Ir recycling step 5

This is a note of contention as to whether or not this step is necessary. Professor Heller suggested that the black Ir/ash was good enough to carry on, while I thought this step would yield better results. As such, I'll do some of the batch both ways and see if the result is the same.

I've used a glassblowing torch in order mix some O2 in with the natural gas. This increases the temperature of the flame considerably, enough so that the bottom of the crucible glows like a light bulb. After a fews tens of minutes of heating, the black Ir/ash has melted into a glowing red lava-like goo. There were two separate layers evident, what I can only guess is metalic iridium made up the glowing red material in the bottom of the crucible, covered by a clearish liquid layer which I'm guessing is molten salts. This step gave off some pretty intense radiant heat, making me wonder if the fire extinguishers in the top of the hood would be triggered, happily this did not occur.


Several attempts were made to get this process to work correctly. I was successful once, shown in the picture, but subsequent attempts led to the crucibles breaking due to thermal shock and uneven heating. I tried to remedy this by using a Meker burner on full blast for hours, but the temperatures achieved was not enough to convert the ash to salts and the (presumably) iridium oxides to metallic iridium. I tried to spread the flame of the glass blowing torch out by loosely affixing the Meker burner grating to the top of the torch, but the O2 content was too high in the cavity in between, leading to a lot of backfiring and me almost crapping my pants. Clearly, a safe, more controlled heating method is needed, either by furnace or adapting the current setup to prevent thermal shock to the crucible and promote even heating. More on this soon....

Ir recycling step 4

The crucible of concentrated nastiness has removed most of the volatiles, which will prevent a huge flame ball from forming in this step. Here, we are simply heating off any of the volatile salts and burning solid organics down to ash. The iridium/ash may be good enough to carry on, however, the recycling will be much easier after heating to higher temperatures. The setup is shown below: a crucible with the iridium residues being fired by a Meker burner with the air mixer on low, gas on low. Lots of smoke (fairly toxic) is given off in this step. Although the picture is taken with the sash up, it was down for the duration of the burn-off, save for the picture.

Ir recycling step 3

Many of the higher boiling solvents and other nasties (mineral acids, oils, phospines, etc.) are still present and the waste residue currently has the consistency of chunky fondue. Unfortunately the smell doesn't resemble fondue in the least. Many of the bad smelling, high boiling residues left are removed by extensive heating in a crucible to 300 - 350 C using a heating mantle and sand bath. This was also a good time to throw in the tissue papers I used to clean up a few spills. No worries, as all of the organics are being decomposed in the hot acid and will be fired off in the next step.

Ir recycling step 2

The next step is to strip all of the volatile materials from the waste, employing a Rotovap. This is merely a contraption which heats the solvent in one pot while cooling the vapors so that they drip into another pot (the solvent trap.) This step happened mostly without incident, save but one batch of waste which was not properly neutralized. Of course, if you take dilute acid and strip the solvents off, what you end up with is concentrated acid. This hazard is inherent, since most of the volatiles are benign, anything which is particularly nasty is going to be concentrated and become nastier. As my labmate says, usually to make himself feel better while pouring waste down the drain with the water on, "The solution to pollution is dilution!" I have discovered the opposite is also true "If you want to make nasty waste even worse, concentrate it!" Its not as catchy, but equally relevant to the task at hand.

This nastiness will all be remedied in the next step.

Ir recycling step 1

The first thing to do is collect the waste. As you can see in the photo, there is a good bit of it from the various labs in the department. Some of it has been evaporated already, so its pretty dense. Most of it, however, is a lot of solvent for not a lot of metal. This picture shows the bulk of what I collected initially. In the present form of whatever it was collected in I would estimate the volume to be 4 to 5 liters.

precious metal recycling

I just had one of the first years make a boat load of the starting material he and I will both be using for our projects over the summer. He scaled up enough to use all of the remaining iridium (Ir) which was in the department, meaning that if we ever need to make this material again, we will have to buy more Ir. Iridium is pretty expensive, at the current market prices it costs just a tad under the price of gold, but that doesn't reflect the actual obtainable price because there are a lot more people out in the world dealing gold than iridium. Strem will sell the hexachloroiridate salt for 50$ per gram.

