Arsenic, a poison for mystery killing : it’s discovery



Arsenic compounds, namely its sulphides As2S3(orpiment) and As4S4(realgar or sandarac), were well known to Greeks and Romans. Orpiment was also known under the name of “arsenic”. Pliny the Elder and Dioscorides mentioned the toxicity of these compounds; Dioscorides noted calcination of “arsenic” to obtain white arsenic (oxide).

Arsenic is sometimes found in nature in native state and is fairly easily extracted from its compounds. It is not known who was the first to produce elemental arsenic. Usually its discovery is ascribed to the alchemist. Albert the great. Paracelsus described the process of preparing metallic arsenic by the calcination of “arsenic” with egg-shells. According to some reports, metallic arsenic was known much earlier but it was considered to be a variety of native mercury. This is due to the fact that arsenic sulphide resembles one of mercury minerals and the extraction of arsenic from its ores is rather simple.

In the Middle Ages arsenic was known not only in Europe but in Asia as well. Chinese alchemists could extract arsenic from its ores. Medieval Europians had no way of knowing whether death of a person was caused by arsenic poisoning but Chinese alchemists had a method of making sure. Unfortunately, their method of analysis is unknown. In Europe the test for estimating arsenic content in human body and the food eaten before death was developed by D. Marsh. This test is very sensitive and is still used.

Since arsenic sometimes accompanies tin, there are reported cases (for instance, in Chinese literature) when people were poisoned by water or wine kept for some time in new tin vessels.

For a long time people confused white arsenic, or its oxide, with arsenic itself believing the two to be the same substance. The confusion was eliminated at first by H. Brand and then by A. Lavoisier who proved that arsenic is an independent chemical element.

Arsenic oxide has for a long time been used to kill rodents and insects. The symbol As originates from the Latin word arsenicum whose etymology is obscure.