Category Archives: Safety

Magnesium still surprises a fellow

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I have spent some time researching basic magnesium chemistry. Not anything synthetic but more safety and thermochemically related. I am not able to give a lot of particulars motivating the study, but I can say that one should consider that nitrogen over activated magnesium may not be as innocent as you think. While lithium is widely known to react with nitrogen gas to form a passivating nitride layer, the reaction of dinitrogen with magnesium is rarely encountered.

Activated magnesium residues from a Grignard or other magnesium metallation reaction may self-heat to incandescence under a nitrogen atmosphere in the right circumstances. Activated residues left isolated on the reactor wall or other features in a nitrogen blanketed reactor during an aqueous quenching procedure may self-heat to incandescence. In the presence of reactive gas-phase components like water vapor in nitrogen, activated metals can self-heat over an induction period of minutes to hours or longer.

Many metals, including magnesium and aluminum, can be rendered kinetically stable to air or humidity by the formation of a protective oxide layer. Once heated to some onset temperature by a low activation reaction, penetration of the protective layer by reactive gas composition can occur, leading to an exothermic reaction.

Performing a “kill reaction” or a quench of a reactive metal at the bench or at scale is always problematic and requires the skill and close attention of the process chemists and operators. I guess what I’d like to pass on is that nitrogen is not an innocent spectator in the presence of finely divided, activated magnesium. Humid nitrogen can support a combustion reaction to produce nitrided magnesium once preheated to an onset temperature.

If you mean to kill any reactive residues, it is important to apply the quenching agent in such a manner that the heat generated can be readily absorbed in the quenching medium itself. A good example of a quenching agent is water. Often a reactive must be killed slowly due to gas generation or some particular. Adding a quenching agent to a solution or slurry by slow feed or titration may be your best bet. If you have another vessel available, a feed to a chilled quenching agent will also work.  Dribs and drabs of water on a neat reactive material will lead to hotspots that may be incendive.

Lithium Fires

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Ran into an interesting recommendation on fighting a lithium fire in Joshi, D.K., et al, Organic Process Research & Development, 2005, 9, 997-1002.

In addition to the usual admonitions on the handling of a reactive metal like Li, they warned that water, sand, carbon dioxide, dry chemical, or halon should not be used. Rather, they suggest dry graphite or lithium chloride instead.  This seems quite reasonable to me, having reacted both silica and CO2 with magnesium powder in chemical demonstrations in a previous life. If Mg will reduce SiO2 and CO2, then hot/burning lithium ought to be reactive as well.

A similar recommendation is given in Furr, A.K. CRC Handbook of Laboratory Safety, 5th Edition, p. 299, ISBN 0-8493-2523-4.

The Company Joules

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We will soon have a new HEL Phi-TEC Adiabatic Reaction Calorimeter up and running. Hopefully this will help solve some nagging questions I have about the thermal stability of certain compounds. Time to maximum rate (TMR) is a useful parameter and ARC testing helps to find this value.

I have spent  a good deal of time with the Mettler-Toledo RC1 and have found it to be very useful in process development. There is a tendency for chemists to design exothermic reactions to start at low temperature and at perhaps some point raise the temperature to take the reaction to completion. The RC1 will indicate accumulation of energy in a vessel following a charge. By varying the temperature of the reaction mass and modulating the dosing rate it is possible to find a reaction temperature and feed rate that affords a steady state (or manageable, at least) output of power with minimal energy accumulation.

With the reactions I have been studying it has become apparent that sometimes a preference for low temperature (-30 C to 0 C) by the chemist may in fact be based on habit rather than need.

Naturally, the thermal picture is not the entirety of the problem. Product stability in the reaction mass and residence time at temperature play a role in how the process is configured. But a reaction calorimeter can help find threshold temperatures below which the reaction substantially shuts down.

The RC1 measures heat of reaction in Joules and power in Watts. After some time on the instrument one comes to view a reaction mass as a power generator or an absorber. Power is reported in Watts and is indicated by the magnitude of the deflection of the power curve from baseline.  Joules of energy are calculated from the area under the power curve.

The instrument has a calibration routine where it determines the Cp of the vessel contents. If you have the reaction mass, heat of reaction, and Cp, you can calculate the adiabatic temperature rise for a given dose of reactant. This is an extremely useful element in sketching out the safe operating parameter space of a reaction.

