Introduction: Easy, Economical, Ecological Distillation
Amateur chemistry can be educational, fun and rewarding; however, it can be intimidating to begin, especially with the cost of professional laboratory equipment. Fortunately, this is amateur chemistry, and we can use amateur equipment, a process which not only saves you money but also helps you to understand what's going on! In this Instructable I'll demonstrate how I built a distillation apparatus for only a few dollars.
This device is useful for a wide range of hobbyists and makers - in addition to amateur chemists, their users include brewers, survivalists, herbalists, and more. Also, I typically make a point of using new material or retail-supplied material as little as possible and have a strong tendency to blur the line between thriftiness and cheapness. Though it can be difficult at times, this also helps me build independence from prefabricated materials and is an avenue through which I can exercise creativity in problem-solving.
Friendly safety reminder: If you want to use this, be sure you check everything out first to make sure your application doesn't involve issues I didn't address in this Instructable. The comments section is a great start - plenty of others with more experience than me have added their thoughts there. I listed what I thought of in the steps, but of course I couldn't have thought of everything.
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Step 1: Motivation
You probably already know why you want to build a distillation apparatus. If not, I can certainly give you a few:
- The application common to all my fellow hobbyists and DIYers is purifying water, since we all use water numerous times daily. If you need to purify water and remove contaminants from it, you could do so by distillation. This might be done for drinking or use in a humidifier. Keep in mind that, while we can purify by distillation with a simple apparatus like this, that a fraction of the impurities will still remain.
- Many hobbyists who construct devices for distillation, however, are doing so with alcohol in mind. When working with alcohol, though, there are more complicated factors that I, being one who doesn't drink, am unfamiliar with. If you do want to distill alcohol, check whether or not it's legal where you are and then consult an experienced guide. Also, be sure it won't cause your distillation tube to degrade - many companies post free solvent/plastic compatibility charts like this one online - and find a heat source that doesn't involve an open flame. (I'm sure you knew better, but a reminder couldn't hurt.)
- But why do I want to build a distillation apparatus? Amateur chemists often find commercial suppliers for reagents in everything from garden to automotive supply stores, and sometimes these finds require concentration, purification, or separation. In my case, I've been interested for a while in polymers and I'd love to make my own - I know of plastics made from borax and glue, milk (its protein casein), corn starch, agar, and gelatin Ethylene glycol is readily available as antifreeze, but other chemicals are added - I want to isolate ethylene glycol because of its dual hydroxyl groups, which I'm hoping will be useful in polymerization.
- I mentioned before that herbalists might use distillation because essential oils can be distilled to concentrate them. As with brewing, I'm not involved with any of the details of essential oils, so it's your responsibility to double-check safety and legality here.
Step 2: Scientific Explanation
To start, we need to think about how distillation works. In short, we're using the facts that different liquids will boil at different temperatures to separate liquids, or to separate them from dissolved solids. It's not quite that simple, but the approximation works well enough for our purposes - if the purity isn't high enough after one distillation, we can simply do it again. Anyway, once the distillate has evaporated and most of the other components of your mixture are left behind, it's forced through the distillate tube into the condenser, as that's the only path available. While there it is cooled by the condenser bath and returns to its liquid state, and gravity then pulls it down through the tube into a its new container, separate from the other solutes.
In reality, each liquid is independently competing against its own gaseous phase. In a pot of water at room temperature, through Brownian motion molecules are constantly flying free from the liquid into the gaseous atmosphere, but just as many water molecules are diving back in. Overall, there is no change, and we say that the system is in dynamic equilibrium. However, if we put the pot of water on a lit stove, the additional thermal kinetic energy of the water molecules means more are able to break free. Eventually, enough are in the atmosphere that as many come back in as are let loose and we reach equilibrium again. We quantify this in terms of vapor pressure, which is the pressure a vapor exerts when in equilibrium with its condensed (usually liquid) state. The boiling point is simply when the vapor pressure reaches the pressure actually exerted by the surroundings (atmospheric pressure, unless the container is sealed). For that reason, above the boiling point equilibrium no longer involves any liquid - it would all be gaseous. Imagine we're trying to distill isopropyl alcohol (boiling at 180.7°F) and water (212°F) - at 180.7°F, when all the isopropyl alcohol has evaporated, much of the water should also have evaporated at equilibrium - see this Wikipedia page. We can work the system, however, by repeating the distillation process to continue removing about the same proportion of the remaining water. I'm not sure if there's any benefit to trying to work quickly before equilibrium is reached since you'll have less of both fluids in the gas phase, not just less of the one with the higher boiling point, but that may also help.
Step 3: Materials List
Now it's time for the list of materials and a little thought behind each:
Distillation vessel - This is the container for your sample you want to distill. Size and shape may matter depending on your heat source - I wanted to keep it simple and use a stove, so the natural choice was a plain old pot. Other thrifty options are a fishbowl or vase if you want glass or a coffee or paint can if metal's your thing. Each has pros and cons. Glass is very inert, has low thermal conductivity, is transparent, and can crack if heated too quickly. Metal is usually stable but can be corroded more easily, has high thermal conductivity, is opaque and won't crack when quickly heated.
