PURester

The phenomenon of intemiolecular exchange is very common. The loss of couplings to hydroxyl protons in all but the very purest etiianol samples was observed at a very early stage. Proton transfer reactions are still probably the most carellilly studied [14] class of intemiolecular exchange. 

Preparation of the Reagent. Grind thoroughly together in a dry mortar 25 g. of pure anhydrous ( Analar ) sodium carbonate and 50 g. of the purest obtainable zinc dust. Preserve the reagent in a wide-necked stoppered bottle until required. 

Note. All but the purest samples of monomethylaniline contain sufficient aniline to give positive (although possibly weak) reactions to certain tests for aniline (particularly Tests i and 4). If it is suspected that aniline is present solely as an impurity, the positive tests for monomethylaniline (particularly Test 4 below) should be applied. 

Method 2. From chloroplatinic acid. Dissolve 3 - 5 g. of the purest commercial chloroplatinic acid (3) in 10 ml. of water contained in a 250 ml. P3rrex beaker or porcelain casserole, and add 35 g. of A.R. sodium nitrate (1), Evaporate the mixture to dryness by heating gently over a Bunsen flame whilst stirring with a glass rod. Then raise the temperature... 

Quality Specifications. Because of the extreme sensitivity of polyamide synthesis to impurities ia the iagredients (eg, for molecular-weight control, dye receptivity), adipic acid is one of the purest materials produced on a large scale. In addition to food-additive and polyamide specifications, other special requirements arise from the variety of other appHcations. Table 8 summarizes the more important specifications. Typical impurities iaclude monobasic acids arising from the air oxidation step ia synthesis, and lower dibasic acids and nitrogenous materials from the nitric acid oxidation step. Trace metals, water, color, and oils round out the usual specification Hsts. 

Iceland spar s the purest limestone, virtually pure calcite of about 99.9% CaCO. It is also known as optical calcite its occurrence is rate. 

The concentrated mother Hquor contains a large amount of sulfuric acid in a free form, as titanium oxy-sulfate, and as some metal impurity sulfates. To yield the purest form of hydrated TiOg, the hydrolysis is carried out by a dding crystallizing seeds to the filtrate and heating the mixture close to its boiling temperature, - 109° C. The crystal stmcture of the seeds (anatase or mtile) and their physical properties affect the pigmentary characteristics of the final product. 

The plutonium extracted by the Purex process usually has been in the form of a concentrated nitrate solution or symp, which must be converted to anhydrous PuF [13842-83-6] or PuF, which are charge materials for metal production. The nitrate solution is sufficientiy pure for the processing to be conducted in gloveboxes without P- or y-shielding (130). The Pu is first precipitated as plutonium(IV) peroxide [12412-68-9], plutonium(Ill) oxalate [56609-10-0], plutonium(IV) oxalate [13278-81-4], or plutonium(Ill) fluoride. These precipitates are converted to anhydrous PuF or PuF. The precipitation process used depends on numerous factors, eg, derived purity of product, safety considerations, ease of recovering wastes, and required process equipment. The peroxide precipitation yields the purest product and generally is the preferred route (131). The peroxide precipitate is converted to PuF by HF—O2 gas or to PuF by HF—H2 gas (31,132). 

In Europe, where an abundant supply of anthracene has usually been available, the preferred method for the manufacture of anthraquinone has been, and stiU is, the catalytic oxidation of anthracene. The main problem has been that of obtaining anthracene, C H q, practically free of such contaminants as carbazole and phenanthrene. Many processes have been developed for the purification of anthracene. Generally these foUow the scheme of taking the cmde anthracene oil, redistilling, and recrystaUizing it from a variety of solvents, such as pyridine (22). The purest anthracene may be obtained by azeotropic distillation with ethylene glycol (23). 

Although vitreous siUca is a simple, single-component glass, its properties can vary significantly, depending on thermal history, the type and concentration of defects, and impurities. Vitreous siUca can, however, be one of the purest commercially available glassy materials. In synthetic vitreous sihcas, for example, total metal contamination is typically measured ia the 50—100 ppb range. Even at such a low level of impurities, differences ia properties, such as uv-transmission, are observed for various siUcas. 

Physical piopeities of suciose aie summarized ia Table 2. Sucrose is one of the purest substances available in bulk quantities, with purities averaging — 99.96%. Water accounts for about half of the nonsugar impurities (17). 

