Colour residual

The methyl alcohol is poured into a round flask (250 c.c.) connected with an upright condenser. The sodium, cut into small pieces, is then added, the flask being detached from the condenser for a moment and replaced. When the sodium has dissolved, the phenol and methyl iodide are added. The mixture IS heated on the water-bath until the solution has no longer an alkaline reaction (two to three hours). As much as possible of the methyl alcohol is distilled off on the water-bath and water added to the amber-coloured residue. A colourless oil separates out, which is e.xtracted with ether. The ethereal solution is dehydrated over calcium chloride and distilled, first on the water-bath until the ether has been driven off, and then over the flame. Almost the whole of the residue distils at 150—155. Yield, nearly theoretical. 

Accoiiding to Hanriot ionone can be detected in very minute amount by the following reaction If traces of it be dissolved in concentrated hydrochloric acid, the liquid becomes of an intense golden colour, and if the solution he warmed with chloral hydrate, a dirty violet colour results. The violet colouring matter is extracted by ether, and if the ether be evaporated a water-soluble violet-coloured residue is left. This test will detect 1 part of ionone in 2b00. 

Harmful chemical exposures are usually characterized by rapid onset of medical symptoms (minutes to hours) and easily observed signs like unusual coloured residue, odours, dead or dying plants, insects, and animals. 

W. D. Bancroft and H. B. Weiser point out that the blue luminescence of sodium is obtained without the yellow luminescence (i) when sodium salts are introduced into a flame of hydrogen in chlorine (ii) when metallic sodium bums slowly in oxygen, chlorine, or bromine (iii) when a sodium salt is fused (iv) when cathode rays act on sodium chloride (v) when anode rays first act on sodium chloride (vi) when one heats the coloured residue obtained by the action of anode rays or cathode rays on sodium chloride and (vii) when sodium chloride is precipitated rapidly from aq. soln. with hydrochloric acid or alcohol. The yellow luminescence of sodium is obtained, accompanied by the fainter blue luminescence (i) when a sodium salt is introduced into the Bunsen flame (ii) when sodium burns rapidly in oxygen, chlorine, or bromine and (iii) when canal rays act on sodium chloride. It is claimed that the yellow luminescence is obtained when sodium vapour is heated but it is very difficult to be certain that no burning takes place under these conditions. 

A mixture of 20 grams of benzeneseleninic acid and 80 c.c. of aniline is heated at 110° to 115° C. for six hours. Excess aniline is then removed by steam distillation and the dark-coloured residue extracted with hot dilute hydrochloric acid. The addition of sodium carbonate to the extract precipitates the selenide as a pink microcrystalline powder (yield, 12 to 15 grams). It dissolves in hot dilute hydrochloric acid, and on cooling the hydrochloride separates as small, feathery needles, M.pt. 159° C. The free base forms almost colourless prismatic needles, M.pt. 93° to 94° C. 

Coloured residue—salt of metal giving coloured oxide. 

The flask A is immersed in a boiling water-bath and connected with a receiver, which is then evacuated by means of a water-pump Exactly 5 c c of the vinegar are next introduced into the funnel, allowed to flow into the flask, and there distilled until the volume is reduced to 2-3 c c, without interruption of the operation, 20 c c of distilled water are then introduced and the volume again reduced to 2-3 c c, two similar additions of distilled water being subsequently made When the volume in the flask is finally reduced to about 5 c c, the operation is stopped and the liquid transferred quantitatively into a conical flask, the fixed acidity being then determined by titration with N/io-sodium hydroxide either m presence of phenolphthalein or, with a highly coloured residue, with the help of litmus paper. 

A solution of 31.0 g (0.42 mol) of glycidol in 85 ml of anhydrous benzene and 46.0 g of sodium carbonate is heated to reflux. At this temperature and under a nitrogen atmosphere a solution of 70.0 g (0.27 mol) of crude 2,6,2, 6 -tetramethylbenzhydryl chloride in 120 ml of anhydrous benzene is added drop-wise. After completion of the addition, the mixture is kept refluxing for another 8 h. After filtration and removal of the solvent under reduced pressure, the yellow coloured residue is subjected to distillation under reduced pressure. There are obtained 64.0 g (80% of the theoretical yield) of a fraction boiling at 175-195°C/1 mm Hg, which slowly solidifies. This distillate, consisting of crude l,2-epoxy-3-[di-(2,6-xylyl)-methoxy]propane, is used for the next reaction step without purification. 

Allow the mixture to cool and then evaporate off the toluene using a rotary evaporator. Dissolve the residue in the minimum volume of dichloromethane (circa 10 mL). Do not attempt to dissolve any yellow-coloured residue on the side of the flask. 