Safety is a political concept. Safety has no basis in physics. It is an artifact of anthropology. It is a fuzzy construct defined by a magnitude of “likelihood” and type of consequence individuals and organizations are willing to absorb to obtain a particular outcome.  But when you sit down in a meeting with thermokinetic data and solid interpretation, all of the stakeholders in a plant can brainstorm and home in on a fairly rational and agreed upon process profile. This is politics at its finest- data driven and substantially rational.

What a Meth Lab is Not

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It is time that someone questions the use of the phrase “meth lab”. Just as a cook would object to the phrase “meth kitchen”,  those of us who spend our careers in the laboratory should push back on the use of the word “lab” in this manner.  The use of this word confers the notion that a workspace is fitted for chemical handling activity and is operated by someone who knows what they are doing. Dubbing a meth operation as laboratory surrenders too much credit to the operator. These people are moonshiners skulking around on the periphery of society.

A meth lab is not a lab. It is the workshop of a criminal enterprise where unscrupulous people manufacture a dangerous substance. Its sole purpose is to profit from the uncontrollable neurological train wreck of methamphetamine addiction. This is not laboratory work. It’s just crime.

ChemSpider Magic with LASSO

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Of late I have been concerned with R&D information and various homebrew means of storing it and retrieving it. Institutionalizing R&D results into easily accessed knowledge can roll into a real hairball if you’re not careful. More on that another time.

My adventures with CHETAH 9.0 have caused me to look deeply into SMILES strings and what utility might be found there. This lead me to rediscover ChemSpider and the many services it provides for free to the user.

Consider the following: if you generate a SMILES structure of acetylsalicylic acid, say, from Chemdraw, O=C(O)C1=C(OC(C)=O)C=CC=C1, and use this character string as a search term in ChemSpider, it will take you to the entry for aspirin. What you get is a treasure trove of information on this substance. Go to ChemSpider, cut and paste the above SMILES string into the search box, and let her rip. I’m not your Momma. Just try it.

The breadth of references is encyclopedic.  But the truly amazing part is found when you scroll to the end of the page. There is a drop down window for SimBioSys LASSO. ChemSpider is working to provide LASSO data on its large database of compounds.  LASSO generates a structure and grinds it through a neural net processor module and produces a score between zero and one. The closer the score is to 1.00, the greater the surface conformity or compatibility of the ligand to a target receptor site.  As you would expect, there is a high score associated with aspirin and the COX-1 receptor. From what I can tell, the software is self-learning in some fashion.

The uses are many. Substances can be screened for drug-like attributes within the 40 receptor types provided.  I would like to hear from someone who might have something to say about the use of LASSO for the estimation of possible toxic effects of substances that have not been biologically tested. I fully realize the hazards of this, but perhaps LASSO scores might help flag particular substances for closer examination by testing.

CT Scans. Who is monitoring a patient’s radiation dose?

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The matter of medical x-radiation dosing is surfacing again. I wrote a post about this in 2009.

Let’s get to the core of the matter. Physicians need to take charge of this since only they have any real control. It’s a pretty goddamned simple concept. Doc’s who are calling for x-ray’s need to begin recording calculated dosing from this hazardous energy. If it is too troublesome for them, then the x-ray techs should record the information.

CT scanning seems to be problematic. There is no business incentive to hold back on CT use in for-profit settings. I suppose that documentation would only reveal the extent and magnitude of x-ray use. It would be fodder for malpractice law firms.

I can just see the billboards- Have you or a loved one ever gotten a tan from x-rays? If you have, call Dooleysquat, Schwartz and Schmuck for a free consultation. Do it Now!

Chemistry Lab Accidents Reports from the Chemical Safety Board.

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Here is a link to a US Chemical Safety Board video summarizing several recent lab accidents.  If you have never visited or heard of the CSB, here is a link to their web site. Have a look around.

This link is to the case CSB case Study of the Texas Tech explosion with nickel hydrazine perchlorate. It has a nice illustration of the Swiss Cheese Model of safety. This model was devised by British Psychologist James T. Reason at the University of Manchester in 1990.

Academic Lab Due Diligence Post-Sangji

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A colleague and I were discussing the Sangji case off-line and I did what I am pathologically prone to do which is to blurt out suggestions.  I’m passing them along to my other friends out in the ether as a rough guideline to thinking about training and due diligence. My suggestions are merely a watered down version of a typical industrial EH&S SOP.

Due Diligence

Your university EH&S department no doubt has some some form of written policy, but having your own arrangement with your student workers will accomplish two things for you- 1) you will have written and signed documentation on having trained your students to use what you might call, if not “best practices”, then “reasonable and ordinary practices” in the lab, and 2) you will have made it perfectly clear to them what kind of expectations you have in regard to their work practices, open lab times, types of activities they may perform unsupervised by you, and your absolute dedication to lab worker safety.

