- 01: Introduction
- 02: History
- 03: Propellants, Firearms, and Ammunition Development
- 04: Modern Firearms Manufacture
- 05: Small Arms Ammunition
- 06: Evidence Handling Procedures
- 07: Equipment and Instrumentation
- 08: Examination of Firearms
- 09: Cartridge and Shotshell Examination
- 10: Characterization and Evaluation of Fired Projectiles
- 11: Bullet Comparison and Identification
- 12: Gunshot Residue and Distance Determination
- Introduction
- Objectives
- AFTE Knowledge and Ability Factors
- Powders and Residues
- Examination
- Distance Determination
- Significance of Results
- Contact Shot
- Nitrite Residues
- Vaporous Lead Residues
- Residues Consistent with the Passage of a Bullet
- Residues Consistent with the Discharge of a Firearm
- Interpretation Challenges
- Reproduction of Results
- Nitrite Residue Patterns
- Shot Patterning
- Chemical Testing
- Shot Pattern Reproduction
- Selected Bibliography
- 13: Toolmark Identification
- 14: Communicating Results
- Resources
Reagents and Test Media
Home > Gunshot Residue and Distance Determination > Examination > Chemical Testing > Reagents and Test Media
The following reagents and test media are required for the Modified Griess Test:
- Nitrite sensitive emulsion-coated test paper
- Nitrite test swabs (nitrite compound positive control samples)
- Solution of glacial acetic acid (15%) and distilled or deionized water
- Nitrite compound-free cheesecloth
Nitrite Sensitive Emulsion-Coated Test Paper
Desensitized photographic paper or photographic printer paper can be used as a medium for capturing the azo dye pigment patterns generated during the Modified Griess Test.
The test paper preparation procedure is as follows:
- Prepare a solution of 7.7 grains (.5 grams) of sulfanilic acid in 100 mL of distilled or deionized water.
- Prepare a solution of 4.3 grains (.28 grams) of alpha-naphthol in 100 mL of methanol.
- Combine equal volumes of the above solutions.
- Pour the combined solutions into a nonreactive photo processing tray. Briefly submerge and remove precut sheets of the test paper into the tray.
- Set the sheets aside to dry on an uncontaminated surface or hang to dry.
- Store any unused solution in a sealed container labeled according to laboratory protocol.
- Store dried test paper in a dry place.
Nitrite Test Swabs
- Prepare a solution of 9.3 grains (0.6 grams) of sodium nitrite in 100 mL of distilled or deionized water.
- Soak cotton tipped swabs in the nitrite solution.
- Set the swabs aside to dry.
- Store swabs in a sealed container labeled according to laboratory protocol.
Glacial Acetic Acid
- Combine 150 mL of glacial acetic acid with 850 mL of distilled or deionized water.
- Store the solution in a sealed container labeled according to laboratory protocol.
Cheesecloth
Cut nitrite-free cheesecloth to the size of the processed test paper. (If the cheesecloth contains nitrites, it may produce an orange background color on the processed test paper.)
