Common Etchants for Copper, Nickel and Cobalt: Copper & Alloys

Composition	Comments
2 5 mL NH4OH 25 mL water (optional) 25-50 mL H2O2 (3%)	General purpose grain contrasts etch for Cu and alloys (produces a flat etch for some alloys). Use fresh, add peroxide last. Use under a hood. Swab specimen 5-45 seconds.
100 mL water 10 g ammonium persulfate orientation.	General purposes etch for Cu and alloys. Immerse or swab for 3-60 seconds. Reveals grain boundaries but is sensitive to crystallographic
100 mL water 3g ammonium persulfate 1mL NH4OH	General purpose etch for Cu and alloys, particularly Cu-Be alloys.
70 mL water 5 g Fe(NO3)3 25 mL HCI	Excellent general purpose etch, reveals grain boundaries well. Immerse specimen 10-30 seconds

Common Etchants for Iron and Steel

Composition	Comments
90-99 mL methanol or ethanol 1-10 mL HNO3	Nital. Most common etchant for Fe, carbon and alloy steels, cast iron. Reveals alpha grain boundaries and constituents. Excellent for martensitic structures. The 2% solution is most common, 5-10% used for high alloy steels (do not store). Use by immersion or swabbing of sample for up to bout 60 seconds.
1 00 mL ethanol 4 g picric acid	Picral. Recommended for structures consisting of ferrite and carbide. Does not reveal ferrite grain boundaries. Addition of about 0.5-1% zephiran chloride improves etch rate and uniformity.
100 mL ethanol 5 mL HCI 1 g picric acid	Vilella’s reagent. Good for ferrite-carbide structures. Produces grain contrast for estimating prior austenite grain size. Results best on martensite tempered at 572-932 °F (300-500 °C). Occasionally reveals prior-austenite grain boundaries in high alloy steels. Outlines constituents in stainless steels. Good for tool steels and martensitic stainless steels.
Saturated aqueous picric acid solution grain plus small amount of a wetting agent	Bechet and Beaujard’s etch, Most successful etchant for prior-austenite boundaries. Good for martensitic and bainitic steels. Many wetting agents have been used, sodium tridecylbenzene sulfonate is one of most successful (the dodecyl version is easier to obtain and works as well). Use at 20-100 °C. Swab or immerse sample for 2-60 minutes. Etch in ultrasonic cleaner Additions of 0.5g CuCl2 per 100mL solution or about 1% HCI have been used for higher alloy steels to produce etching. Room temperature etching most common. Lightly back polish to remove surface smut.
150 mL water 50 mL HCI 25 mL HNO3 1 g CuCl2	Modified Fry’s reagent. Used for 18% Ni maraging steels, martensitic and PH stainless steels.
1 00 mL water 25 g NaOH 2 g picric acid	Alkaline sodium picrate. Best etch for McQuaid-Ehn carburized samples. Darkens cementite. Use boiling for 1-15 minutes or electrolytic at 6 V dc, 0.5 A/in2, 30-120 seconds. May reveal prior-austenite grain boundaries in high carbon steels when no apparent grain boundary film is present.
1 00 mL ethanol 100 mL HCI 5 g CuCl2	Kalling’s no. 2 (“waterless” Kalling’s) Etch for austenitic and duplex stainless steels. Ferrite attacked readily, carbides unattacked, austenite slightly attacked. Use at 20 °C by immersion or swabbing. Can be stored.
1 5 mL HCI 10 mL acetic acid 5 mL HNO3 2 drops glycerol	Acetic glyceregia. Mix fresh; do not store. Use for high alloy stainless steels.
100 mL water 10 g K2Fe(CN)6 10 g KOH or NaOH	Murakami’s reagent. Usually works better on ferritic stainless grades than on austenitic grades. Use at 20 °C for 7-60 seconds: reveals carbides sigma faintly attacked with etching up to 3 minutes. Use at 80°C (176°F) to boiling for 2-60 minutes: carbides dark, sigma blue (not always attacked), ferrite yellow to yellow-brown, austenite unattacked. Do not always get uniform etching.
100 mL water 1 0 g oxalic acid	Use for stainless steels at 6 V dc. Carbides revealed by etching for 15-30 seconds, grain boundaries after 45-60 seconds, sigma outlined after 6 seconds. 1-3 V also used. Dissolves carbides, sigma strongly attacked, austenite moderately attacked, ferrite unattacked.
100 mL water 20 g NaOH	Used to color ferrite in martensitic, PH or dual-phase stainless steels. Use at 3-5 V dc, 20°C, 5 seconds, stainless steel cathode. Ferrite outlined and colored tan.
40 mL water 60 mL HNO3	Electrolytic etch to reveal austenite boundaries but not twin boundaries in austenitic stainless steels (304, 316, etc.). Voltage is critical. Pt cathode preferred to stainless steel. Use at 1.4 V dc, 2 minutes.

