NCJ Number
132313
Journal
Journal of the Forensic Society Volume: 31 Issue: 1 Dated: (January/March 1991) Pages: 31-40
Date Published
1991
Length
10 pages
Annotation
A classification scheme based on the degree of extraction of dyes from cotton fibers is described in reference to forensic fiber comparison.
Abstract
Different cotton fibers dyed with azoic, direct, ingrain, reactive, sulfur, and vat dyes were tested with five different solvent systems. These included water and pyridine, urea in water, 2-clorophenol, sodium dithionite and polyvinyl pyrollidone (PVP) in aqueous sodium hydroxide, sodium sulfide and PVP in water, and hydrazine in water. Four of these extractions were performed at 100 degree Centigrade in a thermostatically controlled blockheater; whereas one was performed at room temperature. Each of the 47 different samples was tested with each of the 5 different extraction systems, and in each instance the extraction efficiency was scored independently by 5 people using a scoring scheme of 0 to 5, with the highest number indicating removal of most of the dye from the fabric into the solvent. In a blind trial, 24 out of 26 additional samples were correctly classified by 3 examiners. Distinguishing vat from azoic dyes and sulfur from reactive dyes, especially if they were brown, appeared problematic. Ingrain dyes could not be extracted, but could thus be classified by default to confirmation. Nevertheless, the class of dye present could be identified in most cases using the proposed scheme. 7 tables, 2 figures, and 10 references (Author abstract modified)