Barium sulfate standardization

A reference beam is used with a plate of BaS04 as the reference standard. Thus, all measurements are relative and are compared to the reflection from a barium sulfate standard. Because the specular reflection from a pearlescent pigment is so much greater than the reflection from a barium sulfate plate, a neutral density filter allowing only 10% of the light to pass was placed in the beam incident on the sample for measurements made at -15/15. 

Barium metal and most barium compounds are highly poisonous. A notable exception is barium sulfate which is nontoxic because of its extreme iasolubihty ia water. Barium ion acts as a muscle stimulant and can cause death through ventricular fibrillation of the heart. Therefore, care must be taken to avoid contact with open areas of the skin. Workers must wear respirators (of type approved for toxic airborne particles), goggles, gloves, and protective clothing at all times. The toxic barium aluminate residue obtained from barium production is detoxified by reaction with a solution of ferrous sulfate and converted iato nontoxic barium sulfate. According to OSHA standards, the TWA value for Ba and Ba compounds ia air is 0.5 mg/m. ... 

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. 

The actual determination of color is made with a photoelectric tristimulus colorimeter fitted with a CIE illuminating source. Measurements are made relative to a standard (usually magnesium oxide or barium sulfate) taken through... 

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. 

Primer Formulations. Coatings were formulated using standard techniques. Mill bases were prepared by dispersing the oligomer solution with pigments (silica, carbon black, titanium dioxide and barium sulfate in a 1 1 1 10 ratio). The viscosity of the formulation was reduced to spray viscosity by addition of solvent. 

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). 

The zinc-sulfide-containing white pigment with the largest sales volume is litho-pone [1345-05-7], which is produced by coprecipitation and subsequent calcination of a mixture of zinc sulfide [1314-98-3], ZnS, Mr 97.43, and barium sulfate [7727-43-7], BaS04, Mr 233.40. For standards, see Table 1 (Lithopone pigments Specification ). Pure zinc sulfide is marketed as Sachtolith. 

Standardize a recording spectrophotometer to 100% reflectance from 420 to 700 nm, using the white standard (powdered barium sulfate) in both the sample and standard ports of the reflectance attachment. 

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. 

FIGURE 8 Reflectance properties of typical white standards in the UV-vis-NIR range. (A) Reflectance of barium sulfate. The measurement was carried out with a PerkinElmer Lambda 9 spectrometer equipped with an integrating sphere, and the reactor cell described in Ref. (Thiede and Melsheimer, 2002). For the background correction one piece of Spectralon was placed at the reference port of the sphere, a second piece was placed inside the reactor cell at the sample port of the sphere. For measurement of the presented spectra, BasS04 was placed in the reactor, while the piece of Spectralon at the reference port remained in position. (B) Reflectance of Spectralon as provided by the manufacturer. 

Such methods are wet oxidation of pulp followed by estimation of sulfate by precipitation of barium sulfate (Canadian Pulp and Paper Association Standard G28 1970), X-ray fluorescence spectroscopy (Rivington 1988, Kibblewhite et al. 1987), and combustion of pulp followed by analysis of sulfur as sulfur dioxide or as sulfate. The sulfur dioxide evolved is determined by iodometric titration (Canadian Pulp and Paper Association useful method G.7U, March 1959). Sulfate can be determined by titration with barium chloride (Ora 1960), back-titration with sulfuric acid after addition of barium perchlorate (Aldrich 1974), potentiometric titration with lead perchlorate using an ion-selective electrode (Ross and Frant 1969), or ion chromatography (Douek and Ing 1989). 

The addition of various modifiers, such as quinoline-sulfitr, thiourea, 52 or, especially, tetramethylthiourea 53 to the reaction mixture, is sometimes necessary in order to inhibit the further hydrogenation of the aldehyde. This is particularly true for the formation of aryl aldehydes that are hydrogenated over palladium under mild conditions. 54.155 barium sulfate support is, itself, a moderate inhibitor and is generally sufficient for regulating the preparation of unsubstituted aliphatic aldehydes. However, if another support, such as charcoal, is used for the palladium, one of the standard inhibitors must be added to moderate the reaction. When these added inhibitors are present, the... 

The amount of hydrochloric acid 50 mL of 1 +5 hydrochloric acid [sp gr 1.16, 32% weight by weight (w/w) as per Indian Standard (IS) of hydrochloric acid] is 1.68N for a 0.5-g test sample of gypsum is too high for any purpose except the quick dissolution of gypsum and other impurities such as carbonate and so forth. This high acidity of the resulting solution before and after barium sulfate precipitation is very likely to introduce errors that affect the results. Reduction of final acidity is therefore necessary for accurate determination of sulfate. 

In the inductively coupled argon plasma emission spectrometer method, nickel, iron, and vanadium content of gas oil samples in the range from 0.1 to 100 mg/kg. Thus a 10-g sample of gas oil is charred with sulfuric acid and subsequently combusted to leave the ash residue. The resulting sulfates are then converted to their corresponding chloride salts to ensure complete solubility. A barium internal standard is added to the sample before analysis. In addition, the use of the ICAP method for the analysis of nickel, vanadium, and iron present counteracts the two basic issues arising from metals analysis. The most serious issue is the fact that these metals are partly or totally in the form of volatile, chemically stable porphyrin complexes and extreme conditions are needed to destroy the complexes without losing the metal through volatilization of the complex. The... 

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. 

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