Barium sulfate method

Some properties of the rock used in this study were measured The cation exchange capacity (cec) was determined by the barium sulfate method as described by Mortland and Mellor (33). Surface area was measured by using a Digisorb Meter (Micromeritics Instrument Corporation) through nitrogen adsorption. Estimation of mineral composition and indentification of the rock were performed by X-ray diffraction. 

A 1 5 soil/water extract is mechanically stirred during measurement to minimise changes in electrode potential associated with suspension effects and positioning of electrodes. Results by this procedure are commonly higher by about 0.5-0.6 of a pH unit (Baker etal. 1983) than those measured in the field by the mixed indicator/barium sulfate method of Raupach and Tucker (1959). The water should have a pH >6.5 but <7.5. If necessary, boil distilled or deionised water for 15 minutes and cool under C02-free conditions. EC should be <10 3dS/m. Standardisation of the equipment is undertaken using standard pH solutions usually pH 4.00, 7.0 and 9.183. Such solutions are normally purchased ready for use. 

Nienow and Inoue (1993) gave an interesting set of examples using a small tank and the semibatch barium sulfate method of Villermaux to demonstrate the importance of feed position, as shown in Figure 13-8. In all cases the mixer speed and rate of addition were held constant only the position of addition was changed. All vessels were at about the same power per unit tank volume. The selectivity given is that of unwanted by-product. High numbers mean that more by-prodnct was formed. 

Bomb Method the sample is burned in a bomb under oxygen pressures of 30 bar. The sulfur contained in the wash water is analyzed via gravimetry as barium sulfate. 

Chemical precipitation and solvent extraction are the main methods of purifying wet-process acid, although other techniques such as crystallisa tion (8) and ion exchange (qv) have also been used. In the production of sodium phosphates, almost all wet-process acid impurities can be induced to precipitate as the acid is neutralized with sodium carbonate or sodium hydroxide. The main exception, sulfate, can be precipitated as calcium or barium sulfate. Most fluorine and siUca can be removed with the sulfate filter cake as sodium fluorosiUcate, Na2SiFg, by the addition of sodium ion and control of the Si/F ratio in the process. 

Quantitatively, sulfur in a free or combined state is generally determined by oxidizing it to a soluble sulfate, by fusion with an alkaH carbonate if necessary, and precipitating it as insoluble barium sulfate. Oxidation can be effected with such agents as concentrated or fuming nitric acid, bromine, sodium peroxide, potassium nitrate, or potassium chlorate. Free sulfur is normally determined by solution in carbon disulfide, the latter being distilled from the extract. This method is not useful if the sample contains polymeric sulfur. 

The classical analytical method of deterruination of barium ion is gravimetric, by precipitating and weighing insoluble barium sulfate. Barium chromate, which is more insoluble than strontium chromate in a slightly acidic solution, gives a fairly good separation of the two elements. 

The catalyst commonly used in this method is 5 wt % palladium supported on barium sulfate inhibited with quinoline—sulfur, thiourea, or thiophene to prevent reduction of the product aldehyde. A procedure is found in the Hterature (57). Suitable solvents are toluene, benzene, and xylene used under reflux conditions. Interestingly, it is now thought that Rosenmund s method (59) originally was successful because of the presence of sulfur compounds in the xylene used, since the need for an inhibitor to reduce catalyst activity was not described until three years later (60). 

All gaseous sulfur products obtained as a result of incubation of sulfur-treated fruit were oxidized with alkaline hydrogen peroxide, precipitated as barium sulfate, and counted with a thin window Geiger counter. The peel and peel proteins were oxidized with magnesium nitrate, the sulfur was precipitated as barium sulfate according to standard methods, and counted as in the case of the gaseous products. Counting data, as reported, are fully corrected. 

Creosol (also called 2-methoxy-jb-cresol, 4-methylguaiacol, and 3-methoxy-4-hydroxytoluene) has been obtained by the fractionation of beach creosote tar,4 by the reduction of vanillin by electrolytic methods,6 6 by hydrogen and palladium on charcoal or barium sulfate,7 8 with hydrazine,9 and by amalgamated zinc and hydrochloric acid.3 10 11 It has also been prepared by methyl-ation of 4-methylcatechol with methyl iodide 12 13 or with methyl sulfate 14 and is reported to be formed by the distillation of the calcium salt of 3-methoxy-4-hydroxyphenylacetic acid.16... 

Lebel [224] has described an automated chelometric method for the determination of sulfate in seawater. This method utilises the potentiometric end-point method for back titration of excess barium against EDTA following precipitation of sulfate as barium sulfate. An amalgamated silver electrode was used in conjunction with a calomel reference electrode in an automatic titration assembly consisting of a 2.5 ml autoburette and a pH meter coupled to a recorder. Recovery of added sulfate was between 99 and 101%, and standard deviations of successive analyses were less than 0.5 of the mean. 

The bomb method for sulfur determination (ASTM D129) uses sample combustion in oxygen and conversion of the sulfur to barium sulfate, which is determined by mass. This method is suitable for samples containing 0.1 to 5.0% w/w sulfur and can be used for most low-volatility petroleum products. Elements that produce residues insoluble in hydrochloric acid interfere with this method this includes aluminum, calcium, iron, lead, and silicon, plus minerals such as asbestos, mica, and silica, and an alternative method (ASTM D1552) is preferred. This method describes three procedures the sample is first pyrolyzed in either an induction furnace or a resistance furnace the sulfur is then converted to sulfur dioxide, and the sulfur dioxide is either titrated with potassium iodate-starch reagent or is analyzed by infrared spectroscopy. This method is generally suitable for samples containing from 0.06 to 8.0% w/w sulfur that distill at temperatures above 177°C (351°F). 

