(Received 23 December 1986; accepted 10 February 1987)
Published Online: September
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The relative aging of ink is the comparison of inks of the same formula and on the same paper to ascertain the order in which they were written. The solvent extraction technique determines how efficiently an ink is extracted into a solvent. This efficiency involves both the rate and extent of extraction and is dependent on the time the ink was placed on the document. Two procedures are presented for obtaining the extraction rates: the R ratio and the Lth extraction time procedure. The third procedure presented, and sequential solvent extraction procedure, measures the extent of extraction as percent extraction. This procedure can be extended to provide extraction rates. Two methods are presented for obtaining either the extent or rate of extraction: a thin-layer chromatographic (TLC) method and a spectrophotometric method. A suggestion is made to obtain the extent of extraction using a modified TLC method.
Research chemist, U.S. Secret Service Technical Development and Planning Division, N.W. Washington, DC
Chemist, previously employed by the FBI, Forensic Science Research and Training Group, Quantico, VA
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