Carbonate fusion

For the most part boric acid esters are quantitated by hydrolysis in hot water followed by determination of the amount of boron by the mannitol titration (see Boron compounds, boric oxide, boric acid and borates). Separation of and measuring mixtures of borate esters can be difficult. Any water present causes hydrolysis and in mixtures, as a result of transesterification, it is possible to have a number of borate esters present. For some borate esters, such as triethanolamine borate, hydrolysis is sufftciendy slow that quantitation by hydrolysis and titration cannot be done. In these cases, a sodium carbonate fusion is necessary. 

The loss of platinum from the crucible is less during a lithium metaborate fusion than with a sodium carbonate fusion. 

It was found that chlorides, chlorates, and nitrates interfere by forming in sol ppts (Ref 6). Later it was found that w sol perchlorates could be analyzed gravimetrically by pptn of the perchlorate ion as tetraphenylarsonium perchlorate (Ksp at 20° = 2.60 0.14 x 10"9). The ppt can be (Tried at 105° and weighed directly (Ref 16). Still more recently a specific perchlorate ion electrode has been developed (Ref 17) which can be used for the potentiometric titration of the perchlorate ion using a soln of tetraphenylarsonium chloride as the titrant (Ref 15). Tetra-phenylphosphonium chloride has been similarly used, but the corresponding Sb compd is too insol in w for practical use (Ref 8), For routine assay of perchlorates for use by the armed forces, a Na carbonate fusion procedure is described in Mil Specs MlL-A-23946 (19 Aug 1964) MIL-A-23948 (19 Aug 1964) (see also under Ammonium Perchlorate). The tetraphenylarsonium chloride procedure has also been proposed for use in Mil Specs (Ref 11)... 

Assay Methods. A Na carbonate fusion prod is currently used for assay of mil grade AP (see below under Specifications), but recently attempts have been made to replace it with a method which is faster and simpler to carry out. Two procs have been proposed a) Titanous Chloride Titration. A measured excess of Ti trichloride is added to a known weight of AP which reacts according to the equation ... 

Applications Basic methods for the determination of halogens in polymers are fusion with sodium carbonate (followed by determination of the sodium halide), oxygen flask combustion and XRF. Crompton [21] has reported fusion with sodium bicarbonate for the determination of traces of chlorine in PE (down to 5 ppm), fusion with sodium bisulfate for the analysis of titanium, iron and aluminium in low-pressure polyolefins (at 1 ppm level), and fusion with sodium peroxide for the complexometric determination using EDTA of traces of bromine in PS (down to 100ppm). Determination of halogens in plastics by ICP-MS can be achieved using a carbonate fusion procedure, but this will result in poor recoveries for a number of elements [88]. A sodium peroxide fusion-titration procedure is capable of determining total sulfur in polymers in amounts down to 500 ppm with an accuracy of 5% [89]. 

Saunders and Williams [79] have discussed ignition methods for the determination of organic phosphorus in soils. Sodium carbonate fusion has also been used to solubilize phosphate in soil analyses. 

Carbon fusion produces neon, sodium and magnesium via reactions of the following type ... 

Total decomposition of the sample, the purpose of which is to release fluorine from inorganic or organic matrixes and convert it to fluoride ions, is usually a prerequisite for determining the amount of total fluorine. Commonly used procedures involve oxygen bomb combustion in a closed bomb [176,180], open ashing [181,182], alkali hydroxide or alkali carbonate fusion [151,183-187], pyrohydroly-sis [187-191], acid extraction [192,193] and microwave acid digestion [194-196]. 

Fruchier rial. (1980), determined by X-ray fluorescence IXRF), except Aland Naby ncuiran activation analysis (NA At. Mg by flame atomic absorption tlidnum borate fusion (FAA), and B by plasma emission spectroscopy (sodium carbonate fusion) (PE5) Saether (1980), determined by XRF after low-temperature ashing (LTA) of raw oil shale samples In = 10). 

Fusion Mixture. A mixt of Na and K carbonates used to fuse in sol substances of high mp s (such as ores) in order to render them soluble in die form of double carbonates. Fusion can also be achieved by heating insol... 

Tantalic Acid and Tantalates. Tantalic acid [75397-94-3], Ta2Os H20, is the name of the white insoluble precipitate formed by hydrolysis of alkali hydroxide or alkali carbonate fusions containing tantalum, or by adding ammonia to an acidic solution containing tantalum ions. Tantalic acid is characterized by a high surface acidity, affording it potential use as a catalyst. 

Zirconium oxide, Zr02 is widely known, both as a mineral, baddeleyite, and as an industrial product obtained horn zircon, Z1SO4. Moreover, the precipitate obtained by action of alkali hydroxides upon solutions of tetravalent zirconium is a hydrated oxide. The latter is readily soluble in acids to form oxysalts, which arc usually formulated in terms of the Zr02+ ion, without including its water of hydration, e.g., as Zr0(H2P04)2. The hydrated Zr02+ ion is not amphiprotic it does not dissolve in alkali hydroxides, While it does react on alkali carbonate fusions, the compounds formed have been shown to be mixed oxides rather than zirconates. 

