-- This is an improvement based on the lessons learned from my first distillation apparatus. The first few introductory steps have been refined to reflect input from the previous Instructable's comments, and the construction steps are of course completely different. I apologize for how long it took; I've been preparing to move across the country for a new job. I hope you enjoy! --
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.
Distillation is useful for a wide range of hobbyists and makers - in addition to amateur chemists, their users include brewers, survivalists, herbalists, and more. Because I don't plan to use mine with flammable, solvating or volatile chemicals, I used scrap material and cheap parts that wouldn't be suitable for all purposes. Read on to get a feel for how things work.
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. I listed what I thought of in the steps, but of course I couldn't have thought of everything. For each substance you plan to distill, be sure to check the specific safety cautions with those who have experience with it.
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. (Before drinking, it's up to you to know your apparatus' capabiliites and limitations!)
Home alcohol distillation probably is the first thing that comes to most of our minds. I'll say right now, though, that although this Instructable may give you ideas, it isn't suitable for alcohol. Alcohol is both flammable and a solvent, which I'll address in a later section. Furthermore, it may or not be legal depending on where you live. In the U.S., for example, distilling requires a federal license even if it's exclusively for personal use, and additional details vary by state. More importantly, alcohol is a drug that holds a wide array of risks and side effects.
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 in antifreeze, but other chemicals are also present - 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. I can say right away, though, that essential oils are flammable, volatile (i.e. they tend to vaporize even when not heated) and have biological effects.
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: Safety Considerations
This is of course not an exhaustive list, but it gives you a good idea of some of the things you need to be aware of.
Some chemicals involved in your particular application may weaken or eat away at parts of the apparatus. In general, it's good to be thinking of what sort of characteristics your fluid has. For example, is it acidic, or maybe a solvent? Plastic is a cheap and convenient material, and differents types of plastic will be affected by the fluids passed through them in different ways. It's not hard to find free solvent/plastic compatibility charts such as this one online.
As I stated earlier, heating a liquid to vaporize it as is done in this apparatus won't separate the solution perfectly and you can always expect to have some contamination by other liquid. How much of a problem this is depends on your intended use.
Depending on what materials you use, what chemicals you distill, and what temperatures you attain, contaminants may also leach from your apparatus. For example, many plastics are known to leach chemicals, and copper also is liable to leach.
Even after being condensed, some distillates may have a tendency to evaporate if they're not properly contained. While in some cases this simply means you're losing some of the product, in others it could be worse. Some distillates can be hazardous to your health via inhalation. Others may be flammable, a risk which is amplified by our use of a heat source. If you're using a stovetop, propane torch, etc. this is especially important, but don't forget to watch out for other possible unintended ignition sources as well.
Sometimes a bit of heat provides the necessary activation energy to initiate chemical reactions. If you're using chemicals for which this is a concern, you probably have enough knowledge or experience that you're already aware of the danger. Nonetheless, be sure you consider whether or not anything in the solution you wish to distill is reactive.
Step 4: Materials and Tools
As I usually do, I used whatever was available and would do the job. Below I list the parts and explian how they'll be used so you know how to make one with alternative parts.
Steel coffee can - This is the vessel that contains your solution you'd like to distill. It'll be heated directly, so I opted for steel; I needed to be able to drill through it and insert a nipple easily, so I chose a coffee can. Lid - The lid simply prevents the evaporated gas from escaping into the atmosphere, so I just found one that fit my can. This time, you don't want one with a hole.
1/4" nipple - This connects the can to the first segment of the condenser tube. If you find a condenser tube of a different size, then your nipple would need to be a different size to match. Only one end needs to fit the condenser tube; the other can be any size.
1/4" sink tubing - For the first part of the condenser tube, which will be attached to the heated distillation vessel and close to the heat source, I wanted something that I could be confident would stand up to the heat it would face. I'm fairly certain there's a plastic tube inside the steel braiding/covering/whatever-it's-called, but these things are made to transport hot water, so I wasn't worried about it melting. On account of the nut-like screw-on endings, its inner diameter is about half its outer diameter, which is important for the next segment.
1/4" tubing - This is the second segment of condenser tube. It will hold the small tube and the coolant, which will probably just be ice water. It needs to fit in the nut-like ending of the sink tube. The closer the fit, the better. Small flexible tube - Because this tube carries the distillate coming out from the sink tubing, it should fit into the smaller inner part of the sink tube. Again, the tighter the fit, the better.
1/4" valve or spigot - This allows for easily controlled drainage of the coolant when it warms up and needs to be replaced.
Drill bits - We need one size to make a hole in the can for the nipple and another that's the size of the small distillate tube.
Caulk - The caulk will fill in gaps where connections are made with tubing, including where the nipple connects to the can, so it needs to be heat-resistant.
Funnel - I only use a funnel to make filling the large tube with ice water easier.
Step 5: Some Design Considerations
Two problems were apparent in my last attempt - first, the tube began to droop and deform under the heat, and second, the tube's slope wasn't great enough for gravity to pull the condensed distillate out unless it was fairly full. The two-segment condenser is my solution to the first problem. As it stands, the first condenser tube (the sink tube) is only cooled by air, which could be improved with a simple heatsink from aluminum cans or foil or by simply wiping it with a cool wet cloth periodically. My main concern for this first tube, though, was just to put some distance between the plastic tubes and the heat source, and it does the job nicely.
For the second problem, merely finding a taller condenser bath than the plastic nut jar I used last time so I could give the distillate tube a steeper declination would mean I'd have a much larger apparatus. That could be somewhat inconvenient, and I had already had some trouble dealing with how everything must be positioned in my previous apparatus. As I thought about how to deal with this, I had a new idea: why not put one tube carrying the distillate inside another carrying the ice water? This not only makes it easy to store but also allows me to position things however is most suitable for where it is being used rather than having things fixed in place.
Step 6: Prepare the Distillation Vessel
Once I had gathered all my materials, I found a drill bit that matched the size of the nipple and drilled a hole in the coffee can. Since the can flexed as I began to apply pressure with the drill, I put in several pieces of scrap wood to hold its shape. The nipple is then screwed into this hole.
Step 7: Assemble the Condensing Chambers
Next, insert the small distillate tube into the sink tube and caulk it if necessary. In my case, the fit was tight enough that it wasn't. Then take the larger condenser tube (the 1/4" tube, in my case), cut it to be as short as or a little shorter than the distillate tube, and drill two holes in it - one near the top for the coolant (ice water) to be funneled in and another near the bottom for the distillate tube to exit through. Thread the distillate tube through the condenser tube and out that latter hole you just drilled and slide the condenser tube up until it connects to the sink tube. Finally, put your spigot or valve in/on the end of the condenser tube.
Step 8: Seal Things With Caulk
Use caulk to seal any gaps where the can and nipple connect, to fix the sink tube and second condenser tube together, and to seal around where the distillate tube exits the second condenser tube. If you have a spigot or valve that fits only loosely into or onto the end of the second condenser tube, use caulk there too.
Step 9: Test That Puppy
Since I have neither a hot plate (though I do have an iron that could be substituted) nor the right kind of thermometer yet, I tested it with good old water on the stovetop. For most other applications, of course, I'd need to control the temperature of the distillation vessel carefully.
As before, I used conductivity as a quick-and-dirty test of its performance. Putting an equal volume of the original tap water in an identical container, I checked the distilled water first. My multimeter detected no current! To double-check, I repeated the test on the tap water, and the multimeter overloaded - whoops, note to self: add a resistor next time. In spite of a possible blown fuse, I'm excited to call this one a success!