Hard & soft water in my bath tub

Hi guys, my chemistry is not so hot but, even so, I've tried to
understand the chemistry of hard water and soft water in my own bath
tub. The info I've read talks about carbonates and sulphates of
calcium and magnesium. And it also mentions that soap scum is
calcium or magnesium stearate. But I am getting a bit lost.

I would like some advice on how to relate my own experience to the
chemistry of what is happening.

I live in ahrd water area and if I use some scented "Creme Bath"
from the supermarket then the amount of scum I get after bathing is
reduced. (Q.1) What is it in this Creme Bath which is doing this?
(Q.2) Is sodium lauryl sulfate a water softener or is someother
ingredient the water softener? The ingredients of the Creme Bath are
as follows:

"Creme Bath" ingredients:

aqua
sodium laureth sulfate
sodium chloride
cocamidopropyl betaine
parfum
disodium EDTA
styrene/acrylates copolymer
terasodium EDTA
formaldehyde
sodium benzoate
benzyl alcohol
sodium lauryl sulfate
magnesium nitrate
methylchloroisothiazolinone
magnesium chloride
methylisothiazolinone
citric acid
polysorbate 20
sodium hydroxide

Alternatively I sometimes use powdered Bath Salts. I get the
impression that my Bath Salts actually *harden* the water with the
result that I get more scum than if I wasn't using theme. (Q.3) Is
this observation true based on the chemicals my Bath Salts contain?
The ingredients of my Bath Salts are as follows:

sodium chloride
sodium carbonate
sodium bicarbonate
sodium lauryl slulfate
parfum
aqua
PEG-40 hydrogenated castor oil
trideceth-9

The strange thing is that I have the *impression* that if I use half
the normal dose of the Creme Bath and half the normal dose of the
Bath Salts then I get less scum forming after the bath than if I used
either one at full dose.

Also this scum seems easier to remove. (Q.4) Am I imagining this
or is there any chemistry-based explanation to support what I think I
experience?

On Thu, 27 Nov 2003 16:56:23 GMT, Vance Roos <[Only registered users see links. ]> wrote:


It's the methylchloroisothiazolinone, silly. Didn't you stay awake in
chemistry class? I thought everyone knew that.

Bill Penrose

Vance Roos <[Only registered users see links. ]> wrote:


Sodium lauryl sulfate is a detergent. One of the great benefits of
detergents relative to soaps is that they retain their effectiveness
in hard water. In contrast, soaps, which are sodium or potassium
salts of alkali metals, give scummy precipitates with magnesium or
calcium ions. This both destroys the soap properties and produces the
scum.

The EDTA derivatives in your creme bath are water softeners in the
sense that they sequester the Ca++ and Mg++ ions.


Suggestion: instead of going on impressions, which are sometimes
wrong, how about doing a scientific experiment or two?

Steve Turner

Real address contains worldnet instead of spamnet

Vance Roos <[Only registered users see links. ]> writes:

Instead of bathing with soap, try lathering with a dab of hair shampoo
instead and see whether the bathring forms as noticeably.
--
John Savage (news address invalid; keep news replies in newsgroup)

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