One of the standard techniques in synthetic chemistry is refluxing, which is performing a reaction at a steady temperature which is above room temperature. This video talks about refluxing and how to do it using micro scale glassware. All chemical reactions are faster at higher temperatures and slower at cooler temperatures. When you synthesising materials, the optimum temperature for speedy reactions is usually above room temperature. There are upper limits if there are side reactions you want to minimise them and you don't want to get your system so hot that reagents or products start decomposing. The easiest way to get a system to a controlled higher temperature and to keep it there is to use the boiling point of a liquid. Humans have been doing this the centuries. We prepare food, we cook it by putting in water and then boiling it. This keeps the food at 100 Celsius, the boiling point of water. The temperature won't get any hotter unless the water actually boils away. This is much more reliable and controllable way of heating and cooking than putting the food say in the hot coals of the fire. Chemists do exactly the same thing, though we use many more solvents than water, so we have a whole range of temperatures to play with. The trick is not letting the solvent boil away. In the kitchen, putting a lid on the saucepan lets the seam condense and drip back into the pad. In the lab, we use condenses to catch and cool the solvent, vapors and return it to the reaction vessel. Condenses are heat exchangers. They come in two varieties. There's the air cooled condenser and the water cooled condenser. You use them in different situations. You use an air condenser if the boiling point of the solvent is fairly low below 50 or 70 degrees. You use a water condenser if the boiling point is higher because you need the water to carry away the heat of the vapor as it condenses. We'll show you how those go together. Here is a reaction vessel with an air condenser attached. Here is a vessel with a water condenser attached. It's a little more tippy, so we actually have to clamp that. We'll show you how that's done. We'll be heating using a hot plate and a reaction vial. It'll be conical bottomed and you'll always put a spin vein inside. There will be a condenser. I'm drawing an air condenser but the same principles apply to a water condenser. It'll be held in place by the cap. The liquid will actually boil and vapor will travel up the condenser like this. It will get cool inside the condenser and eventually you will get droplets of liquid forming on the side of the cool condenser and they will fall down by gravity and drip back into the container. The source of heat here is coming in from the heater. There is energy going in and energy comes out for the condenser. This process can continue. The boiling and condensing will continue as long as the condensers are working and the hot plate is hot. An air condenser is basically a glass tube with a ground glass joint at the end. The thing you need is to put your fitted threaded ring over the top of this joint and then roll an O-ring to just above the ground glass joint. This will act as a seal. Then take your reaction vessel, place this inside and screw. This is now ready to heat. I don't have any liquid or spin vein in there but that is now assembled. You place it in a heating block and clamp and this is how it should look for a reflux reaction. You get your water condenser from your T-A. It comes in a box and you will be handing it back in the box to keep it safe. Taking it out. Notice the water condenser. It's got water inside and two nylon connectors at the end of the tubing. These will connect to the plumbing later on. Just like the air condenser, the first thing you need to do is put the threaded collar over the lower joint and then roll on an O-ring like that. Take your reaction vessel and connect the condenser with the vessel and tighten the screw thread there. This is now ready to put on the heater and get going. I'll put this together here. There we go. It's a good idea to clamp that with your three finger clamp. There are two water connectors which come from the drawer underneath. They fit onto the water inlet and outlet and you slide into place and you hear that click that has firmly attached and I'll do it for the second one like that. When later on I'm going to disconnect. You take this collar and just push it towards the wall and the whole thing pops off. Let's connect it to get the reaction going now. Sometimes you can see when you make the final connection air bubbles like this one here will start to flow and move. As you can see now, cooling water is actually flowing in this system. At the end of the brass connectors are nylon connectors and these go with the water condenser connectors like that. These are designed so that there will be no flow unless there is no back pressure and there we go. Once you make the last connection there is now water flowing through this entire apparatus. When the reaction is actually over you'll want to be able to disconnect this. You do this just by pushing one or other of these to disconnect and again, the other push towards the wall and these come off. You will get a few mills of water leaking out of the joints. Just mop those up with paper towels. One of the things that people tend to do is not be careful to get the tie-gon tubing out of the way of the hot plate. This will very rapidly melt through. You'll get a flood and if you do you'll need to mop it up. So you need to make sure that the water tubes are not touching the hot plate because the plastic will melt. In conclusion, refluxing is the process of speeding a reaction up by heating it to the boiling point of the solvent. You will need a condenser to make sure that the solvent doesn't boil away. You should now understand the process of refluxing and how to do so with micro scale glassware.