Dynamic yield point


When the filtration is complete, run about 25 ml. of the ether solution into A, and place under the latter a water-bath which has been brought to the boil at some considerable distance from the apparatus. (With large classes, or in crowded laboratories, the water-baths may well be heated in fume-cupboards, which are usually at a safe distance for this purpose from the working benches.) As the ether distils off from A, run in more of the solution from B, and thus continue until it appears that all the ether has been distilled off, and only aniline remains in A. To complete the latter stages of the distillation, it may be necessary to reheat the water-bath this should be done as before at a safe distance from the apparatus. Now detach the Buchner flask D, pour the contents into an ether residue bottle, and then replace C by an air-condenser finally replace the funnel B by a thermometer reading to at least 200°. Distil the residual aniline carefully by direct heating over a gauze, and collect the fraction boiling at 180-185°. During the early part of distillation, a small quantity of ether may come over although the recorded temperature may be well above its boiling-point hence ensure that the flame is kept well away from the open end of the condenser. Yield, 17 g.  [c.164]

The infrared region of the electromagnetic spectrum can, perhaps, yield the most information concerning the structure of organic molecules. The masses of the atoms, and the forces holding them together, are of such magnitude that the usual vibration of organic molecules interact with electromagnetic energy so as to absorb and radiate in the infrared region. Overtones and combinations of these vibrational frequencies may appear in the visible region and in the near-infrared (0-8-2(1), but most of the fundamental vibrations occur in the interval from 2 to 25(i. It is this region of fundamental frequencies that is generally of greatest value in the study of organic molecules. Problems of identity, purity, gross structural features, as well as many finer points of structural detail, can be solved through the use of infrared spectroscopy, often faster than by any other analytical method. For a molecule of high complexity and molecular weight and of unknown constitution, it is usually better to break it down to simpler parts just as is done when a structure is elucidated chemically by degradative methods. The infrared spectrum provides a physical constant which is more valuable than the melting point for characterising organic compounds. A mixed melting point can take as much time as is needed to obtain an infrared spectrum, yet it yields only a single fact whilst the spectrum may provide a great deal of information.  [c.1136]

When the filtration is complete, run about 25 ml. of the ether solution into A, and place under the latter a water-bath which has been brought to the boil at some considerable distance from the apparatus. (With large classes, or in crowded laboratories, the water-baths may well be heated in fume-cupboards, which are usually at a safe distance for this purpose from the working benches.) As the ether distils off from A, run in more of the solution from B, and thus continue until it appears that all the ether has been distilled off, and only aniline remains in A. To complete the latter stages of the distillation, it may be necessary to reheat the water-bath this should be done as before at a safe distance from the apparatus. Now detach the Buchner flask D, pour the contents into an ether residue bottle, and then replace C by an air-condenser finally replace the funnel B by a thermometer reading to at least 200°. Distil the residual aniline carefully by direct heating over a gauze, and collect the fraction boiling at 180-185°. During the early part of distillation, a small quantity of ether may come over although the recorded temperature may be well above its boiling-point hence ensure that the flame is kept well away from the open end of the condenser. Yield, 17 g.  [c.164]

In operation, the magnetic section of the hybrid is used to select ions of a particular m/z value. Por example, if a mixture of two substances gives two molecular ions, Mj and Mj, the magnetic sector is used to select one or the other. The selected ions collide with gas in the collision cell (Pigure 21.1), and some of them decompose to yield fragment ions, say P, Pj, and P3. Thus, a stream of ions M, (some of which have not been decomposed) plus P, Pj, and F, leave the collision cell (Pigure 21.3). If this beam went straight to the single-point ion collector, there would be no separation into the individual m/z values, and it would not be possible to measure their m/z values. However, by pulsing the pusher electrode placed just after the collision cell, a section of the beam is sent orthogonally down the TOP analyzer tube, which does separate them according to m/z value, which is related to the length of time they take to reach the multipoint microchannel plate collector (Pigure 21.1). Therefore, molecular ions and fragment ions are obtained in this MS/MS mode.  [c.160]

Why not put new lyrics to an old tune This is an excellent idea, and many have done this very thing. Rice" started w ith the Smith-Brinkley raethod" used to calculate distillation, absorption, extraction, etc., overhead and bottoms compositions, and developed distillation equations for determining the liquid composition on any tray. This together with bubble point calculations yield a column temperature profile useful for column analysis.  [c.403]

There is a vast and often bewildering array of synthetic methods and reagents available to organic chemists today. Many chemists have their own favoured methods, old and new, for standard transformations, and these can vary considerably from one laboratory to another. New and unfamiliar methods may well allow a particular synthetic step to be done more readily and in higher yield, but there is always some energy barrier associated with their use for the first time. Furthermore, the very wealth of possibilities creates an information retrieval problem How can we choose between all the alternatives, and what are their real advantages and limitations Where can we find the precise experimental details, so often taken for granted by the experts There is therefore a constant demand for books on synthetic methods, especially the more practical ones like Organic Syntheses," "Organic Reactions.and "Reagents for Organic Synthesis." which are found in most chemistry laboratories. We are convinced that there is a further need, still largely unfulfilled, for a uniform series of books, each dealing concisely with a particular topic from a practical point of view—a need, that is. for books full of preparations, practical hints, and detailed examples, all critically assessed, and giving just the information needed to smooth our way painlessly into the unfamiliar territory. Such books would obviously be a great help to research students as well as to established organic chemists.  [c.197]

