Potassium ferricyanide (10 percent solution--dissolve 10 grams of potassium ferricyanide in 100
milliliters of water).
(1) Nitric-acid testing. There are two forms of nitric-acid testing; they are concentrated and
diluted.
(a) For concentrated nitric-acid testing, place one drop of concentrated nitric acid on a
clean metal surface. Table 5-6 shows the possible test reactions.
(b) For diluted nitric-acid testing, place one drop of diluted nitric acid (50 percent acid
and 50 percent water) on a clean metal surface. Table 5-7 shows the possible test reactions.
(c) Aluminum, antimony, cobalt, gold, high-temperature alloys, tungsten, lead, platinum,
stainless steels, tantalum, and titanium do not react to nitric-acid (concentrated or diluted) testing.
Table 5-6. Concentrated nitric-acid test reactions
Table 5-7. Diluted nitric-acid test reactions
5-23
EN0562
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