NCJ Number
212920
Journal
Journal of Forensic Sciences Volume: 51 Issue: 1 Dated: January 2006 Pages: 87-89
Date Published
January 2006
Length
3 pages
Annotation
This paper reports on a case in which X-ray analysis of a bead at the end of a soldered wire found in the debris of a fire that lasted nearly a day revealed that the copper wire conductor alloyed only with tin and that lead was lost during the long-term heat of the fire.
Abstract
The cross-section of the bead was uniformly silver-colored, indicating that the copper conductor had become alloyed over the entire area of the bead. Most of the electrical wiring at the fire site turned brittle and broke into small pieces. Only a few beaded wires were found in the debris in the factory area where the fire originated. One bead had the appearance of an arc bead with its round shape and smooth surface. X-ray analysis was performed to determine the cause of the bead. The bead and a control sample for comparison were analyzed to determine what elements they contained. The control sample was prepared by heating an unused wire soldered with tin-lead solder at its end. The heat was provided by an electric furnace at a temperature of 500 degrees centigrade for 3 hours. The solder used for the control sample had the same contents (60 percent tin and 40 percent lead) as the solder used in the factory. The beads and the control sample were mounted in resin and polished with emery paper and diamond paste. Subsequently, the images and characteristic X-ray spectra from the beads were recorded with a scanning electron microscope and an energy dispersive X-ray analyzer using a 20kV electron beam. If this experiment had not determined that lead was lost due to long-term heating in a fire, the bead might have been interpreted differently and would have misled the fire investigation. 8 figures and 4 references