تسجيل الدخول

تسجيل

Interpretation of colour tests , Use of the colour tests lists

المؤلف:  Sue Jickells , Adam Negrusz (Editors)

المصدر:  Clarkes Analytical Forensic Toxicology

الجزء والصفحة:  340

2026-11-01

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Interpretation of colour tests

Use of the colour tests lists

The system typically adopted in colour tests uses ten basic colours: the spectral colours (red, orange, yellow, green, blue and violet), together with pink, brown, grey and black. Where there is a variation in hue, this is indicated by combining two colours (e.g. red–brown) (see Fig. 1). The second-named colour is considered to be the dominant one. For example, red–brown is listed under brown, whereas brown–red is listed under red. When interpreting results, it is often necessary to search lists given for tests under two main colours (e.g. for red–brown the lists under both red and brown should be consulted). This takes account of the subjective nature of colour assessment. An arrow between two colours (e.g. red→brown) indicates that the colour changes during the course of the test. Occasionally, the colour displayed by a test solution in reflected light may be different from that in transmitted light, in which case the solution is described as dichroic. A combined colour may be obtained when more than one drug is present or the drug itself is coloured, which limits the value of the tests for biological samples.

Figure 1 Examples of colour tests: the Fujiwara test for halogenated hydrocarbons and the Marquis test for opiates and amfetamines.