In January, 1799 he was elected a Fellow of the Royal Society and in 1800 awarded their Copley medal for his work on mercury. He discovered mercury fulminate, a powerful primary explosive. In 1813 he invented a method of refining sugar which involved boiling the cane juice not in an open kettle, but in a closed vessel heated by steam and held under partial vacuum. At reduced pressure, water boils at a lower temperature, and so Howard's development both saved fuel and reduced the amount of sugar lost through caramelization. The invention, known as Howard's vacuum pan, is still in use.
Howard also was interested in the composition of meteorites especially those of "natural iron". He found that many of these contained an alloy of nickel and iron that was not found on Earth, and thus they may have fallen from the sky. One type of meteorite is now known as Howardite.