Commonly Used Etchants for Magnesium and Alloys

Composition	Comments
25 mL water 75 mL 3-5 ethylene glycol 1 mL HNO3	Glycol etch, general purpose etch for pure Mg and alloys. Swab specimen seconds for F and T6 temper alloys, 1-2 minutes for T4 and 0 temper alloys.
19 mL water 60 mL ethylene glycol 20 mL acetic acid 1 mL HNO3	Acetic glycol etchant for pure Mg and alloys. Swab specimen 1-3 seconds for F and T6 temper alloys, 10 seconds for T4 and 0 temper alloys. Reveals grain boundaries in solution-treated castings and most wrought alloys.
100 mL ethanol 10 mL water 5 g picric acid	For Mg and alloys. Use fresh. Immerse specimen for 15-30 seconds. Produces grain contrast.

Commonly Used Etchants for Aluminum and Alloys

Composition	Comments
95 mL water 2.5 mL HNO3 1.5 mL HCI 1.0 mL HF	Keller’s reagent, very popular general purpose reagent for Al and Al alloys, except high-Si alloys. Immerse sample 10-20 seconds, wash in warm water. Can follow with a dip in conc. HNO3. Outlines all common constituents, reveals grain structure in certain alloys when used by immersion.
90-100 mL water 0.1-10 mL HF	General-purpose reagent. Attacks FeAl3, other constituents outlined. The 0.5% concentration of HF is very popular.
84 mL water 15.5 mL HNO3 0.5 mL HF 3g CrO3	Graff and Sargent’s etchant, for grain size of 2XXX, 3XXX, 6XXX, and 7XXX wrought alloys. Immerse specimen 20-60 seconds with mild agitation.
1.8% fluoboric acid in water	Barker’s anodizing method for grain structure. Use 0.5-1.5 A/in2, 30-45 V dc. For most alloys and tempers, 20 seconds at 1 A/in2 and 30 V dc at 20 °C is sufficient. Stirring not needed. Rinse in warm water, dry. Use polarized light; sensitive tint helpful.

Hints For Etching

Many etchants can be used by swabbing or by immersion. Swabbing is preferred for those specimens that form a tight protective oxide on the surface in air, such as Al, Ni, Cr, stainless steels, Nb (Cb), Ti and Zr. However, if the etchant forms a film, as in tint etchants, then immersion must be used as swabbing will keep the film from forming. Keller’s reagent reveals the grain size of certain aluminum alloys by forming a film. This will not occur if the etch is used by swabbing. Many etchants, and their ingredients, do present potential health hazards to the user. ASTM E 2014, Standard Guide on Metallography Laboratory Safety, describes many of the common problems and how to avoid them.

Etching Procedures

Microscopic examination is usually limited to a maximum magnification of 1000X — the approximate useful limit of the light microscope, unless oil immersion objectives are used. Many image analysis systems use relay lenses that yield higher screen magnifications that may make detection of fine structures easier. However, resolution is not improved beyond the limit of 0.2-0.3-um for the light microscope. Microscopic examination of a properly prepared specimen will clearly reveal structural characteristics such as grain size, segregation, and the shape, size, and distribution of the phases and inclusions that are present. Examination of the microstructure will reveal prior mechanical and thermal treatments give the metal. Many of these microstructural features are measured either according to established image analysis procedures, e.g., ASTM standards, or internally developed methods.

Etching is done by immersion or by swabbing (or electrolytically) with a suitable chemical solution that essentially produces selective corrosion. Swabbing is preferred for those metals and alloys that form a tenacious oxide surface layer with atmospheric exposure such as stainless steels, aluminum, nickel, niobium, and titanium and their alloys. It is best to use surgical grade cotton that will not scratch the polished surface. Etch time varies with etch strength and can only be determined by experience. In general, for high magnification examination the etch depth should be shallow; while for low magnification examination a deeper etch yields better image contrast. Some etchants produce selective results in that only one phase will be attacked or colored. Etchants that reveal grain boundaries are very important for successful determination of the grain size. A vast number of common etchants have been developed and it is displayed in Table 1 after this section.

