Intro: Convert a Bar of Soap Into Fatty Acids
In this 'ible I will demonstrate unto the Instructables community, and anyone else in the World who cares to read this, how I converted a bar of Ivory(r) soap, and a few hundred milliliters of The Works(r) brand toilet bowl cleaner, into a solid, white, waxy mass, that I believe to be a mixture of fatty acids.
I think this project is interesting, and weird, and I think it definitely qualifies as an "unusual use" for "everyday things" found in a typical bathroom, so I am entering it in the "Unusual Uses: Bathroom Challenge".
If you like this 'ible, and you are viewing it while the U-U-Bathroom contest is still active, please vote for it.
By the way, certain salient features of this ible, and this ible's very existence, were directly inspired by the U-U-Bathroom contest.
What I mean by that is, I probably would not have thought to try this at all, if it were not for the U-U-Bathroom contest. What I mean by "salient features" is the fact that the starting materials are: Ivory(r) soap, the hydrochloric-acid (HCl) based The Works(r) brand toilet bowl cleaner, and water. Each of these being typical bathroom items. These are not the only starting materials that could be used to synthesize a fatty acid mixture (FAM), and maybe these are not the best choice of materials either.
I got interested in FAM by reading this tutorial
which shows how to make fatty-acid coated magnetite nanoparticles, and I found it while while searching for recipes on how to make ferrofluid. The FAM made via the recipe linked above is made using ingredients you might find in your kitchen, like: olive oil, vinegar, and sodium hydroxide (NaOH) drain cleaner. A PDF copy of their paper is attached below.
In fact a kitchen themed method for making FAM is a better method in many ways. Vinegar is less acidic and thus safer to work with than HCl based toilet cleaner. That's the main advantage. Also the raw ingredients should be cheaper, given that they are more raw, i.e less processed. You could probably find oil, vinegar, and lye in a pre-industrial (or even a post-industrial) society. Also the kitchen method produces a valuable by-product: glycerol. These more natural ingredients probably smell better too.
However for the purposes of this instructable, I am going to assume that I'm living in some sort of dystopian over-industrialized consumer society, where the only available ingredients are ones sold as products intended to be used for something else. Another interesting feature of this hypothetical dystopian consumer society is that not only does the television/government tell you what to buy, but they also dictate how you must use these products once you get them home. In many cases the appropriate use for a given consumer product is to literally flush it down the toilet. Then go out and buy some more! Ha!
Which leads me to the best part: This instructable may be a violation of Federal Law (in the Former US) provided it constitutes a use of The Works(r) brand toilet bowl cleaner in a manner inconsistent with its labeling. A screenshot of http://www.theworkscleans.com/toiletcleaner.html is attached as a picture, the 4th in the stack, complete with misspellings.
Seriously though kids, the most dangerous part of this 'ible is probably not the danger of running afoul of the guys who wear jackets with three letters printed on the back. Most of the danger in this 'ible comes from the fact that you're working with hydrochloric acid. The Works(r) brand toilet bowl cleaner is 20% HCl by weight, or about 6 mol HCl per liter. It's kinda nasty stuff. You definitely want to wear eye protection. And gloves too. You should also wear gloves and eye protection in the event of you using that Works(r) stuff to clean stubborn lime scale deposits in your toilet. And that could happen too. You'll have some left over. The recipe presented in this 'ible only uses like one quarter, 200 ml of a 800 ml ,bottle of The Works(r), per 127 gram bar of Ivory(r) soap.
Final note of this intro: I am still kind of a noob on the subject of chemistry, especially with respect to lab work. My knowledge is incomplete, and my garage is not a professional laboratory, yet I believe that what I'm doing in this 'ible is reasonably safe. Some persons reading this 'ible may disagree with my assessment of risk, and I love reading comments that say what I am doing is unsafe, immoral, illegal, or that I'm just plain doing it wrong. So keep that criticism coming!
