FORENSIC SCIENCE PAPER No.5: Forensic Chemistry and Explosives MODULE No. 38 : Explosives-Introduction

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1 SUBJECT FORENSIC SCIENCE Paper No. and Title Module No. and Title Module Tag PAPER No. 5: Forensic Chemistry and Explosives MODULE No. 33: Analysis of Inorganic Anions and Cations of Post Blast Residues FSC_P5_M33

TABLE OF CONTENTS 1. Learning Outcomes 2. Analysis of Post Blast Residue 3. Chemical Tests for inorganic Anions- Water Extract 3.1 Chloride (Cl - ) 3.2 Sulphate (SO 4 2- ) 3.3 Nitrite (NO 2 - ) 3.

2 TABLE OF CONTENTS 1. Learning Outcomes 2. Analysis of Post Blast Residue 3. Chemical Tests for inorganic Anions- Water Extract 3.1 Chloride (Cl - ) 3.2 Sulphate (SO 4 2- ) 3.3 Nitrite (NO 2 - ) 3.4 Thiocynate (SCN-) 3.5 Chlorate (ClO 3 - ) 3.6 Thiosulphate (S 2 O 3 2- ) 3.7 Perchlorate (ClO 4 - ) 3.8 Sulphite (SO 3 2- ) 3.9 Phosphate (PO 4 3- ) 4. Chemical Tests for Cations- Water Extract 4.1 Potassium ion (K + ) 4.2 Barium ion (Ba 2+ ) 4.3 Strontium ion (Sr 2+ ) 4.4 Flame test for Sodium, Potassium, Barium, Calcium, and Strontium 4.5 Aluminum (Al 3+ ) 4.6 Chemical Tests - Alkali Extract 4.7 Antimony (Sb 3+ ) 4.8 Sulphide ions (S 2- ) 5. Chemical Tests for Inorganic Anions - Pyridine Extract 5.1 Sulphur 5.2 Thin Layer Chromatography of Cations (Al, Zn, As, Ba, Hg, Pb) 6. Chemical test for inorganic Anions: pyridine extract 6.1 Test for sulphur 6.2 Thin layer chromatography of Cations 7. Summary.

3 1. Learning Outcomes After studying this module, you shall be able to know: Chemical Tests to be used for detecting inorganic Anions such as Cl -, SO 4 2-, NO 2 -, SCN -, ClO 3 -, S 2 O 3 2-,ClO 4, SO 3 2-,PO 4 3- in the examination of post blast residue. Chemical Tests carried out for Cations- K +, Ba 2+, Sr 2+, Al 3+. Different Flame test performed for Sodium, Potassium, Barium, Calcium, Strontium. Chemical Tests for detecting - Sb 3+, S 2-, S in post blast residue 2. Analysis of Post Blast Residues Tests for explosives are carried out to detect and identify the ions present in the explosive. The tests must be carried out along with the reference standard as well as blank. 3. Chemical Tests for Inorganic Anions-Water Extract 3.1 Test for Chloride (Cl - ) The following three reagents are required for detecting chloride ion in an explosive. Reagent A - It is made by dissolving 128 ml conc. nitric acid in 500mL of distilled water and then diluting it to 1litre. Reagent B - It is prepared by dissolving g of Silver Nitrate in 500mL distilled water and diluting it to 1litre. Reagent C - Reagent C is prepared by dissolving 95g of lead acetate trihydrate in a mixture of 500 ml distilled water and 10mL glacial acetic acid and then diluting the solution with water to 1litre. Take 1mL of water extract in a clean test tube. Put 2-3 drops of reagent A followed by the addition of 2-3 drops of B reagent. The presence of chloride ions are shown by the formation of white ppt. This white precipitate is soluble in NH 4 OH and insoluble in HNO 3. Another method to test for if chloride ion is present or not is carried out by taking 1mL of extract in a fresh test tube followed by the addition of 3 drops of C reagent to it. The presence of Cl - ions are indicated by the formation of White precipitate.

