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在刑事案件的现场勘查中,我们经常遇到案犯遗留的灰尘、灰汗混合手印,但由于灰尘的特殊性,一般方法效果并不理想。我们经过反复研究和试验,采用加热含有氯化钴的乳酸和乳酸乙酯溶液熏后,指纹粉末刷显能有效地显现光滑客体表面上的灰尘及灰汁混合手印。 1 原理 乳酸为浅黄色粘稠液体,加热含有氯化钴的乳酸和乳酸乙酯溶液时,氯化钴失去结晶水,水分子阻止了乳酸脱水形成交酯的过程,乳酸乙酯减小了乳酸蒸汽的浓度,当蒸汽被灰尘手印吸附后,随着乳酸乙酯的挥发使乳酸在灰尘手印上聚
In the on-site investigation of criminal cases, we often encounter the dust left behind by the criminals, mixed with muddy fingerprints, but because of the special nature of the dust, the general method is not effective. After repeated studies and experiments, we found that fingerprinting powder brushes can effectively show mixed hand rubbing of dust and lye on a smooth guest surface by heating lactic acid containing cobalt chloride and ethyl lactate solution. Principle 1 Lactic acid is a pale yellow viscous liquid. When a solution containing lactic acid and ethyl lactate containing cobalt chloride is heated, the cobalt chloride loses its crystal water, and the water molecules prevent the dehydration of lactic acid to form lactide. The ethyl lactate reduces the amount of lactic acid Steam concentration, when the steam is absorbed by the dust fingerprints, with the ethyl lactate volatilization of lactic acid in the dust handprint poly