Step 1: Background: Triglycerides - How Fatty Acids Occur in Nature in Plant and Animal Tissue
Natural oils and fats, a.k.a triglycerides, are esters of glycerol (which has 3 OH groups) and various fatty acids. Soaps are made by hydrolyzing(reacting via water) natural oils with alkaline (e.g Na+, K+) hydroxides. For example 3 mols of NaOH, will react with one mol of a triglyceride to produce one glycerol and three soaps. For the triglyceride stearin, this reaction is:
C3H5(C18H35O2)3 + 3 NaOH → C3H5(OH)3 + 3 NaC17H35COO
stearin +3 NaOH → 1 glycerol + 3 sodium stearate
Step 2: Overview: Converting Soaps to Fatty Acids
A soap is the salt of an alkaline hydroxide and a fatty acid. Typically the cation of this salt is Na+, and the anion is a long hydrocarbon chain ending in COO-. For example, sodium stearate is a soap, and its chemical formula is
and the reaction describing the equilibrium of sodium stearate with its constituent ions is written
NaC17H35COO → Na+ + C17H35COO-
The process, of acidifying a soap to get a fatty acid, is essentially an exchange reaction. I want to swap the soap's Na+ ions with H+ ions. Supposing I use hydrochloric acid, HCl, as my source of H+
HCl + NaC17H35COO → NaCl + C17H35COOH
The Na+ and H+ trade places. The Na+ leaves the fatty anion, so it can go be friends with Cl- in solution, and at the same time the H+ joins with the fatty anion, making a molecule with a COOH group on one end, a fatty acid. The fatty acid is not souble in water at low (acidic) pH, so it "crashes out". It gathers together into droplets and floats on top of the heavier aqueous (water) solution.
The example equations I have written above are for sodium stearate reacted with HCl. The reactions for other soaps, like sodium palmate, and sodium oleate, are exactly the same. The Na+ ion goes into solution, and a fatty acid ending in COOH crashes out.
Different fatty acids (stearate, palmate, oleate) are miscible in one another, so acidifying a mixture of soaps will give a mixture of fatty acids.
And this is what I expect to get as a result of acidifying my bar of Ivory(r) soap. This bar of material, commonly called "soap" is actually a mixture of several different sodium soaps. See section 3 of the attached MSDS for Ivory(r) soap. It is a mixture because the tallow used to make it is itself, a mixture of tryglycerides. Similarly the end result after acidifying this bar of soap is a mixture of fatty acids, also called fatty acid mixture, also called FAM.
Step 3: Ingredients and Tools Used for This 'ible
- 127 g ( 1 bar) of Ivory(r) soap
- 200 mL of The Works(r) hydrochloric acid based toilet bowl cleaner
- 1 FUS gallon (3800 mL) of distilled water
- safety glasses and rubber gloves
- cheese grater
- electric hot plate
- enameled steel stock pot (15 quart or 15 L in volume)
- enameled steel sauce pan (1 quart or 1 L in volume)
- glass measuring cup (1 cup or 250 mL in volume)
- wooden stirring stick
- some vinyl tubing (about 6 mm diameter, 2 m in length)
- string, spring-loaded clamps
- electric fan
- a well ventilated area
Regarding the well ventilated area, the most biting and noxious fumes are produced in the last, and optional, step of heating the finished FAM to drive off the excess HCl as HCl vapor. A fume hood would be nice for that part, but I do not have one of those. So I just directed a fan toards it, and let it blow outside through the open garage door. The smells and vapors produced in the other steps are not bad by comparison.
Step 4: Grate the Bar of Soap Into Powder
The first step is to turn the bar of soap into a pile of powder. This will make it much easier to dissolve the soap in water. A cheese grater works well for this.
During this step I got a little bit of the soap powder on my hands, but that's no big deal because it washes right off.
Step 5: Dissolve the Powdered Soap in Hot Water
I pour one FUS gallon of distilled water into the enameled stock pot, and then heat this till it just starts to boil. It's not a rapid boil. It's just starting to boil. "Simmering" might be the word for this.
Transfer the powdered soap from the newspaper to the measuring cup, to make it easier to pour the powdered soap with one hand.
When the water temperature gets to that "simmering" state I mentioned, it is hot enough to begin adding the powdered soap. I try to get the whole 127 gram mass of soap to dissolve in the hot water, although it's a little hard to see what's going on the pot because of all the soap suds.
Soap dissolved in hot water makes lots of soap suds. How about that?
Step 6: Add Acid to Water
I measure out 200 mL of that funky blue acid toilet bowl cleaner into the same glass measuring cup I previously used to hold powdered soap. Also note that I am wearing gloves and safety glasses while doing this.
Next I slowly, and carefully, add the acid to the hot solution of soap and water. This is not one of those reactions where I have to add the acid agonizingly slowly, drop by drop, pouring down the edge of a glass stirring rod, so it does not splash even a little. At the same time I don't want to pour it in too fast and splash it on myself. It's just slow and easy.
If there was any additional surge of heat produced by this step, it was very subtle. Not at all noticeable. Either there was not much heat evolved, or else the big pot of water did a good job of absorbing it.
Regarding the quantity of acid, 200 mL is about 2 or 3 times the stoichiometric amount required to displace all the sodium ions from the soap. Based on the relative molecular weights, I am guessing the 127 g bar of soap is about 10 g Na+ ions, and about 120 g of fatty anions. Also guessing the concentration of the acid, 20% HCl, is about 6 molar (mol/ L), and that works out to about 80 mL of acid solution to give the same number of mols of H+ ( or Cl-) as mols of Na+ in the soap. I'm using a little more acid, in the hopes of completely reacting all the soap. There are two reasons for this. The first is to make sure I have enough H+, and the second is based on Le Chatelier's principle. I'm also hoping that increasing the concentration of H+ ions will drive the equilibrium for this reaction towards the product side, and make more fatty acid.