4 3.2 Test for Sulphate (SO 4 2- ) Before preforming the test for sulphate ion we have to prepare the following two reagents:- Reagent A: It is prepared by dissolving 61.1g barium chloride dihydrate in 500 ml distilled water and then diluting it to 1 litre. Reagent B: It is freshly prepared by dissolving 0.5g of sodium rhodizonate in distilled water (100 ml). The test is carried out by taking 1mL of extract in a clean test tube and then adding 2-3 drops of dilute HCl to it. The test tube is then placed in a water bath at C for 5 minutes and 2-3 drops of reagent A are added to it. Formation of white crystalline precipitate indicates the presence of Sulphate Ion. 3.3 Test for Nitrite (NO 2 - ) Before analyzing the presence of nitrite in post blast residue the following four reagents are to be prepared: Reagent A: Sulphanilic acid (1g) is dissolved in 100mL of warm 30% acetic acid. Reagent B: Take 0.3 g of -naphthylamine and dissolve it in 70mL of distilled water and it is then kept for boiling and is filtered. And add 30mL of glacial acetic acid to it. Reagent C (Indole Reagent): To prepare this reagent grams of indole is dissolved in 96% alcohol (100 ml). Reagent D: It is prepared by slowly adding 500mL of water under constant stirring to 445 ml of conc. Sulphuric acid. When the mixture cools down, again dilute it with water to 1litre. The test is carried out by taking 1 drop of neutral or acid extract on a clean spot plate. This step is followed by the addition of reagent A and a drop of B reagent. The presence of Nitrite ions are indicated by the formation of red color.

5 Another method for testing the presence of nitrite ion is done by taking 1 drop of the extract in a semi micro test tube. And then added 10 drops of the reagent C followed by adding 2 drops of the reagent D to it. A purplish-red colour indicates the presence of NO Test for Thiocynate (SCN - ) To test the presence of thiocyante in the given sample, firstly, we have to make the following two reagents: Reagent A: It is prepared by dissolving 146g of cobalt nitrate in 500mL of distilled water and then diluting it to 1litre. Reagent B: It is prepared by dissolving 62.42g of CuSO 4.5 H 2 O in 500mL of distilled water and then diluting it to 1litre. Test for Thiocynate is carried out by mixing one drop of the test solution in a micro-crucible with a very small drop of reagent A and then evaporating it to dryness. The residue will be of violet color if thiocynate is present and the color fades away slowly. Blue or green color is obtained when drops of acetone is added to it. Another method for testing the presence of thiocynate is carried out by taking a few drops of pyridine in a clean test tube. To it 3-4 drops of reagent B is added followed by 2mL of chloroform, and 5-6 drops of the extract. Shake the mixture vigorously. The chloroform layer will acquire a green colour which indicates the presence of thiocyante 3.5 Test for Chlorate (ClO 3 - ) To confirm the presence of chlorate in the given sample we will have to prepare the following three reagents: Reagent A: It is prepared by dissolving 1g of aniline sulphate in 100mL of distilled water. Reagent B: Take equal volumes of saturated manganese sulphate solution and syrupy phosphoric acid and then mix them properly, the solution so formed is labelled as Reagent B Reagent C: 1% Alcoholic Diphenyl Carbazide solution is used as a Reagent C Test is carried out by taking 1mL of extract on a spot plate and is left for some time. Cool it and add conc. H 2 SO 4 (2-3 drops) followed by 2-3 drops of reagent A. The presence of chlorate ions are indicated by the formation of blue color.

6 Second procedure for testing for the presence of chlorate ions are carried out by taking 1 drop of the extract in a micro crucible and added to it is 1 drop of the reagent B. Briskly warm this solution over a micro burner and allow it to cool for some time. Appearance of violet coloration can be seen. Very pale coloration may be intensified by adding a drop of reagent C. A deep violet colour is formed, due to oxidation of the diphenyl carbazide. 3.6 Test for Thiosulphate (S 2 O 3 2- ) Two reagents are prepared to test the presence of Thiosulphate Reagent A: It is prepared by dissolving 2 g of mercuric chloride in 100 ml of distilled water. Reagent B: Reagent B is prepared by treating a little nickel nitrate solution with ethylenediamine until a violet colour appears. This violet colour appears due to the formation of the complex [Ni(en) 3 ] +2 ion. Take 1 drop of the water extract in a clean test tube. Add 2 drops of reagent A and mix it thoroughly. And then add little amount of KCl to it. Take a blue litmus paper and dip it in the solution. The presence of S 2 O 3 2- can be indicated if the blue litmus paper changes to red in color. Put 1ml of the neutral/slightly alkaline water extract in a fresh test tube. After this add 2-3 drops of the reagent B to it. Formation of crystalline violet precipitate indicates the presence of thiosulphate. 3.7 Test for Perchlorate (ClO 4 - ) Reagent A: It is prepared by dissolving 28.8 g zinc sulphate hepta hydrate in 100mL of distilled water. Reagent B: It is prepared by dissolving 10.1g potassium nitrate in 100mL of distilled water. Reagent C: Reagent C is prepared by dissolving methylene blue (0.05 grams) in 100mL of distilled water. To detect the presence of Perchlorate in an explosive, take 1 drop of water extract of post blast residue on a piece of filter paper impregnated with Reagent A and Reagent B and then spray Reagent C on it. Violet spot appears which indicates the presence of perchlorate.

