# How can I interpret this solubility data?

I'm currently trying to make incense paper. I've been instructed to mix ethanol 90% with potassium nitrate ($\ce{KNO3}$). As ethanol 90% is hard to get where I'm located I'm currently using methylated spirits (95% alcohol) as an alternative. The $\ce{KNO3}$ however is insoluble with the this. If I dissolve the $\ce{KNO3}$ in water first then add to the methylated spirits the solubility improves but it is still very cloudy. I went onto http://periodic-table-of-elements.org/SOLUBILITY to see if there were any suggestions. The page had the below results for $\ce{KNO3}$ solubility with ethanol:

• ethanol [$\ce{C2H5OH}$]: insoluble
• ethanol [$\ce{C2H5OH}$] 50%: 3,7 (20°)
• ethanol [$\ce{C2H5OH}$] 90%: 0,3 (20°)

I'm not sure what the 3,7 and 0,3 indicate though? I'm not even sure what they refer to perhaps soluble parts per 1000 ? If any one could help with what it means that would be great. As you can guess I barely qualify as a hobbyist chemist.

• SAFETY I'll point out that methanol and ethanol are both flammable. In a chemistry lab we'd do the mixing and drying in a fume hood to avoid a build up of vapors.
– MaxW
Jan 27 '17 at 19:04

Yes, the website is a little bit ambiguous. However, there is a clue in the colour legend. The solubilities are indicated in units of grams per 100 grams of water. (This is also a very common unit for expressing solubilities.) Therefore, a solubility of "$3.7$" means that $3.7~\mathrm{g}$ of $\ce{KNO3}$ dissolves in $100~\mathrm{g}$ of whatever solvent it is listed under. This interpretation is readily confirmed by checking the values against this Wikipedia page.

As for "$50\%$", my educated guess is that it refers to a mixture of $50\%$ ethanol and $50\%$ water.

And lastly "$20^\circ$" refers to $20~^\circ\mathrm{C}$.

It may not be wise to use methylated spirits to make an incense. Also known as denatured alcohol, such solutions deliberately contain hazardous compounds to discourage consumption. Your spirits likely contain methyl alcohol, which is volatile (evaporates easily into gas form) and toxic. Excessive inhalation of the fumes from the solution can potentially poison you. I don't know your procedure to prepare the incense, but I would be wary of combusting or breathing something prepared using toxic liquids.

Here's some background from Wikipedia:

"Denatured alcohol, also called methylated spirits or denatured rectified spirit, is ethanol that has additives to make it poisonous, bad tasting, foul smelling or nauseating, to discourage recreational consumption. In some cases it is also dyed. It is usually blue in colour. Government provides it to health industries and schools so that there is no alcohol consumption in such areas, and only for experiment purposes. Pyridine and copper sulphate is added to it which is poisonous.

Denatured alcohol is used as a solvent and as fuel for alcohol burners and camping stoves. Because of the diversity of industrial uses for denatured alcohol, hundreds of additives and denaturing methods have been used. The main additive has traditionally been 10% methanol, giving rise to the term "methylated spirits". Other typical additives include isopropyl alcohol, acetone, methyl ethyl ketone, methyl isobutyl ketone, and denatonium."

• Methanol burns just fine. Inhaling the combustion products is a lot different than drinking the methanol.
– MaxW
Jan 27 '17 at 5:40
• My main concern was the fumes, methanol is quite volatile yes? Jan 27 '17 at 16:36