This video is to help you with experiments Q1 and Q2, which are about chemical equilibrium. In both cases they are equilibrium with iron 2 plus ions. Q1, you are using phyosionate, which makes a blood-red complex with iron. In Q2 you will be using ortho-finanthrolene, which makes an orange complex. You've actually used iron ortho-finanthrolene before. In both cases what you are going to be doing is making up multiple solutions. I've just got a few small flasks here, but you'll be making up about 20 solutions of different concentrations of iron plus the ligand. In some cases you will be holding the concentration of the ligand constant and varying in the concentration of iron. In other cases you'll be doing the opposite, holding the iron constant and changing the concentration of the ligand. By observing the concentration of the colored complex you will be able to determine the position of the chemical equilibrium, which is iron plus ligand on one side going to colored complex on the other side. You will in all cases be monitoring how much of the colored ligand you have produced using a spec 20. You have used a spectronic 20 before, so I'll just give you a quick review. The machine is here and you turn it on with a left hand knob here. The first thing you're going to do is set it to the appropriate wavelength. I'm going to use whoops going the wrong way here. 509 is exactly what I want. Now the sample compartment is here and if you listen, when there is nothing in there there is a shutter in the light path, so there is zero light getting as far as the detector. With this in transmittance mode I adjust this so that I have got 0% of the transmission of the light being transmitted to the detector. Now I need to tell it what 100% is. So I have another key event and remember they've got quite disks on them on a white line. You line the white line up at the front, put it all the way in and at this point you switch to absorbance mode and you want to use the right hand knob to set this to zero. You can also do this in transmittance mode and set it to 100% transmittance. That's the same thing. There we have it. Now in transmittance mode that's going to start flashing. We've got zero transmittance and with a blank in there it's drifted. Oops going the wrong way. One of my difficulties here is that I'm doing this with a freshly switched on instrument. It's a good idea to turn them on and let them sit for about 10 minutes before you start taking readings. You'll then have a QVET of your colored solution, pop it in and that has an absorbance of 0.176 in this particular case. You will be reading about 20 different solutions. Once you've got them all ready to go it'll be quite quick. So I would take this, dump it out, take my solution, rinse it with the next solution to be measured, dump that as well, fill it again with the second solution, pop it back in and read. And that's all there is to the spectronic 20. You'll be dispensing different amounts of liquid. We've got burets in various sizes. This is a 50, this is a 10. You can also use pipettes to make sure that you dispense the various amounts of the different solutions that you need into the 20 volumetric flasks. For cleaner, all of these solutions can go down the sink with lots of running water. And that is how you perform the experiment, QI, Q1 or Q2, which is an equilibrium of iron with a different ligand.