ETCHING

Metallographic etching encompasses all processes used to reveal particular structural characteristics of a metal that are not evident in the as-polished condition. Examination of a properly polished specimen before etching may reveal structural aspects such as porosity, cracks, and nonmetallic inclusions. Indeed, certain constituents are best measured by image analysis without etching, because etching will reveal additional, unwanted detail and make detection difficult or impossible. The classic examples are the measurement of inclusions in steels and graphite in cast iron. Of course, inclusions are present in all metals, not just steels. Many intermetallic precipitates and nitrides can be measured effectively in the as-polished condition.

In certain nonferrous alloys that have non-cubic crystallographic structures (such as beryllium, hafnium, magnesium, titanium, uranium and zirconium), grain size can be revealed adequately in the as polished condition using polarized light. Figure (1) shows the microstructure of cold-drawn zirconium viewed in cross-polarized light. This produces grain coloration, rather than a “flat etched” appearance where only the grain boundaries are dark.

Figure 1: Mechanical twins at the surface of hot worked and cold drawn high-purity zirconium viewed with polarized light (200X).

DETERMINATION OF CALCIUM, IRON, MAGNESIUM, MANGANESE, POTASSIUM, AND SODIUM by AAS

Reagents and Equipment

1. Lanthanum solution: Transfer 140 g of lanthanum oxide (La₂O₃, 99.997 percent pure) into a 2-L beaker. Slowly add 300 mL of concentrated hydrochloric acid, allowing time for the reaction to be completed after each addition of acid. Then, add 200 mL of distilled water. Each 4 mL of the final solution contains approximately 1 g of lanthanum.

2. Manganese stock solution: Transfer 0.3872 g of pure manganese metal into a glass beaker, add 20 mL of hot 8 M nitric acid, and gently boil the nitric acid for several minutes. After the resulting solution has cooled to room temperature, transfer the solution to a 500-mL volumetric flask and dilute to volume with distilled water. The concentration of MnO in this solution is 1,000 m g/mL.

3. Stock multiple-element standard solution: Transfer 0.8924 g of CaCO₃, 0.9435 g of NaCl, 0.7915 g of KCl. and 2.4556 of FeSO₄(NH₄)₂SO_4· 6H₂O, (all reagent-grade purity) and 0.3045 g of magnesium ribbon to a 500-mL volumetric flask. (Magnesium ribbon generally is 99 percent magnesium; therefore, the weight of the ribbon includes a 1-percent correction.) Add 50 mL of distilled water and 10 mL of concentrated hydrochloric acid. Boil the dilute acid to dissolve all the constituents. After the solution cools to room temperature, add 50.0 mL of the manganese stock solution (1,000 m g/mL of MnO), dilute to volume with distilled water, and thoroughly mix the final solution. This solution contains the equivalent of 1.00 mg/mL each of Fe₂O₃, CaO, MgO, Na₂O, and K₂O, and 0.1 mg/mL of MnO.

4. Working standard solutions: To six 250-mL volumetric flasks, add 0, 6, 12, 18, 24, and 30 mL of the standard stock solution. Then, add 1.2 g of flux mixture, 5 mL of 8 M nitric acid, and approximately 200 mL of distilled water. Agitate the nitric acid solution to dissolve the flux mixture. Then, add distilled water to make the final volume 250 mL and make the solution homogeneous by vigorous mixing. These six solutions represent a blank and 3-, 6-, 9-, 12-, and 15-percent (equivalent in the sample) standard solutions. For MnO, the same six solutions represent a blank and 0.3-, 0.6-, 0.9-, 1.2-, and 1.5-percent standard solutions.

Procedure for Calcium, Iron, Magnesium, and Manganese

1. Transfer 0.750 mL of blank, sample, and standard solutions into small vials or beakers.

2. Dilute 8 mL of lanthanum solution with 200 mL of distilled water. Add 6.5 mL of this solution to all standards, samples, and blanks.

3. Calibrate the atomic absorption spectrometer by setting the concentration scale to zero for the recommended wavelength (table 16) while the blank solution is nebulized into the flame. Then, set the concentration scale with the 6-percent working standard, and verify this setting with solutions of silicate standards. Directly measure the concentrations of calcium, iron, magnesium, and manganese in each of the samples. Most available atomic absorption spectrometers are suitable for these measurements; the optimum operating conditions for each element usually are discussed in the manual provided with the spectrometer. Importantly, the individual measurements of concentration (or, absorbance) for a sample should be "bracketed" between those of standards because the instrumental responses are usually not linear.

