Reagent grade

Acetone. The analytical reagent grade contains about 1 per cent, of water and meets most requirements. Synthetic acetone of a high degree of purity (water content about 1 per cent.) is also available as a technical product. 

Benzene. The analytical reagent grade benzene is satisfactory for most purposes if required dry, it is first treated with anhydrous calcium chloride, filtered, and then placed over sodium wire (for experimental details, see under Diethyl ether, 1). 

The analytical reagent grade is suitable for most purposes. The commercial substance may be purifled by shaking for 3 hours with three portions of potassium permanganate solution (5 g. per litre), twice for 6 hours with mercury, and Anally with a solution of mercuric sulphate (2-5 g. per litre). It is then dried over anhydrous calcium chloride, and fractionated from a water bath at 55-65°. The pure compound boils at 46-5°/760 mm. 

Pyridine. The analytical reagent grade pyridine will satisfy most requirements. If required perfectly dry, it should be refluxed over potassium or sodium hydroxide pellets or over barium monoxide, and then distilled with careful exclusion of moisture (compare Fig. 77, 47, 2). It is hygroscopic, and forms a hydrate of b.p. 94-5°. Pure pyridine has b.p. 115-5°/760 mm. 

Bromine. The commercial product may be dried (and partially purified) by shaking with an equal volume of concentrated sulphuric acid, and then separating the acid. Chlorine, If present, may be removed by fractionation in an all-glass apparatus from pure potassium bromide the b.p. is 59°/760 mm. The analytical reagent grade is satisfactory for most purposes where pure bromine is required. 

Metallic sodium is priced at about 15 to 20 cents/lb in quantity. Reagent grade (ACS) sodium in January 1990 cost about 35/lb. On a volume basis, it is the cheapest of all metals. 

For top ten 2 (Mercuric Acetate method) use the following in place of reagent grade materials ... 

Heat reagent-grade material for 1 hr at 255-265°C. Cool in an efficient desiccator. Titrate sample with acid to pH 4-5 (first green tint of bromocresol green), boil the solution to eliminate the carbon dioxide, cool, and again titrate to pH 4-5. Equivalent weight is one-half the formula weight. 

Standard Manganese(ll) Solution. Dissolve exactly 16.901 g ACS reagent grade manganese(II) sulfate hydrate in water and dilute to 1 E. 

Standard Zinc Solution. Dissolve exactly 13.629 g of zinc chloride, ACS reagent grade, or 28.754 g of zinc sulfate heptahydrate, and dilute to 1 E for O.IOOOM solution. 

Alternatively, grind 0.1 g of murexide with 10 g of ACS reagent grade sodium chloride use about 50 mg of the mixture for each titration. 

AgN03 (P) 169.89 Weigh the desired amount of ACS reagent grade AgNOg, dried at 105°C for 2 hr, and dissolve in double distilled water. Store in amber container and away from light. Check against NaCl. 

Hg(N03)2 H3O 342.62 Dissolve the reagent grade salt in distilled water and dilute to desired volume. Standardize against NaCl. 

Examples of typical packaging labels from reagent grade chemicals. Label (a) provides the actual lot assay for the reagent as determined by the manufacturer. Note that potassium has been flagged with an asterisk ( ) because its assay exceeds the maximum limit established by the American Chemical Society (ACS). Label (b) does not provide assayed values, but indicates that the reagent meets the specifications of the ACS for the listed impurities. An assay for the reagent also is provided. 

Sodium is a common contaminant found in many chemicals. Reagent grade KCI, for example, may contain 40-50 ppm sodium. This is a significant source of sodium, given that its concentration in the salt substitute is about 100 ppm. 

Reagent-grade urea is used in some pharmaceutical preparations. In these appHcations, urea must meet the purity specifications issued by the ACS. 

Standards for sulfuric acid, ranging from technical-grade through dmg-, food-, and reagent-grade, to electronic-grade are shown in Table 1. The advances in purity represented by these various grades of chemicals are based on the special uses of the chemicals. 

Economic Aspects. In the United States fluoroboric acid is manufactured by Atotech USA, Inc., General Chemical, C.P. Chemical Co., Fidehty Chemical Products, and Chemtech Harstan. Research quantities of reagent grade are made by Advance Research Chemical Co., Johnson-Mathey, and Ozark-Mahoning Co. The price for 48% fluoroboric acid in tmcHoad quantities in 1993 was 2.13—2.25/kg (20). 

The 30% reagent-grade hydrogen peroxide is purer than the industrial grades, is covered by ACS reagent specification, and is used as a laboratory reagent and in some specialty uses (see Fine chemicals). Several grades are also marketed for electronics use and thus have exceptionally low impurity levels. Some of these latter contain very Httie or no stabilizers (see Electronic materials). 

Basic Lead Acetate. Basic lead acetate [1335-32-6] (lead subacetate), 2Pb(0H)2-Pb(C2H3 02 )2, is a heavy white powder which is used for sugar analyses. Some physical properties are given in Table 4. Reagent grade is available in 11.3-kg cartons and in 45- and 147-kg fiber dmms. 

The second method of preparation involves precipitation from a cold acidic solution of mercurous nitrate. Mercurous chloride is isolated after washing in a manner similar to the chamber method described. This product, which generally contains small amounts of occluded sodium nitrate, is satisfactory as a technical-grade material. Difficulty may be encountered in having it pass NF or reagent-grade specifications (see Fine chemicals). 

Mercurous Nitrate. Mercurous nitrate [10415-75-5] Hg2N20 or Hg2(N02)2, is a white monoclinic crystalline compound that is not very soluble in water but hydrolyzes to form a basic, yellow hydrate. This material is, however, soluble in cold, dilute nitric acid, and a solution is used as starting material for other water-insoluble mercurous salts. Mercurous nitrate is difficult to obtain in the pure state directly because some mercuric nitrate formation is almost unavoidable. When mercury is dissolved in hot dilute nitric acid, technical mercurous nitrate crystallizes on cooling. The use of excess mercury is helpful in reducing mercuric content, but an additional separation step is necessary. More concentrated nitric acid solutions should be avoided because these oxidize the mercurous to mercuric salt. Reagent-grade material is obtained by recrystaUization from dilute nitric acid in the presence of excess mercury. 

Both technical- and reagent-grade phosphoms pentoxide is typically >99% P O q. Phosphoms pentoxide sublimes near 360°C at atmospheric pressure. Lower oxides, which may account for <0.3% (as P40 ) in technical-grade material, are present at <0.02% in reagent-grade phosphoms pentoxide. Lower oxides are detected by decolorization of a dilute potassium permanganate solution (Table 11). 

Table 11. Specifications of Technical- and Reagent-Grade Phosphorus(V) Oxide...

Silver compounds, available from commercial suppHers, are expensive. Reagent grades of sHver(I) carbonate, cyanide, diethjldithiocarbamate, iodate, nitrate, oxide, phosphate, and sulfate are available. Standardized solutions of silver nitrate are also available for analytical uses. Purified grades of sHver(I) acetate, bromide, cyanide, and iodide can be purchased silver nitrate is also made as a USP XX grade for medicinal uses (6). 

Bulk production of United States Pharmacopeia (USP) and reagent grades is based on the reaction of sodium carbonate or hydroxide with an acidic iodide solution, typically hydriodic acid or a metal iodide. After removal of chemical impurities, the solution is filtered and concentrated. Evaporation gives the anhydrous Nal. Controlled cool-down produces either the dihydrate or the pentahydrate [81626-33-7]. 

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