The green ink that has been used since 1862 to print U.S.
banknotes was invented in 1857 by Thomas Sterry Hunt while he was a
professor at McGill University in Montréal. Hunt was the staff
analytical chemist of the Canadian Geological Survey and it was during
his time in this position that he started becoming familiar with
chromium-containing minerals. For the banknote ink he proposed the use
of chromium sesquioxide, Cr2O3, also known as
chromium trioxide.
This may not seem like a major invention but this green ink is the
reason why so many counterfeiters are unsuccessful at reproducing U.S
currency. This green ink also cannot be destroyed by acid, base or any
other agent. The green ink has another very important characteristic: it
cannot be copied by photography.
It seems that Hunt did not benefit as he would have hoped to from his
invention. He sold his invention to the United States government for
much less than it was worth, considering it has become very widely used.
In a letter to a friend he wrote, "As yet it has been rather more
trouble than profit." Hunt's invention also led to the nickname
"greenbacks" for American currency. |
