On Oct 3, 12:06 pm, Nosterill wrote:
On Oct 3, 10:57 am, Weatherlawyer wrote:



On Oct 3, 12:35 am, "RyderCup&PrezCupSux"

wrote:
Hello,

I know that most volcano movies are crap as far as real science is
concerned. I have a question about one specific scenario in "Dante's Peak".
Some people get trapped in a metallic boat on an acidic lake. Boat starts
dissolving as it is proceeding on the lake and water starts to come into
the boat. The propellers dissolve in the acidic water stranding the boat in
the lake.

How realistic, if at all, is that scenario?

What acid would be involved? The only one I can think of is carbonic
acid. Sulphur will burn in oxygen to form sulphur dioxide but getting
that to form an acid is rather difficult. Maybe there are life forms
in the earth that will convert sulphur into sulphuric acid.

Sulphur dioxide forms an acid very easily by dissolving in water to
produce the relatively weak sulphurous acid (H+ HSO3-). This is a
reducing acid and not too tough on metals. Sulphur dioxide can "burn"
in excess oxygen to produce the trioxide which dissolves in water to
produce the far more aggressive oxidising sulphuric acid and then, if
all the water molecules have been used, it continues to dissolve
producing something variously called fuming sulphuric acid or oleum.
That stuff is truly viscious and would certainly make short work of
most metals - however! I don't imagine that would happen "in the
wild". Far more probable is the bacterial theory and there are plenty
of examples. Villa Luz cave in Mexico is a classic case. This too is
unlikely to occur in an above ground lake in a realistic timescale.

So - in summary - there are ways of making boat eating acid from
sulphur but not in the scenario presented in the film.

Nice try but I actually looked the chemistry up for a thread in a
meteorology discussion on glowballs.

According to a somewhat dated text book used in schools to teach 16
and 17 year olds when I were a lad, the gas sulphur dioxide hadn't
been turned into an acid by dissolving in water.

Or something to that effect. However I have just installed
Encyclopedia Britannica 2006 and this is what it says:

On acid rain:

A "form of precipitation containing a heavy concentration of sulfuric
and nitric acids. The term is also commonly applied to snow, sleet,
and hail that manifest similar acidification.

Such precipitation has become an increasingly serious environmental
problem in many areas of North America, Europe, and Asia. Although
this form of pollution is most severe in and around large urban and
industrial areas, substantial amounts of acid precipitation may be
transported great distances."

And that article linked to this:

"The process that results in the formation of acid rain generally
begins with emissions into the atmosphere of sulfur dioxide and
nitrogen oxide. These gases are released by automobiles, certain
industrial operations (e.g., smelting and refining), and electric
power plants that burn fossil fuels such as coal and oil.

The gases combine with water vapour in clouds to form sulfuric and
nitric acids. When precipitation falls from the clouds, it is highly
acidic, having a pH value of about 5.6 or lower. (The term pH is
defined as the negative logarithm of the hydrogen ion concentration in
kilograms per cubic metre.

The pH scale ranges from 0 to 14, with lower numbers indicating
increased acidity.) At several locations in the eastern United States
and western Europe, pH values between 2 and 3 have been recorded. In
areas such as Los Angeles, San Francisco, and Whiteface Mountain in
New York, fog is often 10 or more times as acidic as the local
precipitation.

Reactions and uses

Pure H2SO4 undergoes extensive self-ionization (sometimes called
autoprotolysis).

2H2SO4 H3SO4+ + HSO4

This autoprotolysis reaction is, however, only one of the equilibrium
reactions that occur in pure H2SO4 to give it an extremely high
electrical conductivity. There are three additional equilibrium
reactions that take place because of the ionic self-dehydration of
sulfuric acid.

2HSO4 H3O+ + HS2O7
H2O + H2SO4 H3O+ + HSO4
H2S2O7 + H2SO4 H3SO4+ + HS2O7

Thus, there are at least seven well-defined species that exist in
"pure" H2SO4. The value of the dielectric constant of the acid is also
quite high ( = 100).

Concentrated sulfuric acid is not a very strong oxidizing agent unless
it is hot. When it acts as an oxidizing agent, however, it can be
reduced to several different sulfur species, including SO2, HSO3 ,
SO32 , elemental sulfur (S8), hydrogen sulfide (H2S), and the sulfide
anion, (S2 ). Concentrated sulfuric acid is a good dehydrating agent,
as it reacts with many organic materials to remove the elements of
water."

A bit of a mouth-full to digest but what is the reaction involved in
the fog where it can be measured as acid but not precipitated?

And if the reaction to sulphuric acid is very cost intensive, tending
to revert how is the first article so glib to jump that difficulty?

Most reasonable people won't dig much deeper than that article which
is about as far as glowballers seem to get.