Technical grade reagent

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. 

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). 

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...

Chromates and dichromates are sold in both technical and reagent grades (90,91). Chlorides and sulfates are the principal impurities. Both manufacturers ... 

Technical-grade dimethylformamide is stirred over anhydrous cupric sulfate, filtered, and distilled under reduced pressure. The submitters used reagent-grade dimethylformamide without purifieation. 

Mallinckrodt technical grade may be used. If Mallinckrodt analytical reagent zinc dust is used, the reaction temperature must be maintained at 50-55° instead of 75-80°. 

Technical grade DMF is available from the Grasselli Chemicals Department of E. I. duPont de Nemours and Company. The 1,4-dichlorobutane was obtained from the Electrochemicals Department, E. I. duPont de Nemours and Company. Technical Baker and Adamson fused chip sodium sulfide assaying 60% sodium sulfide was used. The checkers obtained somewhat lower yields when the appropriate amount of reagent grade Na2S OHjO was employed instead of the technical material. 

Technical-grade (F)-stilbene obtained from Fluka AG gives satisfactory results, although a better grade is preferable. The checkers used reagent-grade material obtained from Aldrich Chemical Company, Inc. 

Pyridinium-1-sulfonate was prepared according to the procedure of Sisler and Audrieth. The submitter reports that this procedure may be conveniently carried out at 5 times the specified scale. The reagent should be dry and used soon after its preparation. The checkers found that a technical grade of pyridinium-1-sulfonate (sulfur trioxide pyridine complex) purchased from Aldrich Chemical Company, Inc., gave substantially lower yields of product. 

The submitters used reagent-grade solvents and reagents without further purification. The yield of 2-hydroxyimino-2-phenylacetonitrile was 76% when the checkers used technical-grade benzyl cyanide purchased from Wako Pure Chemical Industries, Ltd., Osaka, Japan. The yield was improved to 81% with distilled material, b.p. 75-77° (3 mm.). Benzyl cyanide is also available from Aldrich Chemical Company, Inc. 

The hydrobromic acid should be colorless. Reagent grade 47-49% hydrobromic acid, obtained from J. T. Baker Chemical Co., was used as supplied. A technical grade of the constantboiling acid is suitable if purified by distillation from stannous chloride. 

Note Reagent grades of 2,4-toluene diisocyanate usually contains minor quantities of the isomer 2,6-toluene diisocyanate. This compound is present in greater concentrations in technical grades. 

Freshly distilled Merck reagent grade or du Pont technical grade, dimethylformamide, b.p. 151-153°, was used. 

Fresh reagent grade acetonitrile was purchased from Fisher Scientific Co. and used without additional purification. Chromium hexacarbonyl was purchased from Strem Chemical Co. Celite and cycloheptatriene (90% technical grade) were purchased from Aldrich Chemical Company, Inc., and used without purification. THF was distilled from sodium/benzophenone ketyl. 

Ethyl acetate (technical grade) was purified by distillation. The checkers found that reagent grade ethyl acetate could be used without purification. 

Yields from products of g od technical grade and of analytical reagent purity give almost identical yields. 

Potassium cyanate (technical grade) was supplied by Degussa AG, Hanau, Germany. Alternatively, sodium cyanate may we used. The checkers used the practical grade reagent purchased from Wako Pure Chemical Industries, Ltd., Japan. 

SPITC-reagent Dissolve 2.55 mg 4-sulfophenyl isothiocyanate sodium salt monohydrate (SPITC, technical grade, Sigma Aldrich, St. Louis, MO store at 4°C) in Tris-buffer at a concentration of 2.55 mg/mL. Prepare always a fresh solution and use immediately. 

The submitters used Merck styrene 99%, stabilized with 4-tert-butylpyrocatechol. Triethylbenzylammonium chloride was prepared by refluxing equimolar amounts of triethylamine and benzyl chloride in ethanol for 2 hr and removing the solvent in vacuo. The salt is commercially available. The other reagents were technical grade. 

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