Residue trace

Residual traces of zinc are released during vacuum sintering of cemented carbides made with recovered powders. This can be troublesome when a buildup of zinc occurs in the furnace. Teledyne Advanced Materials further developed this process on a commercial basis by achieving zinc levels in the low ppm range (<30 ppm). The fact that the materials were vacuum-sintered in their original form where certain impurities are removed leads to lower impurity levels in the recovered powders. There is a slight oxidation or loss of carbon that must be compensated, otherwise the recycled powder is not in any way inferior to the original. 

The most common impurities are the corresponding acid and hydroxy compound (i.e. alcohol or phenol), and water. A liquid ester from a carboxylic acid is washed with 2N sodium carbonate or sodium hydroxide to remove acid material, then shaken with calcium chloride to remove ethyl or methyl alcohols (if it is a methyl or ethyl ester). It is dried with potassium carbonate or magnesium sulfate, and distilled. Fractional distillation then removes residual traces of hydroxy compounds. This method does not apply to esters of inorganic acids (e.g. dimethyl sulfate) which are more readily hydrolysed in aqueous solution when heat is generated in the neutralisation of the excess acid. In such cases, several fractional distillations, preferably under vacuum, are usually sufficient. 

Biphenylyl diphenyl phosphate [132-29-6] M 302.4, n l.5925. Vacuum distd, then percolated through an alumina column. Passed through a packed column maintained at 150° to remove residual traces of volatile materials by a counter-current stream of nitrogen at reduced pressure. [Dobry and Keller J Phys Chem 61 1448 1957.]... 

Tri-p-tolyl phosphate [20756-92-7, 1330-78-5 (isomeric tritolyl phosphate mixture)] M 368.4, b 232-234 , d 1.16484, n 1.56703. Dried with CaCl2, then distd under vacuum and percolated through a column of alumina. Passage through a packed column at 150°, with a counter-current stream of nitrogen, under reduced pressure, removed residual traces of volatile impurities. 

Residual traces of these impurities must thus be removed by some technique such as recrystallisation from chlorobenzene or acqueous alcohol. The melting point is a useful measure of purity and for polycarbonate resins the melting point should be in the range 154-157°C compared with values of 140-150°C for epoxy resin grade bis-phenol A. 

Preparation of Di-n-Propyl Acetyl Tropine Hydrochloride Tropine (11.12 grams) was dissolved in 100 ml of anhydrous pyridine and to this solution was added 15.64 grams of din-propyl acetyl chloride. The mixture was refluxed for 6 hours. This solution was then cooled and the pyridine removed in vacuo. The residue was dissolved in chloroform. The chloroform solution was washed with 10% hydrochloric acid to remove the residual trace of pyridine. The hydrochloride of the product ester is soluble in chloroform and is not extracted from chloroform by hydrochloric acid. This is an unexpected property. 

Couper reports cracking of an Fe-36 Ni alloy in 10-55 days in this medium. Radd eta . have noted cracking of Fe-36 Ni alloys at ambient temperatures in an unspecified environment, but this possibly may have been residual traces of acid copper chloride etching solution. 

Sterilised sealed cans of foodstufifs, including fruit, vegetables, meat, fish and milk, which should contain only residual traces of oxygen. Cans for beer and soft drinks. 

Although notable improvements have been made in methods used by the control laboratories serving the canning industry, a great deal of room remains for further improvement. A survey of some of the functions of control laboratories demonstrates the need for better methods of determining spray residues, traces of metals, vitamins, moisture, and head-space gases. As is the case in other industries, improved instrumentation offers a solution to some of the existing problems. 

Triturating with diethyl ether was found to be necessary to successfully remove residual di-tert-butyl dicarbonate and di-tert-butyl iminodicarboxylate which may be produced as a result of residual traces of ammonia from step A. 

The explosive decomposition of the solid has been studied in detail [6], The effect of moisture upon ignitibility and explosive behaviour under confinement was studied. A moisture content of 3% allowed slow burning only, and at 5% ignition did not occur [7], Thermal instability was studied using a pressure vessel test, ignition delay time, TGA and DSC, and decomposition products were identified [8], The presence of acyl chlorides renders dibenzoyl peroxide impact-sensitive [9], There is a further report of a violent explosion during purification of the peroxide by Soxhlet extraction with hot chloroform [10], Residual traces of the peroxide in a polythene feed pipe exploded when it was cut with a handsaw [11]. The heat of decomposition has been determined as 1.39 kJ/g. The recently calculated value of 69° C for critical ignition temperature coincides with that previously recorded. 

Though a powerful oxidant, the difluoride is not explosively unstable. Safe procedures for the use of xenon difluoride in fluorination reactions are detailed. Residual traces of the fluoride are rapidly destroyed by dichloromethane at ambient temperatures. 

The degree of branching was initially reported to be close to 0.8 [1], but was recently reevaluated after it was shown that the hydroxy-functional hyperbranched polyesters undergo facile acetal formation. The acetal formation was catalyzed by residual trace amounts of acid remaining in the sample. After reevaluation in DMSO the degree of branching was close to 0.45 which is in accordance with most other hyperbranched polymers. (1. Malmstrom, E., Johansson, M. and Hult, A. Macromolecules, 28, 1698 (1995) 2. Malmstrom, E., Trollsas, M., Hawker, C.J., Johansson, M. and Hult, A. Polym. Mat. Sci. Eng., 77,151 (1997). 

The excess of bromine is removed by warming the acidic solution gently till the vapours show a negative test with starch-iodide paper. However, the residual traces of Br2 are reduced by treatment of the resulting solution with phenol to yield the corresponding 2,4,6-tribromophenol as shown below ... 

Solution polymerizafion. Highly exothermic reactions can be handled by this process. The reaction is carried out in an excess of solvent that absorbs and disperses the heat of reaction. The excess solvent also prevents the formation of slush or sludge, which sometimes happens in the bulk process when the polymer volume overtakes the monomer. The solution process is particularly useful when the polymer is to be used in the solvent, say like a coating. Some of the snags with this process its difficult to remove residual traces of solvent, if that s necessary the same is true of catalyst if any is used. This process is used in one version of a low-pressure process for high-density polyethylene and for polypropylene. 

After the first wash, leave PBS a couple of minutes to promote the detachment of strongly adherent cells. Raise one side of the plate to remove any residual trace of PBS. Remaining PBS would loosen the interaction of the cloning cylinder with the plate surface. 

Remove uncoupled reagents by extraction with Soln. C. For this purpose, add 200 pi of Soln. C to the reaction mixture, centrifuge, carefully withdraw the supernatant and repeat extraction twice. Discharge the supernatants and dry the aqueous phase in vacuum. To remove residual traces of water, add 10 pi of ethanol to the tube and dry again. 

Added as an inorganic stabilizer for NC (used in propellants) to neutralize residual traces of H2S04 in the fibers of NC... 

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