I've embarked upon recycling the iridium waste in the division for both practical reasons as well as pure interest in the brute force methods required to recover iridium residues back into usable materials. The procedure is basically this:
1. collect the waste
2. evaporate the low boiling solvents (<100 degrees C with partial vacuum)
3. evaporate the high boiling materials (heating mantle at about 300 degrees C)
4. fire the residues to ash (Bunsen burner with the air mixer open pretty far)
5. crush the ash and fire to redness (Meker burner with the air mixer open as far as possible.)
That gets to the raw metal, which is where I'll leave it for now. I think this whole process is pretty interesting, so I'll keep the individual steps updated on the blog. The method isn't proprietary and can be found in "The Journal of Less Common Metals", a tome of which I have never seen nor heard of until I starting this process.

glassblowing and joint sweating

Glassblowing is necessary from time to time in order to fix something you just broke, make a piece of glassware which you need right now, and so forth. Our glassblower arrives biweekly, so if you want something done by him it usually takes a long time, which could be remedied if the physics shop (which houses the glassworks) would just let us use the damn annealing oven.

We needed a piece of tube with a 3/8th inch outer diameter attached to a length of 1 inch tube with a standard taper 24/40 joint. This is nothing more than a tube, attaching one end straight on to the other. I tried for some time to make the first attachment to no avail. I could get as far as blowing out the end of the tube to make an even edge, but I was completely inept at attaching the two pieces. After several poor attempts Professor Heller learned of what I was doing, and although he thought it was admirable, was quick to point out exactly where I was failing.

I was missing a swivel joint used so that you could blow into a tube connected to the end of the glass and spin it at the same time. I distinctly remember that the last time I watched Heller connect two tubes together he did it without the aid of the swivel joint and did just fine. Apparently he was just showing off.

Hand annealing is another issue entirely, as Heller doesn't seem to have the patience to do it properly and as stated earlier, the physics shop doesn't let us use the oven. So even though the piece has been made it still can't be used because its too brittle in the present form.

On a similar note, sweating a joint in copper tubing was also on the day's chore list. I've seen my father and grandfather do it several times. The made it look ridiculously easy, just polish, flux, and sweat. This is a lot easier if you remember that you need the flux, which I forgot about on the first several attempts. I read on line that if you were doing this on household plumbing the best way to keep the water out is to jam a wad of white bread into the pipe before you sweat the joint, then just flush it out after you're done.

Curiously enough chemical stores does not stock white bread.

clean

The lab has been cleaned. This ordeal took two days with 5 diligently working lab mates and a couple of lazy sacks who pretended to care and only took the time to clean up their own personal messes. I try not to cuss a lot in this blog, so I won't comment further on the efforts of the lazy sacks. The lab is now just about as clean as a lab with a clean group would have it when it was dirty, and I think I'll have to settle for that. The real score comes in counting how many incidents there were, in which we scored very well. While cleaning and disposing of over 300 different containers with poor or non-existent labels, there were no occasions of damage to person or property. Broken glass, while amounting to several decently sized boxes, did not result in any cuts or glass dust inhalation. The main source of excitement came while cleaning out a badly degraded bomb flask which used to contain KCp* (a commonly used ligand). The usual routine, starting with an iPrOH quench followed by EtOH followed by MeOH followed by water, failed. The remaining potassium in the flask did not react until the water had been added, causing the entire flask to smoke for a minute or two before catching fire or an additional minute or two (a nice bright yellow flame, quite pretty actually if your not distracted by the fact that the flask could explode momentarily). This prompted detaching the D fire extinguisher from the wall and rushing it over, although its use was never necessary. It did, however, warrant a date change on the wall for "Days since last lab fire" from last August to yesterday.

A note on fire extinguishers: There are three commonly used types, A, B, and C, which are distinguished by their contents: water under pressure, compressed CO2, and a chemical flame retardant. Most people are aware of the difference because they have been told that spraying compressed water on an electrical fire is a poor idea. Just to show why a type D is necessary in this lab, consider that the fire started BECAUSE we put water (a type A extinguisher) on the metal. A type B is CO2 and no, using a type B is not going to cause global warming, but letting your house burn down will. We can't use a type B here because concentrated CO2 is an accelarant for combustible metals.

I don't know why type C doesn't work, but I'm guessing that the chemicals in a type C react similarly with the burning metal. Type D is just powdered NaCl (table salt) with high pressure argon gas. Think of it as the most expensive salt shaker money can buy.

update

After some gentle urging from an adoring fan, a quick update, although not much of interest has happened.