Sugar is one of the purest foods made, from natural sources, and has never been known to contain any toxic or harmful components. Intensive investigations by the U.S. Food and Dmg Administration resulted in a book in 1986 on the health and safety factors of sugar (cane and beet) in the diet (18). The conclusion was that sugar has no deleterious effect on health in regard to heart disease, diabetes, or other metaboHc disorder. 

Although most impurities have k < 1, there are exceptions, and it caimot be automatically assumed that the purest material is at the front end of the iagot sometimes it is ia the middle. 

Purity. Electrolytic copper is one of the purest of the materials of commerce. The average copper content of ETP copper, for instance, is over 99.95%, and even the highest level of impurities other than oxygen are found only to the extent of 15—30 ppm. Up to 0.05% oxygen is present in the form of copper(I) oxide. Even at these low impurity levels, properties of interest to fabricators are affected in varying degree. 

CP-1 was assembled in an approximately spherical shape with the purest graphite in the center. About 6 tons of luanium metal fuel was used, in addition to approximately 40.5 tons of uranium oxide fuel. The lowest point of the reactor rested on the floor and the periphery was supported on a wooden structure. The whole pile was surrounded by a tent of mbberized balloon fabric so that neutron absorbing air could be evacuated. About 75 layers of 10.48-cm (4.125-in.) graphite bricks would have been required to complete the 790-cm diameter sphere. However, criticality was achieved at layer 56 without the need to evacuate the air, and assembly was discontinued at layer 57. The core then had an ellipsoidal cross section, with a polar radius of 209 cm and an equatorial radius of309 cm [20]. CP-1 was operated at low power (0.5 W) for several days. Fortuitously, it was found that the nuclear chain reaction could be controlled with cadmium strips which were inserted into the reactor to absorb neutrons and hence reduce the value of k to considerably less than 1. The pile was then disassembled and rebuilt at what is now the site of Argonne National Laboratory, U.S.A, with a concrete biological shield. Designated CP-2, the pile eventually reached a power level of 100 kW [22]. 

When this reaction has occuiTcd accidentally sufficient hydrogen chloride has been liberated to explosively burst the vessel. The purest form of hydrogen chloride is made by the action of water on silicon tetrachloride ... 

The purest form is obtained by passing a mixture of sulphur vapour and hydrogen over finely divided niekel at 450°C. 

The Jordi PDVB family of columns has very nonpolar packings with a high degree of aromatic character. They are made from the purest DVB available and currently serve as the base material for all other Jordi packings (Fig. 13.13). 

Hyperflne Si is one of the purest materials ever made on an industrial scale the production of transistors (p. 332) requires the routine preparation of crystals with impurity levels below 1 atom in 10 , and levels below 1 atom in 10 can be attained in special cases. 

H28 is readily prepared in the laboratory by treating Fe8 with dilute HCl in a Kipp apparatus. Purer samples can be made by hydrolysing Ca8, Ba8 or AI283, and the purest gas is prepared by direct reaction of the elements at 600°C. 

It is obtained from American turpentine as dextro-o-pinene, or from French turpentine as laevo-a-pinene. It is also obtained in a very pure form as dextro-a-pinene from Greek oil of turpentine. Optically inactive o-pinene can be obtained by regeneration from the nitrosochloride. The purest specimens of a-pinene yet obtained have the following characters —... 

This is the purest D-Z-fenchene prepared, and it yielded a dibromide CjoHigBrj, melting at 87° to 88°. Wallach considers that D-Z-fenchene has the following constitution —... 

He found that the d-phellandrene from elemi and bitter fennel oils were identical, and that i-phellandrene from eucalyptus oil is the laevo-rotatory variety of the same terpene. To these he assigned the names d-a-phellandrene and i-a-phellandrene. The d-phellandrene from water fennel oil differs from these and is named d-/3-phellandrene. The following are the characters of the purest specimens of natural phellandrene yet obtained —... 

Santene has also been examined by Aschan. The following are the characters of the purest specimens which have been isolated from sandalwood and Siberian nine oils —... 

The purest specimens of cadinene prepared have the following characters —... 

The above figures are for the purest specimen of natural cedrene which has been prepared. 

The purest laevo-bornyl formate examined had a specific gravity 1 016, optical rotation — 48° 56, refractive index 1-47121, and boiling-point 97° at 15 mm. pressure. The ester has the constitution... 

The purest specimens which have been prepared of natural citral, either from lemon-grass oil, lemon oil, or the oil of Tetranthem citrata, have the following characters —... 

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