The chemistry of garlic The characteristic taste and odor of garlic is due to an oily, slightly yellow
organosulfur compound S-Allyl prop-2-ene-1-sulfinothioate, commonly called
allicin. Fresh garlic has little odor until it is chopped or crushed. Allicin is produced from
alliin (a derivative of the amino acid
cysteine) by the enzyme
alliinase. Allicin is unstable and breaks down to form other sulfur compounds such as diallyl sulfides. These compounds contribute to the smell of fresh garlic. When on the hands these sulfur compounds can further degrade into other sulfur compounds, including sulfuric acid, in the presence of water.
The chemistry of stainless steel Steel is an alloy made up of
iron mixed with
carbon. Stainless steel is composed of steel mixed with at least 10.5% chromium, and often other elements such as nickel and
molybdenum, etc. Chromium is added to make it resistant to rust. Stainless steels that are corrosion and oxidation resistant typically need more than 11% chromium. Nickel is added to increase the corrosion resistance further, and protect it from harsh environmental conditions. Molybdenum may be added to avoid pitting or scarring. The chemical properties of stainless steel can be further improved for specialized uses by adding other elements, e.g. titanium, vanadium and copper.
Possible mechanism The
chromium in stainless steel forms a passive oxide film on the surface of the metal, resulting in corrosion resistance. It is suggested that allicin and the other sulfur compounds (including sulfuric acid) react with the chromium oxide layer, some possibly being
adsorbed onto it. Washing the stainless steel soap in water would remove this layer and with it the smelly sulfur compounds. The oxide film would then reform and the stainless steel soap can be reused. Mark Lorch, Professor of Science Communication and Chemistry at the University of Hull and Joanna Buckley, Materials chemist and science communicator, at the University of Sheffield conducted some "
citizen science" in 2016 to test this mechanism but there is no conclusive, rigorous evidence for it. ==Usage==