Barium suspension

Typical barium suspensions range from 31) to more than 120% weight/volume (w/v). and because they are eolloidal suspensions, they cannot be given intruvaseularly the colloidal particles would produce fatal pulmonary embolism. Tlie barium suspensions used for UGI or BE studies are too dense to be u.sed for gut opacification during CT studies of the abdomen, because they produce unacceptable radiographic artifacts. Instead, commercial barium preparations are diluted to I to 4% w/v. 

Water and water-methylcellulose solution have been replaced by polyethylene glycol (PEG) electrolyte solution or low Hounsfield value barium suspension, 0.1% ultra-low-dose barium with sorbitol, a nonadsorbable sugar alcohol that promotes luminal distention and limits resorption of water across the length of the small bowel (Megibow et al. 2006). 

In their study Megibow et al. prospectively evaluated bowel wall distention and bowel wall appearance after an orally administered 0.1% barium suspension, VoLumen (E-Z-Em, USA) as a bowel marking agent for MDCT and they concluded that this oral contrast agent provides an excellent distention and visualization of mural features in the gastrointestinal tract. 

Iafrate Low Hounsfield barium suspension (VoLumen) 120 Smart MA 64 X 0.625 0.984 3 mm... 

Faecal tagging is performed with a 40% weight/ volume barium suspension (Tagitol V , E-Z-EM). The patients only have to drink a total of 60 ml 20 ml at breakfast, lunch and dinner respectively. The patients are instructed to drink the barium at once after the meal. 

Last but not least, Pickhardt et al. (2003) obtained tbe best results of polyp detection to date with virtual colonoscopy in a large cohort of 1233 asymptomatic patients. The day before CT colonography they combined a clear liquid diet with a double dose of oral sodium phosphate and two bisacodyl tablets. Faecal tagging was performed with 2x250 ml of a 2.1% w/v barium suspension and 60 ml of Gas-trografin. Excellent results of polyp detection were obtained. 

Callstrom et al. (2001) performed laxative-free CT colonography without dietary restrictions in 58 patients. Faecal tagging was obtained with a combination of iodine and barium administered over one or two days. The best results of tagging were obtained by combining 6x225 ml of a 2.1% w/v barium suspension and 1x225 ml dilute diatrizoate meglumine and diatrizoate sodium. All residue with a density >150 H.U. was electronically labelled. In that way a 100% sensitivity for lesions >1 cm was obtained (5/5 lesions). 

Tagging of feces, especially fluid, by an oral contrast agent such as a barium suspension or water-soluble iodinated contrast material, is a promising method for differentiating residual feces from polyps and thus improving the accuracy in the detection of polyps (Bielen et al. 2003 Lefere et al. 2002,2004a, b, PicKHARDT et al. 2003 Thomeer et al. 2003). 

Adequate mucosal coating is achieved by the use of a high-density barium suspension. The type of harium used significantly affects the quality of the examination, as mucosal coating depends on the physical and chemical properties of the barium sulphate suspension. The best results are achieved using either high-density barium (200% wt/vol - i.e. E-Z-HD) or intermediate density (100% wt/vol) barium such as Baritop. Gaseous distension is required in order to distend normal folds and properly visualise the mucosa (Levine et al. 1988). 

The reaction mechanism for these products is not clearly understood, but the introduction of organo-metallic compounds (barium or iron salts in colloidal suspension) has been shown to have a beneficiai action on the combustion of diesel fuel in engines and reduce smoke. However, these products cause deposits to form because they are used in relatively large proportions (on the order 0.6 to 0.8 weight %) to be effective. 

The palladium - barium sulphate catalyst Is prepared by treating a suspension of20g. of barium sulphate (which has been precipitated in hot solution) in 400 ml. of hot water with a solution of I - 7 g. of palladium chloride (equivalent to I - 0 g. of palladium) in 50 ml. of water and with I - 5 ml. of 40 per cent, formaldehyde solution. The mixture is rendered faintly alkaline to litmus by the addition of sodium hydroxide solution and then boiled for a short time. When the supernatant liquid is clear, the grey precipitate is filtered oS, and wa.shed with hot water until the... 

Prepare a solution of 41 g. of anhydrous palladium chloride (1) in 10 ml. of concentrated hydrochloric acid and 25 ml. of water (as in A). Add all at once 60 ml. of 6iV-sulphuric acid to a rapidly stirred, hot (80°) solution of 63 1 g. of A.R. crystallised barium hydroxide in 600 ml. of water contained in a 2-htre beaker. Add more 6iV-sulphuric acid to render the suspension just acid to htmus (5). Introduce the palladium chloride solution and 4 ml. of 37 per cent, formaldehyde solution into the hot mechanically stirred suspension of barium sulphate. Render the suspension slightly alkaline with 30 per cent, sodium hydroxide solution, continue the stirring for 5 minutes longer, and allow the catalyst to settle. Decant the clear supernatant hquid, replace it by water and resuspend the catalyst. Wash the catalyst by decantation 8-10 times and then collect it on a medium - porosity sintered glass funnel, wash it with five 25 ml. portions of water and suck as dry as possible. Dry the funnel and contents at 80°, powder the catalyst (48 g.), and store it in a tightly stoppered bottle. 

