Would someone please explain the "pros and cons" and "how tos"
of dealing with nitric?
G'day Alice Sauer et al; I have worked with and around nitric acid
from when I became a lab assistant at the age of 14 - and I still
occasionally use it now at 80.
But let there be no mistake; nitric acid is a very hazardous
chemical, especially in untrained and unknowledgable hands. I discuss
the strong acid:-
1) It is a very strong acid and as such will eat holes in clothing
even when diluted down to 10%. If allowed to come into contact with
flesh it must be washed off with plenty of water, but will leave a
bright yellow stain which can only be removed by wear - or the
application of pumice. If washed away quickly it will do no harm.
When 15, I put my arm into a tall jug which I thought was empty, but
was half full of concentrated nitric acid. After a good wash I was
none the worse except for a bright yellow arm and hand which became
it's more usual dirty colour in a week.
2) It is a very powerful oxidising agent. If a little is poured
into warm, dried sawdust it will burst into flame. Same with pure
turpentine. With oils it can possibly form explosive, and
spontaneously flammable compounds.
3) It constantly gives off a vapour of choking fume which is acid
and poisonous and which is bad for lungs. It will eat away corks and
rubber stoppers in a day or two.
4) It dissolves (etches) copper and brass very quickly giving off a
noxious and very poisonous brown gas called nitric oxide, or nitrogen
dioxide; (NO2) very bad for the respiratory system. The acid does not
dissolve iron easily, for it covers the surface of the metal in a
coating of oxide which it penetrates no further unless strongly
heated. This is used industrially and is called pacification.
5) Nitric acid will easily dissolve silver, also giving off the brown
poisonous fume, leaving silver nitrate, which can be crystallized
out. A mixture of nitric and hydrochloric acids is called aqua regia
(Royal Water) will dissolve gold, giving a solution of auric (gold)
6) A mixture of nitric and sulphuric acids combines with many organic
oily substances like glycerine to produce explosives such as nitro
glycerine which are extremely sensitive to rough handling and explode
violently. (Alfred Nobel began the Nobel Prize tradition to atone for
inventing dynamite, which contains the substance.)
I have been given conflicting on > how to use it,
when to use it and how to handle it.
So handle it with care, wearing protective goggles with side pieces,
wear rubber gloves and a plastic apron, washing them afterwards. I was
never told about that as a lab boy, and topped up about 30 reagent
bottles of it every morning for several years with no protection at
all, except a cotton lab coat which was always full of holes. And
which we had to supply ourselves.
As it will quickly eat away cork and rubber, it used to be supplied
in glass stoppered bottles, but polythene plastic lasts well - and is
Do you folks find it a frequently needed item in the studio?
Few jewellers use it. It is however, used in the famous 'acid test'
for golden metals. Streak the metal on a bit of slate and look at the
streak; certain shades provide clues to the metal. Add nitric acid
to the streak, and again observation of the streak can tell one about
the carat value of the metal if a gold alloy
What do you use it for?
Etching, some cleaning up of jewellery; See above
How do you store it?
In glass bottles with ground glass or polythene stoppers. Or
polythene bottles of heavy high grade polythene. Keep it in a cool
dark place away from the sunshine which will help it decompose. When
removing the stopper, avert the face (complete with eye protection) as
a little pressure may have built up, causing a small spray of acid. If
one has to use it often, it is preferable to store it in small bottles
rather than the 2� litre bottles I used to have to cart around the
labs. As when any acid is in frequent use, have a large plastic
bottle of baking powder (sodium bicarbonate) always handy. In the
case of spillage simply tip an excess of the dry powder over it, leave
a while, then sweep up the mess - which will still be a powder if
you've used plenty; it's cheap enough. Wash down the drain (No it
won't hurt the pipes, the septic tank or the sewer lines.) Later in
my laboratory life I supervised the cleaning up of smashed half gallon
bottles of conc. nitric acid; about 3 kilos of baking powder dropped
on the mess made it easy to clear up. (didn't do the parquet flooring
much good though)
Well, there you are; I could even go on, but enough is sometimes too
much. If there is anything I haven't covered, just email me
personally. -- Cheers now,
John Burgess; @John_Burgess2 of Mapua Nelson NZ