Near filters

By choosing the proper correlation algorithm, it is possible to realise sensitive filters for other types of defects (e.g. corrosion). Fig. 5.2 shows an example for the suppression of signals which do not exhibit the expected defect stmcture (Two parallel white lines near upper central rim portion of Fig. 5.2). The largest improvement in SNR is obtained here by using the expression (ai ai+x /ai+yj), since for a gradiometric excitation, one expects the crack response to show two maxima (a, aj+x) with a minimum (a m) in the centre (see Fig. 5.3). 

Furthermore, it was possible to suppress liftoff and offset effects by using efficient digital filter algorithms. These measures provide the tester with a nearly unbiased picture of the wheel that is to be tested and he can thus conduct a reliable evaluation. 

Figure Bl.7.9. (a) Stability diagram for ions near the central axis of a quadnipole mass filter. Stable trajectories occur only if the and values lie beneath tire curve, (b) Stability diagram (now as a fiinction of U and F) for six ions with different masses. The straight line miming tlirough the apex of each set of curves is the operating line, and conesponds to values of UIVthat will produce mass resolution (reproduced with pennission of Professor R March, Trent University, Peterborough, ON, Canada).

The Mathieu equation for the quadnipole ion trap again has stable, bounded solutions conesponding to stable, bounded trajectories inside the trap. The stability diagram for the ion trap is quite complex, but a subsection of the diagram, correspondmg to stable trajectories near the physical centre of the trap, is shown in figure Bl.7.15. The interpretation of the diagram is similar to that for tire quadnipole mass filter. 

To prepare the hydrochloride, add about i g. of aminoazobenzene to 200 ml. of dilute hydrochloric acid and boil until nearly all the solid material has dissolved. Filter hot and allow to cool slowly. Aminoazobenzene hydrochloride separates as beautiful steel-blue crystals filter and dry. If a small quantity of the powdered hydrochloride is moistened with water and a few drops of ammonia added, the blue hydrochloride is converted back to the yellowish-brown base. 

In a 1 litre round-bottomed flask provided with an efficient double surface condenser, place 40 g. (39 ml.) of aniline, 50 g. (40 ml.) of carbon sulphide CAUTION inflammable) (1), and 50 g. (63-5 ml.) of absolute ethyl alcohol (2). Set up the apparatus in the fume cupboard or attach an absorption device to the top of the condenser (see Fig. 11, 8, 1) to absorb the hydrogen sulphide which is evolved. Heat upon an electrically-heated water bath or upon a steam bath for 8 hours or until the contents of the flask sohdify. When the reaction is complete, arrange the condenser for downward distillation (Fig. 11, 13, 3), and remove the excess of carbon disulphide and alcohol (CA UTION inflammable there must be no flame near the receiver). Shake the residue in the flask with excess of dilute hydrochloric acid (1 10) to remove any aniline present, filter at the pump, wash with water, and drain well. Dry in the steam oven. The yield of crude product, which is quite satisfactory for the preparation of phenyl iao-thiocyanute (Section IV.95), is 40-45 g. Recrystalhse the crude thiocarbanihde by dissolving it, under reflux, in boiling rectified spirit (filter through a hot water funnel if the solution is not clear), and add hot water until the solution just becomes cloudy and allow to cool. Pure sj/m.-diphenylthiourea separates in colourless needles, m.p, 154°,... 

Place 20 g. of Orange II (Section IV,79) in a 600 ml. beaker and dissolve it in 250 ml. of water at 40-50°. Add, with stirring, 24-25 g. of sodium hyposulphite (Na SjO ) this discharges the colour and yields a pink or cream-coloured, finely-divided precipitate of a-amino-p-naphthol (compare Section IV,76). Heat the mixture nearly to boiling until it commences to froth considerably, then cool to 25° in ice, filter on a... 

What s left in the water now needs to be vacuum filtered and dried. This should be done carefully and under the fume hood. Up to this point the chemistry will have taken around 30 minutes, the drying might take a day or so. Often bromine liquid stays hanging around the crystals which makes them nasty, leave in the buchner funnel of your vacuum filter overnight to get rid of all that bromine. Unless all the bromine has gone, don t go near them without a fume cupboard or a mask. 

Sodium bismuthate (oxidation of manganese) heat 20 parts of NaOH nearly to redness in an iron or nickel crucible, and add slowly 10 parts of basic bismuth nitrate which has been previously dried. Add 2 parts of sodium peroxide, and pour the brownish-yellow fused mass on an iron plate to cool. When cold break up in a mortar, extract with water, and collect on an asbestos filter. 

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