Bindings and Thickenings Ag ent. The rheological properties of a dentifrice are primarily determined by the agent used to bind and thicken the product and allow its extmsion as a firm, but easily dispersible, ribbon. A weU-formulated toothpaste exhibits a high yield point and thixotropy, that is, it is easily Uquified (see RpiEOLOGiCALmeasurements). Gums and resins are employed to obtain the desired thickening and binding. Each has a characteristic rheological spectmm and lends stmcture to the toothpaste accordingly. Gums and resins widely used include acrylic acid polymers, carrageenan [9000-07-17, sodium carboxymethyl cellulose [9004-32-4], xanthan gum [11138-66-2], and hydrated siUca [10279-57-9]. Each is available in several variations having different properties. Selection of an optimal gum or resin along with the selection of appropriate other ingredients results in a paste that extmdes with the apphcation of minimal pressure to form a smooth, cohesive ribbon, which stands up on the toothbmsh bristles and breaks down and disperses quickly in the mouth during bmshing.  [c.502]

Purification of commercial salicylaldehyde. When comparatively large quantities of salicylaldehyde are required, it is more economical to purify the relatively inexpensive commercial product. This may be done either through the bisulphite compound (compare Section III,74,A) or by the following method. Add the commercial salicylaldehyde to a large excess of a luke-warm solution of copper acetate (previously saturated near the Doihiig point), shake well, and allow to stand several hours in ice. Filter, wash the precipitate thoroughly first with alcohol and then with ether. Decompose the solid with dilute (10 per cent.) sulphuric acid, extract the aldehyde with ether, dry (anhydrous magnesium sulphate), and distil. The yield from a good commercial sample may be as high as 80 per cent.  [c.704]

The PLM can be used in a reflection or a transmission mode. With either mode, light of various wavelengths from ultraviolet to infrared, polarized or unpolarized, is used to yield a wide variety of physical measurements. With just ordinary white light, a particle or any object detail down to about 0.5 p.m (500 nm) in diameter can be observed to detect shape, size, color, refractive index, melting point, and solubiUty in a group of solvents, all nondestmetively. Somewhat larger particles yield UV, visible, or IR absorption spectra.  [c.333]

Several other tests of agglomerate quaUty are done routinely, the details depending on the practice accepted in a specific industry. For iron ore, a drop test is used on wet agglomerates as a measure of their abiUty to withstand handling up to the point in the process at which they are dried and fired (3). A test might consist of dropping a number of agglomerates from a height of 300 or 450 mm onto a steel plate. The average number of drops required to cause fracture is the drop number. In the ASTM tumbler test for iron-ore pellets (E279) an 11.3-kg sample in the size range 6.4—38.1 mm is placed in a tumbler dmm ca 910 mm diameter by 460 mm long and rotated at 24 rpm for a total of 200 revolutions. The dmm is equipped with two equally spaced lifters 51 mm high. The abrasion index is given by the weight percentage of plus 6.4 mm material surviving the test and the dust index by the yield of minus 0.6 mm (30 mesh) material. In addition to the tumble dmm attrition test, there is wide industry use of screen abrasion tests (35). Preweighed samples of rock salt or potassium granules, for example, are shaken on sieve shakers, with the abraded fines recorded as abrasion index. This can be done with or without the addition of steel ball grinding media in the sieve shaker. Other strength tests such as the Linder rotating-fumace procedure are used with iron-ore pellets in an attempt to determine their reducibiUty and breakdown under reducing conditions simulating those of a blast furnace (36).  [c.111]

An average zero-point libration amplitude of 14° can be extracted from the data, which compares favorably with the 18° from quasiharmonic lattice dynamics [339] for ZI-N2 at OK in three dimensions. Since the validity of such approximations is very difficult to estimate a priori, exact full quantum reference simulations, as presented here, are clearly required to control such approximation schemes. This becomes clear when one considers the shift in Tq as obtained from the second-order Feynman-Hibbs simulation it breaks down essentially at the same temperature at which the transition occurs and a breakdown at a slightly higher temperature would give wrong results. In addition, one does not know where to match the regimes where different approximations are still valid. The PIMC simulations, however, yield exact results over the whole temperature range from the classical to the quantum regime.  [c.117]

The reaction mixture, of this composition, was then heated to 250°C. The water of the reaction distilled off during the heating as the ether formation proceeded, this removal of water from the reaction chamber being promoted by the presence of the excess of phenol, some of which also continued to distill over. Towards the end of the reaction, after about 12 hours, when about 60% of the glycerol had been converted,at which point the reaction slowed down and the distillate was mainly cresol, the batch was cooled and 50 gallons of water were added to it along with 150 lb of xylene. As the result of these additions and the cooling down of the material the batch stratified into an aqueous layer containing unreacted glycerol, polyglycerols and sodium acetate, and a nonaqueous layer containing the ethers that had been formed in the reaction, together with unreacted cresol which remained in the reaction chamber, dissolved in the xylene that had been added to the batch. The aqueous layer was then separated and the water content removed therefrom by evaporation to a degree suitable for the recovery of the glycerol and sodium acetate contents of the layer, for their reuse in the process in a succeeding batch therein. The separated nonaqueous layer containing the ethers was distilled to recover the xylene and cresol contents respectively as the early fractions of the layer thus subjected to distillation. The cresol thus recovered, together with the cresol recovered from the distillate obtained during the heating of the reaction mixture, was returned to the process for reuse in a succeeding betch. Redistillation of the ether mixture recovered is usually necessary and desirable, particularly from the point of view of removing last traces of cresol therefrom. The yield of mixed ethers in this example was about 200 lb, in the relative proportions stated of about 70 parts of monoether to 30 of diether.  [c.934]


See pages that mention the term Dynamic yield point : [c.129]    [c.39]    [c.764]    [c.72]    [c.243]    [c.161]    [c.122]    [c.505]    [c.211]    [c.1549]    [c.274]   
Solids under high-pressure shock compression - mechanics, physics, and chemistry (1992) -- [ c.28 ]