Stills apparatus

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. 

The liquid becomes progressively darker in colour, and then effervesces gently as ethylene is evolved. Allow the gas to escape from the delivery-tube in T for several minutes in order to sweep out the air in F and B. Now fill a test-tube with water, close it with the finger, and invert the tube in the water in T over the delivery-tube so that a sample of the gas collects in the tube. Close the tube again with the finger, and then light the gas at a Bunsen burner at a safe distance from the apparatus. If the tube contains pure ethylene, the latter burns with a clear pale blue (almost invisible) flame if the ethylene still contains air, the mixture in the test-tube ignites with a sharp report. Allow the... 

The reaction is best carried out in the apparatus used in the preparation of quinoline, a 1500 ml. flask being fitted with a wide-bore air-condenser carrying in turn a water-condenser a still-head to fit the flask for subsequent steam-distillation should be assembled in advance. 

Ether. The most satisfactory method for the removal of (diethyl) ether is either on a steam bath fed from an external steam supply or by means of an electrically-heated, constant-level water bath (Fig. 77, 5, 1). If neither of these is available, a water bath containing hot water may be used. The hot water should be brought from another part of the laboratory under no circumstances should there be a free flame under the water bath. It caimot be too strongly emphasised that no flame whatsoever may be present in the vicinity of the distillation apparatus a flame 10 feet away may ignite diethyl ether if a continuous bench top lies between the flame and the still and a gentle draught happens to be blowing in the direction of the flame. 

Some simple apparatus, suitable for high vacuum distillation, are collected in Figs. 11, 26, 1-4. Fig. 11, 26, 1 represents an apparatus, which is particularly well adapted for solids the ground glass joint must be lubricated with a grease of negligible vapour pressure. Hickman s vacuum still is shown in Fig. 11, 26, 2 it is about 60 mm. in diameter. 

The top of the bench should always be kept clean and dry this can easily be done if a wet and a dry rag are kept at hand. Apparatus not immediately required (a) should be kept as far as possible in a cupboard beneath the bench if it must be placed on the bench, it should be arranged in a neat and orderly manner. All apparatus should be washed immediately after use and placed in a position to drain at the first opportunity, the apparatus should be dried. It must be emphasised that as a general rule a deposit of dirt or tar is more easily removed when it is freshly formed a suitable cleaning agent can usually be found while one still remembers the nature of the material or the circumstances attending its formation. It is hardly necessary to add that sohd waste and filter papers must not be thrown into the sink, and that all operations requiring the handhng of unpleasant and noxious materials sliould be carried out in the fume cupboard ( hood ). 

Reduction adapters. These may be employed to connect condensers, still-heads, etc. to flasks, extraction apparatus and the like. Numerous combinations (Fig. II, 56, 2) are, of course, possible, but the commonest sizes are socket 514 to cone 519 or 524 socket 519 to cone 524, 529... 

In a 500 ml. three-necked flask, equipped with a thermometer, mechanical stirrer and efficient reflux condenser, dissolve 16 g. of sodium hydroxide pellets in 95 ml. of hot methyl alcohol. Add 49 g. of guanidine nitrate, stir the mixture at 50-65° for 15 minutes, and then cool to about 20°. Filter oflF the separated sodium nitrate and wash with two 12 ml. portions of methyl alcohol. Return the combined filtrates to the clean reaction flask, add 69 g. of sulphanilamide (Section IX,9) and stir at 50-55° for 15 minutes. Detach the reflux condenser and, with the aid of a still-head ( knee-tube ), arrange the apparatus for distillation from an oil bath with stirring about 100 ml. of methyl alcohol are recovered. Add 12 g. of pure cycZohexanol. Raise the temperature of the oil bath to 180-190° and continue the distillation. Reaction commences with the evolution of ammonia when the uiternal temperature reaches 145°. Maintain the... 

A variety of commercial instruments are available for the determination of the viscoelastic behavior of samples. Figure 3.15 shows one such apparatus, the Rheovibron Viscoelastometer. This instrument also takes advantage of the complementarity that exists between time and temperature It operates at four frequencies over a 175°C temperature range. With accessories, both the frequency range and the temperature range can be broadened still further. 

Patent laws provide for several stages in the life of an application for a patent on an invention. The pattern followed by patent laws in effect in most industrialized countries during the nineteenth and early twentieth centuries, and still in effect in the United States in 1995, calls for the examination of all patent appHcations to certify that the claimed invention meets the national standards for novelty, usehilness, and inventiveness. The owner of the technology to be patented files appHcation papers that include a specification containing a description of the invention to be patented (called the disclosure) and claims defining the limits of the invention to be protected by the patent, a formal request for the issuance of a patent, and fees. Drawings of devices and apparatuses, electrical circuits, flow charts, etc, are an important part of the disclosures of most nonchemical and many chemical patents. 

The efficiency of a distillation apparatus used for purification of liquids depends on the difference in boiling points of the pure material and its impurities. For example, if two components of an ideal mixture have vapour pressures in the ratio 2 1, it would be necessary to have a still with an efficiency of at least seven plates (giving an enrichment of 2 = 128) if the concentration of the higher-boiling component in the distillate was to be reduced to less than 1% of its initial value. For a vapour pressure ratio of 5 1, three plates would achieve as much separation. 

If the pump is a filter pump off a high-pressure water supply, its performance will be limited by the temperature of the water because the vapour pressure of water at 10°, 15°, 20° and 25° is 9.2, 12.8, 17.5 and 23.8 mm Hg respectively. The pressure can be measured with an ordinary manometer. For vacuums in the range lO" mm Hg to 10 mm Hg, rotary mechanical pumps (oil pumps) are used and the pressure can be measured with a Vacustat McLeod type gauge. If still higher vacuums are required, for example for high vacuum sublimations, a mercury diffusion pump is suitable. Such a pump can provide a vacuum up to 10" mm Hg. For better efficiencies, the pump can be backed up by a mechanical pump. In all cases, the mercury pump is connected to the distillation apparatus through several traps to remove mercury vapours. These traps may operate by chemical action, for example the use of sodium hydroxide pellets to react with acids, or by condensation, in which case empty tubes cooled in solid carbon dioxide-ethanol or liquid nitrogen (contained in wide-mouthed Dewar flasks) are used. 

To reiterate the definition of chromatographic resolution a separation is achieved in a chromatographic system by moving the peaks apart and by constraining the peak dispersion so that the individual peaks can be eluted discretely. Thus, even if the column succeeds in meeting this criterion, the separation can still be destroyed if the peaks are dispersed in parts of the apparatus other than the column. It follows that extra-column dispersion must be controlled and minimized to ensure that the full performance of the column is realized. 

The term still is applied only to the vessel in which liquids are boiled during distillation, but the term is sometimes applied to the entire apparatus, including the fractionating column, the condenser, and the receiver in which the distillate is collected. If a water and alcohol distillate is returned from the condenser and made to drip down through a long column onto a series of plates, and if the vapor, as it rises to the condenser, is made to bubble through this liquid at each plate, the vapor and liquid will interact so that some of the water in the vapor condenses and some of the alcohol in the liquid vaporizes. The interaction at each plate is equivalent to a redistillation. This process is referred to by several names in the industry namely rectification, fractionation, or fractional distillation. 

Since it still is not a simple matter to heat a TLC plate really homogeneously there is a danger of reaction inhomogeneities on the plate. The usual types of apparatus employed for heat production and transfer are drying cupboards, hotplates and IR sources. The success obtained using microwaves has been modest up to now. 

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