Period 6 element also dissolves in alkaline solutions of cyanide, which have been used in mining. Gold dissolves in mercury, forming amalgam alloys. Gold is insoluble in nitric acid, which dissolves silver and base metals, a property that has long been used to confirm the presence of gold in items, giving rise to the term "the acid test." Gold has been a valuable and highly sought-after precious metal for coinage, jewelry, and other arts since long before the beginning of recorded history. Gold standards have been a common basis for monetary policies throughout human history, later being supplanted by fiat currency starting in
Nervonic acid Recent studies show that cord nervonic acid levels were lower in women with preeclampsia delivering male babies as compared to normotensive control group. But this does not happen with girl babies. These results suggest that male babies born to mothers with preeclampsia may be at an increased risk of developing neurodevelopmental disorders as compared to female babies. This acid is present in the composition of aged eye lens, but it does not appear in normal eye lens. This data shows that we can use the presence of nervonic acid (together with heneicosylic acid and docosahexaenoic acid) as biomarkers of aging