Grey filter

After 3 hours the stirring is stopped and the solution allowed to settle. By this time just about all the foil will have turned to dust, which is going to make the next step of vacuum filtration very difficult because it will plug up the filter paper in a second. So the chemist lets it settle, then pours off the liquid through the vacuum filtration setup (see methodology section). The flask is rinsed with lOOmL methanol, the methanol poured through the grey filter cake and the filter cake discarded. All of the filtrate is placed in a flask and vacuum distilled to remove all the methanol, isopropyl alcohol and water which will leave the chemist with oil and junk in the bottom of the flask. 

The sky, in fact, was one big cloud. And daylight was dimming behind its grey filter. 

FIG- S. 12 (A) Evolution of the birefringence. An. , induced by poiarized white ii in a copolymer film (KWI9,22 pm) without filters (/) or through grey filters of different optical density (2-f) (B) the An value Induced for 10 min, versus the light intensity. 

Differential spectrophotometry [22,23] consists in the measurement of the absorbance of a solution of the given element, not with reference to the solvent used, but with reference to a solution of this element (in the form of a coloured complex) of known concentration, slightly lower than the concentration of the solution studied. In this technique, the measuring error is in proportion to the difference of concentrations (and not to the concentration of the analyte in the solution under test), which enables one to reduce the relative error. Grey filters of appropriate absorbance have been proposed as references [24]. 

Neutral density (ND), or grey , filters are uniform filters absorbing and/or reflecting a fraction of the intensity of an incident hght beam. The term neutral is used in the sense that the absorption/reflection characteristics of the filter are constant over a relatively wide range of wavelengths, as shown schematically in Figure 11.2. 

The data of individual measurements fluctuate irregularly around an effective value (random errors). These deviations are caused by the noise of the signal source. The absolute value of the noise, which depends on different experimental conditions, can be estimated from the deviations of the base line. In spectroscopy it is also possible to use the spectra of optical attenuators, e.g., of a sieve or a grey filter. Then the noise must be minimized by optimizing the on-line low-pass output filter of the apparatus or the gate filter of the derivative device. The dimension of the noise is given in [mm]. 

If double-beam spectrophotometers are used, a 10% Tor 1% T optical attenuator (hole sieve, grey filter, opalescent glass), or preferably the same optical arrangement (fiber optic cable, lenses, adapters, etc.) must be taken. 

Although it has been shown that high resolution can be reached with PCM, its feasibility in a process is still problematic. As in CEL, intermixing occurs at the interface of the bottom and top layers, but in the case of PCM this phenomenon is more severe. It not only hampers the development of the bottom resist, but it also acts as a grey filter during deep UV exposure in the areas which should be transparent to deep U V. Several improvements have been described recently. It was shown that the composition of the top resist has a considerable influence on the degree of intermixing On... 

Ffe. 2. 3 Scheme of basic configurations of a typical Raman experiment a 90° scattering geometry Iot macroscopic samples, b 180° scattering geometry Iot microscopic samples using an optical microscope. GF grey filters, IF interference filter, NF notch filter... 

Dissolve 0-5 g. of the substance in 10 ml. of 50 per cent, alcohol, add 0-5 g. of solid ammonium chloride and about 0 -5 g. of zinc powder. Heat the mixture to boiling, and allow the ensuing chemical reaction to proceed for 5 minutes. Filter from the excess of zinc powder, and teat the filtrate with Tollen s reagent Section 111,70, (i). An immediate black or grey precipitate or a silver mirror indicates the presence of a hydroxyl-amine formed by reduction of the nitro compound. Alternatively, the filtrate may be warmed with Fehling s solution, when cuprous oxide will be precipitated if a hydroxylamine is present. Make certain that the original compound does not aflfect the reagent used. 

The palladium - barium sulphate catalyst Is prepared by treating a suspension of20g. of barium sulphate (which has been precipitated in hot solution) in 400 ml. of hot water with a solution of I - 7 g. of palladium chloride (equivalent to I - 0 g. of palladium) in 50 ml. of water and with I - 5 ml. of 40 per cent, formaldehyde solution. The mixture is rendered faintly alkaline to litmus by the addition of sodium hydroxide solution and then boiled for a short time. When the supernatant liquid is clear, the grey precipitate is filtered oS, and wa.shed with hot water until the... 

The aniline and sulphuric acid are cautiously mixed in a round flask (250 c.c.) and heated to 180—190° in an oil or metal bath for four to five hours until a sample dissolved in water remains clear on the addition of caustic soda in excess and no aniline separates. The product is poured into cold water, which precipitates the sulphanilic acid as a grey ciystalline mass.It is filtered, washed with a little cold water, recrystallised from hot water with the addition of a little animal charcoal, and dried in the air. Yield, 25 — 30 grams. 

Sulphanilic add from water. Use 5 - 0 g. of crude (grey) sulphanilic acid and proceed as in 2. Add 1 g. of decolourising carbon to the solution at 70-80°, and continue the boiling for several minutes. If the filtered solution is not colomless, it must be boiled with a further 1 g. of decolourising carbon. Filter the cold solution at the pump, wash with a little cold water, dry and weigh the yield of recrystallised product. 

Figure 3. Distribution coefficient (Ka) versus particle concentration for Th. Note that, for typical open-ocean particle concentrations, Th is about lO times more likely to adhere to a mass of particles than to remain in the same mass of water. This tendency to be found in the particulate phase decreases with particle concentration, probably due to the presence of a larger number of colloids which, because they pass through filters, appear to be in the dissolved phase (Honeyman et al. 1988). Grey squares are " Th data from Honeyman et al. (1988) gray triangles are " Th data from the continental shelf from McKee et al. (1986) and black circles are a compilation of open ocean °Th data from Henderson et al. (1999a).

Figure 10.2 Adsorbed sulfur structures on Cu(lll). (a) Model of the (x/7 x x/7) R19° phase showing the Cu4S tetramers large grey circles are added coppers, smaller circles represent S. (b) Filtered 50 x 50 nm STM image of coexisting ( /l x y 7) R19° and complex structures, (c) 5 x 5nm STM image of domain boundary between the two phases. (Reproduced from Refs. 6 and 7).

Figure 27 Edited broadband HMBC spectrum of cyclosporine using the pulse sequences shown in Figure 26 in an interleaved manner. The two subspectra, CH + CH3 (left) and C + CH2 (right), exemplify the editing properties. The spectrum in the bottom displays the two subspectra, CH + CH3 (black) and C + CH2 (grey) in the same frame. The number of scans was 32 for each of the 128fi increments, the relaxation delay was 1 s, and the range for the third-order low-pass. /-filter was 115 Hz < Vch < 165 Hz. The spectra were processed to maintain the absorptive profiles in F, while a magnitude mode was done in F2.

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