Sulfur analysis gravimetric method

The network is implemented by the participating countries through WHO. Sulfur Dioxide (SO,) and suspended particulate matter (SPN) data are routinely reported from each of the participating countries to WHO for entry into the global data base, which is maintained by the United States Environmental Protection Agency (U.S. EPA) at Research Triangle Park, North Carolina. Methods of collection and analysis varies by country. SPN is reported either as a gravimetric or a photometric (transmittance or reflectance) measurement converted to mass units. Since the accuracy of the conversion of the photometric measurement to mass units is... 

Polymerization Method. To a solution of 5.18 mmole of HFB or PFB and 5.18 mmole of the appropriate bisphenol or bisthiophenol in 20 ml of solvent was added 22.4 mmole anhydrous of K2CO3 and 1.43 mmole of 18-crown-6 ether. The magnetically stirred, heterogenous mixture was heated in an oil bath and maintained under N2. Upon cooling to room temperature, the mixture was slowly poured into ca. 150 ml of methanol and was vigorously stirred. The filtered solids were washed three times in a blender with 300-ml portions of distilled water. The solids were air dried and subsequently placed in a vacuum oven (80 ) for 24 hr. Where soluble, the polymers obtained were characterized by IR and PMR analysis. Elemental analyses for all polymers were satisfactory. Polymer solubility was determined in THF, DMF, dioxane, toluene, m-cresol, chloroform, and sulfuric acid. The percent insoluble polymer was determined gravimetrically. Inherent viscosities of soluble polymers were determined in ca. 0.5% wt. solutions in either chloroform or THF. 

Phosphorus can serve as a benehcial adjunct or as a deleterious agent. There are several test methods for the determination of phosphorus. In addition to the three test methods described here, reference should also be made to multielement analysis methods such as inductively coupled plasma atomic emission spectroscopy (ICPAES) (ASTM D-4951, ASTM D-5185) and X-ray fluorescence (XRF) (ASTM D-4927, ASTM D-6443) described above in this guide. Phosphorus can also be determined by a photometric procedure (IP 148) or by a test method (ASTM D-1091) in which the organic material in the sample is destroyed, phosphorus in the sample is converted to phosphate ion by oxidation with sulfuric acid, nitric acid, and hydrogen peroxide, and the magnesium pyrophosphate is determined gravimetrically. Another method (ASTM D-4047, IP 149) in which the phosphorus is converted to quinoline phosphomolybdate is also available. 

Like cements, the elemental composition is determined by XRF or AAS techniques. The XRF bead is made using lithium tetraborate at 1050°C. Sulfide content cannot be determined by XRF. Sulfite, SO3 , and sulfate, S04 , are safely analyzed by XRF. Na2C03 -I- K2CO3 fusion is carried out for Ca, Mg, Fe, and A1 analysis by AAS. Lanthanum chloride is used as a sulfate interference suppressant. Gravimetric sulfate determinations are also carried out by precipitation as barium sulfate. The Leco Carbon-Sulfur Analyzer can also be used for quality control purposes. The fluoride is determined by XRF or a pyrohydrolysis method. The measurement of particle size distribution is carried out in a manner similar to that for cements and clays. 

The total sulfur content may be determined by one of several methods that convert it to sulfate by wet chemical analysis. One of these, the Eschka method, involves combustion of coal at 800°C in the presence of alkaline/oxidant medium (e.g., two parts of calcined MgO and one part anhydrous sodium carbonate) all sulfur is converted to sulfate that by the addition of barium chloride precipitates as barium sulfate, which is calcined to BaO and measured gravimetrically (see ASTM D3177). This is a standard method in many countries. Another is the high-temperature method where the coal is burned in oxygen at 1350°C, converting all sulfur present into SO2. The SO2 is then converted to sulfuric acid for titrimetric determination. 

The copper content in cupric compounds is usually determined by gravimetric analysis. In the conventional method, Cu is usually reduced to Cu by the addition of sulfurous acid, ammonium hydrogen sulfite, ascorbic acid, or ferrous sulfate. It is then precipitated as cuprous thiocyanate by the addition of ammonium thiocyanate and estimated gravimetrically. 

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