Gallery, Projects and General > How do I??

One for the Chemists - water softening solution.

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awemawson:
I've been rejuvenating the automatic water softening / de-calcification system on my Karcher MPDS steam cleaner.

It's probably worth pointing out that this is an ex-military 'Multi-Purpose-Decontamination-System' designed to clean vehicles and personnel after battlefield nuclear weapons had been used. Not much technical information about. However this bit of the design is relatively simple. A small tank holds a reservoir of dosing liquid that is dispensed via a solenoid valve into the 'suck' orifice of a venturi thence on into the machines pipe work. Solenoid valve is worked by a timing board pulsing it every minute or so. Built into the tank are a pair of electrodes used (presumably by conductivity) to warn of an empty tank.

So far so good - the electronics of the timer have been sorted, the tank repaired but what fluid to use? Obviously it needs to shift limescale, so something like citric acid or phosphoric acid would fit the bill. Saturated solutions of citric acid are insufficiently conductive for the sensing but 40% phosphoric acid works ok.

However what is it supposed to use? I have a Nato stock number for the correct stuff but no details.

It seems that the MPDS evolved from the HDS 1000 DE and it's manual stated Karcher RM110 fluid FOR WHICH THERE IS AN MSDS SHEET  :ddb:

The MSDS sheet says it contains  hydrochloric acid 1-3%  and sodium hydroxide 5-8% with a pH of 7.0-7.5

Now as far as I remember my school chemistry here we have an acid and a base being mixed producing a salt plus water with a pretty much neutral pH

so what is the resultant chemical ????

(No photographs as the forum has problems at the moment with photos!)

philf:
Andrew,

You are spot on with salt + water.

HCl + NaOH = NaCl + H2O

But I think because the concentration of NaOH is stronger you'll end up with a mix of NaOH + NaCl. If that's the case why bother with the HCl in the first place?

It's 50 years since I did chemistry so I may be missing something.

I wanted to be a chemistry teacher until we started doing organic chemistry and I totally lost interest.

Phil.

eskoilola:
The result is table salt.

awemawson:
But again back to school chemistry - table salt NaCl isn't going to do much to shift calcium deposits - or am I missing something here  :scratch:

millwright:
Dendritic Dairy Salt was we used in the water softener for the steam boiler feed water at work,  Two 10,000lb an hour heavy fuel oil fired Babcock boilers 40 od yrs old and lovely and clean inside and corrosion free when opened up for the annual inspection.

John

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