Sulfates are precipitated as BaS04, and then reduced with carbon at 1,000°C to produce CO2 and CO. The CO is either measured directly or converted to CO2 by electrical discharge between platinum electrodes (LonginelU and Craig 1967). Total pyrolysis by continuous flow methods has made the analysis of sulfate oxygen more precise and less time-consuming than the off-line methods. Bao and Thiemens (2000) have used a C02-laser fluorination system to liberate oxygen from barium sulfate. 

Gross alpha and gross beta activity can be determined by various radioactive counters, such as internal proportional, alpha scintillation, and Geiger counters. Radium in water can be measured by co-precipitating with barium sulfate followed by counting alpha particles. Radium-226 can be measured from alpha counting of radon-222. Various methods are well documented (APHA, AWWA, and WEF 1998. Standard Methods for the Examination of Water and Wastewater, 20 ed. Washington DC American Public Health Association). 

Rubidium alum obtained by either method above is decomposed by treatment with alkali solutions for removal of aluminum and sulfate. Aluminum is precipitated as aluminum hydroxide. Addition of barium hydroxide to the filtrate removes sulfate, precipitating barium sulfate. Evaporation of the solution crystallizes rubidium as hydroxide. 

The palladium-barium sulfate is prepared by the method described by Houben.2 The barium sulfate should be freshly precipitated material. 

A classical method for the preparation of a-amino aldehydes is the conversion of N -pro-tected a-amino acid chloride derivatives to aldehydes by hydrogenation in the presence of palladium on charcoal 15 or barium sulfate. 16 This method is especially used for the conversion of phthalyl-a-amino acid chlorides into the corresponding aldehydes. N -Protected amino acid chlorides or fluorides are also readily reduced by lithium tri-ferf-butoxyaluminum hydride1 7 at low temperature without epimerization, but this method is of limited application because overreduction into the respective alcohols also occurs. 

Analytical Methods. Insoluble barium sulfate precipitate, one of the two criteria by which growth of the bacteria was established was determined by standard gravimetric methods. The amount of barium sulfate is directly proportional to the amount of sulfide that has been oxidized by the sulfur bacteria. 

The gravimetric determination of sulfate can be and is most often used to finish the Eschka and bomb washing methods. The most serious concern is that the barium sulfate precipitated may be extremely fine and difficult to filter. This can be overcome by adding the barium chloride (BaCE) rapidly to the hot solution and stirring the mixture vigorously to obtain a barium sulfate (BaS04) precipitate,... 

Fusion with anhydrous potassium fluoride in a platinum dish is undoubtedly the simplest, most effective and reliable method available for the complete dissolution of a wide variety of siliceous materials. The potassium fluoride cake can then be transposed in the same container to a pyrosulfate fusion with rapid and complete volatilisation of both hydrogen fluoride and silicon tetrafluoride [54]. Except for a small quantity of barium sulfate, the pyrosulfate cake will dissolve completely in dilute hydrochloric acid. The resulting pyrosulfate fusion is one of the simplest and most effective methods available for rapid, complete and dependable dissolution of nonsiliceous materials, particularly high-fired oxides. This fusion has the distinct advantage that the flux can be obtained by simply adding easily purified alkali metal sulfates to sulfuric acid, and the fusion can be carried out in either borosilicate flasks or platinum vessels with very little contamination from either reagents or containers. 

No satisfactory method for the quantitative determination of bile pigments in urine has yet been evolved (W9). Direct spectrophotometry is impossible on account of the presence of yellow pigments other than bile pigments. Diazotization procedures necessitate the application of correction factors, which are not entirely adequate. Some purification can be effected by absorption of the bile pigments onto barium sulfate but their subsequent elution is by no means quantitative. 

After removal of barium sulfate and fractionation of the alkaloid salts, the glycol sulfate ester is recovered as alkali salt and saponified -with alkali.48, 48 The method is tedious and not yet well developed, but it may be noted that the glycols cannot be resolved by the phthalic ester procedure described below because they tend to form polymeric esters instead of simple hydrogen phthalates when treated with phthalic anhydride. 

Note The following steps describe a specific method of filtering, weighing and mounting the sample. The instructor may provide alternate instructions for preparing the barium sulfate source appropriate for the available counting facilities. 

Phenylethylamine has been made by a number of reactions, many of which are unsuitable for preparative purposes. Only the most important methods, from a preparative point of view, are given here. The present method is adapted from that of Adkins,1 which in turn was based upon those of Mignonac,2 von Braun and coworkers,3 and Mailhe.4 Benzyl cyanide has been converted to the amine by catalytic reduction with palladium on charcoal,5 with palladium on barium sulfate,6 and with Adams catalyst 7 by chemical reduction with sodium and alcohol,8 and with zinc dust and mineral acids.9 Hydrocinnamic acid has been converted to the azide and thence by the Curtius rearrangement to /3-phenyl-ethylamine 10 also the Hofmann degradation of hydrocinnamide has been used successfully.11 /3-Nitrostyrene,12 phenylthioaceta-mide,13 and the benzoyl derivative of mandelonitrile 14 all yield /3-phenylethylamine upon reduction. The amine has also been prepared by cleavage of N- (/3-phenylethyl) -phthalimide 15 with hydrazine by the Delepine synthesis from /3-phenylethyl iodide and hexamethylenetetramine 16 by the hydrolysis of the corre-... 

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