Detection of Poison by Colour Tests

1.    Ammonium Molybdate Test

Procedure: Add Ammonium Molybdate and Nitric Acid to extract, observe for yellow crystalline precipitate on boiling.

Observation: Formation of yellow crystalline precipitate.

Result: Distinction from Arsenites and Phosphates.

2.    Cobalt Thiocyanate Test

Procedure: Dissolve 0.38 gram of ammonium thiocyanate in 25 ml water, and then slowly add 0.63 gram cobaltous acetate with stirring.

Observation: observe the colour

Result:

• PCP – blue
• Cocaine – blue

3.    Copper Sulphate – Pyridine Test

Procedure: Add 1 ml of extract to a dilute solution of Copper Sulphate with Pyridine and observe for a lilac-blue precipitate.

Observation: Formation of a lilac-blue precipitate.

Result: Presence of Cyanate.

4.    Dille – Koppayani Test

Procedure: Mix extract with Cobalt Acetate and Isopropylamine solutions, observe for purple or blue violet colour.

Observation: Appearance of purple or blue violet colour.

Result: Presence of Barbiturates.

5.    Duquenois Levine Test

Procedure:

• Step I- Small amount of suspected residue of extract is placed in a test tube and shaken with 2ml of duquenois reagent for one minute.
• Step II- 2 ml of Conc. Hydrochloric acid is added.
• Step III-Shaken and allowed to stand for 10 Minutes
• Step IV-Add 2ml chloroform if a color develops.

Observation: Violet

Result: Cannabis

6.    Ferric Chloride

Procedure: Dissolve 1.5 grams of ferric chloride in 29.0 milliliters of water.

Observation: Observe the colour

Results: 

• Acetaminophen – violet-purple
• GHB – red/brown

7.    Ferricyanide Test

Procedure: To 50 ml of filtered stomach contents or scene residue add 100ml of aqueous hydrochloric acid(2 mol/L) and 50ml of aqueous potassium ferricyanide solution (10 gm/l). To a further 50 ml of sample add 100 ml of hydrochloric acid and 50ml potassium ferrocyanide solution (10gm/l).

Observation: A deep blue precipitate with Potassium Ferricyanide indicates the presence of ferrous.

Result: Ferrous

8.    Fujiwara Test

Procedure: Dilute 1ml of sample with 2ml of Sodium Hydroxide solution

Observation:  Blue

Result: Cyanide

9.    FPN Test

Procedure: 5ml of ferric chloride solution. 45ml of 20% solution of perchloric acid and 50 ml of 50% solution of nitric acid is added to make a final solution.

Observation: Color Ranging from pink to red, orange, violet or blue

Result: Phenothiazines

10. Fuchsine Test

Procedure: Place 1 drop of Fuchsine reagent on a spot plate, add neutral extract solution, and observe for discharge of magenta colour.

Observation: Discharge of magenta colour.

Result: Presence of Sulphites.

11. Gerrard’s Test

Procedure: 1-2 ml of 2% Mercuric chloride solution in 50% of alcohol is added to a portion of residue of the extract.

Observation: Red

Result: Hyoscyamine

12. Gunzberg’s Test

Procedure: Evaporate Gunzberg’s reagent to dryness, add material to be tested, warm gently, and observe for purplish red colouration.

Observation: Formation of purplish red colouration.

Result: Presence of free Hydrochloric Acid.

13. Gutzeit Test

Procedure: Take 1 ml of solution into a Gutzeit apparatus. Add 2 pellets of pure Zinc metal and 5 ml of dilute Sulphuric Acid. Purify the evolved gas by passing over Lead Acetate paper and react with Mercuric Chloride test paper.

Observation: Yellow stain on the paper.

Result: Presence of Arsenic.

14. Liebermann’s Test

Procedure: Evaporate alkaline distillate to dryness, add Sodium Nitrite, then concentrated Sulphuric Acid, and observe for colour changes.

Observation: Colour changes indicating presence of specific compounds.

Result: Presence of specific compounds such as Phenol, Resorcinol, Alpha naphthol, Beta-naphthol, Cresols, and p-Amino-phenol.

