[Tittywahah]

When I bought this I did not know that it was insoluble in water, everytime I read about using this in titrations the books simply said: "...use phenolphthalein 1 drop or 2 drops....".  So my question: All that I have is surgical spirits, which according to the label contains 90% ethanol, 5% methanol, and blank..obviously 5% something else.  Would this be ok to make up a solution of phenolphthalein?  Oddly, I could find no references on the web about how one makes a solution other than in ethanol.  Thankyou.

[Arkcon]

The remainder of this denatured alcohol solution you have is likely water.  Its hard to remove from alcohol, and there's not reason to waste the effort and expense if the application doesn't call for water-free alcohol.  Since you use only a trace of the indicator, the water and methanol impurity won't (likely) have a big effect.

[Borek]

Solubility of phenolphthalein in water is very low, which is why it is used in the form of ethanol solution.

[Tittywahah]

Thankyou.  Does it matter how much of the indicator you use when titrating?  Just measured small amounts in the region of 0.25 gram for example? Or are there rules? I have never used the dry form before and there really is nothing in the texts or in documents on the web about this.  (I guess it's something taken for granted by most which is understandable), unfortunately I am not a student or on a course.

[Borek]

Does it matter how much of the indicator you use when titrating?

Yes. Without getting into details - use as small amount as possible. Indicator is an acid (or base) itself, so when you add too much you may have to titrate it as well, changing the titration result. Then, in the case of one-color indicators like phenolphthalein, pH at which they become visible is a function of their concentration, so using too much/not enough can shift the end point. See discussion here:

http://www.titrations.info/acid-base-titration-indicators

http://www.titrations.info/acid-base-titration-end-point-detection

[Tittywahah]

Borek, many grateful thanks for those references. Can't believe that in all the info I was resourcing I never came across this one.

[Arkcon]

The concentrations I've seen on Google, for the indicator solution phenolphthalein, is 0.1% or even 0.05%.  Sigma chemical, for example, sells a 0.1% solution.  Note that the titration calls for drops ... that is 1 ml or less, for 100 mL or more titration reaction.  So we're really looking for vanishingly small quantities of indicator.

Note that I'm assuming you're just reinventing the wheel here for a reason of no importance -- you have dry phenolphthalein and don't want to buy some pre-made, you want to learn, you're just casually curious about methanol, or some reason like that.  But we have had some very weird questions on the topic of the chemistry of indicator solutions:

http://www.chemicalforums.com/index.php?topic=22851.0

http://www.chemicalforums.com/index.php?topic=30197.msg115166#msg115166

[Tittywahah]

Hi Arkcon, to satisfy any curiosity you have, nothing to do with methanol, don't know the first thing about alchohols.  Yes I want to learn, but also am an avid experimeter with regards to old photography, I'm talking 1830 to 1890 style.  Strange compunds and mixtures involved, especially in toning and archiving.  But I want to know always Why and How, not simply do it with ready made stuff.  It's a mixture of creative satisfaction combined with the whole wide range of an academic interest in inorganic chemistry, though I have had to deviate frustratingly into a bit of organic learning.  If I come across a new chemical requirement my first instinct has always been  to make it rather than buy it. Strange as that sounds. However the phenolpthalein in solution was twice the price and I have to watch the pennies, it seemed sensible to buy 100 times the amount for next to nothing - especially since it keeps forever.  Not to mention the water into wine tricks and other stuff I can entertain my children with.