Acid Test Kit - Refill
 

Several months a go I purchased an Acid Test "kit". A few months
ago I purchased another Acid Test "kit" from a different retailer.
The first one had Sodium Hydroxide solution of N/10 and the
Phenolphthalein was 1%. The 2nd kit had Sodium Hydroxide solution of
1/5N and the Phenolphthalein appears to also be 1%.

The calculation needed to arrive at the acid percent is different
between the two kits ... I assume due primarily to double strength of
the Sodium Hydroxide solution in the 2nd kit.

I have run out of the Sodium Hydroxide solution in both kits but I
still have lots of the Phenolphthalein solution. I'd like to order
just the chemicals rather than the "kits" due to lower price and
larger quantities. It looks like the Phenolphthalein solutions are the
same.

My question is can I continue to use the Phenolphthalein solution that
I still have regardless of the Sodium Hydroxide solution strength that
I order? Do these chemicals have a shelf life (or do they keep for at
least a few years)?

Thanks again for your feedback.

Roger L. Pelletier , Aurora, NE USA

Roger-

What you're asking is entirely possible. The solutions you're
referring to are 'normal' and not 'molar' solutions- that would be the
only little surprise you'd see.

You can make your own solutions fairly easily- see
http://www.carolina.com/chemistry/re...reparation.asp

at the bottom you'll see a description of how to make them. Basically
Normal solutions are easier to make- they weigh/volume out the water
and then add the chemical. Molar solutions are made 'to volume',
meaning they add the chemical and then dilute to EXACTLY the required
volume. See the difference?

So a N/10 (1/10th Normal Solution) of NaOH would require 1/10th
equivelent of 1 Mole of hydroxide ion, which means 1/10th of 40g/1OH =
4g per Litre water. See
http://www.biology.ewu.edu/Biosubsit.../Solution.html

If I've thoroughly confused you.... let me know. But basically all you
need is some lab grade NaOH 4g and then you add it to 1 litre of pure
DI water and you've got your 1/10 N solution.

Jason
Wino-Nouveau wrote:
> Several months a go I purchased an Acid Test "kit". A few months
> ago I purchased another Acid Test "kit" from a different retailer.
> The first one had Sodium Hydroxide solution of N/10 and the
> Phenolphthalein was 1%. The 2nd kit had Sodium Hydroxide solution of
> 1/5N and the Phenolphthalein appears to also be 1%.
>
> The calculation needed to arrive at the acid percent is different
> between the two kits ... I assume due primarily to double strength of
> the Sodium Hydroxide solution in the 2nd kit.
>
> I have run out of the Sodium Hydroxide solution in both kits but I
> still have lots of the Phenolphthalein solution. I'd like to order
> just the chemicals rather than the "kits" due to lower price and
> larger quantities. It looks like the Phenolphthalein solutions are the
> same.
>
> My question is can I continue to use the Phenolphthalein solution that
> I still have regardless of the Sodium Hydroxide solution strength that
> I order? Do these chemicals have a shelf life (or do they keep for at
> least a few years)?
>
> Thanks again for your feedback.
>
> Roger L. Pelletier , Aurora, NE USA

Roger) sodium hydroxide indeed does have a shelf life. The problem
with it is taht it will absorb CO2 out of the air and form bicarbonate
buffer, which will dink with your titrations.

Jason) When dealing with NaOH normality and molarity are the same
thing. Normality is a term that deals with molar equilivants. Since
NaOH only has one OH equivalent a 1 N solution is the same as a 1 M
solution. Now, Calcium hydroxide Ca(OH)2 has two basic equilivants, so
a 1 M solution of Ca(OH)2 is a 2 N solution. That page you supplied
is misleading. Look instead at:
http://environmentalchemistry.com/yo...Normality.html

Absolutely correct. I was mistaking mass percent and Normal- and I
just googled without reading too far into how they were applying the
math.

Silly me. Good thing my old chem prof isn't around reading this
*whistles innocently*

(B.S. Chemical Engineering and ACS Chemistry and I can mess this up...
*sheezus*)