ZINC CHLORIDE

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Chemical Name:
ZINC CHLORIDE
Surface Used On:
Porous surfaces.
Sensitive To:
Ninhydrin, 5-MTN & 1,2-Indanedione compounds.
Development Color: Method to Record: Hazard: Protective Clothing: Fume Hood Use:

Orange fluorescence.

Orange or Red filter.

Yes
Reagent Characteristics

Development Complete When:

Source of Error:

Incompatibilities:

Precautions:

Storage Container:

Safety:

Recommendations:


Similar Reagents



Sequential Reagents
(Not necessarily in this order.)



Abridged Reagent Sequence


Visual Examination
|
Forensic Light
|
D.F.O.
|
Ninhydrin / 1,2-indanedione
|
*** Zinc chloride ***
|
Forensic Light

ZINC CHLORIDE FORMULA #1:

  30 g Zinc chloride dissolved in
 500 ml methyl-tert-butylether (MTBE)
  20 ml of anhydrous Ethanol.

Use magnetic stirrer until completely 
dissolved. Dissolution may be slow.
Add 10 ml  Glacial acetic acid.
Dilute with 500 ml Petroleum ether.
ZINC CHLORIDE FORMULA #2:

*** ZINC CHLORIDE STOCK SOLUTION ***

  	8 grams Zinc chloride crystals
	 180 ml Ethanol
add	  20 ml Glacial Acetic acid

Combine and stir with a magnetic stirrer
until ALL the ingredients are dissolved. 


*** ZINC CHLORIDE WORKING SOLUTION ***

	6 ml Zinc chloride stock solution 
      100 ml Petroleum ether 
             or Pentane or Heptane

PROCEDURE OF APPLICATION
1. Spray the item lightly.
2. Air-dry the item.
3. Process & dry a second time.
4. Oven bake at 80 - 100 degrees C 
at 65% humidity for 40 minutes.


NINHYDRIN & 5-MTN TREATED ITEMS:

View under a forensic light 
source around 490nm to 505nm.  
Use dark orange filter or a 
550nm to 590nm bandpass filters.


Photograph results using a 
orange colored or 550nm(BP 35) 
bandpass filter.



1,2-INDANEDIONE TREATED ITEMS:

For most papers ......

View @ 515 nm with orange barrier
filter.

For manila, brown paper bags,
cardboard items & craft paper ....

View @ 515 - 570 nm with
orange or red 600(BP 35)
barrier filters.


Ridge Detail Visualized by:

Forensic Light Source induced.


Reagent Applicabilities:

Porous sufaces
Fluorescent technique
Post-Ninhydrin


Other Chemical Name(s):

None


Working Solution Shelf-life:

Six (6) months.

Process Summary:

Zinc chloride is applied as post-ninhydrin , post 1,2-Indandione & post 5-MTN treatments in order to improve the strength of the fluoresence of the ridge detail for viewing and photography. When viewing the enhanced ridge detail, two approaches may be utilized ... 1). the Zinc chloride color-shifted ridge detail may be darkened with the appropriate wavelength and viewed without any barrier color filter, or, 2). the appropriate wavelength may illumine the latent print, which is viewed with the appropriate barrier color filter.

Zinc chloride treated ninhydrin ridge detail is color-shifted to an orange color, and Zinc chloride treated 5-MTN ridge detail is color-shifted to a reddish-purple color.

Accepted Deviations:

Other hydrocarbon solvents such as Pentane and Heptane may be subsitituted for Petroleum ether. The Zinc chloride treated item may also be viewed under white light using a blue or a green filter, which should darken the light pink or orange colored ridge detail.

The treated exhibit may be placed in an insulated container (polystyrene foam tray) and covered with a layer of liquid nitrogen for enhanced luminescence of the ridge detail.

Supporting Reference Materials:

1. "Chemical Formulas and Processing Guide for Developing Latent Prints", U.S. Dept. of Justice, pg. 47-48, 1994.

2. Manual of Fingerprint Development Techniques 2nd. Ed., Home Office - Police Scientific Development Branch, White Crescent Press, Ltd., Luton, England, 2001.

3. Advances in Fingeprint Technology 2nd. Ed., Lee, H.C. & Gaensslen, R.E., CRC Press, Boca Raton, FL., 2001.

4. Fingerprint Detection with Lasers 2nd. Ed., E. Roland Menzel, Marcel Dekker, Inc., New York, 1999, pp. 180-184.

5. Fingerprints and Other Ridge Skin Impressions, C. Champod, C. Lennard, P. Margot, and M. Stoilovic, CRC Press LLC, Boca Raton, FL., 2004, pp. 120 - 124, pg. 240.

6. "Evaluation of a 1,2-Indanedione Formulation Containing Zinc Chloride for Improved Fingermark Detection on Paper", Stoilovic, M., Lennard, C., Wallace-Kunkel, C. and Roux, C., Jor. Forensic Identification, vol. 57, no. 1, 2007, pp. 4-18.

7. "Synthesis and Structure of the Zinc(II) and Cadmium(II) Complexes Produced in the Photoluminescent Enhancement of Ninhydrin Developed Fingerprints Using Group 12 Metal Salts", Davies, P.J.; Kobus, H.J.; Taylor, M.R.; Wainwright, K.P., Jor. Forensic Sciences, Vol. 40, No. 4, July 1995, pp. 565-569.

8. "Modifications to the 1,2-Indanedione/Zinc Chloride Formula for Latent Print Development", Russell, S.E., John, G.L., Naccarato, S.L., Jor. Forensic Identification, Vol. 58, No. 2, 2008, pp. 182-192

9. "Laser Detection of Latent Fingerprints: Ninhydrin Followed by Zinc Chloride", Herod, D.W., Menzel, E.R., Jor. Forensic Sciences, Vol.27, No. 3, July 1982.

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