Barium sulfate, temperature

This reaction is favored by moderate temperatures (100—150°C), low pressures, and acidic solvents. High activity catalysts such as 5—10 wt % palladium on activated carbon or barium sulfate, high activity Raney nickel, or copper chromite (nonpromoted or promoted with barium) can be used. Palladium catalysts are recommended for the reduction of aromatic aldehydes, such as that of benzaldehyde to toluene. 

Thennodynamic inhibitors are complexing and chelating agents, suitable for specific scales. For example, for scale inhibition of barium sulfate, common chemicals are ethylenediaminetetraacetic acid (EDTA) andnitrilotriacetic acid. The solubility of calcium carbonate can be influenced by varying the pH or the partial pressure of carbon dioxide (CO2). The solubility increases with decreasing pH and increasing partial pressure of CO2, and it decreases with temperature. 

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). 

Barium sulfide may also be made by high temperature reduction of barium sulfate with methane. 

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. 

Both zinc sulfide and barium sulfate are insoluble in water. To improve the stability of lithopone, a small amount of a cobalt salt is added to the precipitated mixture. The mixture has to be filtered off, dried, and calcined. The calcination is carried out in rotary calciners at temperatures between 600 and 700°C. During calcination, the particle size of zinc sulfide grows from its original size (about 0.1 Jim) to the pigmentary optimal size of 0.4—0.6 Jim. 

To 33.2g of pure (recrystallized) sulfamic acid (No. 92) in 250ml of water are added 54.0g of pure barium hydroxide 8-hydrate. When all the solids have dissolved, any precipitate of barium sulfate is filtered off and the clear filtrate evaporated in vacuo at room temperature with the water pump. Successive crops of crystals are isolated, washed with 95% alcohol and the mother liquor with rinsings is further evaporated. Depending on the completeness of the water removal, yields of over 90% are readily attained. 

A material that is added to a formulation that increases the quantity of formulation required for a process without actually changing the formulation s reactivity. Example Barium sulfate is sometimes added during processing to increase the density of polyurethane (solid) foam. (CAPICO) A system in which potential cosmetic emulsion ingredients are numerically categorized so that one may calculate their influence on the phase inversion temperature of a formulated emulsion. 

The high-temperature reduction of barium sulfate with coke yields the water-soluble barium sulfide (BaS), which is subsequently leached out. Treatment of barium sulfide with the relevant chemical yields the desired barium salt. Purification of the product is complicated by the impurities introduced in the coke. Pure barium carbonate and barium sulfate are made by precipitation from solutions of water-soluble barium salts. 

In this problem, assume that the temperature remains constant at 25°C. Ksp for barium sulfate, BaS04, is 1.1 X 10-10, and Ksp for barium fluoride, BaF2, is 1.8 X 10 7. 

Entropy Change. The entropy change in the adsorption of water on barium sulfate is shown in Figure 8. The integral entropy, AS, calculated from AG and A ffl decreases monotonically with increasing amount adsorbed. AS can also be calculated from the temperature coefficient of v by... 

O Results calculated from temperature coefficient of x AHit. Change m partial molal entropy of barium sulfate... 

Alternative catalysts such as palladium-on-barium sulfate (poisoned by synthetic quinoline) (24), "P-2" nickel boride (with ethylenediamine) (25), and other nickel catalysts (19c) can be used in place of Lindlar catalyst. However, in our hands selective hydrogenation of triple bonds to Z olefins proceeds with the greatest stereoselectivity with Lindlar catalyst. Palladium-on-barium sulfate (in ethanol with quinoline) can give considerable over-reduction and isomerization to the E isomer (22a). Use of "P-2" nickel boride as the catalyst at room temperature usually gives a. 2% of the J5 isomer (e.g. 23). 

This intermediate was alkylated with tert. -butyI-cj-iodohexanoate to the ester 30. Conversion to the acid 31 was achieved by cleavage of the fed.-butylester with trifluoroacetic acid at low temperature. The triple bond was reduced to a trans-double bond and simultanously the benzylether groups had been removed with lithium in ethylamine, under formation of the desired 15-deoxy-7-oxaprostaglandin Fla 32 in crystalline form. The ds-isomer was prepared by first reducing the triple bond of compound 30 with palladium on barium sulfate to 33, removal of the ted. -butylgroup with formic acid to 34 and debenzylation of the acid with lithium in ethylamine to 35. 

The mixture is filtered with suction through an asbestos mat supported on a filter paper in a 25-cm. Buchner funnel, and the barium sulfate is washed with two 100-cc. portions of water. The filtrate and washings are combined, and the clear colorless solution of the sugar is concentrated to about 300 cc. under reduced pressure (water pump) on a water bath whose temperature does not exceed 60°. The mixture is filtered, and the solid is washed on the filter with a little water. The combined filtrate and washings are then concentrated to a volume of 100 cc. under the conditions described above. The warm, slightly tan-colored syrup is poured into a 500-cc. Erlenmeyer flask. The transfer is com-... 

Another commercial aldehyde synthesis is the catalytic dehydrogenation of primary alcohols at high temperature in the presence of a copper or a copper-chromite catalyst. Although there are several other synthetic processes employed, these tend to be smaller scale reactions. For example, acyl halides can be reduced to the aldehyde (Rosemnund reaction) using a palladium-on-barium sulfate catalyst. Formylation of aryl compounds, similar to hydrofomiylation, using HCN and HQ (Gatterman reaction) or carbon monoxide and HQ (Gatterman-Koch reaction) can be used to produce aromatic aldehydes. 

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