Acids concentration

If the filtrate has a faint p>ermanganate colour, add a few drops of sodium bisulphite solution until the solution is colourless. In this case (compare o-chlorobenzoic acid) concentration of the solution before precipitation only increases the yield by about 1 g. and may cause occlusion of inorganic salts. 

The values are precisely defined only for a given nitric acid concentration, as the dependence of rate on nitric acid concentration varies from one compound to another... 

METHOD 2 [113]-Phenol can be oxidized with either performic, formic or acetic acids to catechol. For example phenol, formic acid, concentrated H2O2 and polyphosphoric acid are heated 2 hours at 80 C to give 53% catechoi. Addition of phosphorus pen-toxide (P2O5) is said to increase the yieid. 

The cyclization of a-thiocyanatoketones (183) in aqueous acid, concentrated sulfuric acid in acetic acid and water, or alkaline solution leads to 2-hydroxythiazoles after dilution in water. 

Mixed with additives, urea is used in soHd fertilizers of various formulations, eg, urea—ammonium phosphate (UAP), urea—ammonium sulfate (UAS), and urea—phosphate (urea + phosphoric acid). Concentrated solutions of urea and ammonium nitrate (UAN) solutions (80—85 wt%) have a high nitrogen content but low crystallization point, suitable for easy transportation, pipeline distribution, and direct spray appHcation. 

Although the reaction is second order in acryUc acid concentration, the rate of dimer formation for neat acryUc acid available commercially is quite adequately expressed by... 

Pentaerythritol may be nitrated by a batch process at 15.25°C using concentrated nitric acid in a stainless steel vessel equipped with an agitator and cooling coils to keep the reaction temperature at 15—25°C. The PETN is precipitated in a jacketed diluter by adding sufficient water to the solution to reduce the acid concentration to about 30%. The crystals are vacuum filtered and washed with water followed by washes with water containing a small amount of sodium carbonate and then cold water. The water-wet PETN is dissolved in acetone containing a small amount of sodium carbonate at 50°C and reprecipitated with water the yield is about 95%. Impurities include pentaerythritol trinitrate, dipentaerythritol hexanitrate, and tripentaerythritol acetonitrate. Pentaerythritol tetranitrate is shipped wet in water—alcohol in packing similar to that used for primary explosives. 

Aldehydes, enals, dienals, ketones, and hydrocarbons, which are responsible for disagreeable odors, generally bok at lower temperatures than fatty acids. Analysis showkig a free fatty acid concentration of less than 0.05% is an kidication that deodorization is sufficientiy complete. Some of the dienals have very low odor thresholds and sensory evaluation of the finished ok is a judicious quaHty assurance step. 

Type of process Operating temperature, °C Extraction Crystal conversion Acid concentration, % P3O3 Acid impurity level vs dihydrate acid P3O3 recovery, %... 

A flow sheet of the basic TVA process for granular diammonium phosphate is given in Figure 12. The raw materials are wet-process phosphoric acid and anhydrous ammonia. Feed acid concentration of at least 40% P2 5 required to give a satisfactory water balance. This average concentration usually is provided by two separate feed streams, one of 54% P2 5 concentration and one of about 30% P2 5 arrangement shown, the 54% acid is... 

In the batch methylene chloride process, the sulfuric acid concentration can be as low as 1% and only limited desulfonation is required to reach a combined acetic acid content of 62.0%. With perchloric acid catalyst, the nearly theoretical value of 62.5% combined acetic acid is obtained. 

Only acids are sour. Sourness is not identical to chemical acidity or pH, which is a function of the hydrogen ion concentration, but also appears to be a function of the entire acid molecule. A combination of pH and acid concentration determines the actual degree of the sour taste. At the same pH, any organic acid, eg, citric acid, exhibits a far greater sourness than a mineral acid, eg, hydrochloric acid (27,28). 

As opposed to gaseous, pure formaldehyde, solutions of formaldehyde are unstable. Both formic acid (acidity) and paraformaldehyde (soHds) concentrations increase with time and depend on temperature. Formic acid concentration builds at a rate of 1.5—3 ppm/d at 35°C and 10—20 ppm/d at 65°C (17,18). Trace metallic impurities such as iron can boost the rate of formation of formic acid (121). Although low storage temperature minimizes acidity, it also increases the tendency to precipitate paraformaldehyde. 

The specific heat of aqueous solutions of hydrogen chloride decreases with acid concentration (Fig. 4). The electrical conductivity of aqueous hydrogen chloride increases with temperature. Equivalent conductivity of these solutions ate summarized in Table 8. Other physicochemical data related to... 

The effect of pressure on the solubility of chlorine ia hydrochloric acid has been reported for pressures varying from about 100 to 6500 kPa (1—6.5 atm) (20). At pressures above 200 kPa, there is a linear dependence of pressure on the solubility in the acid concentration range of 0.1—5.0 N. 

Nickel-based aUoys have superior corrosion resistance to Hon-based aUoys. The only aUoys recommended for hot hydrochloric acid use are Ni—Mo aUoys containing 60—70% Ni and 25—33% Mo. Chlorimet (63 Ni, 32 Mo, 3 Fe) and HasteUoy (60 Ni, 28 Mo, 6 Fe) are found to be stable at aU acid concentrations in the absence of aH and Hon chlorides. Electroless nickel, a Ni—P aUoy containing 2—10% P, shows exceUent resistance to hot hydrogen chloride (71). The corrosion resistance increases with phosphoms content. This coating can be deposited on cast Hon, wrought Hon, mild steel, stainless steels, brass, bron2e, and aluminum (qv). 

The solution leaving the flotation cell, containing about 0.4 g/L iodine, is sent to a kerosene solvent extraction process to recover the dissolved product. After neutralization with soda ash to the initial incoming alkalinity, the solution is returned to the nitrate lixiviation process. The iodine-chaiged kerosene is contacted with an acidic concentrated iodide solution containing SO2, which reduces the iodine to iodide. 

Cation exchangers are regenerated with mineral acids when used in the form. Sulfuric acid [8014-95-7] is preferred over hydrochloric acid [7647-01-0], HCl, in many countries because it is less expensive and less corrosive. However, the use of hydrochloric acid is the best method of overcoming precipitation problems in installations which deionize water with high concentrations of barium or calcium compared to other cations. A 4% acid concentration is common, although sulfuric acid regenerations may start as low as 0.8—1% to minimize calcium sulfate [7718-18-9] precipitation. 

The Mn ion is so unstable that it scarcely exists in aqueous solution. In acidic aqueous solution, manganic compounds readily disproportionate to form Mn ions and hydrated manganese(IV) oxide, Mn02 2H20 in basic solution these compounds hydroly2e to hydrous manganese(III) oxide, MnO(OH). Sulfuric acid concentrations of about 400 450 g/L are required to stabilize the noncomplexed Mn ion in aqueous solutions. 

Zinc and Zinc Alloys. Zinc metal is highly reactive in acid solutions such as sulfuric, hydrochloric, and nitric dissolving rapidly at acid concentrations normally used to pickle steel and aluminum. Dilute (1—4%) solutions of these acids can be used with caution to remove zinc oxides. 

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