Flames, adjustment

Light the test flame, adjusting it to the size of the small bead on the cover. Operate the mechanism on the cover in such a manner as to introduce the test flame into the vapor space of the cup, and immediately bring it up again. The time consumed for the full operation shall be about 1 sec, or the time required to pronounce distinctly the words "thousand and one . Avoid any jerkiness in the operation of depressing and raising the test flame... 

Procedure Use an atomic absorption spectrophotometer equipped with a 4-in., single-slot burner head. Set the instrument to previously determined optimum conditions for organic solvent aspiration (3 to 5 mL/min) and at a wavelength of 283.3 nm Use an air-acetylene flame adjusted for maximum lead absorption with a fuel-lean flame. Aspirate the blanks, the Standard Solutions, and the Sample Solution, flushing with water and then with Aqueous Butyl Acetate between... 

Gradually increase gas flow and ignite the flame. Adjust the air/gas mix to give a quiet, hot flame. 

The tube and tool are turned as before till the end is slightly opened out. There is no time to lose as the glass quickly sets hard. The tube should now be shaped as in Fig. 6.12b. Uniform heating is essential for this operation and much practice will be required. Soda glass must always be pre-heated in a flame with very little ah flowing, or the tube may crack and be spoiled. The air-flow can then be increased and the flame adjusted to melt the glass. 

A constriction is now made at each shoulder as shown in Fig. 6.40b. These constrictions must be reasonably thick and strong-the virtues of substantial points will now be apparent. All the glass between these constrictions is now heated in a flame adjusted so that it is just hot enough to gather the glass. The hulb is now blown up with steady, continued rotation and carefully modulated pressure. The tubes are now joined to the constrictions without disturbing the bulb. 

Place the rubber stopper equipped with the zinc dosing tube and the argon supply hose into an empty 500-ml Erlenmeyer flask (see Figure 5.1), and ignite the hydrogen-argon entrained air flame. Adjust the baseline and zero the instrument. 

To start the operation, Fg is passed through the entire apparatus until a gas flame or, better, an oil-soaked piece of fabric can be ignited by the exit gases. Then the burner is quickly unscrewed and the CO stream ignited. The burner is replaced in the reactor with its flame adjusted to a small size so that the CO continues to bum in the fluorine stream. The CO and Fg streams are then controlled to give a constant excess of fluorine. A CO flow of 2.5 liters/hour per 10 amp. of current in the fluorine cell is optimum. 

When using organic solvents, the initial flame adjustment before aspirating the solvent should generally be very lean because the solvent must be burned as well as the fuel. If the flame is too rich in fuel, the solvent will not be completely burned and the flame will be very smoky. The proper flame condition can be adjusted with the solvent aspirating. Solvent should be aspirated between samples because the hot lean flame will tend to heat up the burner. 

The ignition source consists of a small premixed butane air flame adjusted to give a 40 mm height in the vertical orientation. Butane flows through a jet and draws air in via radical inlets, and the premixed fuel is burned at a 6 mm diameter nozzle. The flame may be positioned at the lower edge or on the face of the fabric in different test methods. 

Measured in MJ/m or Btu/ft, the Wobbe Index has an advantage over the calorific value of a gas (the heating value per unit volume or weight), which varies with the density of the gas. The Wobbe Index Is commonly specified in gas contracts as a guarantee of product quality. A customer usually requires a product whose Wobbe Index lies within a narrow range, since a burner will need adjustment to a different fuel air ratio if the fuel quality varies significantly. A sudden increase in heating value of the feed can cause a flame-out. 

The basin A is then gently heated by a small Bunsen flame, which should be carefully protected from side draughts by screens, so that the material in A receives a steady uniform supply of heat. The material vaporises, and the vapour passes up through the holes into the cold funnel C. Here it cools and condenses as fine crystals on the upper surface of the paper B and on the walls of C. When almost the whole of the material in A has vaporised, the heating is stopped and the pure sublimed material collected. In using such an apparatus, it is clearly necessary to adjust the supply of heat so that the crude material in A is being steadily vaporised, while the funnel C does not become more than luke warm. 

Diethylbarbituric acid. In a dry 250 ml. distilling flask, fitted with a thermometer reaching to within 3-4 cm. of the bottom and a condenser, place 51 g. of clean sodium and add 110 g. (140 ml.) of super-dr ethyl alcohol (Section 11,47,5). When all the sodium has reacted, introduce 20 g. of ethyl diethylmalonate and 7 0 g. of dry imea (dried at 60 for 4 hours). Heat the flask in an oil bath and slowly distil off the ethyl alcohol. As soon as the temperature of the liquid reaches 110-115°, adjust the flame beneath the bath so that the contents of the flask are maintained at this temperature for at least 4 hours. Allow the flask to cool somewhat, add 100 ml. of water and warm until the solid (veronal-sodium) dissolves. Pour the solution into a beaker, and add a further 100 ml. of water but containing 7 0 ml. of concentrated siilplmric acid this will hberate the veronal from the sodium derivative. The veronal usually crystallises out if it does not, add a few more drops of dilute sulphuric acid until the solution is acid to Congo red. Heat the contents of the beaker, with stirring and the addition of more water if necessary, until all the veronal dissolves at the boiling point. Allow the hot solution to cool, filter off the crystals of veronal and diy in the air. The yield is 12 g., m.p. 190°. 

The burner is mounted on an adjustable stage that allows the entire burner assembly to move horizontally and vertically. Horizontal adjustment is necessary to ensure that the flame is aligned with the instrument s optical path. Vertical adjustments are needed to adjust the height within the flame from which absorbance is... 

When the identity of the matrix interference is unknown, or when it is impossible to adjust the flame to eliminate the interference, then other means must be used to compensate for the background interference. Several methods have been developed to compensate for matrix interferences, and most atomic absorption spectrophotometers include one or more of these methods. 

Sensitivity Sensitivity in flame atomic emission is strongly influenced by the temperature of the excitation source and the composition of the sample matrix. Normally, sensitivity is optimized by aspirating a standard solution and adjusting the flame s composition and the height from which emission is monitored until the emission intensity is maximized. Chemical interferences, when present, decrease the sensitivity of the analysis. With plasma emission, sensitivity is less influenced by the sample matrix. In some cases, for example, a plasma calibration curve prepared using standards in a matrix of distilled water can be used for samples with more complex matrices. 

After the skimmer, the ions must be prepared for mass analysis, and electronic lenses in front of the analyzer are used to adjust ion velocities and flight paths. The skimmer can be considered to be the end of the interface region stretching from the end of the plasma flame. Some sort of light stop must be used to prevent emitted light from the plasma reaching the ion collector in the mass analyzer (Figure 14.2). 

In this case, the components are mixed, the pH adjusted to about 6.0 with sodium hydroxide, and the solution appHed to the textile via a pad-dry-cure treatment. The combination of urea and formaldehyde given off from the THPC further strengthens the polymer and causes a limited amount of cross-linking to the fabric. The Na2HP04 not only acts as a catalyst, but also as an additional buffer for the system. Other weak bases also have been found to be effective. The presence of urea in any flame-retardant finish tends to reduce the amount of formaldehyde released during finishing. 

The flame-space walls are stainless steel and are water cooled. No mechanical coke scraper is required. A water quench cools the cracked gas stream rapidly at the poiat of maximum acetyleae and this is followed by a secondary water quench. The primary quench poiat can be adjusted for variation ia throughput, to accommodate the depeadeace of acetyleae yield oa resideace time ia the flame space. 

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