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View Full Version : Measuring KOH concentration with hydrometer



BoyntonStu
08-03-2008, 11:44 PM
Specific Gravity of KOH :

27% = 1.2592
28% = 1.2695
29% = 1.28
30% = 1.2905


BoyntonStu

More complete table here: http://www.ashtachemicals.com/products/kohchem.htm#sg

computerclinic
08-04-2008, 02:37 AM
Good info boyntonstu...I was wondering that...

Roland Jacques
09-18-2008, 02:04 AM
Thats good info . now all we have do is fine a hydrometer or Refractometer that can read that range.

Roland Jacques
10-09-2008, 12:51 PM
Any luck on finding a hydrometer that can read these ranges.

I found these, I think the lower one should be OK. http://sciencekit.com/hydrometer/p/IG0023641/

Roland Jacques
10-10-2008, 02:53 AM
Is it 28% by weight the Ideal concentration?
If so would 0.5 lbs of Noah or KOH and 1.0 lbs of water = 33% concentration?

hg2
10-10-2008, 03:14 AM
Is it 28% by weight the Ideal concentration?
If so would 0.5 lbs of Noah or KOH and 1.0 lbs of water = 33% concentration?

28% is ideal for most dry cells,but an openbath type would overheat quickly and the amps would spike high as well.I use 33% in my dry cell which works out to over a pound of koh per gallon distilled water.
I think the hydrometer you mentioned is the same that saltwater aquarium owners use to test salt content in their tanks

Painless
10-10-2008, 03:26 AM
Is the purpose of this to determine when the maximum efficient concentration has been reached?

If so, why not use a multimeter to measure the resistance across your electrolyte as KOH is added, and stop once the resistance becomes static?

hg2
10-10-2008, 03:38 AM
Is the purpose of this to determine when the maximum efficient concentration has been reached?

If so, why not use a multimeter to measure the resistance across your electrolyte as KOH is added, and stop once the resistance becomes static?

I think measuring your ammount once you've determined the ideal concentration that's giving the best results would be the easiest way.If you always buy your koh from the same source it will always remain a constant.This can be done by either weight or dry measure.

Roland Jacques
10-10-2008, 01:37 PM
I think the hydrometer you mentioned is the same that saltwater aquarium owners use to test salt content in their tanks

No, aquarium hydrometers are a much lower range. 1.010-1.036

Roland Jacques
10-10-2008, 01:43 PM
Is the purpose of this to determine when the maximum efficient concentration has been reached?

If so, why not use a multimeter to measure the resistance across your electrolyte as KOH is added, and stop once the resistance becomes static?


Will the resistance become static?

I read somewhere the Ideal concentration is 28%, so is that where the resistance would go static? Or would be a lot higher than that with just diminishing returns?

Painless
10-10-2008, 02:01 PM
Will the resistance become static?

I read somewhere the Ideal concentration is 28%, so is that where the resistance would go static? Or would be a lot higher than that with just diminishing returns?

From what I've understood, past 28% adding further KOH does not improve the conductivity of the water (someone else please jump in here if you think I'm mistaken), this tells me that adding KOH or any other catalyst is reducing resistance. At the particular catalysts saturation point further reductions in resistance cannot be reached.

On a side note, I think resistance would be the ideal universal way of expressing the state of electrolyte and would be translatable over to NaOH or any other catalyst. It would also provide a means of comparing new catalysts by expressing the resistance achievable in a known volume of water. What we need is an agreed setup, for example, a 2" square container filled to the brim with multimeter electrodes or some other approved conductor at approved places in the container to maintain a current travel distance and hence a comparable electrolyte resistance reading.

Roland Jacques
10-14-2008, 01:55 PM
I did find a nice good size battery hydrometer In the 1.20 - 1.30 range, at O'Reily's auto parts. I'll be testing the conductivety also.