ferric chloride and ferric nitrate are not acids, are they? I was
under the impression that they were bases. Am I wrong?
G’day Noel et al.; Before I try to answer that, let’s have a go at
a general (rather loose) definition of an acid. But I don’t want to
get into complications (there’s many) as I don’t want to confuse or
"blind you with science!"
An acid is a substance which has an easily replaceable hydrogen
atom; HCl; HNO3; H2SO4. It turns certain vegetable colourings
like litmus from blue to red. It has a pH below 7.0 (don’t worry
about the exact meaning of that; it can get very abstruse and
confusing) It has a sour taste. It combines vigorously with
alkalies and bases.
Alkalis have an easily replaceable hydroxyl group; NaOH, KOH etc.
Turn litmus from red to blue, have a pH higher than 7.0, combine with
acids to form a salt. Many salts are neutral, but some are acidic;
others are alkaline. Sodium bisulphate does have a poorly attached
hydrogen atom, so it has an acid reaction. Some salts like sodium
carbonate have an alkaline reaction because carbonic acid is one of
the weakest, and a hydroxyl group becomes available when dissolved in
Ferric nitrate and ferric chloride are both salts within the meaning
of the definition; they are the result of a combination of an acid
and an alkali. But in both of these there is a weakly held hydrogen
atom, and this makes them acidic; they have a pH lower than 7, turn
litmus red, taste acid and combine with alkalis and bases. (metals
are basic; neither acid nor alkaline. Their oxides are another story
and things get complicated)
The main reason that this matters is that I want to be sure
what to use to neutralize them, particularly a spill.
From what I have said above, it follows that spilt acids and liquids
of of dubious origin should be neutralised with a mild alkali, such
as sodium carbonate, or sodium bicarbonate.
When I was responsible for the technical operation of chemical
laboratories, I insisted that close to every bench a large wide
mouth 3 kilo jar of sodium bicarbonate must be always available, to
simply tip the contents over any acid spill. The resultant heap can
later be disposed of by sweeping up with a dustpan and brush. This
was used for smashed 3 litre bottles of concentrated acids. It is
the only safe method of clearing up the mess, which can safely be
disposed of in the usual way. For spent jewellers-pickle, neutralise
it with bicarbonate, mix with sawdust or sand, allow to dry, wrap in
newspaper and have it taken to the usual trash tip.
Sodium bicarbonate is very cheap (I used to purchase it by the
hundred weight sack) and is available at any supermarket. “Baking
Powder” is not the same and is not suitable.
Finally, make it an unbreakable rule that all chemicals of any kind
(including table salt and sugar) are clearly labelled, and the label
kept up to date and easily readable. Poisons must be out of reach
of children and clearly labelled. Keep to the rule:- ’ if it is
unlabelled, it MUST be thrown out’ Thinking you know what it is
isn’t good enough. – Cheers for now, John Burgess; @John_Burgess2
Mapua, Nelson NZ