7 3.8 Test for Sulphite (SO 3 2- ) Reagent A: Saturated solution of zinc sulphate is used as reagent A. Reagent B: It is prepared by dissolving 10.4 g potassium ferrocyanide in 100 ml of distilled water. Reagent C: It is prepared by dissolving 1g sodium nitroprusside in 100mL of distilled water. The test is carried out by adding a drop of reagent B to a drop of reagent A followed by a drop of reagent C. White zinc ferrocyanide precipitates is formed. And a drop of neutral water extract is added to it. Red precipitate appears which confirms the presence of sulphite in it. 3.9 Test for Phosphate (PO 4 3- ) Reagent A: It is prepared by dissolving e 0.5g of Ammonium molybdate in 10mL of distilled water and then 3ml conc. HNO 3 is added to it. Reagent B: It is prepared by dissolving 6.5g Benzidine in 10mL of glacial acetic acid and diluted it to 35ml with distilled water. Reagent C: Dissolve 16 g sodium hydroxide in 100 ml of distilled water and the solution so formed used as Reagent C. To identify the presence of PO 4 3-, put a drop of water extract on a spot plate. Add a drop of A reagent to it, wait for 30 seconds followed by the addition of one drop of reagent B. Wait for half a minute. Now add saturated solution of sodium acetate (3 drops). Blue gray colour indicates the presence of phosphate. 4. Chemical Tests for Cations: Water Extract 4.1 Test for Potassium ion (K + ) Reagent A: It is prepared by dissolving 0.2 g of dipicrylamine in 2mL of 2N sodium carbonate and 15 ml distilled water. Filter paper strips which are placed in reagent A should be freshly prepared and then dried. Reagent B: It is prepared by dissolving 6.73g sodium cobalt nitrite in 100mL of distilled water.

8 Place one drop of water extract on paper of reagent A and then add 0.1N Nitric acid (2 drops). A red stain at the side of the spot appears, while all other parts of the reagent paper turn bright yellow which indicates the presence of potassium ion. Second method for confirming the presence of potassium is done by taking 5 drops of water extract in a watch glass, and then evaporate it to half of its volume and then leave the remaining residue to cool down for some time, then add 4 drops of reagent B and warm if necessary. Yellow precipitate is formed which is insoluble in dilute acetic acid. This indicates the presence of K Test for Barium ion (Ba 2+ ) Reagent A: It is prepared by dissolving sodium rhodizonate(0.2 grams) in distilled water(100 ml). Reagent B: It is prepared by diluting 4.5mL of conc. HCl with 100mL of distilled water. Put a drop of neutral or slightly acidic water extract on the filter paper followed by the addition of reagent A. The presence of barium ion is indicated by the presence of reddish brown spots. A brilliant red acid salt is formed on addition of B reagent. In case barium is absent, this red color will disappear. 4.3 Test for Strontium ion (Sr 2+ ) Reagent A: It is prepared by dissolving 0.2 g of sodium rhodizonate in 100mL of distilled water. Reagent B: It is potassium chromate (saturated solution). Put one drop of neutral extract of sample on a filter paper or on a spot plate. Add a drop of reagent A. A brownish red coloration or precipitate is formed which indicates the presence of strontium. If barium is also present then proceed as follows: Impregnate the filter paper with reagent B and dry it. Place a drop of extract on this paper and after a minute place a drop of reagent A on the moistened spot. Brownish red spot or ring is formed which indicates the presence Strontium ion.

9 4.4 Flame test for Sodium, Potassium, Barium, Calcium, Strontium Put drops of the water extract in a beaker till it evaporates and is dry. After this step cool it. Take conc. HCl in a watch glass. Perform flame test with the help of platinum wire in the non-luminous flame of the burner. The response of various ions to the flame test is given below in the table: IONS Na + K + Ca 2+ Ba 2+ Sr 2+ COLOUR OF FLAME Golden Yellow Violet (lilac), Crimson through cobalt blue glass Brick-red Yellowish-green Crimson 4.5 Test for Aluminum (Al 3+ ) Table 1: Showing Response of Various Ions to Flame Test Reagent A (Aluminon reagent): Reagent A is prepared by adding saturated solution of Morin in 5mL of methyl alcohol in a small bottle. Reagent B (Quinalizarin Reagents): Dissolve about 0.25 grams of aluminon in distilled water(250 ml). Reagent C: 1,2,5,8-Tetra hydroxy anthraquinone is used as reagent C. To prepare reagent paper, immerse quantitative filter paper in the solution of quinalizarin which is attained by mixing 0.01 grams of quinalizarin in pyridine (2 ml). Now dilute it with 18 ml of acetone. Take water extract and add a small amount of 1N acetic acid in order to make it slightly acidic. Place 3 drops of the acidified solution in a black spot plate. Now add 2 drops of reagent A. Observe the spot under UV light if Green fluorescence appears it indicates the presence of aluminium.

