Lab Procedure 1) Obtained fabric with gunshot residue 2) Sprayed filter paper wi

Question

Lab Procedure

1) Obtained fabric with gunshot residue

2) Sprayed filter paper with 15% acetic acid

3) Placed filter paper on fabric, covered with aluminum foil and pressed with hot iron

4) Sprayed filter paper with saturated sodium rhodizonate solution (red spots appeared on filter paper in fabric areas with gunshotresidue)

5) Covered filter paper with aluminum foil and pressed with hot iron

6) Sprayed with 5% HCl (orange sodium rhodizonate on filter paper disappeared leaving only gunshot residue)

7) Color turned from red to blue confirming presents of lead in gunshot residue

Questions:

A. What is the chemical reaction that is occurring for the gunshot residue test performed in lab?

B. What is the purpose of the acetic acid in this method?

C. What are the advantages and disadvantages to using the filter paper transfer technique as is used in the method suggested in this lab exercise?

D. What kind of pattern would you expectfrom using the sodium rhodizonate method on a substrate through which a copper jacketed bullet was fired?

E. Why is it necessary to report a range for the muzzel-to-target distance for your unknown as opposed to a specific distance?

If you could help me understand any of the parts, it would be much appreciated! (especially parts A, C and E)

Explanation / Answer

B) The acetic acid vapors will penetrate the exhibit and a reaction takes place between any nitrite residues on the exhibit and the chemicals contained in the photographic paper. The resulting reaction will appear as orange specks on the piece photographic paper

E) It is necessary to reprort a range as The muzzle-to-target distance can vary considerably depending upon the firearm and the type of ammunition being used. Short-barreled firearms (pistols) will not throw residue as far as long-barreled firearms (rifles). At shorter distances, however, the residue concentration might be greater.

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