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The Joy of Citrus pickle

one of the chemicals used in the print making process was made from
pure citric acid. It was sold as glacial, or possibly galactic
acid. Very nasty in its undiluted form but very inexpensive.
Perhaps this might be used to make a pickeling solution.

Don’t use this stuff as it is Glacial Acidic Acid and is lots more
active than citric acid.

Both posts are off. The second, just in spelling. The referred to
acid is glacial acetic acid. It is the stuff that, when diluted to
4-8 percent, is what we call vinegar, and is unrelated to citric
acid other than the fact that both are acids and both are found in
foods. Citric acid is what gives citrus fruits their sour taste.
(More than the also present ascorbic acid, commonly known as vitamin
C) Concentrated acetic acid is called “Glacial” because it’s
freezing point is only a little below room temp, and in a colder
room, might well be found frozen solid. Glacial acetic acid contains
about 80 percent or more acid, the remainder is water. It’s
flammable, and HIGHLY corrosive (so are the fumes), causing severe
burns on skin, and reacting strongly with several types of organic
compounds. Combined with cellulose (wood, cotton, etc), it converts
it to cellulose acetate, for example, a material once widely used for
the production of film, and as an early plastic. It’s a key reagent
in the production of aspirin. In photography, it’s used in the
preparation of “stop bath”, which stops the action of developing
agents on film. Despite it’s corrosive and nasty nature, it’s
actually chemically classed as a “weak” acid, and it’s effects on
metal are slower and weaker than that of stronger acids like Nitric
or Sulphuric. Nevertheless, it is corrosive to most common metals
other than aluminum…

Pure glacial acetic acid is not likely to be safe enough to use as a
pickle. But diluted with water (remember to do that safely…), it
becomes much tamer, and concentrations somewhat stronger than normal
vinegar might well have some use as a pickle, perhaps with the
addition of some salt, which introduces chloride ion, producing the
chemical equivalent of dilute HCL as well as the acetic acid. That
would make it more effective on copper and it’s oxides… If you try
the stuff as a pickle, be aware that it may, if concentrated enough,
or perhaps even if not concentrated much, be able to affect (etch, or
react with) the metal itself, not just oxides. Might be worth some
cautious experiments. Just be careful with the concentrated stuff.
It is indeed, nasty. Look up an MSDS on the web before using it.


Don’t use this stuff as it is Glacial Acidic Acid and is lots more
active than citric acid.

G’day; There is no such thing as galactic acid. (though there is an
uncommon sugar called galactose) But glacial acetic acid does exist.
It is called glacial because it freezes solid at 15C then looks just
like water ice. It causes unpleasant painful burns on human flesh,
and it’s vapour is flammable. However, the white vinegar you see in
the supermarket is very diluted glacial acetic acid which will sting
in a cut but won’t burn you. You could probably use vinegar as a
pickle, as it would dissolve copper oxides, giving green copper
acetate - also called verdigris.

Cheers for now,
JohnB of Mapua, Nelson NZ

You are right regarding citric acid. Penland School in Penland, N.C.
uses it in their metal studios. I don’t know where to get it, but it
does work great.

Ventura, CA