Acetic precipitation

Poly(methyl methacrylate) and poly(vinyl acetate) precipitate from the resin solution as it cures. This mechanism offsets the contraction in volume as the polyester resin cross-links, resulting in a nonshrinking thermoset. Other polymer additives such as poly(butylene adipate) provide similar shrinkage... 

The first compound studied (56) was quinolizidine (41), which can be readily converted to J >-dehydroquinolizidine (42) in 60% yield by the action of 4 moles of mercuric acetate in 5% aqueous acetic acid on 1 mole of the amine. Mercurous acetate precipitates as the reaction progresses at... 

Common ion effect The tube at the left contains a saturated solution of silver acetate (AgC2H302). Originally the tube at the right also contained a saturated solution of silver acetate. With the addition of a solution of silver nitrate (AgNOs), the solubility equilibrium of the silver acetate is shifted by the common ion Ag+ and additional silver acetate precipitates. 

FIGURE 11.16 (a) A saturated solution of zinc acetate in water, (b) When additional acetate ions are added (as a single crystal of solid sodium acetate in the spatula shown in part (a)), the solubility ot the zinc acetate is significantly reduced and more zinc acetate precipitates. 

The progress of the partial saponification can be checked by a simple solubility test. About 1 ml of the solution is withdrawn and the cellulose acetate precipitated with water. The small sample is quickly washed free of acid and dried as much as possible by pressing between two filter papers. Some fibers of the still damp material are placed in a test tube with 15-20 ml oholuene/ethanol (volume ratio 1 1) and heated to boiling in a water bath. If the fibers go into solution, then after about 15 min the whole charge can be worked up as described above. 

For the latter reaction very pure chromium is required to prevent formation of Cr34, but the reaction with a zinc amalgam is clean and is a convenient source of the strongly reducing species. Addition ofCr2 solutions to saturated solutions of sodium acetate precipitates chromium(U) acetate ... 

Much decolorisation Orange-red coloration and yellowish-white (yellow with acetic precipitate acid)... 

Four substances have been described as having pressor effects, which are probably amines or aminelike. Urosympathin, described by Holtz, Credner, and Kronberg (34), is a substance found in normal urine in amounts per day, giving a pressor response equal to 2 to 3 mg. of hydroxytyramine or 100 to 150 micrograms of epinephrine or arterenol. In cases of essential hypertension the amount is said to be increased three- to fourfold. Because its action was intensified by cocaine and lessened by ergotoxin and yohimbine, they believed that it represented a mixture of hydroxytyramine, epinephrine, and arterenol. The material was recovered by lead acetate precipitation of urine with subsequent acid hydrolysis. 

In Figure 3.9, a SEM micrograph of a powder sample of a BaCe0 95Yb0 05O3 5 perovskite, which was synthesized following the previously described acetate precipitation procedure, is shown [51],... 

Precipitation is incomplete owing to the free mineral acid produced. If the hydrogen ions, arising from the complete ionization of the mineral acid, are removed by the addition of the salt of a weak acid, such as ammonium or sodium acetate, precipitation is almost complete. This is the basis of one of the methods for the removal of phosphates, which interfere with the precipitation of Group IIIA metals, in qualitative analysis. 

The precipitate is refluxed with a solution made up of 20 ml. of glacial acetic acid, 20 ml. of acetic anhydride, and 3.0 ml. of concentrated hydrochloric acid. Zinc chloride, being soluble in acetic acid, goes into solution, and the ura-nium(IV) acetate precipitates. The product is recovered and freed from the solvent as described under Part A. The yield is 5.2 g. (90%). 

After the final washing of the chromium(II) acetate precipitated in Part A, a small amount of deaerated water is introduced into the reaction fiask, and the cake of washed chromium(II) acetate is broken up and returned to the reaction flask by sloshing the water into the filter chamber. The 2,4-pentanedione [10 ml. (9.76 g. or 0.098 mol) for the quantity of chromium(II) acetate 1-hydrate (6.2 g.) prepared in Part A] is added through chamber E and the chamber is rinsed with a small amount of water. A yellow-brown color appears immediately. However, adequate reaction time must be allowed, since the reaction is one... 

This acid is prepared from the nitro-acid by reduction with alkaline hydrosulphite. It crystallises in bushy needles, decomposing at 150° C. and containing 1 molecule of water. It is sparingly soluble in the usual solvents sodium acetate precipitates it from solution in mineral acids. 

The aiiltydride may also be prepared by the interaction of crotonic acid and mercuric acetate, precipitating the product with alcohol. 

Lead sub-acetate precipitates gum arabic in aqueous solution. In presence of sugar, addition of alcohol prevents the precipitation of dextrin if the latter is present. 

Suspend pellet in 200 pL TE buffer. Add 200 pL 5 M ammonium acetate. Precipitate DNA with 1 mL 95% ethanol (ATP should not precipitate in ammonium acetate). Centrifuge in microfuge for 10 min at room temperature. Wash pellet in 95% ethanol (not 70%). Air-dry pellet. 

Calcium acetate, Ca(CH3COO)2, is more soluble in cold water than in hot water. When a cold, concentrated solution of calcium acetate is heated, sohd calcium acetate precipitates. 

Melanoma Isopropanol precipitation Ammonium acetate precipitation PEG precipitation SEC 26... 

The formation of solid sodium acetate from supersaturated sodium acetate solutions is slow by comparison and the supersaturated solutions can exist for long periods of time without a precipitate forming. Many collisions between the spherical Na ion and the linear CH3COO" (acetate) ion occur that do not result in reaction because the only collision that can result in reaction is between Na" " and the oxygen end of CH3COO" (Fig. 2-1). A collision between Na and any other part of the acetate ion cannot form a sodium acetate precipitate. 

Hops (Humulus lupulus L.) belong to the mulberry family (Moraceae). The leaf and flower cone with luplin (yellow secreted particles) are used to flavor beer, and to alleviate thirst as a nutraceutical. Air-dried hops contain a-acids in 2-12% yields [102]. The a-acids are found in a lead-acetate-precipitate derived from the methanol extract of hop. The chemical structures are shown in Fig. 14a [103,104]. Humulone is the most easily obtainable a-acid by repeated crystallization. Isomerization of the a-acids is the most important reaction in beer brewing, and is easily induced by boiling. Beer contains 20-25 mg/L of iso-a-acids, which mainly contribute to its bitterness. 

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