Dipping apparatus

In spite of these acknowledged advantages, low volume dipping chambers and automated, time-controlled dipping apparatus (Fig. 40 and 41) have only been available commercially for a few years. 

The advantage of such dipping apparatus is that the insertion and removal of the chromatogram is performed at a uniform speed and the time of immersion can be set as necessary. Interfering ripple marks", such as are observed on manual dipping, do not occur. Care must be taken, however, to clean off the back of the... 

Such a dipping apparatus can also be employed with advantage for applying substances to preserve or intensify fluorescence after chromatography or derivati-zation is complete (cf. Section 3.2.7.3). 

A dipping apparatus can also be employed to impregnate adsorbent layers with a detection reagent prior to sample application. This preimpregnation method has been used successfully with silver nitrate and phosphomolybdic acid. 

The LbL assembly has not yet found industrial application in spite of its versatility. The main reason for this is the time-consuming multistep assembly procedure, which often is additionally complicated with particle agglomeration. As noted elsewhere, deposition of a film consisting of dozens of layers takes more than 10 h using a robotic dipping apparatus [57]. Nonetheless, recently the use of spray-assisted LbL assembly, both for planar films as well as for the construction of polymeric particles, has emerged as a possible strategy to reduce the deposition times per layer from tens of minutes to a few seconds [57]. 

Place 36 -0 g. of redistilled acetophenone, b.p. 201° (Section IV,136), 300 ml. of diethylene glycol, 30 ml. of 90 per cent, hydrazine hydrate and 40 g. of potassium hydroxide pellets in a 500 ml. Claisen flask provided with a reflux condenser and a thermometer dipping into the liquid (compare Fig. Ill, 31, 1). Warm the mixture on a boiling water bath until most of the potassium hydroxide has dissolved and then reflux (free flame) for one hour. Arrange the apparatus for distillation and distil until the temperature in the liquid rises to 175° (1) keep the distillate (ca. 50 ml.). Replace the reflux condenser in the flask and continue the refluxing for 3 hours. 

Assemble the apparatus shown in Fig. 1 V, 67, 1 this is self-explanatory. The distilling flask has a capacity of 250 ml. and the beaker contains 150 ml. of 10 per cent, sodium hydroxide solution. All corks must fit well and should be coated with paraflSn wax (by dipping into molten wax, and allowing to drain). Place half of the yield of the dry phenyldiazonium fluoborate in the distilling flask. Heat the solid gently with a small luminous flame at one point near its surface until decomposition begins withdraw the flame and allow the reaction to continue... 

Apparatus 250-ml two-necked flask, provided with a reflux condenser and a thermometer, dipping into the liquid. 

Apparatus. 250-ral flask, provided with a gas inlet, a thermometer (dipping in the liquid) and a reflux condenser. 

Apparatus 500-ml three-necked, round-bottomed flask with a thermometer, dipping well into the liquid, a 40-cm Widmer column and a dropping funnel the column was connected to a condenser and receiver. 

Apparatus 500-ml round-bottomed, three-necked flask, provided with a gas inlet tube, a mechanical stirrer and a thermometer-vent combination for the preparation of the a-chloroether 500-inl round-bottomed flask, provided with a gas inlet, a reflux condenser and a thermometer, dipping in the liquid for the elimination of HCT and the 3,3-sigmatropic rearrangement. 

Fit up the apparatus as shown in Fig. 43. The distilling -flask should have a capacity of not less than i litre, and is attached to a long condenser. An adapter is fixed to the end"of the condenser, dipping into a conical flask (250 c.c.), which serves as receiver. The alcohol and sulphuric acid are mixed in the distilling flask and cooled to the ordinary tempeiatuie under the tap. The potassium biomide, coarsely pou dered, is then added. The flask, which is closed with a cork, is fixed to the condenser and heated on the sand-bath. A sufficient quantity of water is poured into the receiver to close the end of the adapter. After a short tune the liquid in the flask begins to boil and froth up, and the ethyl bromide, in the form of heavy... 

This apparatus can also be used as reflux condenser or for collecting ovolve d gas if the side piece is furnished with a delivery tube dipping under water 01 mfrcury. 

The apparatus consists of a 100-ml distilling flask equipped with a dropping funnel and arranged for distillation through an efficient condenser. The condenser is connected to two receiving flasks in series, the second of which contains 20-30 ml of ether. The inlet tube of the second receiver dips below the surface of the ether and both receivers are cooled in ice baths. All connections in the setup are made with bored cork stoppers and all glass tubing is fire polished (Fig. 17.1). 

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