Dry Tests.—Iron salts, when moistened with hydrochloric acid and heated on a loop of platinum wire in a Bunsen flame, emit a shower of sparks. When heated on charcoal with sodium carbonate in the blowpipe flame, the compound is converted into a dark-coloured residue. If potassium cyanide is added to the sodium carbonate and iron compound, and the whole heated on charcoal in the inner flame of the blow-pipe, metallic iron is obtained as a grey, magnetic powder. 

Toxic) Preliminary drying is accomplished by stirring over potassium carbonate for 24h. A further 24h over 3A sieve or boric anhydride gives moderately dry solvent (- 50ppm) but much better results are obtained by stirring over phosphorus pentoxide (5% w/v) for 24h and then distilling. Drawbacks of this method are the formation of substantial quantities of coloured residue, and the possibility that the product is contaminated with traces of acidic impurities. If the acetonitrile is required for use with very acid sensitive compounds it is best to redistil it from potassium carbonate. 

If this is required it is achieved by using either hydrogen peroxide or chlorine (or a hypochlorite) dissolved in water to remove the coloured residues that are in the cellulose fibres. It is usual to bleach only the chemical pulp made from the sulphite or soda processes, as these are grades probably used for white paper and the white plies of board. 

Dye ion exchange is carried out using slurries of 2 g zeolite in 25 ml of 1.5 nmole aqueous solutions of MB at 298 K under constant mechanical shaking for up to 30 days. Following to filtration the coloured residue is extracted with ethanol in a Soxhiet until the boiled over solvent is colourless. The dried residue is characterized by X-ray analysis and Nz physisorption and is analyzed by optical spectroscopy. 

The preparation can be shortened by omitting this stage and extracting the black residue by boiling it first with the water already present in the flask. In this case the yield of p-nitrophenol is increased somewhat, but the product is usually verv dark in colour. 

To obtain the free acid, dissolve the potassium salt in 50 ml. of cold water, filter the solution if a small undissolved residue remains, and then boil the clear solution gently whilst dilute sulphuric acid is added until the separation of the acid is complete. Cool the solution and filter off the pale orange-coloured crystals of the benzilic acid wash the crystals on the filter with some hot distilled water, drain well, and then dry in a desiccator. Yield of crude acid, 4 g. Recrystallise from benzene (about 50 ml.) to which a small quantity of animal charcoal has been added, filtering the boiling solution through a preheated funnel fitted w ith a fluted filter-paper, as the benzilic acid readily crystallises as the solution cools alternatively, recrystallise from much hot water. The benzilic acid is obtained as colourless crystals, m.p. 150°. 

Now cork the flask securely, and shake it vigorously for about 5 minutes the solution should now have only a faint brown colour due to unchanged iodine. Cool the mixture in ice-water, pour it into a separating-funnel, and extract it twice with water to remove sodium iodide and most of the ethanol. Then shake the residual ethereal solution with a dilute aqueoussolution of sodium thiosulphate the excess of iodine is thus removed and the... 

Whilst the solution is still hot, add dilute hydrochloric acid until the stirred solution is just acid to litmus, and then distil off as much ethanol as possible, using the water-bath. Now add more dilute hydrochloric acid to the residual hot solution until it is just acid to methyl-orange. The 5,5-dimethyl-cyclohexan-1,3-dione separates as an oil which solidifies on cooling. Filter the product at the pump, wash it with ice-cold water, and dry it in a desiccator. Yield of the pale cream-coloured crystals, 12 g. m.p. 136-145 (preliminary softening). 

Place about 1 g. of the nitro-hydrocarbon in a boiling-tube and add 5 ml. of cone. HCl and several pieces of granulated tin. Warm the mixture and shake continuously to break up the oily drops of the nitro-compound. When all the oil has disappeared (about 3 minutes heating) pour off the liquid from any undissolved tin into a 100 ml. conical flask. Cool and add cautiously 30% aqueous NaOH solution until the precipitate formed redissolves to give a dark-coloured solution. Cool the latter thoroughly and shake well with about 15 ml. of ether. Separate the ethereal layer in a separating-funnel, wash with water and evaporate the ether in a basin on a previously heated water-bath in a fume-cupboard atoay from all flames. The residue is either... 

In a 1-litre three-necked flask, fitted with a mechanical stirrer, reflux condenser and a thermometer, place 200 g. of iodoform and half of a sodium arsenite solution, prepared from 54-5 g. of A.R. arsenious oxide, 107 g. of A.R. sodium hydroxide and 520 ml. of water. Start the stirrer and heat the flask until the thermometer reads 60-65° maintain the mixture at this temperature during the whole reaction (1). Run in the remainder of the sodium arsenite solution during the course of 15 minutes, and keep the reaction mixture at 60-65° for 1 hour in order to complete the reaction. AUow to cool to about 40-45° (2) and filter with suction from the small amount of solid impurities. Separate the lower layer from the filtrate, dry it with anhydrous calcium chloride, and distil the crude methylene iodide (131 g. this crude product is satisfactory for most purposes) under diminished pressure. Practically all passes over as a light straw-coloured (sometimes brown) liquid at 80°/25 mm. it melts at 6°. Some of the colour may be removed by shaking with silver powder. The small dark residue in the flask solidifies on cooling. 