Lid - I used a glass lid with a ventilation hole I found for $1 at Goodwill. This makes it easy to remove and return the lid if I want to add something to the distillation vessel, and I can see inside. The ventilation hole makes it extremely easy to add the condenser tube - if you can't find one, you could try unscrewing the handle and putting the tube through the screwhole. I wasn't worried about the lid cracking as I turned up the heat because it's not taking heat directly from the stove's flames. It will still be subjected to the high temperatures inside the vessel eventually, though, so it still needs to be able to withstand them.
Distillate tube - I don't quite know what mine is made of since I picked it up at the Habitat for Humanity ReStore. I tested it and it seems to work fine, and in fact I was able to take advantage of the way it becomes formable under heat. If you have a metal tube, that would probably be even better since it could dissipate heat more quickly. Plastic and metal (if it's thin enough) can both be wound up inside the condenser too. If your sample is reactive, you may have to find a glass tube and pick a longer container for a condenser. Be warned that in my case the tube began to droop (i.e. it started to melt, but the fire wasn't hot enough for it to melt completely) near the distillation vessel, and some plastics may release undesirable chemicals when heated. I definitely will be improving this design with a metal tube.
Condenser bath - I used a plastic jar from Costco's mixed nuts since that was the right size, on hand, and easy to work with. Since we'll be keeping this cool (in comparison to the distillate, at least) I'm not concerned with its stability under high heat.
Drainage tube - This tube doesn't need to be anything special; it'll be used to let out warm water and only needs to be flexible and longer than the condenser is tall. That way, we can stop drainage by simply bending the tube upward so gravity holds it in. Alternatively, if you want to be fancy and happen to have a nice manually controlled valve, you could just use that instead.
Caulk - I found a tube of kitchen and sink caulk already open in our workshop - lucky me! This is how we'll seal holes we drill in the condenser for the tube. All it needs to be is watertight, so if you don't have this and can find something else that prevents leakage, go for it.
Distillate receptacle - When your distillate comes out of the condenser, it'll need somewhere to go. Your choice again depends on the distillate, for as usual, you don't want the distillate and container to react. You may need to think about other properties of the distillate as well - for example, will much evaporate at room temperature and pressure?
Step 4: Prepare the Distillation Tube
Let's get to building it! The first step is shaping our distillation tube. If yours is metal, bending it should be straightforward - you won't have to worry about it bouncing back into its original shape. If you're using plastic that can be repositioned when heated like I am, you can use some binder clips and twist-ties to wrap it up the way you want and then put it into a pot of boiling water. Mine kept its new shape after about two minutes in the water. This step may not be absolutely necessary, but it certainly makes the tube easier to work with, and it's convenient to do if you were already hardboiling eggs anyway. (I don't know where the tube has been, so I was sure to cook the eggs before the tube.)
Afterward, I found that it would have been better to have more unwound tube on the ends so that I would be less restrained when positioning everything.
Step 5: Start Adding the Tubes
Next it's time to secure the tubes inside the condenser bath. I simply found bits that roughly matched my tubes' sizes and drilled holes where I wanted them. It's best to put the drainage tube in first since the distillation tube will be in the way otherwise... unfortunately, I didn't decide to add one until after I put in the distillation tube, but it still worked out find. Put the drainage tube somewhere low, since only water above the tube will be able to drain out. I wouldn't put it on the bottom, though, because that would be problematic when you want to set it down somewhere. I kept mine long enough that I could simply tuck it into the top when I'm not draining it.
This was my first time working with caulk, so if you're new to it I encourage you to seek more experienced sources. All I can say is that you want to be sure you have a good seal on it; it's best to get both the inside and outside of the condenser. I used disposable gloves so I could push it into crevices manually and be sure it was well-sealed.
Step 6: Add the Other Tube
You want the distillation tube to be in contact with the water which will later fill this container as much as possible, so if you used a flexible coil like me or something similar, try to situate it such that it's not bunched up but instead has some space between turns. Also consider the height of your distillation vessel - ideally you won't have to set your condenser on a pedestal to connect everything together. As the gas condenses back into a liquid, gravity will be responsible for pulling it down through the tube, so be sure you also have the tube going downward all the way, including the spout at the very end where the distillate will eventually exit.
Step 7: Testing the Apparatus and Future Modifications
When you're all done, what better to do then test it? The boiling temperatures of the components of your sample will determine the temperatures you need to work with, which in turn may influence your choice of heat source and condenser bath fluid. You'll need your heat to reach the boiling points and you'll need your condenser to be at a temperature lower than that - in each case, the greater the difference, the more quickly you can do things, although you should keep the temperature of the distillation vessel under control so you can boil off one fluid and then another rather than just boiling everything off. To get an idea of some common flame temperatures, see Wikipedia. For my purposes right now, a stove flame and tap water (with some ice to keep the temperature lower for a longer time) are perfectly sufficient.
Retrospectively, I'd like to have given it a longer distillation tube so my condenser wouldn't be as close to the heat source as it is. I also would like to add a thermometer so I can infer what should be boiling and what should be mostly liquid from the temperature. In keeping with the made-from-scratch spirit of this project, I'd go for a barbecue or oven thermometer that can read temperatures up to 500°F.
There's more to be done and I plan to build another with the insights I've gained from this first try. Nonetheless, it worked, for using a 9V battery and multimeter, I tested it the water's conductivity by measuring the current before and after distillation and found a decrease by a factor of ten! Thanks for reading, everyone, and I hope you enjoyed this Instructable and found it useful! I'm entering this into the Explore Science and Guerilla Design contests, so if you feel it is worthy, I would be honored if you vote for it!