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Chemical Compatibility Guidlines

Wet Chemical chloroform


This is how I have started storing our stock of wet and dry chemicals.  Most labs have an abundance of both dry and wet chemicals that must be kept for reagent solutions, media mixes, pH calibration and other.  Depending on the size of the lab, chemicals might be stored inside of specially designed cabinets that are prevent accidental spills.  Sometimes the chemicals will be put on a shelf, countertop, refrigerator or freezer.  This is an issue in most of the clinical, research and academic laboratories I have worked in and may be for many others.  Over the years and out of want to be safe, I have designed a suitable solution for storing both wet and dry chemicals that is safe for everyone to use.



Chemicals can be hazardous if they leak, spill or come in contact with other non-compatible chemicals.  Therefore is it the duty of someone who cares to make sure this never happens.  For instance, I take chemicals very seriously, not because my mother was a chemist for so many years that she lost her sense of smell but because I was a victim of a small histology company and its lack of safety procedures.

The chemical storage protocol here has been modified from a hazardous waste guideline.  This guideline provides details of specific chemicals that can and cannot go together as a waste stream.  Therefore I conclude that these chemicals should also be stored in the same way.  There are some obvious conditions I would like to point out anyway.  Flammable cabinets should be used, not only for your sake, but for the firemen who might come to rescue you.  This tells everyone to beware.  This also goes for acid and base cabinets.  I feel these are necessary for the Modern laboratory.  Acids and bases do not go together, obviously. Secondary containers are helpful when space is limited and chemicals must be stored close together.  The container would contain a spill or leak from reaching other non-compatible chemicals.

Chemical incompatability
Chemical incompatibility


The chemical chart breaks down what chemical can and cannot be stored together, essentially making safety a top priority.  The PDF of the chart is below and will also be placed in the protocols page.

I hope this helps.

How do you store chemicals in your lab?


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Hygroscopic Chemicals Cause Stress

Last year I had problems with the trichrome stain. The nuclei would not stain that dark purple back color. I tried making new chemicals one after the other. They were not out of code but maybe someone had poured one into the other or it had become diluted by excess carry over or water. In between each chemical change, the stain had to be tested and quality assessed, a tedious process. After all 7 chemicals had been replaced, the nuclei still appeared washed out.
What could it be, the hematoxylin? I ran the tissues in Weigert’s hematoxylin for the range of 10, 20 and 30 minutes. The nuclei were a little darker at 30 minutes but not enough to get happy over.
After months of trial and error, mostly error, I somehow stumbled upon a clue. During my search of the internet and really just grasping for any hint pointing to anything, I began reading the MSDS of all the chemicals. Let me tell you how to fall asleep even when you’re not to, read the MSDS of all the chemicals used by histology labs. There was a word “hygroscopic” that I was not familiar with. My definition taken from reading many others, a chemical that absorbs water from the atmosphere unless protected against. The Wikipedia definition is:

Masson's TrichromeOne of the recent questions on histonet was “Recently we started having problems with our 10% nb formalin not completely fixing our animal tissues. We haven’t done anything different in making up the solutions, but we’re finding incomplete fixation in the center of the tissues. We are letting it stay in formalin the same amount of time (24-48 hrs.) as we’ve always done. The pH has not changed. Does anyone have any suggestions as to where we can look to troubleshoot correcting this problem? Our recipe method is: 4g Sodium Phosphate, monobasic monohydrate (Fisher Chemical co.) 6.5g Sodium Phosphate, dibasic anhydrous (EMD Chemical co.) 37% Formaldehyde (EMD 10 parts formaldehyde to 90 parts Dh20. Any helpful thoughts would be appreciated.”

My response was as follows:
Hello Fran, I did not see any other replies to your question and hope I am not the
only one. Your recipe looks good and the only thing I notice is the
Sodium Phosphate, dibasic anhydrous. This chemical is hygroscopic,
meaning it takes on water very easily, even out of the air. When this
happens, your intended solution concentration is skewed and may not
do as intended. All of our chemicals that have this property are either stored in
glass desiccate jars in the refrigerator or wrapped with parafilm
after each use and stored in a desiccate jar at room temp.

Update:  We now store all our hygroscopic chemicals in the refrigerator at 4C.

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Chemical dangers in Histology from personal experience

I feel like the dangers of histology chemicals, those that I know of, should be addressed. I work in a histology lab that is situated within many other different labs. It is the general belief within the histology world, that the chemicals (wet and dry) we deal with are harmful to breath, touch and be around. Maybe not in the short run (most of them) but definitely in the long haul. I know that the chemicals used in the other industries are by comparison are far worse. That may be, but the use in histology research by all labs seems to be unregulated for the most part. This is the opposite for clinical histology labs, they are highly regulated and controlled to a T.  In this country (US) everything to do with humans is highly regulated. For those researchers working in labs, safety may not always be a great concern. I realize, their focus is on something grander and may not be focusing on the day-to-day idiosyncrasies. This is all well and good for them, but their actions set the tone for others to follow. I call this monkey see monkey do. I know this happens because I did it.  In the past, I worked for a research lab that did not even have chemical, dissection, and safety hoods. Lab coats could not be found unless you bought your own. No one wore safety glasses, ever. There was no paid chemical waste removal. All chemicals went down the drain, regardless of what it was. The drain led into a septic system that was next to a river. Once I asked the owner if we could hire a company to remove our waste. He laughed and said it would cost too much money and if I wanted to get paid, I should never bring it up again. I did not agree with this practice but felt bad like my job was in jeopardy if I rocked the boat. Not a good situation for anyone there and anyone living in the neighborhood. I remember one day while I was there, one of the wet chemicals leaked through its container. I smelled something and got up to investigate. The smell was very strong and filled the entire building. My eyes watered and my nose began to clog. I found the offending liquid on the shelf leaking down to the next level. It was ammonium hydroxide (28-30%). The container was the wrong kind of plastic bottle and it leaked about 100 mills before I found it. Standing in front and on top of it I put gloves on and grabbed gauze to soak it up. After about 5 minutes, a co-worker came in and hauled me out of the room into the outdoors.  Out into the cold light and winter conditions, I still could not see the problem.  I was blinded by the habits of another that now were my own.  My throat and nasal passages had closed, eyes stinging, ears not hearing but still I protested.  Someone has to clean it up, I can’t leave it there, it’s dangerous.  5 1/2 years of negative conditioning had led me to a destructive path.  The owner sat less than 10 yards away but never came to see what was going on.  He could not smell it and had no idea that there was a spill.  We did not have a safety plan in place.  The fire department was never alerted, no report was ever written, but I suffered.  The physical damage was done in a matter of minutes.  In the weeks following, I came to realize I could no longer smell many substances that before the accident were easily identified.  In hindsight, I realize that I took on characteristics of my former boss who did not use safety guidelines in his company.  This took me years and a couple different lab settings to realize the gross negligence of safety.  This will never happen again.  Too bad I had to learn the hard way.  Today, safety is my number one concern for others and myself when working in a laboratory setting.