In a civil or criminal action you will be under court order to surrender your documents in a process called “discovery”. Your attorney, being an officer of the court, is legally obligated to ensure that you surrender all of your documentation related to the action.

So, wouldn’t it be useful to surrender documentation of your diligence in all matters of safety?

Making a student or other lab worker’s activity in your lab contingent upon some basic operating rules is not at all unreasonable. And, if the rules are clearly written with consequences for violation of policies, then everyone knows the expectations.

No one can predict the future. But what you can do is some due diligence. Have a written training program with goals and scope. Run your research students and other coworkers through it every year and have them sign off on their attendance. Put it in a file and hope that you never have to pull it out in self-defense.

Such a program would be a solid basis for your defense attorney to argue that you went to reasonable measures to train students on escape plans, shower and eye wash use, sharps, proper PPE, fire extinguisher use, lab hygiene, proper storage, and special techniques to use when handling reactive/toxic/corrosive/flammable materials.

A policy on the amount of flammable materials you have in your lab space is a good thing as is a policy of segregating chemicals in storage according to their flammability and corrosiveness.

Get a signature from coworkers on the policies as well and file it away. I think this is critical. Give a copy of your policies and training plan to the department chairman.

Possible Blowback

Once you have given instruction on your policies, collected all of the signatures, and neatly filed them away, the hard part begins. You must be consistent in enforcing the policies. You have to tear yourself away from the word processor and make periodic safety inspections. If you’re off to a week-long NSF study session, a proxy should be appointed to monitor your labs.

The last thing you want is to have a plan that crumbles under scrutiny. You want to have a gap free history of due diligence.  Former coworkers may be called to testify as to your enforcement of safety rules. Nothing rings hollow like a safety plan that was constructed only for show.

Benefit

A benefit to all of this due diligence is that you may have actually made your lab a safer place to work and have instilled a level-headed safety mentality in your coworkers. Fancy that.

The Sheri Sangji Case

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Many readers know that research assistant Sheri Sangji died from burns sustained in a laboratory fire in the lab of UCLA professor Patrick Harran. Harran and university Regents are up on felony charges for their part in the incident. I understand that the charges are based on occupational health and safety violations related to the incident.

[The excellent blog Chemjobber has been following this story.  I might add that this blog should be put on your Favorites list if it isn’t already there. The author puts a lot of work into it and it shows.]

Sangji was transferring t-butyllithium when her plastic syringe came apart and a quantity of the pyrophoric solution was splashed on her and ignited. She sustained fatal burns when her clothing caught fire and she died 18 days later.

Syringe techniques are common and the use of plastic syringes in such transfers of lithium alkyls is not unusual or automatically over-dangerous. However, some syringes have what is called a Luer tip where a syringe needle is attached solely by friction.

Another design has a Luer lock where the needle is affixed with a twist of the needle into a friction lock.  The former design, with the tubular tip and no locking mechanism is prone to disconnection under tension and on withdrawl of the needle from the septum on a pressurized bottle, the needle is likely to squirt bottle contents onto the worker. The Luer lock largely prevents this type of accident.

Another failure mode is when the plunger is inadvertantly withdrawn completely from the barrel of the syringe. Minimally, this would release the contents from the barrel, possibly on the operator. If the plunger is pulled completely out while the needle is still in a pressurized bottle, a fountain of liquid may discharge, possibly on the operator.

Syringe plungers with a rubber tip are prone to swelling in organic solvents and may become difficult to move during a single use. If the plunger is pulled with great force, it might release suddenly causing it to come out of the barrel along with the contents.

Other syringes have plungers that provide a seal by plastic-on-plastic pressure. The seal depends on the elasticity of the barrel to accomodate the slightly oversized plunger. These syringes do not come with Luer locks and as such, are not forgiving of less than skillful use.

I do not know exactly what technique Sangji was using. Aldrich distributes literature on the use of a cannula in the transfer of air sensitive liquids. That is fine, but if you want 0.1 to 60 mL of RLi, a syringe is the most expeditious method for delivering a precise aliquot in my opinion.

Experimentalists are often stricken with a cowboy mentality. If you have never had a serious incident with a material, it is easy to get a bit cavalier. But handling metal alkyls is a lot like handling rattle snakes- you have to be careful every single time.

A subsequent post offers suggestions on due diligence for ressearch professors.