Step 7: Stir. Turn Up the Heat. Stir Some More.
I keep stirring the solution, and the suds go away. However it looks like I still have a bunch of white islands of white undissolved soap floating around. I decide to turn up the heat, and I keep stirring. Eventually the white islands dissolve, and I am left with what I am hoping is clear, oily, fatty acids floating around on the top of the mixture.
Seeing the white floaties turn clear is very encouraging. I don't remember the exact amount of time it took to reach this point, but I think it was less than one hour total of heating and stirring, including the initial step of dissolving just the soap.
At this point there is a definite funky chemical smelling fragrance coming off from the mixture, but it is not overpowering.
Step 8: Let It Chill
For this step I just put the lid on it and let it cool, and be still, for several hours. The hope is that all the immiscible and lighter-than-water fatty acids are floating to the top and forming a layer there.
Step 9: Assemble a Siphon and Pre-fill It With Water
There are number of possibilities for the step of separating the floating layer of fatty acid mixture (FAM). If it is sufficiently cold and solid, maybe it could be lifted off in one piece. I have also read that a syringe can be used to carefully extract just this floating top layer, assuming it is in a liquid state.
The method I use is a siphon, to slowly move the acid water out from underneath the FAM layer.
Sucking one end of the tube with one's mouth to get the siphon started is NOT advised, as that could lead to drinking acid water, and that would be bad.
The smart way to do this is by pre-filling the siphon tube, and the easiest way I have found to do this is by stuffing one end down a running garden hose. I wait until the flow forces out all the air bubbles. This trick is shown in the second picture.
Then I hold a finger over one end to keep the water from flowing out of the siphon tube while I manipulate the whole serpentine arrangement into place in my big pot of fragrant blue fatty-acid-plus-acid-plus-salt-water.
Step 10: Siphon Out the Acid-plus-salt Water
I have secured one end of the tube wooden stirring stick with string to keep it straight. I use a spring-clamp to hold the wooden stiring stick in place, and this holds that end of the tube in place against the bottom of the pot. Using a second spring clamp, I secure the other end of the siphon to a plastic bucket on the floor intended to catch the acid-plus-salt-water. Then I release my finger from the end of the siphon tube (in the bucket on the floor), and the acid-plus-salt-water starts flowing.
To get the very last few mL, it helps to tilt the pot a little bit, so that the siphon is emptying out of the very lowest part of the pot. I think when I was doing this the FAM layer was warm enough that it was still liquid. So I had to be ready to stop the siphon at the last second, before it could pull any of the warm liquid FAM through the tube.
Step 11: So What's This Stuff Good for Anyway?
This last step shows me moving the fatty acid mixture from the large 15 L stock pot to a much smaller 1L saucepan using plastic spoons.
The properties of this FAM stuff are very different from either the soap, or the HCl acid, that went into this reaction. The most notable property of FAM is that it does not mix with water, and with just a little bit of heat it melts into an oily liquid.
By the way, the FAM in that other tutorial I mentioned in the introduction, the one from OpenSourceNano
their FAM, made from olive oil soap, was a clear yellow liquid at room temperature. And this seems to demonstrate that different FAMs have different melting points. It may be that FAs inherit their melting point from the triglycerides they are made from. That's just a guess based on the following observations:
Tallow is a white solid at room temperature. So is the FAM I made from Ivory(r) soap, which is supposedly made from tallow.
Olive oil is a yellow liquid at room temperature. So is the FAM made from olive oil, according to OpenSourceNano.
That's just an untested hypothesis, so you know, don't quote me on that.
For some more info on the properties of some pure FAs look at these Wiki entries:
Wikipedia describes oleic acid as a "pale yellow or brownish yellow oily liquid". It describes stearic acid as a "waxy solid". And those descriptions kinda mesh with OSNano's olive oil soap based FAM, and my Ivory(r) soap based FAM, respectively.
This instructable has been a fun little science project so far, a sort of chemical look-under-the-hood to see what soap is made out of. So it's educational, and that's good.
But my original objective here, besides trying to win the U-U-Bathroom contest, was to make some ferrofluid.
The OSNano tutorial made it look really easy. They just mixed some rust they scraped off an old piece of steel, with their kitchen-made FAM, and well... Well, they made it sound really easy...
Anyway that's what's next for my homemade FAM. I mix it with ferric oxide, and try to some magnetite particles! But that's a story for another instructable...