Drying of Reagents

Rubber stoppers should be used throughout, including the drying of reagents, as corks contain some moisture. The stoppers should be boiled in 10 per cent sodium hydroxide solution for two hours, thoroughly washed with dilute acetic acid, and dried. 

In this section we will describe some typical techniques for purification and drying of reagents. There are several other more specialized texts which should be consulted if you need to purify other reagents. T2,3... 

Sodium and potassium hydroxides. The use of these efficient reagents is generally confined to the drying of amines (soda lime, barium oxide and quicklime may also be employed) potassium hydroxide is somewhat superior to the sodium compound. Much of the water may be first removed by shaking with a concentrated solution of the alkali hydroxide. They react with many organic compounds (e.g., acids, phenols, esters and amides) in the presence of water, and are also soluble in certain organic liquids so that their use as desiccants is very limited... 

The individuality of received complexes was proved by X-ray phase analysis (DRON-3.0). Preparative investigation of complexes was made. Infrared spectrums of complexes were made (Uh-20, KBr). It was proved that in the III complex hydroxylamine is coordinated with Fe (II) by oxygen in the form of n-oxyde-o-NH -and in IV - by nitrogen in the form of NH OH. The composition of IV hasn t been proved in dry ruminant because of surplus age of reagent. Tire composition of III responds to formula of [Fe(NH,OH) Cl,]. 

Carbonate ionophore I [ETH 6010] (heptyl 4-trifluoroacetylbenzoate) [129476-47-7] M 316.3, b 170°/0.02 Torr, d 0.909. Purified by flash chromatography (2g of reagent with 30g of Silica Gel 60) and eluted with EtOAc/hexane (1 19). The fractions that absorbed at 260nm were pooled, evapd and dried at room temp (10.3 Torr). The oily residue was distd in a bubbled-tube apparatus (170°/0.02 Torr). Its IR (CHCI3) had peaks at 1720, 1280, 940cm and its sol in tetrahydrofuran is 50mg/0.5mL. It is a lipophilic neutral ionophore selective for carbonate as well as being an optical humidity sensor. [Anal Chim Acta 233 41 1990.]... 

Manganese (II) acetylacetone [14024-58-9] M 253.2, m -250°. Purify by stirring 16g of reagent for a few min with lOOmL absolute EtOH and filter by suction as rapidly as possible through coarse filter paper. Sufficient EtOH is added to the filtrate to make up for the loss of EtOH and to redissolve any solid that separates. Water (15mL) is added to the filtrate and the solution is evapiorated with a stream of N2 until reduced to half its vol. Cool for a few min and filter off the yellow crystals, dry under a stream of N2, then in a... 

A mixture of 1.38 grams of the above compound and 15 cc of dioxane was treated with 1.9 cc of a 0.5 N aqueous solution of perchloric acid and 600 mg of N-bromoacetamide, adding the latter in the dark, in three portions, in the course of half an hour and under continuous stirring. It was then stirred for a further 1% hours in the dark, then the excess of reagent was decomposed by the addition of aqueous sodium bisulfite solution and ice water was added the product was extracted with methylene chloride, washed with water, dried over anhydrous sodium sulfate and the solvent was evaporated under reduced pressure, thus giving a yellow oil consisting of the 16,21-diacetate of 6a-fluoro-9a-bromo-16o-hydroxy-hydrocortisone which was used for the next step without further purification. 

The yield of product is increased to 81% (analyzed by evolution of M-butane) if 0.67 g. (0.0033 mole) of aluminum isopropoxide is added to the suspension of magnesium before addition of the halide solution. Alternatively, an equivalent amount of 2-propanol and iodine (giving 0.01 mole of CsII OMgl) may be added. These modified procedures (particularly the second) also shorten the induction periods and render unnecessary any special drying of the reagents and apparatus and the use of fresh magnesium. 

A very large number of both inorganic and organic solvents have been used for non-aqueous determinations, but a few have been used more frequently than most. Some of the most widely applied solvent systems are discussed below. In all instances pure, dry analytical reagent quality solvents should be used to assist in obtaining sharp end points. 

Add 3 mL of reagent solution (dissolve 5g reagent in 12 g glacial acetic acid and dilute to 100 mL with water) for every 10 mg of magnesium present and then add concentrated ammonia solution until the pH is at least 9.3 (or no further precipitate forms). Heat at 60- 80 °C for 20 minutes, filter and wash the precipitate with hot water. Dry at 130-140 °C and weigh as Mg(C10H8ON)2 (Section 11.31). 

Hydroxyqninoline (oxine). Iron (III) ca 30 mg in 25 mL of weakly acidic (HCl) solution). Add a solution of 3 g ammonium acetate in 125 mL water, followed by 12-15mL of reagent solution 2 per cent in 2M acetic (ethanoic) acid. Heat the solution at 80-90°C for 30 minutes, filter and wash the precipitate with 1 per cent acetic acid and with water. Dry at 130-140 °C and weigh as Fe(C9H6ON)3 (Section 11.28). 

Drop time in polarography, 597, 608 Dropping mercury electrode 608, 628 Dry ashing 114 Dry box lOl Drying reagents 99 comparative efficiencies of, (T) 99 Drying of precipitates 119 Duboscq colorimeter 656 Duplication method 701... 

Chloroaeetophenone oxime was prepared by a modification of the method described by Shriner, Fuson, and Curtin.5 A mixture of 100 g. (0.65 mole) of reagent-grade 4-chloroacetophenone, 300 ml. of water, 200 ml. of aqueous 10% sodium hydroxide, 50g. (0.72 mole) of hydroxyl-amine hydrochloride, and 500 ml. of ethanol is heated at reflux in a 2-1. round-bottomed flask for 2 hours. The crystals that separate on cooling in an ice bath are recovered by filtration and air dried. The product is added to approximately 1 1. of hexane, and the mixture is... 

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