The latter may be identified by dissolving the residue in 5 ml. of water and adding 1 op of very dilute copper sulphate solution and 2 drops of 10 per cent, sodium hydroxide solution a violet colour is produced. 

It is advisable to test a small portion of the filtrate for platinum by acidifying with hydrochloric acid and adding a few drops of stannous chloride solution a yellow or brown colour develops according to the quantity of platinum pVesent. The yellow colour is soluble in ether, thus rendering the t t more sensitive. If platinum is found, treat the filtrate with excess of formaldehyde and sodium iQrdroxide solution and heat,- platinum black septarates on standing and may be filtered and worked up with other platinum residues (see Method 3). 

Method 2. Transfer the dark-coloured reaction product to a separatory funnel and shake successively with water, with sufficient 5-10 per cent, sodium hydroxide solution to ensure that the washings are alkaline to litmus, and finally with water. Dry with anhydrous magnesium sulphate or calcium chloride. Filter through a fluted filter paper into a small distilling flask and distil slowly. Collect the crude bromobenzene at 150-170° pour the residue whilst still hot into a small porcelain basin. Redistil the hquid of b.p. 150-170° (3) and collect the bromobenzene at 154-157° the yield is about 60 g. 

Note on the laboratory preparation of monoethylaniline. Although the laboratory preparation of monomethyl- or monoethyl-aniline is hardly worth whUe, the following experimental details may be useful to those who wish to prepare pure monoethylaniline directly from amline. In a flask, fitted with a double surface reflux condenser, place 50 g. (49 ml.) of aniline and 65 g. of ethyl bromide, and boU gently for 2 hours or until the mixture has almost entirely sohdified. Dissolve it in water and boil off the small quantity of unreacted ethyl bromide. Render the mixture alkaUne with concentrated sodium hydroxide solution, extract the precipitated bases with three 50 ml. portions of ether, and distil off the ether. The residual oil contains anihne, mono- and di-ethylaniline. Dissolve it in excess of dilute hydrochloric acid (say, 100 ml. of concentrated acid and 400 ml. of water), cool in ice, and add with stirring a solution of 37 g. of sodium nitrite in 100 ml. of water do not allow the temperature to rise above 10°. Tnis leads to the formation of a solution of phenyl diazonium chloride, of N-nitrosoethylaniline and of p-nitrosodiethylaniline. The nitrosoethylaniline separates as a dark coloured oil. Extract the oil with ether, distil off the ether, and reduce the nitrosoamine with tin and hydrochloric acid (see above). The yield of ethylaniline is 20 g. 

Transfer 30 g. of the hydrochloride to a 500 ml. separatory funnel, add 100 ml. of water and shake until a thin paste of uniform consistency is obtained add 10 per cent, aqueous sodium hydroxide solution in the cold with shaking until the whole mass has become bright green (the colour of the free base) and the mixture has an alkaUne reaction. Extract the free base by shaking with two 60 ml. portions of benzene (1). Dry the combined benzene extracts with a Uttle anhydrous potassium carbonate, and filter into a distiUing flask fitted with a water condenser. Distil off about half of the benzene, and pour the residual hot benzene solution into a beaker. Upon cooUng, the p-nitrosodimethylaniUne erystallises in deep green leaflets. Filter these off and dry them in the air. The yield of p-nitrosodimethylaniUne, m.p. 85°, from the hydrochloride is almost quantitative. 

Dissolve 1 g. of the secondary amine in 3-5 ml. of dilute hydrochloric acid or of alcohol (in the latter case, add 1 ml. of concentrated hydrochloric acid). Cool to about 5° and add 4-5 ml. of 10 per cent, sodium nitrite solution, and allow to stand for 5 minutes. Add 10 ml. of water, transfer to a small separatory funnel and extract the oil with about 20 ml. of ether. Wash the ethereal extract successively with water, dilute sodium hydroxide solution and water. Remove the ether on a previously warmed water bath no flames should be present in the vicinity. Apply Liebermann s nitroso reaction to the residual oil or solid thus. Place 1 drop or 0 01-0 02 g. of the nitroso compovmd in a dry test-tube, add 0 05 g. of phenol and warm together for 20 seconds cool, and add 1 ml. of concentrated sulphuric acid. An intense green (or greenish-blue) colouration will be developed, which changes to pale red upon pouring into 30-50 ml. of cold water the colour becomes deep blue or green upon adding excess of sodium hydroxide solution. 

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