Litmus "Lecanora tartarea" (Norway, Sweden), "Variolaria dealbata", "Ochrolechia parella", "Parmotrema tinctorum", and "Parmelia". Currently, the main sources are "Roccella montagnei" (Mozambique) and "Dendrographa leucophoea" (California). The main use of litmus is to test whether a solution is acidic or basic. Wet litmus paper can also be used to test for water-soluble gases that affect acidity or alkalinity; the gas dissolves in the water and the resulting solution colors the litmus paper. For instance, ammonia gas, which is alkaline, turn the red litmus paper blue. Blue litmus paper turns red under acidic conditions and red litmus paper turns blue under basic or
Marsh test test in Strong Poison to demonstrate that the culprit was secretly in possession of arsenic. In Alan Bradley's "As Chimney Sweepers Come To Dust", 12-year old sleuth and chemistry genius Flavia de Luce uses the Marsh test to determine that arsenic was the murderer's weapon. In the first episode of the 2017 TV series "Taboo" a mirror test, referencing the Marsh test, is used to verify the protagonist's father was killed via arsenic poisoning. However, as the setting of the series is between 1814-1820, a different/earlier process should have been used. Marsh test The Marsh test is a highly sensitive