Conductivity preparation

According to the literature, the product obtained in this manner may contain ethyl adipate. To remove this, the product is cooled to 0° and run slowly into 600 cc. of 10 per cent potassium hydroxide solution maintained at 0° with ice-salt. Water is added until the salt which separates has dissolved, and the cold alkaline solution is extracted twice with 200-cc. portions of ether. The alkaline solution, kept at 0°, is run slowly into 900 cc. of 10 per cent acetic acid solution with stirring, the temperature remaining below 1° (ice-salt). The oil which separates is taken up in 400 cc. of ether, and the aqueous solution is extracted with four 250-cc. portions of ether. The ether extract is washed twice with cold 7 per cent sodium carbonate solution and dried over sodium sulfate. After removal of the ether the residue is distilled, b.p. 7g-8i°/3 mm. The recovery is only 80-85 per cent, and in a well-conducted preparation the ethyl adipate eliminated amounts to less than one per cent of the total product. Unless the preparation has proceeded poorly the tedious purification ordinarily is best omitted. 

J. Li Y. Yamada K. Murakoshi Y. Nakatoa, Sustainable metal nanocontacts showing quantized conductance prepared at a gap of thin metal wires in solution. Chem. Commun. 2001, 2170-2171. 

Lin H, Zhao C, Jiang Y, Ma W, Na H (2011) Novel hybrid polymer electrolyte mranbranes with high proton conductivity prepared by a silane-crosslinking technique for direct methanol fuel cells. J Power Sources 196 1744—1749... 

Fall-out from the considerable activity in the development of liquid chromatography systems has shown itself in some of the latest experimental variations for conducting preparative TREF. In addition to the use of valves, tubing, fittings and pumps normally associated with LC systems, progratmned ovens have also... 

Luo, W.-H. and Zhao, L.-H. (2014) Inorganic-organic hybrid membranes with anhydrous proton conduction prepared from tetraethoxysilane, 3-glycidyloxypropyltrimethoxysilane, trimethyl phosphate and diethylethylammonium trifluoromethanesulfonate./. Membr. Sci., 451, 32-39. 

The chromatogram can finally be used as the series of bands or zones of components or the components can be eluted successively and then detected by various means (e.g. thermal conductivity, flame ionization, electron capture detectors, or the bands can be examined chemically). If the detection is non-destructive, preparative scale chromatography can separate measurable and useful quantities of components. The final detection stage can be coupled to a mass spectrometer (GCMS) and to a computer for final identification. 

Blocks have been prepared of 7075-T6 aluminum alloy 20 mm thick, with electrical conductivity of 1.89x10 S/m. The discontinuity has been machined by milling at a width of 0.2 mm. 

These limitations have recently been eliminated using solid-state sources of femtosecond pulses. Most of the femtosecond dye laser teclmology that was in wide use in the late 1980s [11] has been rendered obsolete by tliree teclmical developments the self-mode-locked Ti-sapphire oscillator [23, 24, 25, 26 and 27], the chirped-pulse, solid-state amplifier (CPA) [28, 29, 30 and 31], and the non-collinearly pumped optical parametric amplifier (OPA) [32, 33 and 34]- Moreover, although a number of investigators still construct home-built systems with narrowly chosen capabilities, it is now possible to obtain versatile, nearly state-of-the-art apparatus of the type described below Ifom commercial sources. Just as home-built NMR spectrometers capable of multidimensional or solid-state spectroscopies were still being home built in the late 1970s and now are almost exclusively based on commercially prepared apparatus, it is reasonable to expect that ultrafast spectroscopy in the next decade will be conducted almost exclusively with apparatus ifom conmiercial sources based around entirely solid-state systems. 

Refractionation of the low-boiling impurities gives a further quantity of the acetoacetate, but if the initial distillation has been carefully conducted, the amount recovered is less than i g., and the refractionation is not worth while. If possible, complete the preparation in one day. If this is not possible, it is best to allow the cold crude sodium derivative (before acidification) to stand overnight, the flask being closed by a cork carrying a calcium chloride tube the yield will now fall to about 38 g. Alternatively, the crude ester may be allowed to remain overnight in contact with the sodium sulphate, but in this case the yield will fall to about 30 g. 

After the butyl chloride fraction has been collected, change the receiver and continue the distillation untU the zinc chloride commences to crystallise. Allow to cool and stopper the flask. The anhydrous zinc chloride thus obtained may be used in another preparation and recovered repeatedly. This results in considerable economy when the preparation is conducted by a large number of students. 

