determination in Quantitative Analysis Laboratory, /. Chem. Educ. 1995, 72, 355-356. 

Thermal decomposition of perchlorate salts to chloride, followed by the gravimetric determination of the resulting chloride, is a standard method of determining quantitatively the concentration of perchlorates. Any chlorates that are present in the original sample also break down to chloride. Thus results are adjusted to eliminate errors introduced by the presence of any chlorides and chlorates in the original sample. 

A.STM D4100, ed, Test Methodfor Gravimetric Determination of Smoke Earticulates from Combustion of Elastic Materials Vol. 8.02, ASTM, Philadelphia, Pa., 1989. 

The alkah metals are commonly separated from all other elements except chlorine before gravimetric determination. In the absence of other alkaUes, sodium maybe weighed as the chloride or converted to the sulfate and weighed. WeU-known gravimetric procedures employ precipitation as the uranyl acetate of sodium—2inc or sodium—magnesium. Quantitative determination of sodium without separation is frequently possible by emission or atomic-absorption spectrometric techniques. 

For colorimetric or gravimetric determination l-nitroso-2-naphthol can be used. For chromatographic ion exchange (qv), cobalt is isolated as the nitroso-(R)-salt complex. The cyanate complex is used for photometric determination and the thiocyanate for colorimetry. A rapid chemical analysis of... 

Bromo-2-pyridyla2o)-5-diethylamiQophenol (5-Br-PADAP) is a very sensitive reagent for certain metals and methods for cobalt have been developed (23). Nitroso-naphthol is an effective precipitant for cobalt(III) and is used in its gravimetric determination (24,25). Atomic absorption spectroscopy (26,27), x-ray fluorescence, polarography, and atomic emission spectroscopy are specific and sensitive methods for trace level cobalt analysis (see... 

As the gas stream proceeds through the sampling apparatus, the particulate matter is trapped on a filter, the moisture is removed, and the volume of the sample is measured. Upon completion of samphng, the collec ted material is recovered and sent to a laboratory for a gravimetric determination or analysis. 

The only anhydrous trioxide is UO3, a common form of which (y-U03) is obtained by heating U02(N03).6H20 in air at 400°C six other forms are also known.Heating any of these, or indeed any other oxide of uranium, in air at 800-900°C yields U3O8 which contains pentagonal bipyramidal UO7 units and can be used in gravimetric determinations of uranium. Reduction with H2 or H2S leads to a series of intermediate... 

Thermogravimetry may be used to determine the composition of binary mixtures. If each component possesses a characteristic unique pyrolysis curve, then a resultant curve for the mixture will afford a basis for the determination of its composition. In such an automatic gravimetric determination the initial weight of the sample need not be known. A simple example is given by the automatic determination of a mixture of calcium and strontium as their carbonates. 

Cyclohexane-1,2-dione dioxime (nioxime) (IV) is more soluble in water (8.2 g L 1 at 21 °C) than is dimethylglyoxime it is an excellent reagent for the gravimetric determination of palladium. 

For all gravimetric determinations described in this chapter, the phrase Allow to cool in a desiccator should be interpreted as cooling the crucible, etc., provided with a well-fitting cover in a desiccator. The crucible, etc, should be weighed as soon as it has acquired the laboratory temperature (for a detailed discussion, see Section 3,22). 

Discussion. Some of the details of this method have already been given in Section 11.11(C), This procedure separates aluminium from beryllium, the alkaline earths, magnesium, and phosphate. For the gravimetric determination a 2 per cent or 5 per cent solution of oxine in 2M acetic add may be used 1 mL of the latter solution is suffident to predpitate 3 mg of aluminium. For practice in this determination, use about 0.40 g, accurately weighed, of aluminium ammonium sulphate. Dissolve it in 100 mL of water, heat to 70-80 °C, add the appropriate volume of the oxine reagent, and (if a precipitate has not already formed) slowly introduce 2M ammonium acetate solution until a precipitate just appears, heat to boiling, and then add 25 mL of 2M ammonium acetate solution dropwise and with constant stirring (to ensure complete predpitation). 

Calcium oxalate monohydrate has a solubility of 0.0067 g and 0.0140 g L 1 at 25° and 95 °C respectively. The solubility is less in neutral solutions containing moderate concentrations of ammonium oxalate owing to the common-ion effect (Section 2.7) hence a dilute solution of ammonium oxalate is employed as the wash liquid in the gravimetric determination. 

