Phosphoric acid purified

Suitable catalysts include the hydroxides of sodium (119), potassium (76,120), calcium (121—125), and barium (126—130). Many of these catalysts are susceptible to alkali dissolution by both acetone and DAA and yield a cmde product that contains acetone, DAA, and traces of catalyst. To stabilize DAA the solution is first neutralized with phosphoric acid (131) or dibasic acid (132). Recycled acetone can then be stripped overhead under vacuum conditions, and DAA further purified by vacuum topping and tailing. Commercial catalysts generally have a life of about one year and can be reactivated by washing with hot water and acetone (133). It is reported (134) that the addition of 0.2—2 wt % methanol, ethanol, or 2-propanol to a calcium hydroxide catalyst helps prevent catalyst aging. Research has reported the use of more mechanically stable anion-exchange resins as catalysts (135—137). The addition of trace methanol to the acetone feed is beneficial for the reaction over anion-exchange resins (138). 

Most of the phosphoms produced as the element is later converted to high purity phosphoric acid and phosphate compounds the remainder is used in direct chemical synthesis to produce high purity products. In contrast, phosphoric acid produced by the wet process is used in lower purity apphcations, especially in fertiliser and to a lesser degree in animal feed (see Feeds AND FEED ADDITIVES). More recendy, a small portion of wet acid is purified in a second process and then also used in high purity acid and phosphate compound apphcations. 

About 264,000 metric tons of elemental capacity is available in North America, plus another 79,000 t (P equivalent) of purified wet phosphoric acid (14). About 85% of the elemental P is burned to P2 5 hydrated to phosphoric acid. Part of the acid (ca 21%) is used direcdy, but the biggest part is converted to phosphate compounds. Sodium phosphates account for 47% calcium, potassium, and ammonium phosphates account for 17%. Pinal apphcations include home laundry and automatic dishwasher detergents, industrial and institutional cleaners, food and beverages, metal cleaning and treatment, potable water and wastewater treatment, antifree2e, and electronics. The purified wet acid serves the same markets. 

A method suitable for analysis of sulfur dioxide in ambient air and sensitive to 0.003—5 ppm involves aspirating a measured air sample through a solution of potassium or sodium tetrachloromercurate, with the resultant formation of a dichlorosulfitomercurate. Ethylenediaminetetraacetic acid (EDTA) disodium salt is added to this solution to complex heavy metals which can interfere by oxidation of the sulfur dioxide. The sample is also treated with 0.6 wt % sulfamic acid to destroy any nitrite anions. Then the sample is treated with formaldehyde and specially purified acid-bleached rosaniline containing phosphoric acid to control pH. This reacts with the dichlorosulfitomercurate to form an intensely colored rosaniline—methanesulfonic acid. The pH of the solution is adjusted to 1.6 0.1 with phosphoric acid, and the absorbance is read spectrophotometricaHy at 548 nm (273). 

Although usually handled as an aqueous solution, formaldehyde cyanohydrin can be isolated in the anhydrous form by ether extraction, followed by drying and vacuum distillation (23). Pure formaldehyde cyanohydrin tends to be unstable especially at high pH. Small amounts of phosphoric acid or monochloroacetic acid are usually added as a stabiLher. Monochloroacetic acid is especially suited to this purpose because it codistiHs with formaldehyde cyanohydrin (24). Properly purified formaldehyde cyanohydrin has excellent stability (25). 

Tetrapropylene is manufactured from propylene (containing 50% propane) with the use of a phosphoric acid catalyst at 70-bar pressure and 200°C. Under these conditions a product mixture is obtained which has to be purified by distillation. Unconverted propane is obtained as the first fraction, followed by tripropylene which can either be sent back to the polymerization or used as motor fuel. The third fraction consists of the desired tetrapropylene. 

Almost all phosphoric acid is produced directly from apatite. The ore is partially purified, crashed, and then slurried with aqueous sulfuric acid ... 

While earlier papers cited buffer systems or aqueous o-phosphoric acid to achieve satisfactory peak resolution, most recent investigations involved acetic acid or formic acid systems. " Representative examples are 0.2% and 1% HCOOH for betacyanins and betaxanthins, respectively, the latter requiring a lower pH for chromatographic resolution. Methanol or acetonitrile are most commonly used as modifiers, either undiluted or diluted with purified water at ratios of 60 40 or 80 20 (v/v), respectively. - Typical HPLC fingerprints for yellow and red beet juice are shown in Figure 6.4.1. 

The purified tetraethyl pyrophosphate is a colorless, odorless, water-soluble, hygroscopic liquid (24, 4 )- It possesses a very high acute toxicity (28), exceeding that of parathion, and is rapidly absorbed through the skin. There is no spray-residue problem, however, for tetraethyl pyrophosphate hydrolyzes even in the absence of alkali to nontoxic diethyl phosphoric acid. Hall and Jacobson (24) and Toy (47) have measured its rate of hydrolysis, which is a first-order reaction. Its half-life at 25° C. is 6.8 hours and at 38° C. is 3.3 hours. Coates (10) determined the over-all velocity constant at 25° C. k = 160 [OH-] + 1.6 X 10 3 min.-1 Toy (47) has described an elegant method for preparing this ester as well as other tetraalkyl pyrophosphates, based upon the controlled hydrolysis of 2 moles of dialkyl chlorophosphate ... 

Phorex [Phosphoric acid extraction] A process for purifying phosphoric acid by solvent extraction with -butyl or n-amyl alcohol. Developed by Azote et Produits Chimiques, France. 

The probable impurities in radioactive phosphorus trichloride are hydrogen chloride and phosphorous acid the trichloride is, therefore, purified by fractional evaporation and fractional condensation in the high-vacuum system. Pure ethylphosphonous dichloride is prepared according to the equation ... 

Distillation can be used to purify a compound by separating it from less volatile substances in a reaction mixture. You may have used this technique to prepare cyclohexene from cyclohexanol. In this reaction, cyclohexanol is mixed with concentrated phosphoric acid and an elimination reaction takes place. 

N-Methylmorphinane. 2.7 g of the decahydro compound above in 25 ml of 85% phosphoric acid is refluxed for 70 hours and then poured onto ice. The aqueous phase is extracted with ether and the product is salted out with potassium carbonate. It is then taken up with ether, dried, and distilled at 130-132° at 0.7 mm of vacuo to give 1 g ofN-Methyl morphinane mixed with a small amount of octahydroisoquinoline, which can be removed by column chromatography. Use 0.5 g of product in 4 ml of low boiling petroleum ether and add onto the top of 30 g of aluminum oxide in a 50 ml buret or column. Elute with 20 ml portions of low boiling ether to which is added 0,0,0,1,3,5,5, and 5 ml of ethyl ether, respectively. The last three portions eluted over 0.3 g of purified product. 

For prepn of 1,1-DNEt, ADL Rept (Ref 6, p 108) recommends acidifying the K salt by means of 85% phosphoric acid and purifying the resulting product by vacuum distillation behind a barricade. A small amt of boric acid was added before the distillation operation. The water-white distillate boiled at 73—74.5° at 13mm pressure... 

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