Reagent bottle

P-Naphthyl acetate. Dissolve 5 0 g. of p-naphthol in 25 ml. of 10 per cent, sodium hydroxide solution in a 250 ml. reagent bottle, add 60 g. of crushed ice, and 5-7 g. (5 -5 ml.) of acetic anhydride. Shake vigorously for 10-15 minutes the p-naphth acetate separates as colourless crystals. Filter with suction, wash with water, drain and dry in the air. Recrystallise from light petroleum (b.p. 60-80°) or from dilute alcohol. The yield of pure product, m.p. 71°, is 6-5 g. 

Dissolve 27 g. of potassium hydroxide in 25 ml. of water contained in a beaker or conical flask, and cool the solution to about 20° in ice water. Pour the solution into a 250 ml. reagent bottle, and add 30 g. (29 ml.) of pure benzaldehyde ("1) cork the bottle securely and shake the mixture vigorously until it has been converted into a thick emulsion. Allow the mixture to stand overnight or for 24 hours in the stoppered bottle. Add just sufficient water (about 105 ml.) to dissolve the potassium benzoate. Pour the liquid into a separatory funnel, rinse out the bottle with about 30 ml. of ether and add this ether to the solution in the funnel. Shake the... 

In a 500 ml. wide-mouthed reagent bottle place a cold solution of 25 g. of sodium hydroxide in 250 ml. of water and 200 ml. of alcohol (1) equip the bottle with a mechanical stirrer and surround it with a bath of water. Maintain the temperature of the solution at 20-25°, stir vigorously and add one-half of a previously prepared mixture of 26-5 g. (25 -5 ml.) of purebenzaldehyde (Section IV,115) and 7 -3 g. (9-3 ml.) of A.R. acetone. A flocculent precipitate forms in 2-3 minutes. After 15 minutes add the remainder of the benzaldehyde - acetone mixture. Continue the stirring for a further 30 minutes. Filter at the pump and wash with cold water to eliminate the alkali as completely as possible. Dry the solid at room temperature upon filter paper to constant weight 27 g. of crude dibenzalacetone, m.p. 105-107°, are obtained. Recrystallise from hot ethyl acetate (2-5 ml. per gram) or from hot rectified spirit. The recovery of pure dibenzalacetone, m.p. 112°, is about 80 per cent. 

Place 10 ml. of pure benzaldehyde (Section IV,115) and 100 ml. of concentrated aininonia solution (sp. gr. 0-88) in a 250 ml. wide-mouthed reagent bottle. Cork the bottle securely, shake vigorously for 10 minutes and allow to stand with occasional shaking for 24 hours. By this time the benzaldehyde should be converted into a hard mass of hydrobenz-amide. Break up the solid mass with a spatula or a thick glass rod, filter with suction, wash with water, and drain thoroughly. RecrystalUse from absolute alcohol (or absolute methylated spirit). The yield of hydrobenzamide (colourless crystals), m.p. 101°, is 7 g. It is easily hydrolysed by cold dilute acids. 

Dissolve 5 g. of phenol in 75 ml. of 10 per cent, sodium hydroxide solution contained in a wide-mouthed reagent bottle or conical flask of about 200 ml. capacity. Add 11 g. (9 ml.) of redistilled benzoyl chloride, cork the vessel securely, and shake the mixture vigorously for 15-20 minutes. At the end of this period the reaction is usually practically complete and a sohd product is obtained. Filter oflf the soUd ester with suction, break up any lumps on the filter, wash thoroughly with water and drain well. RecrystaUise the crude ester from rectified (or methylated) spirit use a quantity of hot solvent approximately twice the minimum volume required for complete solution in order to ensure that the ester does not separate until the temperature of the solution has fallen below the melting point of phenyl benzoate. Filter the hot solution, if necessary, through a hot water funnel or through a Buchner funnel preheated by the filtration of some boiling solvent. Colourless crystals of phenyl benzoate, m.p. 69°, are thus obtained. The yield is 8 g. 

To determine the exact perbenzoic acid content of the solution, proceed as follows. Dissolve 1 -5 g. of sodium iodide in 50 ml. of water in a 250 ml. reagent bottle and add about 5 ml. of glacial acetic acid and 5 ml. of chloroform. Introduce a known weight or volume of the chloroform solution of perbenzoic acid and shake vigorously. Titrate the liberated iodine with standard O lA sodium thiosulphate solution in the usual manner. 