The best known oxoanion of iron is the ferrate(VI) prepared by oxidizing a suspension of hydrous iron(III) oxide in concentrated alkah with potassium hypochlorite or by anodic oxidation of iron in concentrated alkah. Crystals of potassium ferrate [13718-66-6], K FeO, are deep purple, orthorhombic, and contain discrete tetrahedral [FeOJ anions. Barium ferrate [13773-23A] can be precipitated from solutions of soluble ferrate salts. 

Because the regions of the alimentary tract vary widely ia pH and chemical composition, many different commercial formulations of barium sulfate are available. The final preparations of varyiag viscosity, density, and formulation stabiUty levels are controlled by the different size, shape, uniformity and concentration of barium sulfate particles and the presence of additives. The most important additives are suspending and dispersiag agents used to maintain the suspension stabiUty. Commercial preparations of barium sulfate iaclude bulk and unit-dose powders and suspensions and principal manufacturers are E-Z-EM (Westbury, New York), Lafayette-Pharmacol, Inc. (Lafayette, Indiana), and Picker International, Inc. (Cleveland, Ohio). 

In the oil-weU drilling industry, the barite suspension used as drilling mud can be destabilized by the presence of soluble materials such as gypsum. Addition of barium carbonate precipitates the gypsum, inhibits coagulation, and thus permits the mud to retain the desired consistency and dispersion. 

A recent addition to the many examples of octahedral coordination of O (Table 14.3) is the unusual volatile, hydrocarbon-soluble, crystalline oxo-alkoxide of barium [H4Ba6(/i(i-0)(0CH2-CH2,OMe)i4l, which forms rapidly when Ba granules are reacted with Me0CH2CH20H in toluene suspension. ... 

A suspension of palladium on barium carbonate (3.7 grams of 30%) in water (20 ml) is shaken in an atmosphere of hydrogen at room temperature. The catalyst is then filtered and washed well with water, care being taken that it does not become dry, A solution of the... 

Dispersants To keep insoluble combustion and oxidation products in suspension and dispersed Salts of phenolic derivatives polymers containing barium, sulphur and phosphorus calcium or barium soaps of petroleum sulphonic acids... 

Discussion. The turbidity of a dilute barium sulphate suspension is difficult to reproduce it is therefore essential to adhere rigidly to the experimental procedure detailed below. The velocity of the precipitation, as well as the concentration of the reactants, must be controlled by adding (after all the other components are present) pure solid barium chloride of definite grain size. The rate of solution of the barium chloride controls the velocity of the reaction. Sodium chloride and hydrochloric acid are added before the precipitation in order to inhibit the growth of microcrystals of barium sulphate the optimum pH is maintained and minimises the effect of variable amounts of other electrolytes present in the sample upon the size of the suspended barium sulphate particles. A glycerol-ethanol solution helps to stabilise the turbidity. The reaction vessel is shaken gently in order to obtain a uniform particle size each vessel should be shaken at the same rate and the same number of times. The unknown must be treated exactly like the standard solution. The interval between the time of precipitation and measurement must be kept constant. 

A solution of dibenzo[c,g][l,2]diazocine (206 mg, 1 mmol) and barium hydroxide octahydrate (0.5 g, 1.68 mmol) inluxing EtOH (50 mL) was treated with powdered zinc (0.5 g). Afterluxing for a few minutes, the solution became colorless and heating was discontinued. Dry ice (ca. 5 g) was added in small portions and the resulting suspension was filtered. The filtrate was evaporated to 20 mL and cooled to 0 C to afford colorless crystals yield 82 ing (40%) mp 168-169 C (dec.). 

V Gallardo, L Zurita, A Ontiveros, JDG Duran. Interfacial properties of barium sulfate suspensions. Implications in their stability. J Pharm Sci 89 1134— 1142, 2000. 

Shafi KVPM, Felner I, Mastai Y, Gedanken A (1999) Olympic ring formation from newly prepared barium hexaferrite nanoparticle suspension. J Phys Chem B 103 3358-3360... 

By hydrolysis under very mild alkaline conditions (with a boiling suspension of barium carbonate), ribonucleic acids have been shown to yield small quantities of cyclic phosphates as well as the normal nucleotides.96 These materials were identical electrophoretically with synthetic cyclic phosphates and were readily hydrolyzed to mixtures of 2- and 3-phosphates. Their formation in this way constitutes strong support for Brown and Todd s theory. The precise way in which the alkaline hydrolysis of the polynucleotide occurs has been studied using isotopically labeled water, and the results are in agreement202 with the scheme outlined above. 

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