The process for converting the vegetation sample to a soluble form is selected for convenience, familiarity, safety, and optimal removal of interfering substances. A problem in dissolving salts of heavier Group IIA elements with mineral acids is that they may be insoluble sulfates. The most common method for bringing insoluble sulfates into solution is to subject the sample to hydroxide-carbonate fusion (fusion is discussed in Section 4.6.2 of your Radioanalytical Chemistry text). The fusion is performed in a metal crucible that is relatively insoluble under the fusion conditions. The temperature must be sufficiently high to melt the sulfates and convert them into carbonates. The carbonates are then dissolved to prepare the sample for analysis. 

Sodium carbonate fusion The residue left undissolved after operations 1 and 2 have been carried out, should be treated according to the scheme outlined inTableV.il. 

Table V.ll Sodium carbonate fusion The residue, R, free from lead and silver salts, or the original substance, if lead and silver salts are absent, is mixed with 5-6 times its weight of pure, sulphate-free, anhydrous Na2C03 or with a mixture of equal parts of Na2C03 and K2C03 (fusion mixture). The mixture is heated upon Pt foil or in a Pt crucible until a tranquil melt is obtained. (It may be necessary to heat over the blowpipe flame.) Allow to cool, extract the melt thoroughly by boiling it with water. Filter.

Uranium melts at a white heat, but the exact temperature has not been determined Guertler and Pirani found it to be about 1850° C., which is in agreement with a statement by Moissan that uranium is more difficult to melt than platinum. Rideal melted in a vacuum a specimen of uranium containing O-f per cent, carbon fusion occurred between 1300° and 1-100° C. The boiling-point has not been determined, but Moissan found that the metal could be distilled more readily than iron in the electric furnace. 

Rhodium was determined as the metal, and fluorine as lead chloride fluoride, following sodium carbonate fusion [Found F, 47-3 Rh 62 4. RhFj requires F, 48-0 Rh, 52-0%]. 

Radium is obtained from pitchblende, UgOg, in which it is formed by the disintegration of (p. 15), the equilibrium ratio being 3.4 x The sulphate is co-precipitated with BaS04 when BaClg is added to a sulphuric acid extract of the ore. After boiling with NaOH to remove lead, the sulphates are converted to carbonates by sodium carbonate fusion and dissolved in HCl to the chlorides. Fractional crystallisation of these removes much of the barium the final separation is effected by the same means after conversion to bromides. 

A carbonate fusion was needed to free the Bi from a 0.6423-g sample containing the mineral eulytite (2Bi203 35102). The fused mass was dissolved in dilute acid, following which the Bi + was titrated with 27.36 mL of 0.03369 M NaH2P04. The reaction is... 

Casting Sands. The production of metal products requires that the molten metal be cast into near-net shapes. The steel industry uses casting sand because it is inexpensive, is readily available, efficiently absorbs heat at a predictable rate, and is easy to use. The sand is blended with water, carbon, and other admixture compounds to improve the compaction of the sand, the heat capacity, and other properties. The sand is pounded around a mold, the mold is removed and the molten metal is poured into the sand molds. Unfortunately, the sand immediately next to the cast part is typically not reusable. Carbonization, fusion, and other factors make this material unusable and must be disposed of in landfills. Many of the companies that cast parts are implementing new programs to separate the burned material from undamaged sand to recycle the sand for more castings and reduce the amount shipped to landfills. 

In a 25-ml standard flask place 5 ml of a 1 1 mixture of ammonium molybdate solution and 1 M sulphuric acid, and add 3 ml of acetone and an aliquot of sample solution e.g., neutralized solution from sodium carbonate fusion) containing not more than 0.2 mg of Si. Dilute to the mark with water, mix well, let stand for 15 min, and measure the absorbance at... 

When sodium carbonate is present in excess, the uranyl ion forms a soluble carbonate complex, whereas most metals separate as carbonates, basic carbonates, or hydroxides [62] — with the exception of V, Be, and Th, which remain partly in solution together with uranium. If the precipitate contains several metals, double precipitation is necessary. The amount of uranium retained by the precipitate does not exceed a few percent. When a carbonate fusion is used for decomposition of the sample, and the melt is leached with water, uranium passes into solution. 

In stars with very heavy average masses, helium burning may last for only a few million years before it is replaced by carbon fusion. In time this leads to the production of elements such as calcium, titanium, chromium, iron, and nickel fusion partly by helium capture, partly by the direct fusion of heavy nuclides. For example, two Si can combine to form Ni that can decay to Co which then decays to stable Fe. These last steps of production may occur rather rapidly in a few thousand years. When the nuclear fuel for fusion is exhausted, the star collapses and a supernova results. 

Sodium carbonate fusion has been used to decompose silicate, oxide, phosphate, and sulphate minerals. A Pt crucible is usually used to carry out the fusion and the cooled melt is leached with a dilute acid solution. 

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