Sciencemadness Discussion Board

what is 100% NaOH solution?

chemrox - 21-5-2010 at 13:27

I have a journal procedure I want to adapt to a synthesis I'm doing. The procedure contains this instruction: "In a two neck round bottom flask equipped with a condenser, 0.10 moles of the base (6) from Step 1 and 50 ml of %100 NaOH was added." It goes on to say the mixture was heated to 50-60 *C and another reagent added and everything stirred for 5 hrs.

Is the %100 NaOH a typo? Is there or was there in the 1950's a common understanding of what this meant? Does anyone have any ideas about the meaning of %100 NaOH in this context?

I apologize for not posting the original article. I'm reading this off of a sheet I copied for placement in my notebook. I will track down the cite eventually but this should be enough information to appreciate the issue.

I edit to add: this has got to be a typo and the real concentration is 10% w/w. That would provide the strong base needed to run the next step.

Thanks,
CRX

[Edited on 21-5-2010 by chemrox]

franklyn - 27-5-2010 at 05:38

I had posted this before elsewhere , it bears repeating.
Quote:
Excerpted from Crystallization 4th ed. J.W. Mullin , pgs 90-91
Many methods of solubility expression can lead to the use of the potentially
misleading term ' percentage concentration '. For instance, an expression
such as ' a 1O per cent aqueous solution of sodium sulfate ' without further
definition, could be taken to mean anyone of the following:

10 g of Na2S04 in 100 g of water
10 g of Na2S04 in 100 g of solution
10 g of Na2S04•10H2O in 100 g of water
10 g of Na2 S04•1OH20 in 100 g of solution

If 10 g of anhydrous Na2S04 in 100 g of water were the intended description
of the solution concentration, this would then be equivalent to :

9.1 g of Na2S04 in 100 g of solution
20.6 g of Na2S04•10H2O in 100 g of solution
26.0 g of Na2S04•10H2O in 100 g of water

which gives some measure of the magnitude of the possible misinterpretation.
To make matters even worse, the term ' percentage concentration ' is often
applied on a volume basis, e.g. 10 g of Na2S04 in 100 mL of water, of solution,
and so on.


I suggest looking for a related expression of the terminology used
in the same article or journal that is not ambiguous , to infer from.

.