Procedure for Potassium and Sodium

1. Transfer 0.200 mL of blank, sample solutions, working standards, and silicate standards into a small vial or beaker.

2. Dilute 1.2 mL of lanthanum solution with 200 mL of distilled water. Add 5.0 mL of this solution to the blank and to each of the standards and samples.

3. Calibrate the atomic absorption spectrometer using the concentration mode with the 6-percent working standard, and check appropriate silicate standards for known values. Measure directly the concentration of samples.

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CONCLUSIONS

Methods based on AAS and spectrophotometry provide accurate determinations of 10 inorganic elements in coal ash. Although not as rapid as X-ray fluorescence (XRF) spectrometry, these methods furnish an approach to determining major oxides in coal ash that is both inexpensive and accurate (table 18). The agreement between our measurements and the NBS-certified concentrations for10 elements in NBS 1633a coal fly ash, demonstrated by data in table 18, is quite acceptable. Results from XRF spectrometry for SiO₂, Al₂O₃, and Fe₂O₃ in ash sample number 1 and for SiO₂ in sample number 7 (table 18) are outside the range covered by the standards used for calibration. Thus, extrapolations beyond this range could introduce error into these determinations.

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REFERENCES

Bunting, W.E., 1944, The determination of soluble silica in very low concentrations: Industrial and Engineering Chemistry (analytical ed.), v. 16, p. 612-615.

Parker, C.A., and Goddard, A.P., 1950, The reaction of aluminum ions with alizarin-3-sulfonate, with particular reference to the effect of calcium ions: Analytica Chimica Acta, v. 4, no. 5, p. 517-536.

Shapiro, L., 1975, Rapid analysis of silicate, carbonate, and phosphate rocks: U.S. Geological Survey Bulletin 1401, revised ed., 76 p.

Yoe, J.H., and Armstrong, A.R., 1947, Colorimetric determination of titanium with disodium-1,2-dihydroxybenzene-3,5-disulfonate: Analytical Chemistry, v. 19, p. 100-102.

Sodium (Na+): Perkin Elmer AAnalyst 100 Atomic Absorption Spectrometer

I) Principle

The ground state sodium atom absorbs light energy at 589.0 nm as it enters the excited state. As the number of sodium atoms in the light path increases, the amount of light absorbed also increases. By measuring the amount of light absorbed, a quantitative determination of the amount of sodium present can be made. 0.5 % lanthanum solution is added to each standard, control and sample to prevent chemical and ionization interference.

II) Preparation of Stock Standard

In a 1000 mL volumetric flask, dissolve 2.5420 g sodium chloride (NaCl) to the mark with deionized water. This standard stock solution is 1000 mg Na⁺/L.

III) Preparation of Reagents

0.5 % Lanthanum Solution

In a 1000 mL volumetric flask, dissolve 13.37 g lanthanum chloride (LaCl₃.7H₂O) to the mark with deionized water.

IV) Analysis Procedure

A) Spike each standard, control and sample 9:10 with 0.5 % Lanthanum Solution (1 part 0.5 % Lanthanum Solution and 9 parts standard, control or sample).

B) Install Na-K hollow cathode lamp. Perkin-Elmer part #N305-0204.

C) Ensure that the correct Default Conditions are entered.

1) Recall Method=2

2) Lamp Current=12

3) Slit=0.2

4) Full Height=Y(Yes)

5) Wavelength(nm)=589.0

6) Int. Time=5.0

7) Replicates=5

8) Cal=1(Nonlinear)

9) Cal=1(Hold)

10) STD1-----

11) Read Delay(sec)=3

D) Use an oxidizing (lean, blue) air-acetylene flame.

E) Calibrate with standards that bracket the sample concentration. Check the calibration curve for drift, accuracy and precision with standards and controls every 20 samples. Correlation coefficient should be greater than or equal to 0.990.

Manganese (Mn): Perkin Elmer AAnalyst 100 Atomic Absorption Spectrometer

I) Principle

The ground state manganese atom absorbs light energy at 279.5 nm as it enters the excited state.  As the number of manganese atoms in the light path increases, the amount of light absorbed also increases.  By measuring the amount of light absorbed, a quantitative determination of the amount of magnesium present can be made.  0.5 % lanthanum solution is added to each standard and sample to prevent chemical and ionization interference.