15. Prussian Blue Test

Procedure: Mix extract with freshly prepared Ferrous Sulphate solution, add Hydrochloric acid, and observe for a blue colouration or precipitate.

Observation: Blue colouration or precipitate.

Result: Presence of Cyanide.

16. Mandelin’s Test

Procedure: Add Mandelin’s reagent to residue, observe for deep violet-blue or deep purple colour turning to yellow.

Observation: Appearance of deep violet-blue or deep purple colour turning to yellow.

Result: Presence of Strychnine.

17. Marsh’s Test

Procedure: Boil the solution with pyrogallol and sulphurated water to reduce pentavalent Arsenic to trivalent state. Perform the test in a Marsh apparatus and observe for a mirror of black metallic lustre.

Observation: Black metallic lustre mirror.

Result: Detection of minute traces of Arsenic.

18. Marquis Reagent Test

Procedure:

• Step I- prepare a marquis reagent first by adding 3ml of conc. Sulphuric acid and 3 drops of formalin.
• Step II- place a Drop of Marquis Reagent on the sample.
• Step III- Observe the colour

Result:

• Opiates (heroin, oxycodone) – purple
• Phenethylamines (meth)amphetamine – orange/brown
• MDA/MDMA – purple/black
• Aspirin – slow cherry red

19. McNally’s Test

Procedure: Add Acetone, water, Copper Sulphate solution with Acetic Acid, and Sodium Nitrite. Heat and observe for red colouration.

Observation: Formation of red colour.

Result: Presence of Salicylates or Salicylic Acid.

20. Mecke Test

Procedure:

• Step I: This color test reacts with a wide range of aromatic compounds to produce colored intermediates.
• Step II: Add 0.25 grams of selenious acid to 25 milliliters of concentrated sulfuric acid with stirring.

Observation: Observe the color

Results:

• Bufotenine – brown to black/purple
• Diphenhydramine HCl – yellow
• Heroin HCl – green/blue
• Hydrocodone bitartrate – dark blue
• Methadone – green/brown
• MDMA – green to dark blue
• MDA – green to blue

21. Reinsch Test

Procedure:

• Step I- take a copper wire and clean it with nitric acid until it gets a bright surface.
• Step II- Rinse the cleaned copper wire with purified water.
• Step III- Add 10ml of conc. Hydrochloric acid and 20ml of test solution in 100ml conical flask.
• Step IV- Heat on a boiling waterbath in a fume cupboard for 1 hour.
• Step V- Maintain the volume of solution by adding dilute hydrochloric acid as necessary.

Observation: Color staining on copper can be interpreted as follows:

Result:

• Copper Black-Antimony
• Dull Black-Arsenic
• Shiny Black-Bismuth
• Silver Color-Mercury

22. Simon’s Test

Procedure:

• Step I- Reagent A: 1 % Sodium Nitroprusside/10 % by Volume of Acetaldehyde

Dissolve 1 gram of sodium nitroprusside in 100 milliliters of water, then discard 10 milliliters of this solution. Add 10 milliliters of acetaldehyde to the remaining 90 milliliters of sodium nitroprusside/water.

• Step II- Reagent B: 2 % Sodium Carbonate

Dissolve 2 grams of sodium carbonate in 100 milliliters of water.

• Step III- Place a small amount of sample in a culture tube or clean spot well and add one drop of Reagent A, then add 2 drops of Reagent B.

Observation: Observe any reaction or color.

Result:

• Methamphetamine and secondary amines – blue-violet
• Amphetamine and primary amines – Negative reaction (light  pink is the color of the reagent.)  

23. Trinders Test

Procedure: Add 100ml of trinders reagent to 2 ml urine and mix for 5 seconds.

Observation: Violet

Result: Salicylate

24. Zwikker’s Test

Procedure: Take up the residue of extract in Chloroform, add Pyridine, and observe for colour change.

Observation: Colour change from purple to weak blue or green.

Result: Presence of Thiobarbiturates or non-Thiobarbiturates.