Lagging

Phase lag = total depth of metal/skin depth, therefore phase lag is given by dV7t[Pg.321]

The obtained signal is filtered with a low-pass filter having the cut-off frequency of 5Hz and a slope of 6 dB/octave. Since we are working with e.m.f modulus, the phase lag does not influence the control. 

MBRS Molecular beam spectroscopy [158] A modulated molecular beam hits the surface and the time lag for reaction products is measured Kinetics of surface reactions chemisorption... 

The kinetics of crystal growth has been much studied Refs. 98-102 are representative. Often there is a time lag before crystallization starts, whose parametric dependence may be indicative of the nucleation mechanism. The crystal growth that follows may be controlled by diffusion or by surface or solution chemistry (see also Section XVI-2C). 

Figure Cl.4.5. Population modulation as the atom moves through the standing wave in the Tin-periD-lin one dimensional optical molasses. The population lags the light shift such that kinetic is converted to potential energy then dissipated into the empty modes of the radiation field by spontaneous emission (after 1171).

In practice, colloidal systems do not always reach tlie predicted equilibrium state, which is observed here for tlie case of narrow attractions. On increasing tlie polymer concentration, a fluid-crystal phase separation may be induced, but at higher concentration crystallization is arrested and amorjihous gels have been found to fonn instead [101, 102]. Close to the phase boundary, transient gels were observed, in which phase separation proceeded after a lag time. 

Fig. 11.38 Lag ejfects in ab initio molecular dynamics. (Figure redrawn from Payne MC, M P Teter, D C Allan, R A Arias and D ] Joannopoidos 1992. Iterative Minimisaticm Techniques for Ab Initio Total-Energy Calculations Molecular Dynamics and Conjugate Gradients. Reviews of Modern Physics 64 1045-1097.)...

Experiment 6. Fractional Distillation of a Mixture of Benzene and Toluene. Fractionally distil about 40 ml. of a mixture of equal volumes of benzene and toluene, using the type of fractionating column shown in Fig. ii(b), in which about 18-20 cm. of the column are actually filled with glass sections, but in which the cotton-wool lagging is not used. Distil very slowlyy so that the total distillation occupies about hours. Shield the apparatus very carefully from draughts. Collect the fractions having the b.ps (a) 80-85°, ( ) 85-107°, (c) 107-111°. A sharp separation should be obtained, e.g.y these fractions should have volumes of about 19, 2, and 17 ml. respectively. 

The furnace and thermostatic mortar. For heating the tube packing, a small electric furnace N has been found to be more satisfactory than a row of gas burners. The type used consists of a silica tube (I s cm. in diameter and 25 cm. long) wound with nichrome wire and contained in an asbestos cylinder, the annular space being lagged the ends of the asbestos cylinder being closed by asbestos semi-circles built round the porcelain furnace tube. The furnace is controlled by a Simmerstat that has been calibrated at 680 against a bimetal pyrometer, and the furnace temperature is checked by this method from time to time. The furnace is equipped with a small steel bar attached to the asbestos and is thus mounted on an ordinary laboratory stand the Simmerstat may then be placed immediately underneath it on the baseplate of this stand, or alternatively the furnace may be built on to the top of the Simmerstat box. 

The 40-45 per cent, hydrazine solution may be concentrated as follows. A mixture of 150 g. (144 ml.) of the solution and 230 ml. of xylene is distilled from a 500 ml. round-bottomed flask through a well-lagged Hempel (or other efficient fractionating) column fitted into a cork covered with tin foil. All the xylene passes over with about 85 ml. of water. Upon distillation of the residue, about 50 g. of 90-95 per cent, hydrazine hydrate (5) are obtained. 

The efficiency of all the above columns (and also those described below) is increased by lagging with asbestos cloth. The best results are obtained by surrounding each column with two glass jackets and heating the inner jacket electrically to a temperature within 5-10° of the fraction... 

Trimethylene Di-iodide. Use 76 g. of trimethylene glycol, 27 - 52 g. of pmified red phosphorus and 254 g. of iodine. Lag the arm C (Fig. Ill, 40, ) with asbestos cloth. Stop the heating immediately all the iodine has been transferred to the fiask. Add water to the reaction mixture, decolourise with a httle sodium bisulphite, filter, separate the crude iodide, wash it twice with water, dry with anhydrous potassium carbonate and distU under reduced pressure. B.p. 88-89°/6 mm. Yield 218 g. (a colourless liquid). 

Finally distil from a well-lagged Widmer flask (compare Figs. II, 24, 2-5) over a little sodium. Collect the cycZo hexyl ethyl ether at 148-150°. The yield is 21 g. If the sodium is appreciably attacked, repeat the distillation from a fresh quantity of sodium. 

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