I've been working carefully on two projects, a new ligand synthesis, and isolating some final compounds for what I hope will soon become a complete body of work, ready to be written up and published.

The new ligand synthesis is slow, as stated before its only useful solubility is in pyridine, and once the deprotonation is accomplished it is no longer soluble in this either. After trying to get the arms on the ligand it resolublizes, but only to show in NMR that the deprotonation was not complete, even after overnight sonication. The solution in this case is the cook it good and hard for a couple days. So that is where my NMR tube sits right now, trying to deprotonate the starting material, bathed in 120C oil, bumping away.

The other final synthesis I have been messing with has been postponed until I can completely purify the starting materials. Its this kind of fervid obsession with purity is probably the cause of most OCD which chemists experience outside of the lab. For instance, I am constantly skeptical that the dish washer we have actually gets the dishes clean. This is a manifestation of a fear that my lab mates simply rinse their glassware and place it on the drying rack, which requires me to wash every piece of glassware I use thoroughly before I use it, even if I pull it right out of the drawer.

Some of the booted material has gone from red to deep blue-green, and partially soluble in hexane. I've thrown together some crystallization chambers to see what's really in there after my stuff hits the air. One is a slow evaporation of a saturated hexanes solution, the other is a vapor diffusion of hexanes into a nearly saturated THF solution.

On the positive side of things, the lab has acquired a wiffle bat and some wiffle balls. The good weather and large lawn outside the chemistry hall has drawn us out on several occasions to take our frustrations out on each other in a non-deconstructive manner. I highly recommend this for graduate students everywhere.

pyridine

The ligand that I've been working on (the A+B = C+D thing in a previous post) has been one tough cookie to crumble. The main reason for this is (I think) that the solubility of the starting material is pretty poor in THF, which is the solvent of choice for analogues of the target compound. The smart move here is to switch to a better solvent. After testing solubility of the starting material in a number of different solvents (THF, fluorobenzene, nitromethane, glyme, pyridine, DMSO, and methylene chloride) it turns out that this stuff is soluble only in pyridine and DMSO. DMSO is a great solvent if you never want to isolate your product again. Everything is soluble in DMSO. I'm soluble in DMSO. It boils somewhere up around 180C which doesn't really make it strippable. This leaves pyridine, which is what I've been using, but I can't say I'm terribly excited about this either. It stinks(if you can smell it, you're not working carefully enough), its tough to dry, tough to vacuum transfer and is particular bad for gentlemen such as myself, if you know what I mean. (For those that don't know, pyridine could be used as a very effective male sterilizer, so long as you don't mind not having lungs, a liver, or several other major organs as well.) The upshot of all this is that when I get frustrated trying to get the pyridine to pump over in time for me to get down to my NMR time, I can't throw the bomb to the floor in frustration for consideration of my future kin.

in the opposite direction

I've spent the last two weeks working on new compounds, one is a variation on a ligand we've been using here, and the other is a new metal complex. After a considerable amount of effort I have made (I think) both of them, but they are so unstable they fall apart into starting material. That is to say, there is more than one way to make these things. Say I can get complex P (the desired product) either starting with A + B or C + D. What I have essentially done is found a way to fleetingly make P from A + B but ultimately what I have done is to make C and D from A + B in a really fantastically expensive and time consuming way. Not that this is uncommon, but to have it occur to two different projects at the same time is extraordinarily frustrating.

steady progress

I did get my line back from the glassblower and in fine condition. I reset all the clamps and got the pump oil warmed back up. All the pins are greased, the inert gas manifold now has an inlet and an outlet at the opposite end (as it should) and a shiny new Hg bubbler/monometer vented (through a sulfur trap of course) up into the hood. Proffesor Heller was not particularly pleased about the Hg, and pointed out (rather after the fact) that we had some stop-flow valves in the lab for that purpose, but I don't have a port for a pressure gauge, nor do I really want one, so the Hg monometer still serves some purpose. Enjoy this picture of my hood, and notice that this is as clean as its ever going to be for the rest of existance. The line is repaired, the inside is clean from when the sash was fixed. (Those stains are happy accidents of years gone by.) A fix on the fridge is in the works and soon my chemistry might even start to work again. Keep your fingers crossed.