Discussion. This gravimetric determination depends upon the separation and weighing as elementary selenium or tellurium (or as tellurium dioxide). Alkali selenites and selenious acid are reduced in hydrochloric acid solution with sulphur dioxide, hydroxylammonium chloride, hydrazinium sulphate or hydrazine hydrate. Alkali selenates and selenic acid are not reduced by sulphur dioxide alone, but are readily reduced by a saturated solution of sulphur dioxide in concentrated hydrochloric acid. In working with selenium it must be remembered that appreciable amounts of the element may be lost on warming strong hydrochloric acid solutions of its compounds if dilute acid solutions (concentration <6M) are heated at temperatures below 100 °C the loss is negligible. 

A process for the gravimetric determination of mixtures of selenium and tellurium is also described. Selenium and tellurium occur in practice either as the impure elements or as selenides or tellurides. They may be brought into solution by mixing intimately with 2 parts of sodium carbonate and 1 part of potassium nitrate in a nickel crucible, covering with a layer of the mixture, and then heating gradually to fusion. The cold melt is extracted with water, and filtered. The elements are then determined in the filtrate. 

Fluoride ion, and weak acids and bases do not interfere, but nitrate, nitrite, perchlorate, thiocyanate, chromate, chlorate, iodide, and bromide do. Since analysis of almost all boron-containing compounds requires a preliminary treatment which ultimately results in an aqueous boric acid sample, this procedure may be regarded as a gravimetric determination of boron. 

The generated polysulfide dianions of different chain-lengths then establish a complex equilibrium mixture with all members up to the octasulfide at least see Eqs. (5) and (6). For this reason, it is not possible to separate the polysulfide dianions by ion chromatography [6]. The maximum possible chain-length can be estimated from the preparation of salts with these anions in various solvents (see above). However, since the reactions at Eqs. (22) and (23) are reversible and Sg precipitates from such solutions if the pH is lowered below a value of 6, the nonasulfide ion must be present also to generate the Sg molecules by the reverse of the reaction at Eq. (22). The latter reaction (precipitation of Sg on acidification) may be used for the gravimetric determination of polysulfides [11]. There is no evidence for the presence of monoprotonated polysulfide ions HS - in aqueous solutions [67, 72]. 

Gemand, W., Steckenreuter, K., and Wieland, G., Greater Analytical Accuracy through Gravimetric Determination of Quantity, Fresenius Z. Anal. Chem. 334, 1989, 534-539. 

MDHS 14 General method for the gravimetric determination of respirable and total dust MDHS 15 Carbon disulphide MDHS 16 Mercury vapour in air Laboratory method using hopcalite adsorbent tubes, and acid dissolution with cold vapour atomic absorption spectrometric analysis MDHS 17 Benzene in air Laboratory method using charcoal adsorbent tubes, solvent desorption and gas chromatography MDHS 18 Tetra alkyl lead compounds in air Continuous on-site monitoring method using PAC Check atomic absorption spirometry... 

MDHS14 General methods for the gravimetric determination of respirable and total inhalable dust. 

Cadmium and inorganic compounds of cadmium in air (atomic absorption spectrometry). Cadmium and inorganic compounds of cadmium in air (X-ray fluorescence spectroscopy). Chromium and inorganic compounds of chromium in air (atomic absorption spectrometry). Chromium and inorganic compounds of chromium in air (X-ray fluorescence spectroscopy). General methods for the gravimetric determination of respirable and total inhalable dust. Carbon disulphide in air. 

Many explosions have been experienced dining the gravimetric determination of either perchlorates or potassium as potassium perchlorate by a standard method involving an ethanol extraction. During subsequent heating, formation and explosion of ethyl perchlorate is very probable. 

Pyrolysis of pine wood biomass was conducted at 400°C followed by catalytic deoxygenation at 450°C. The yield of the different product phases was gravimetrically determined. The gas yield was calculated by the difference. The water content of the bio oil was measured by Karl Fischer titration. The yield of the different product phases is given in Table 3, calculated from the pyrolyzed biomass. The non-catalytic experiment was carried out in the same way as the catalytic ones with the exception that the upper catalyst bed was empty. 

TABLE 11.20 Elements Precipitated by General Analytical Reagents This table includes the more common reagents used in gravimetric determinations. The lists of elements precipitated are not in all cases exhaustive. The usual solvent for a precipitating agent is indicated in parentheses after its name or formula. When the symbol of an element or radical is italicized, die element may be quantitatively determined by the use of the reagent in question. ... 

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