Physical developer (PD) is a set of solutions used to develop latent fingerprint
ID: 1007635 • Letter: P
Question
Physical developer (PD) is a set of solutions used to develop latent fingerprints on different porous and nonporous surfaces. It is often used to develop fingerprints on currency. Below is the FBI recipe for PD. Solution 1 serves as a cleaning solution before using a mixture of solutions 2 through 4 in which the fingerprint is developed due to a redox reaction causing the deposition of metallic silver within the ridges of the fingerprint. Determine the concentration of each ingredient in the four solutions. The final volume for each solution is 1.00 L. (6.5) Solution 1: 25.0 g of maleic acid (C4H4O4) Solution 2: 30.0 g of iron(III) nitrate 80.0 g of iron(II) ammonium sulfate (Fe(NH4)2(SO4)2) 20.0 g of citric acid (C6H8O7) Solution 3: 3.00 g of n-dodecylamine acetate (C14H31NO2) 4.00 g of synperonic-n (skip—this is a mixture) Solution 4: 200.0 g of silver nitrate
Explanation / Answer
Sol1: M = 25/116*1/1 = 0.2155 mol/L
Sol2: concentration of Fe(NO3)3 = 30/241.86*1/1 = 0.124 mol/L
concentration of Fe(NH4)2(SO4)2 = 80/284.047*1/1 = 0.2816 mol/L
concentration of C6H8O7 = 20/192*1/1 = 0.1041 mol/L
Sol3: concentration of C14H31NO2 = 3/245*1/1 = 0.0122 mol/L
Sol4: concentration of AgNO3 = 200/170*1/1 = 1.1765 mol/L