[Histonet] 4N HCL

[Morken, Tim - Labvision]

Although histology and old chemistry books are full of Normal solutions, it
is an out-of-date term as far as I can tell. HCl is easy because it has only
one valence, but if you have more than one valency,  with two or more ions
with different valences, it becomes complicated as to what "normal" means
("normal" to what?). A more clear method is to express it in terms of
equivilent molarity. 


An  note about the use of "Nomal" soutions:
http://www.madsci.org/posts/archives/2005-02/1108587746.Ch.r.html
Comment is reproduced below:

"Anyone who learnt any chemistry after about 1970 has probably never heard
of a "gram equivalent weight" nor of the "normality" of a solution. But this
is what Webster's definition a. is referring to. These terms were
extensively used 50 years ago and before. In modern terms, the gram
equivalent weight of a substance is equal to the molar mass divided by the
valency. A 1 normal solution of hydrochloric acid is exactly the same as a 1
molar solution of hydrochloric acid, but a 1 normal solution of sulfuric
acid is the same as a 0.5 molar solution of sulfuric acid (because the
'valency' of sulfuric acid is 2). The problem with normality as a measure of
concentration was that the normality of the same solution could vary
depending on the context of what you wanted to do with it. For example,
dilute nitric acid has a 'valency' of 1 as an acid, but a 'valency' of 3 as
an oxidant. So a solution of nitric acid that was 1 normal for the purpose
of neutralizing with caustic soda was 3 normal for the purpose of dissolving
up copper foil. Sometime in the 1960s, the International Union of Pure and
Appplied Chemistry wisely decided that normality was a concept that chemists
would be better off without, and that thenceforth concentrations would be
expressed in terms of molarity. 

The bottom line as far as your question is concerned is that there are two
possibilities. If the reference is to sodium chloride as 'normal saline' in
a medical context, it means 155 millimolar; if, on the other hand it is a
very old-fashioned chemical reference, then it means 1 molar, because the
'valency' of sodium chloride in any context is 1. "




And this from  International Union of Pure and Applied Chemistry
(www.iupac.org)

Seet their nomenclature book
http://www.iupac.org/publications/analytical_compendium/

Chapter six covers equivilent solutions:
 ( www.iupac.org/publications/analytical_compendium/Cha06sec3.pdf  )
Note the last sentence on page 6-5. (paragraph reproduced below)

Normal solution
A solution in which the amount-of-substance concentration of the equivalent
of the reagent is1 mol dm-3(i.e. 1 mol l-1) was termed a Normal solution,
symbol N. Decimalised fractions of N was used, e.g. 0.326 N H2SO4, that is a
solution with c(1/2H2SO4) = 0.326 mol l-1.  Note: Because confusion may
exist when a reagent has different equivalence factors according to
circumstances, the statements of normality must be accompanied by the
equivalence factor, e.g.0.1 N KIO3; feq(KIO3) = 1/60.05 N KIO3; feq(KIO3) =
1/4.
The use of the terms "Normal solution, Normality" are not recommended.


Tim Morken
Lab Vision - Neomarkers
www.labvision.com

Free webhosting for US State Histotechnology Societies:
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-----Original Message-----
From: histonet-bounces <@t> lists.utsouthwestern.edu
[mailto:histonet-bounces <@t> lists.utsouthwestern.edu] On Behalf Of Steven
Coakley
Sent: Monday, October 17, 2005 3:52 PM
To: Histonet <@t> lists.utsouthwestern.edu
Subject: [Histonet] 4N HCL

I haven't had to figure normality for ages.  would a 4N HCL solution be 4
times the HCL strength of a 1N HCL solution?  Or is that to simple.
 
Styeve