Preparing a solution of known concentration is perhaps the most common activity in any analytical lab. The method for measuring out the solute and solvent depend on the desired concentration units, and how exact the solution s concentration needs to be known. Pipets and volumetric flasks are used when a solution s concentration must be exact graduated cylinders, beakers, and reagent bottles suffice when concentrations need only be approximate. Two methods for preparing solutions are described in this section. 

A reagent bottle containing 1 kg of benzene accidentally falls to tlic floor of a small enclosed storage area iiicasuring 10 m in vohnne. In time, the spilled liquid benzene completely evaporates. With this iiiformalion answer the following questions ... 

Reagenzien, Reagentien, n.pl. reagents, -flasche, /. reagent bottle, -hasten, m. reagent box or case, -raum, m. reagent apace or room. 

Reagent bottles must never be allowed to accumulate on the bench they must be replaced on the reagent shelves immediately after use. 

Tilting pipettes, which are attached to a reagent bottle, are only suitable for delivering approximate volumes of solution. 

One millilitre of this solution is equivalent to about 20 pg of lead. The solution should be freshly prepared using the analytical-grade reagent, ideally taken from a new or recently opened reagent bottle. 

Notes. (1) The reagent solution should be freshly prepared using analytical-grade dithizone and 1,10-phenanthroline, preferably taken from new or recently opened reagent bottles. 

Procedure. Weigh out accurately 0.08-0.1 g of hydrazinium sulphate into a 250 mL reagent bottle, add a mixture of 30 mL of concentrated hydrochloric... 

Procedure. Weigh out accurately about 2.5 g of finely powdered mercury(II) chloride, and dissolve it in 100 mL of water in a graduated flask. Shake well. Transfer 25.0 mL of the solution to a conical flask, add 25 mL water, 2mL 1M hydrochloric acid, and excess of 50 per cent phosphorous(III) acid solution. Stir thoroughly and allow to stand for 12 hours or more. Filter the precipitated mercury(I) chloride through a quantitative filter paper and wash the precipitate moderately with cold water. Transfer the precipitate with the filter paper quantitatively to a 250 mL reagent bottle, add 30 mL concentrated hydrochloric acid, 20 mL water, and 5 mL carbon tetrachloride or chloroform. Titrate the mixture with standard 0.025M potassium iodate in the usual manner (Section 11.127). 

G.10 (a) A sample of 1.345 m I<2S04(aq) of volume 12.56 mL is diluted to 250.0 mL. What is the molar concentration of K2S04 in the diluted solution (b) A sample of 0.366 m HCl(aq) of volume 25.00 mL is drawn from a reagent bottle with a pipet. The sample is transferred to a flask of volume 125.00 mL and diluted to the mark with water. What is the molar concentration of the dilute hydrochloric acid solution ... 

There are two important safety measures that can be taken at very low cost. The first is to equip shelves with guard rails to keep reagent bottles from falling. The height of such rails should be adapted to the size of the containers. This is a requirement in California. The second is to fasten tall objects to the wall, a simple and inexpensive procedure. With bookcases, for example, the books may fall out but the case will stay in position and not tumble down with the whole load. 

Inexpensive plastic dishes can be placed under reagent bottles. There should be beakers beneath burets when they are not in use. Some laboratories cover their reagent shelves with thin sheets of ribbed polyethylene, w hich is available in rolls at a reasonable price. 

Observing and Inferring Why were the excess reagents not put back into the original reagent bottle ... 

Do not take reagent bottles to your work area unless specifically instructed to do so. Use test tubes, paper, or beakers to obtain your chemicals. 

Do not insert droppers into reagent bottles. Pour a small amount of the chemical into a beaker. 

Bottle-top dispensers, often called Repipets , are quite popular. These are devices that fit on the top of reagent bottles threaded to receive screw caps. The dispensers themselves have screw caps that screw onto the bottles. The caps, however, are fitted with a hand pump with a plunger that draws liquid from the bottle in the upstroke and then dispenses a calibrated volume on the downstroke through a glass tip. Such devices are convenient and help prevent contamination of the reagent from the various pipets that the analyst might use for a transfer. 

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