 

II) Preparation of Stock Standard

 

Stock standard of 1000 mg Mn/L is purchased commercially.  Discard on expiration date.

 

III) Preparation of Reagents

 

0.5 % Lanthanum Solution

In a 1000-mL volumetric flask, dissolve 13.37 g lanthanum chloride (LaCl₃.7H₂O) to the mark with deionized water.

 

IV) Analysis Procedure

 

A) Dilute each standard and sample 9:10 with 0.5 % Lanthanum Solution (1 part 0.5 % Lanthanum Solution and 9 parts standard or sample).

B) Install a Mn hollow cathode lamp.

C) Ensure that the correct Default Conditions are entered.

1) Recall Method=5

2) Lamp Current=20

3) Slit=0.2

4) Full Height=Y(Yes)

5) Wavelength(nm)=279.5

6) Int. Time=5.0

7) Replicates=5

8) Cal=1(Nonlinear)

9) Cal=1(Hold)

10) STD1____

11) Read Delay(sec)=3

 

D) Use an oxidizing (lean, blue)air-acetylene flame.

E) Calibrate with standards that bracket the sample concentration.  Correlation coefficient should be greater than or equal to 0.990.  Check the calibration curve for drift, accuracy and precision with standards and controls every 20 samples.

Perkin Elmer AAnalyst 100 Atomic Absorption Spectrometer: Operating Procedure

I) Principle

The Perkin Elmer AAnalyst 100 system consists of a high efficiency burner system with a Universal GemTip nebulizer and an atomic absorption spectrometer.  The burner system provides the thermal energy necessary to dissociate the chemical compounds, providing free analyte atoms so that atomic absorption occurs.  The spectrometer measures the amount of light absorbed at a specific wavelength using a hollow cathode lamp as the primary light source, a monochromator and a detector.  A deuterium arc lamp corrects for background absorbance caused by non-atomic species in the atom cloud.

II) Instrument Setup

A) Empty waste container to mark.  Add deionized water to drain tubing to ensure that water is present in the drain system float assembly.

B) Drain moisture from air compressor.

1) Unplug compressor.

 

2) Reduce compressor pressure to nearly zero by opening the pressure release valve and the drain plug located at the bottom of the tank.

 

3) Close pressure release valve and drain plug.

 

4) Plug in compressor to restart the motor.

C) Install the appropriate Hollow Cathode Lamp for the analyte to be analyzed.

D) Power AAnalyst 100 and printer ON.

E) Ensure that instrument is in AA mode.

F) Recall Method to be analyzed.

G) Ensure that the correct Default Conditions are entered.

H) Align the Hollow Cathode Lamp.

1) Press Energy.

 

2) Press Energy a second time if the bar needs to be brought on scale.

 

3) Adjust the vertical and horizontal lamp adjustment screws to obtain maximum energy.

 

I) Store Method changes in Parameter Entry, Option, Store and #.

 

J) Adjust Burner height.

 

1) Place a white sheet of paper behind the burner to confirm the location of the light beam.

 

2) Lower the burner head below the light beam with the vertical adjustment knob.

 

3) Press Cont (Continuous) to display an absorbance value.

 

4) Press A/Z to Autozero.

 

5) Raise the burner head with the vertical adjustment knob until the display indicates a slight absorbance (0.002).  Slowly lower the head until the display returns to zero. Lower the head an additional quarter turn to complete the adjustment.

 

K) Ignite flame.

 

1) Turn Fume Hood switch ON.

 

2) Open air compressor valve. Set pressure to 50 to 65 psi.

 

3) Open acetylene gas cylinder valve. Set output pressure to 12 to 14 psi.  Replace cylinder when pressure falls to 85 psi to prevent valve and tubing damage from the presence of acetone.

 

4) Press Gases On/Off. Adjust oxidant flow to 4 Units.

 

5) Press Gases On/Off. Adjust acetylene gas flow to 2 Units.

 

6) Press Flame On/Off to turn flame on.

Note: Do not directly view the lamp or flame without protective ultraviolet radiation eyewear.

 

L) Aspirate deionized water through the burner head several minutes.

 

M) Adjust Burner Position and Nebulizer.

 

1) Aspirate a standard with a signal of approximately 0.2 absorbance units.

