Barium sulfate ignition

Fillers (qv) are occasionally used in flexible slab foams the two most commonly used are calcium carbonate (whiting) and barium sulfate (barytes). Their use level may range up to 150 parts per 100 parts of polyol. Various other ingredients may also be used to modify a flexible foam formulation. Cross-linkers, chain extenders, ignition modifiers, auxiHary blowing agents, etc, are all used to some extent depending on the final product characteristics desired. 

Dimethyl Sulfate. Dimethyl sulfate ignites on contact with barium chlorite.2... 

To determine cobalt, it is merely necessary to ignite the compound in an electric furnace to about 825° for one hour and weigh the residue as C03O4. To analyze for sulfur, 0.3 to 0.4 g. of the compound is placed in 200 ml. of distilled water, and a few drops of bromine are added. When all the cobalt (II) sulfoxylate has reacted, the excess bromine is boiled off and the sulfur is precipitated as barium sulfate. Anal Calcd. for CoS02-2H20 Co, 37.07 S, 20.13. Found Co, 36.93 S, 19.62. By checkers Co, 36.7 S, 19.3. The Co S ratio here is 1.00 0.98. Because of the variability of the water content, the Co S ratio is more useful than either analysis alone. 

The white crystalline precipitate of barium sulfate is filtered, washed with water, ignited, and weighed. 

Both hydrochloric acid and barium chloride cause occlusion of chloride. Hydrochloric acid is worse than barium chloride in this respect. Therefore the sulfate solution before the precipitant is added should not contain more than 0.1% of hydrochloric acid by volume 17, J]. A further complication caused by excess acidity is adsorption of H ions, which causes liberation of sulfuric acid when barium sulfate is ignited [2, J]. In addition to this, high acidity of reaction solution will cause error because of the solubility of barium sulfate in hydrochloric acid. The solubility of barium sulfate in water, though small, is not negligible (4 mg/ L at 20°C). The presence of mineral acid increases the solubility to a considerable extent, that is, in 0. IN hydrochloric acid the solubility of barium sulfate is about 10 mg/L at 20°C [4]. This limits the amount of hydrochloric acid that can be used. A concentration of O.OSN with respect to hydrochloric acid before precipitation has been found to be most suitable [4,5]. 

Old solutions of barium chloride or fresh solutions filtered through fine filter paper are reported to be more effective than the fresh solutions in promoting the formation of large crystals of barium sulfate precipitate 4.SI. For the purpose of rapid filtering and for avoiding transfer of barium sulfate precipitate and ignition of filter paper, the use and type of filtering crucibles should be specified. 

Total sulfur is determined by combustion in a bomb calorimeter (ASTM D-129, IP 61) and is often carried out with the determination of calorific value. The contents of the bomb are washed with distilled water into a beaker after which hydrochloric acid is added and the solution is raised to boiling point. Barium chloride is added drop by drop to the boiling solution to precipitate the sulfuric acid as granular barium sulfate. After cooling, and standing for 24 h, the precipitate is filtered off on an ashless paper, washed, ignited, and weighed as barium sulfate. 

Sulfate is precipitated as barium sulfate with barium chloride. After the filtering with filter paper, the paper is charred off, and the precipitate is ignited to constant weight. The SO3 content is calculated from the weight of BaS04. 

Vanadium is determined by ignition of the sulfate in air to vanadium(V) oxide. Sulfate is determined by dissolving a sample of the vanadium(III) sulfate in hot 3 N HNO3, adding about 1 ml. of 65 % hydrazine hydrate to reduce any vanadates which may have formed, and precipitating the sulfate as barium sulfate. Anal. Calcd. for V2(S04)s V, 26.12 SO4—, 73.88. Found V, 26.13 SO4", 74.16. 

Barium sulfate, as such or in the form of lithopones (BaS04 + ZnS, or + CdS) is used as pigment. It also constitues a weighting material in the manufacture of special papers. It can be easily detected in pigments or the ash of papers because it is completely converted into barium chloride by ignition with ammonium chloride. The conversion is due to the production of hydrogen chloride in the thermal decomposition of ammonium chloride and the gas is formed at about 400 C, in other words at a temper-... 

Procedure. A micro crucible is used. A few grains of the solid (or ignition residue) is mixed with about 0.5 g of ammonium chloride and heated over a bare flame until fumes are no longer evolved. The residue is transferred to a small test tube and treated with a drop or two of freshly prepared 0.2 % sodium rhodizonate solution. The formation of a red to red-brown precipitate indicates the presence of barium sulfate in the sample. 

Sulfate (the lower limit of determination is 0.002 g as SO3) Sulfate is determined gravically by precipitation as barium sulfate which is filtered off. washed, ignited, and weighed. 

Determination of the level of total sulfur in a rubber can give information on the type of cure system used, for example, elemental sulfur plus accelerator or sulfur donor system, etc. The ISO 6528-1 1992 method — Rubber — Determination of total sulfur content — Part 1 Oxygen combustion flask method is often employed. The principle of the method is oxidation by ignition in an atmosphere of oxygen in the presence of hydrogen peroxide, conversion of sulfur to sulfuric acid and determination of the sulfate by titration with barium perchlorate. The method is... 

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