From: SFPhysics@aol.com
Date: Thu Apr 22 2004 - 01:36:19 PDT
From: SFPhysics@aol.com Message-ID: <15b.3329bcac.2db8de03@aol.com> Date: Thu, 22 Apr 2004 04:36:19 EDT Subject: Seawater Alkalinity
I came across a statement in a CSET reviewer that saltwater will turn red
litmus paper blue because it is alkaline. I know salts are neutralization
products of the reaction between acids and bases and thus, are supposed to form
neutral solutions.
Are there basic impurities in salt that might make saltwater alkaline?
Sheila Lacanaria
Greetings Sheila:
Seawater composition is the result of eons of runoff from the land, volcanic
activity, and a great number of other interactions. Where the runoff cannot
reach the sea you end up with alkaii lakes, often dry, commonly seen in places
like the Mojave Desert. As anyone who has ever maintained a salt water
aquarium can attest, the chemical interactions are too numerous to list here. If we
were to oversimplify things we might say that the leaching action (chemical
weathering of land) frees into ocean bound water the acid binding ions of
sulfates, phosphates, borates, hydroxides, etc., but it is *mostly* the carbonates
that create the alkalinity. Limestone, calcium carbonate CaCO3, accounts for
the majority of the chemical action. Once in the ocean you find the Ca and the
CO3 dissociating and a wide range of reactions with other ions results. As
with balancing a swimming pool, the total alkalinity is tied to the calcium
carbonate concentrations. Whole books have been written about this. Try F. J.
Millero, *Chemical Oceanography* 1996
Hope that helps,
Al Sefl
Whose ideas about seawater chemistry may be all wet...
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