Home Production of Bases

[PeterB2]

I've been experimenting lately with producing bases at home. From what I've read, pratically any base can be produced from Ca(OH)2 (pickling lime, hydrated lime), baking soda, and ashes. Allow me to elaborate: heating baking soda (even on the stove in a sausepan) drives off H2O and CO2 leaving Na2CO3 (this can also be purchased cheaply as washing soda at a grocery store; I got mine locally at Kroger).

By taking advantage of potassium carbonate's solubility in water, K2CO3 can be separated from ashes. Add hot water to ashes, let sit to separate, decant, filter, recrystallize. Dissolve this crude product in hot water again and repeat the process to produce purified potassium carbonate. It requires a lot of ashes to get much though, but I tried it and it works quite well!

After a bonfire, I collected all the ashes and put them into a 5 gallon bucket "for use at a later time".

Sodium and potassium hydroxide can be produced from the metathesis reaction between Ca(OH)2 and the carbonate salt. Since the Ca(OH)2 is not very soluble in water, only sodium or potassium hydroxide will be left in the solution which can easily be filtered and recystallized.

Be careful what kind of lime you get though: limeSTONE is CaCO3, QUICKlime is CaO, and HYDRATED lime is Ca(OH)2. I bought it as pickling lime at the local Kroger for a good amount (probably about a pound). I think you can also get it in larger quantities at the hardware store for garden use.

Most of the information I found was from http://cavemanchemistry.com/oldcave/. (Although its apparently the syllabus for a college class, this site has some great proceedures and ideas for a home lab, everything from the production of sulfuric acid to making purifying potassium carbonate from ashes. Most of the "lab equipment" is 2 liter soda bottles :D) Scroll down to the "Projects" section of the page, about half-way down.

Please excuse me if this is common knowledge, but trying some of this really excited me!

EDIT

I tried the link, and it works but takes a while. If it doesn't work, you might try copying and pasting the address into the URL...

[DONMAN]

Hah, I actually own that book. It has a very novel approach to explaining chemistry and its history.

[megalomania]

The information is derived from even earlier works, like "The Golden Book of Chemistry Experiments." My copy dates from 1960.

Indeed the preparation of many bases can be accomplished just as PeterB2 has said.

Sodium hydroxide (lye) is made from the reaction between calcium hydroxide (slaked lime) and sodium carbonate (washing soda).

Potassium hydroxide can be made by reacting potassium carbonate (potash from wood ashes) with calcium hydroxide.

Magnesium hydroxide can be made by mixing hot solutions of magnesium sulfate (epsom salts) and sodium bicarbonate or carbonate. The reaction only happens when heated. Magnesium hydroxide precipitates from the solution, carbon dioxide is given off,and sodium sulfate is left behind along with one of the reactants unless stoichiometric quantities are used. If you don't have a scale try to form saturated solutions of both reactants, look up the solubility data at room temp, calculate the volumes of saturated solution to mix to achieve a stoichiometric ratio, and commence reacting.

My parents use their fireplace quite regularly, and I can get a heap of ashes by the end of winter. It takes many hundreds of pounds of wood to fill a 5 gallon bucket with ashes. The extraction process can be messy and dirty, but it does yield a good bit of product. I soak my ashes in hot water for a long time, filter off the charred wood bits and insoluble mud that remains with a shop towel, filter the solution again with paper towels or coffee filters to remove small particles, boil down the filtrate to get a crop of crude crystals, recrystallize, and filter again with filter paper to get an "acceptable" product. ACS purity this is not, but it good enough for certain applications.

I have read sodium bicarbonate (baking soda) can be converted to sodium carbonate (washing soda) by boiling a solution of the bicarb. You can just as easily buy washing soda, but I think it may be somewhat cheaper to get baking soda in the long run; I need to check on that.

Be careful using garden lime as it is commonly a mixture of calcium oxide, calcium carbonate, carbon hydroxide, magnesium oxide, magnesium carbonate, and magnesium hydroxide. Real lime, that is pure calcium oxide, seems to be something of a rarity around where I am. You can transform calcium carbonate (marble, chalk, seashells, limestone) and calcium hydroxide into calcium oxide by calcining at over 1000 C.

I was reading an old analytical chemistry book last week about separating magnesium and calcium ions for the analysis of lime. Since I can get a lot of garden lime that's nice, but with its impurities it is less than useful. Peter2B's suggestion of using pickling lime might be a better way to go since it should be pure calcium hydroxide. Calcining this would lead to pure calcium oxide.

[asilentbob]

I was considering making sodium hydroxide last year via calcium oxide. I never got around to it though and ended up finding a local pure OTC source.

I was going to make the calcium oxide in an electric pottery kiln by decomposition of calcium carbonate. The main thing that set me back was possible splattering of the calcium carbonate / calcium oxide. I didn't want to ruin the expensive kiln refractory. However, looking back this was pretty stupid as it would be contained in a covered ceramic crucible. (Hand thrown to boot.) Sodium carbonate would be store bought for "pool maintenance."

Keep in mind that hydroxides react with CO2 in the air:
ex.
NaOH + CO2 ---> NaHCO3
NaOH + NaHCO3 ---> Na2CO3 + H2O

So if your trying to get CaO from ashes make sure to burn the fire very hot and save the ashes in an air-tight container unless your going to process them shortly. Otherwise you might just end up with alot of carbonates.

It would be nice to see someone write up a tutorial or their experiences going from calcium carbonate all the way to around soap or technical grade sodium hydroxide.