In a 1500 ml. round-bottomed flask, carrying a reflux condenser, place 100 g. of pure cydohexanol, 250 ml. of concentrated hydrochloric acid and 80 g. of anhydrous calcium chloride heat the mixture on a boiling water bath for 10 hours with occasional shaking (1). Some hydrogen chloride is evolved, consequently the preparation should be conducted in the fume cupboard. Separate the upper layer from the cold reaction product, wash it successively with saturated salt solution, saturated sodium bicarbonate solution, saturated salt solution, and dry the crude cycZohexyl chloride with excess of anhydrous calcium chloride for at least 24 hours. Distil from a 150 ml. Claisen flask with fractionating side arm, and collect the pure product at 141-5-142-5°. The yield is 90 g. 

An alternative method of conducting the preparation consists in treating 100 g. of cycZohexanol with 250 ml. of concentrated hydrochloric acid, refluxing slowly whilst a stream of hydrogen chloride gas is passed into the mechanically stirred... 

Care must be exercised in handling n-amyl and the other alkyl nitrites inhalation of the vapour may cause severe headache and heart excitation. The preparation must therefore be conducted in an efficient fume cupboard. 

Ethyl bromoacetate vapour is extremely irritating to the eyes. The preparation must therefore be conducted in a fume cupboard provided with a good draught the material should be kept in closed vessels as far as possible. 

The preparation may be conducted on a quarter or half scale in a 500 ml. flask with equally satisfactory results. 

This is an alternative experiment to the actual preparation of the ester and will give the student practice in conducting a distillation under diminished pressure. Commercial ethyl acetoacetate generally contains inter alia some ethyl acetate and acetic acid these are removed in the following procedure. 

Conduct the preparation in the fume cupboard. Dissolve 250 g. of redistilled chloroacetic acid (Section 111,125) in 350 ml. of water contained in a 2 -5 litre round-bottomed flask. Warm the solution to about 50°, neutralise it by the cautious addition of 145 g. of anhydrous sodium carbonate in small portions cool the resulting solution to the laboratory temperature. Dissolve 150 g. of sodium cyanide powder (97-98 per cent. NaCN) in 375 ml. of water at 50-55°, cool to room temperature and add it to the sodium chloroacetate solution mix the solutions rapidly and cool in running water to prevent an appreciable rise in temperature. When all the sodium cyanide solution has been introduced, allow the temperature to rise when it reaches 95°, add 100 ml. of ice water and repeat the addition, if necessary, until the temperature no longer rises (1). Heat the solution on a water bath for an hour in order to complete the reaction. Cool the solution again to room temperature and slowly dis solve 120 g. of solid sodium hydroxide in it. Heat the solution on a water bath for 4 hours. Evolution of ammonia commences at 60-70° and becomes more vigorous as the temperature rises (2). Slowly add a solution of 300 g. of anhydrous calcium chloride in 900 ml. of water at 40° to the hot sodium malonate solution mix the solutions well after each addition. Allow the mixture to stand for 24 hours in order to convert the initial cheese-Uke precipitate of calcium malonate into a coarsely crystalline form. Decant the supernatant solution and wash the solid by decantation four times with 250 ml. portions of cold water. Filter at the pump. 

Nitro derivatives. No general experimental details for the preparation of nitro derivatives can be given, as the ease of nitration and the product formed frequently depend upon the exact experimental conditions. Moreover, some organic compounds react violently so that nitrations should always be conducted on a small scale. The derivatives already described are usually more satisfactory for this reason the nitro derivatives have been omitted from Table IV,9. 

To prepare the solid phenyldlazonlum chloride or sulphate, the reaction is conducted in the absence of water as far as possible. Thus the source of nitrous acid is one of its organic esters (e.g., amyl nitrite) and a solution of hydrogen chloride gas in absolute alcohol upon the addition of ether only the diazonium salt is precipitated as a crystalline solid, for example ... 

About 200 ml. of light petroleum is required for recrystallisation. It is therefore advisable, for the sake of economy when the preparation is conducted by a large class of students, that onl about I g. of the crude material be recrystallised from this solvent. The crude compound may be employed in the preparation of p-amino-azobonzene. 

It is recommended that the preparation be conducted in the fume cupboard (hood) with the window protecting the face. 

Dissolve 0 01 mol of the phenohc ether in 10 ml. of warm chloroform, and also (separately) 0 01 mol of picric acid plus 5 per cent, excess (0 -241 g.) in 10 ml. of chloroform. Stir the picric acid solution and pour in the solution of the phenohc ether. Set the mixture aside in a 100 mb beaker and ahow it to crystallise. Recrystahise the picrate from the minimum volume of chloroform. In most cases equahy satisfactory results may be obtained by conducting the preparation in rectified spirit (95 per cent. CjHgOH). The m.p. should be determined immediately after recrystallisation. It must be pointed out, however, that the picrates of aromatic ethers suflFer from the disadvantage of being comparatively unstable and may undergo decomposition during recrystaUisation. 

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