Charles wrote <>

In the case of your catalog designations, the N-designation denotes the
concentration of the acid. It simply allows you to calculate how much to use
in a given mixture.

The "N" refers to Normality, a reference to the gram-equivilant solute
concentration of the acid or base. A Normal solution is used to equilibrate
the concentrations of acids or bases that have different amounts of
dissociable molecules, so you can compare, say, HCl and H2SO4. The
Gram-equilvalent is a measure of the amount of dissociable ions equal to a
mole.

The reason acids and bases are not calculated in moles is that when they
dissociate in a solution the molar concentration may not equal the actual
proton or hydroxyl concentration. For instance, moles of HCl and H2SO4 do
not equal each other in acid strength. A mole of HCl has only one-half the
dissociable H+ as a mole of H2SO4.

A 1N, or One Normal solution of a simple acid, like HCl is identical to a
One-molar concentration of the molecule. So, there is one mole H+ per liter.
A 2N means two moles of H+ per liter. 

If a mole of H2SO4 is dissolved in a liter of water, you will have a
one-molar solution, but also a 2-normal (due to twice as many H+). So, if
you want a solution of sulferic acid that is equivlent in strength to a 1N
hydrocloric acid solution, you will use one-half the molar concentration of
the sulferic acid, since it has twice the number of protons (H+). It would
then be 1N.

It gets more complicated as the molecules become more complex, especially
with molecules that do not fully dissociate. Any basic chemistry book will
give you the formula to calculate normal solutions.



Tim Morken
CDC, Atlanta 

-----Original Message-----
From: Charles Read [mailto:csu15397@mail.claytonstate.net]
Sent: Monday, January 20, 2003 3:36 PM
To: histonet@pathology.swmed.edu
Subject: HCl Question....


Hello!  While reading through the  Fisher Sci. chemical catalog I noticed
that in the Hydrochloric Acid section there were many types of HCl, but the
only difference was one was labeled 0.5N, another labeled 1N and some were
labeled 2N, what does this refer to?  How does it change it's use?  Thanks
guys!