10 5. Chemical Tests using Alkali Extract Alkali extract is used for analyzing the presence of Antimony and sulphide ions. 5.1 Test for Antimony (Sb 3+ ) The method of preparing the reagent is to dissolve 0.01grams of Rhodamine-B in 100mL of distilled water. Take a small portion of NaOH extract in a spot plate. Add 1-2 drops of conc. hydrochloric acid and a few mg of NaNO 3. Now put 10 drops of the prepared reagent and mix it. A change of colour from bright red to violet indicates the presence of Antimony. 5.2 Test for Sulphide ions (S 2- ) Reagent A: It is prepared by dissolving 0.1 g Methylene blue in 100 ml of distilled water. Reagent B: It is prepared by dissolving 0.1 grams Sodium nitroprusside dihydrate in 10 ml of distilled water. Use freshly prepared solution before carrying out the test Reagent C: it is prepared by dissolving g Ferric chloride hexa-hydrate in 500 ml water. Put few drops of conc. hydrochloric acid and dilute with water to make it up to one liter. In case the solution turns dark, add more Hydrochloric acid. To conduct the test, place a drop of alkali extract on a spot plate, add a drop of conc. HCl, and mix it properly. Add 2-3 drops of reagent A to it, followed by a drop of reagent C. A clear blue coloration appears after a short time (2-3 minutes). Mix a drop of B reagent with the alkaline extract on the spot plate. The presence of S 2- is indicated by the presence of violet color.

11 6. Chemical Tests for Inorganic Anions: Pyridine Extract 6.1 Test for Sulphur To test for the Sulphur, take a small portion of pyridine extract in a small test tube. And then boil it for one minute. Add a drop of 2M sodium hydroxide to it. A blue to green colour for low and red to brown for high concentrations of sulphur is observed. 6.2 Thin Layer Chromatography of Cations (Al, Zn, As, Ba, Hg, Pb) Thin Layer Chromatography of cations such as Aluminium, Zinc, Arsenic, Barium, Mercury and Lead compounds is carried out by using n-butanol and Glacial Acetic Acid in 8:2 ratio as a solvent system. This is used as a solvent system and samples are applied on the pre-coated TLC plate of size 20cmx20cmx0.25mm silica 60F. Spraying Reagents: Dimethlyaminobenzaldehyde and Pyridine (A) Dimethlyaminobenzaldehyde is prepared by dissolving 5g of Dimethyl amino benzaldehyde and 5g of Ammonium thiocyanate in 50mL of methanol (B) Pyridine reagent is prepared by adding 2mL Pyridine and 5g of Ammonium thiocyanate in 50mL of methanol. Spraying Reagent and Color of Spot Rf Metal Ion Dimethlyaminobenzaldehyde Reagent Pyridine Reagent n-butanol:glacial Acetic acid (8:2) Aluminium Brown Pink 0.28 Zinc Orange Brown 0.58 Arsenic Yellow Light Brown 0.30 Barium Violet Brownish 0.38 Pink Barium Green Blue 0.63 Cobalt Light Brown Parrot Green 0.66 Mercury Yellow Faint Pink 0.84 Lead Deep Violet Dark Brown 0.34 Table 2: Response of Various Cations to Thin Layer Chromatography

12 The above table shows the response of various cations to the solvent system n- Butanol:Glacial acetic acid in the ratio of 8:2 and after spraying the TLC plate with Dimethlyaminobenaldehyde Reagent and Pyridine Reagent. 7. Summary Test for explosives are carried out to detect and identify the ions present in them. The tests must be carried out along with the reference standard as well as blank. Chemical Tests for ions such as Cl -, SO 4 2-, NO 2 -, SCN -, ClO 3 -, S 2 O 3 2-,ClO 4, SO 3 2-,PO 4 3-, K +, Ba 2+, Sr 2+, Al 3+, Sb 3+, S 2-, S and other can be carried out with the post blast residues by using water, alkali and pyridine extracts. Flame test for Sodium, Potassium, Calcium, Barium, Strontium gives Golden Yellow, Violet (lilac) &Crimson through cobalt blue glass, Brick-red, Yellowish-green, Crimson. The technique of Ion Chromatography is used for the analyzing anions as well as cations.

Systematic Procedure for Inorganic Qualitative Analysis Systematic Analysis of Anion

Systematic Procedure for Inorganic Qualitative Analysis Systematic Analysis of Anion S.No Experiment Observation Inference 1 Preliminary Reactions Colourless Absence of Fe 2+, Fe 3+, Ni 2+, Co 2+. 2 Appearance