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?


microscopic breast stained with H&E

Homemade Histology Equipment

I originally went into histology because I love to work with my mind and hands at the same time.  Creating new original pieces that I can use or look at over time gives me satisfaction.  This field of histology keeps me wanting more, always looking for new and different information to add to a growing repertoire of knowledge.  This keeps me going, day after day to contribute to the field and the people who need histology for pathology diagnosis.   I work 2 jobs, one for myself as the owner of a histology company and two for a private college WPI in Worcester, MA as the histology manager.  The histology core provides services to mostly the professors and students who do biomedical engineering research.  Since the college has the resources for me to come up with and execute my histology based experiments, I have been compelled to create new products that may help me and others in the future.  One of these experiments, an old extra hot plate we had, turned into a paraffin wax trimmer (block melter) (see picture 1 & 2).  There are companies that make these paraffin trimmers but they are $350.00 to $800.00.  My cost nothing but a few hours of my time and I get the satisfaction of building like an engineer.

*Sorry Facebook, you have seen this already.


The next equipment I made, and i just did this in my garage with Baltic birch laying around, is slide holders.  These are used next to the microtome when cutting.  They make it easy to put the slides standing up but not in a rack.  I used the table saw to cut plywood down to the chosen size, then angled grooves at an inch apart for the slides to stand in.   Everything in the medical field does not have to cost so much, why would I pay for something that I can just make.  These also are sold as histology extras but not as cheap or fun as the one’s I make in my garage.  These will be used by all the people doing histology at the college and any doing work for me.

Homemade Wax Trimmer 1 Homemade Wax Trimmer 2


























Slide holder 1 Slide holder 2




























15 Most Health Hazardous Professions

On Monday, Yahoo posted a news piece about “the 15 jobs that are most Damaging to your health”.  This report identifies histotechnologists and histotechnicians as the most health hazardous job out of 974 professions.  No wonder there are no histology technicians left to replace the baby boomers who are now trying to retire.  There was a lot of commotion on the histology forum (histonet,  Tuesday and Wednesday about this controversial subject.  Some were giving examples of the lab conditions they worked in the past.  I’ve heard the stories from some of the older histotechs about them eating, drinking and smoking in the labs while performing gross dissection on patient tissues.  They also told stories about how there were no fume hoods, MSDS sheets or safety precautions taken for any chemicals.  Techs were encouraged to melt paraffin off their hands using xylene.  In the past 25 years those safety precautions and regulations have been put into place but still do not mean much unless the lab adheres to them.

The first histology lab I worked (2004-2010) in had little or no safety precautions set up for the workers.  All the chemicals that did not go down the drain, went into the techs blood stream working in the lab.  The owner a 30 year veteran of histology explained that he had been grossing tissues without gloves for 30 plus years and did not believe in any of the health risks associated with histology chemicals, because he did not exhibit any abnormal symptoms.  That’s too bad for all the employees who have ever worked for him or continue to do so.  This is a prime example of gross negligence by a professional employer.

The forum also talked about trying to set up a system like the nursing association, with all the histology technicians submitting their doctors yearly check-ups to categorize and identify possible health and safety issues associated with the profession of histology.  After years of data was compiled on all the histotechs who completed the surveys, this would give rise to a database that might correlate and predict life expectancy for the average histology technician.  The possibility for new safety regulations and precautions may also result.


Hematoxylin and Eosin Quality Control

We need to ensure quality of H&E sections, so when reviewing the daily H&E, we are looking for blue nuclei with chromatin and a well stained nuclear membrane. Also we are looking for 3 shades of eosin, light, medium and dark red/pink. Some of this is determined by the kind of eosin used.  If a control is questionable we should run a second control that we are sure of to ensure that the problem, is a staining problem and not a tissue problem. Over decalcified, over heated or poorly processed/fixed tissue can stain poorly even if all solutions in the H&E stain are OK. When doing H&E on frozen sections extra care must be taken if the slides are fixed in Formalin after cutting. Formalin or concentrated formaldehyde can act as a reducing agent. The best way to remedy this problem is to change the hematoxylin frequently. Frequently can be defined by the lab.  Some labs like clinical hospitals, where the volume is high, may determine a frequency based on number of slides, day or weeks.  Clinical labs are usually controlled by the pathologist, therefore whatever the pathologist wants, is what will become the norm. For smaller labs this is not the case.  Generally a smaller lab will inspect the color intensity of the hematoxylin on a weekly basis to determine the right time to change it.  As a rule of thumb, hematoxylin must be filtered before each days use.  This helps to keep the floating precipitate out, removes any extraneous cells and lets it keep longer.  The time in the 95% alcohols after eosin is where the three shades of eosin are differentiated so these times may need to be adjusted for best results.

Rat Liver H&E 20x
Rat Liver H&E 20x

reducing agent (also called a reductant or reducer) is the element or compound in an oxidation-reduction reaction that donates an electron to another species. Because the reducing agent is losing electrons, we say it has been oxidized. (