Laws regulating the sale of poisons and the purity of foods and medicinals imply the existence of methods for detecting offences, and of persons qualified to employ them. The 1804 Stamp Duty Act named 453 proprietary medicines, many of extreme complexity. Synthetic drugs tended to diminish the polypharmacy of earlier days, and the rise of the health salt trade brought further simplification, but analysis was still made difficult by the practice of substitution. Advertising of nostrums was assiduously developed by Holloway and Beecham. Chemical analysis had its roots in mining for metals. The blowpipe enabled metals to be detected in complex environments. Group analysis developed from the work of Klaproth, Thomson, Rose and Fresenius. The systematic use of H(_2)S is due to Berthollet and Gay-Lussac. Analysis of animal and vegetable products was slower to develop: significant stages were destructive distillation, solvent extraction, element tests, melting points, characteristic group reactions, and instrumentation. Positive identification was difficult to achieve. Chemical evidence in poisoning trials was given usually bymedical men: the consequent forensic disasters (Palmer case, 1856, Smethurst case 1859) brought chemical analysis into disrepute.Landmarks in chemical toxicology were Marsh's test for arsenic (1836) and the Stas-Otto method for extracting poisons from stomach contents (1852). Examples of social problems in the chemical detection of poisons were the easy confusion of oxalic acid with Epsom salt, and the prevalence of opium-containing soothing syrups for infants. Apothecaries, druggists and pharmacists concerned themselves with the adulteration of drugs. General chemical analysis was undertaken by such 'practical' chemists as F. Accum. Pharmacists acquired the right to be called chemists: chemistry was often made to appear as a frivolous science. The l863Alkali Act and the 1860 Food Act paved the way for the professional analyst. The Society of Public Analysts was founded in 1874 and the [Royal] Institute of Chemistry in 1877. The adulteration of food is not treated in this study.