 

2) Obtain maximum burner position absorbance by rotating the horizontal and rotational adjustment knobs.

 

3) Loosen the nebulizer locking ring by turning it clockwise.  Slowly turn the nebulizer adjustment knob to obtain maximum absorbance. Lock the knob in place with the locking ring.

Note: An element, such as Magnesium, which is at a wavelength where gases do not absorb is optimal for adjusting the Burner and Nebulizer.

 

N) Allow 30 minutes to warm-up flame and lamp.

III) Calibration Procedure

A) Calibrate with standards that bracket the sample concentrations.

 

B) Enter ------ for Std1 in the Default Conditions to obtain absorbance units for each standard.  Construct a data regression curve on a computer spreadsheet. Use standard concentrations as the X axis and absorbances as the Y axis.

 

C) Enter Standard Concentration Values in the Default Conditions to calculate an AAnalyst 100 standard curve.

 

1) Enter the concentration of the lowest standard for STD1 using significant digits.

 

2) Enter the concentrations of the other standards of the calibration curve in ascending order and the concentration of the reslope standard.

 

3) Autozero with the blank before each standard.

 

4) Aspirate Standard 1, press 0 Calibrate to clear the previous curve. Aspirate the standards in numerical order.

Press standard number and calibrate for each standard.

 

5) Press Print to print the graph and correlation coefficient.

 

6) Rerun one or all standards, if necessary.  To rerun Standard 3, aspirate standard and press 3 Calibrate.

 

7) Reslope the standard curve by pressing Reslope after aspirating the designated reslope standard.

 

D) The correlation coefficient should be greater than or equal to 0.990.

 

E) Check the calibration curve for drift, accuracy and precision with standards and controls every 20 samples.

 

IV) Analysis Procedure

 

A) Autozero with the blank before and after each standard, control and sample.

 

B) Aspirate sample and press Read. Wait until Read light goes out.  Record absorbance or concentration value.  Record the five replicate standard deviation.  Rerun the sample if the standard deviation is greater than 10% of the sample result.

 

V) Instrument Shutdown

 

A) Aspirate 5 % concentrated hydrochloric acid (HCl) for 5 minutes and deionized water for 10 minutes to clean the burner head.  Remove the capillary tube from the water.

 

B) Press Flame On/Off to turn off flame.

 

C) Close air compressor valve.

 

D) Close acetylene cylinder valve.

 

E) Press Gases On/Off three times to bleed the acetylene gas from the lines.  The cylinder pressure should drop to zero.

 

F) Power OFF the AAnalyst 100, the printer and the fume hood.

 

Magnesium (Mg 2+): Perkin Elmer AAnalyst 100 Atomic Absorption Spectrometer

I) Principle

The ground state magnesium atom absorbs light energy at 285.2 nm as it enters the excited state.  As the number of magnesium atoms in the light path increases, the amount of light absorbed also increases.  By measuring the amount of light absorbed, a quantitative determination of the amount of magnesium present can be made.  0.5 % lanthanum solution is added to each standard and sample to prevent chemical and ionization interference.

 

II) Preparation of Stock Standard

In a 1000-mL volumetric flask, dissolve 8.3632 g magnesium chloride (MgCl₂.6H₂O) to the mark with deionized water. This standard stock solution is

1000 mg Mg²⁺/L.

 

III) Preparation of Reagents

0.5 % Lanthanum Solution

In a 1000-mL volumetric flask, dissolve 13.37 g lanthanum chloride (LaCl₃.7H₂O) to the mark with deionized water.

 

IV) Analysis Procedure

A) Dilute each standard and sample 9:10 with 0.5 % Lanthanum Solution (1 part 0.5 % Lanthanum Solution and 9 parts standard or sample).

B) Install a Ca-Mg hollow cathode lamp. Perkin-Elmer part #N305-0202.

C) Ensure that the correct Default Conditions are entered.

1) Recall Method=4

2) Lamp Current=15

3) Slit=0.7

4) Full Height=Y(Yes)

5) Wavelength(nm)=285.2

6) Int. Time=5.0

7) Replicates=5

8) Cal=1(Nonlinear)

9) Cal=1(Hold)

10) STD1____

11) Read Delay(sec)=3

D) Use an oxidizing (lean, blue)air-acetylene flame.

E) Calibrate with standards that bracket the sample concentration.  Correlation coefficient should be greater than or equal to 0.990.  Check the calibration curve for drift, accuracy and precision with standards and controls every 20 samples.