Sodium emission

Sodium lamps glow pink before orange because of the neon they hold, which kick starts the sodium emission process. 

In this case, sodium emission is monitored at a wavelength of 589.6 nm and potassium at a wavelength of 769.9 nm. The intensity of emission is calibrated with appropriate standards for the samples to be analyzed. In this way it is possible to automatically determine 100 values of sodium and potassium for 100 samples/h using modern clinical instruments. Limits of detection are sub-ppm and for serum values 140 mg/m the range of reproducibility is on the order of 2-3%. 

The ability to produce monochromatic radiation is a very desirable feature of photometric instruments because the Beer-Lambert relationship is only strictly true for monochromatic radiation. A good spectrophotometer may provide radiation of a specified wavelength with a range or bandwidth of as little as 0.1 nm, but it can be appreciated that even this is still not monochromatic when it is considered that the bandwidth of the sodium emission line is about 1 X 10-5 nm. This fact provides one of the major problems in the design of photometric instrumentation, namely the production of so-called monochromatic radiation. 

An intense emission line at 5900 A was believed to be the unresolved sodium doublet (5890 and 58% A). The appearance of sodium emission spectra is probably related to the presence of this element in the glass bottom. 

The ratio of number of sodium atoms in 3p excited states to the number in the ground state at 2500 K calculated. The average wavelength of the two sodium emission lines involving the 3p to 3s transition is 5892 A ... 

The effect of potassium. Take five replicate emission readings of each of the six potassium standards. Remember to zero the instrument between each standard while aspirating a blank. Calculate the mean emission and RSD for each standard and plot a graph of sodium emission intensity against potassium concentration. The RSD is defined as standard deviation (s) of the emission intensities divided by the mean emission intensity (jf)[RSD = (s/x) x 100]. 

An amazing variety of glass apparatus can be constructed by using simply a torch and low-pressure natural gas and oxygen supplies. Also, a pair of didym-ium-tinted glasses is a necessity to eliminate the yellow glare of sodium emission which occurs when borosilicate glass is heated. 

A kinetic analysis of the results, based on (17) and its O+OH analog, is in satisfactory agreement with observations on a wide variety of flames. These flames are relatively cool, and the concentrations of H and OH exceed their equilibrium values even in the burned gases, so that the observed sodium emission is definitely chemiluminescent. The third order rate coefficients for excitation by H+H and H+OH are estimated to be 8 x 109 and 2x 1010 l2.mole-2.sec-1, corresponding to an efficiency near unity per triple collision. The possible importance of mechanisms of the type (14,15) has not been carefully studied. 

Procedure Concomitantly determine the absorbance values of the Test Solutions at the sodium emission line at 589.0 nm with a suitable atomic absorption spectrophotometer equipped with an air-acetylene flame, using water as the blank. Plot the absorbance values of the Test Solutions versus... 

Procedure Use a suitable atomic absorption spectrophotometer equipped with a sodium hollow-cathode lamp and an oxidizing air-acetylene flame. After using the Blank Solution to zero the instrument, concomitantly determine the absorbances of the Standard Solutions and the Test Solution at the sodium emission line of 589 nm. Plot the absorbances of the Standard Solutions versus concentration, in micrograms per milliliter, of sodium, and draw the straight line that best fits the plotted points. From the graph so obtained, determine the concentration, C, in micrograms per milliliter, of sodium in the Test Solution. Calculate the percentage of sodium in the portion of potassium lactate taken by the formula... 

The reactions, which cause the thennal decon osition of black liquor, are varied. Several mechamstns can be found in literature, most of then are centered in sodium emissions from black liquor during their pyrolysis and gasification [6]. Some of them are the following ... 

Problem 5.11 Interpret the diagram below regarding the D lines of the sodium emission spectrum. 

Figure 28-1 Origin of three sodium emission lines.

The intensity of sodium emission in a flame at 589.0 run is compared with that of standards. If an internal standard instrument is available, the ratio of sodium to lithium emission is measured. 

The interfering effect of cross sensitivity which occurs in the presence of alkaline earths, particularly calcium, can be suppressed by adding aluminium nitrate. Sparingly volatile alkaline-earth-aluminium compounds are formed which no longer influence the intensity of sodium emission. (See Chapter 2, Flame Emission). 

Cations are simply identified by acidifying the water extract of the sample with hydrochloric acid and conducting a flame test with a platinum wire loop. The lavender color of potassium is best observed through cobalt blue glass, which filters out the yellow sodium emission. High levels of strontium will also be seen through the cobalt glass but, because of its... 

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