The iron must be in the ferrous state, and hence a reducing agent is added before the color is developed. Hydroxylamine, as its hydrochloride, can be used to reduce any ferric ion that is present: 2 Fe3+ + 2 NH 2OH + 2 OH 2 Fe2+ + N 2 + 4 H2O The pH is adjusted to a value between 6 and 9 by addition of ammonia or sodium acetate. An
March 3, 1999: A metalmaking process known to the ancient Romans could be pressed into service to bring Mars into the Iron Age and start opening the solar system to human habitation. "If you look at the soil composition of Mars, the one thing that really strikes you is that it's 5 to 14 percent iron oxide," said Dr. Peter Curreri, a materials scientist at NASA's Marshall Space Flight Center.