A Few Risk, Hazard, and Safety Issues

   For Amateur Microscopists

by Richard L. Howey, Wyoming, USA



You may very well be getting tired of reading cautions and warnings about laboratory safety in Micscape and elsewhere. If you’re in your teens or twenties, you may still be indulging in an “immortality complex” and if you’re ancient like me, you may think that it’s worth taking a few risks if you get some interesting results. I politely, but vehemently disagree.

I recently ordered some chemicals from two different companies and I always check their listings to see if they are marked as hazardous. One item from the first company was marked as mildly hazardous and required special shipping, but not the more expensive “Poison Pack” shipping. The other item arrived in a box marked “Hazardous” along with a number of other ostensibly non-hazardous chemicals. The items in question was not indicated as being a special hazard in the company’s catalog, but it turned out on checking to be a highly dangerous substance. Over the years, I have had a few laboratory experiences that make me wary, maybe overly cautious, possible even obsessively neurotic, so I decided to go on the Internet and find the relevant Material Safety Data Sheets The hazard ratings run from 0 (zero) to 4 (extremely dangerous, life-threatening). Both of the items had health risk ratings of 3 (Severe) and even inhalation of dust particles of the substances on skin contact could prove fatal! At this point, I decided to inventory all of my chemicals and, by using cut and paste, create from the MSDS, a reference for myself of the relevant data for each chemical. I included the following items: 1) General description, synonyms, and composition of the chemical, 2) Hazards, 3) Dangerous decomposition by-products and interactions with other chemicals, and 4) toxicological data. After looking at this data for about 30 chemicals (a fraction of my inventory), I about decided to give up microscopy and do jigsaw puzzles. However, on reflection, I decided that I was over-reacting (but only a little). Even some of my old trustworthy friends like Magnesium sulfate (Epsom salts) and Magnesium chloride turned out to be treacherous under certain conditions. In fact, I am now leery of even recommending that any amateurs try making crystal slide melts, unless you have access to an academic or professional laboratory with a vented fume hood. It is difficult to control the heat of an alcohol lamp or Bunsen burner when holding a slide over the flame and there is a real danger of quickly and inadvertently reaching the decomposition temperature of the crystals and this can lead to the production of deadly gases, such as, chlorine, cyanide, hydrogen sulfide, sulfuric, hydrochloric, or nitric acid vapors or explosive gases, such as, acetone vapors or the vapors of other solvents. Decomposition products of chemicals are often a very serious danger and need to be a concern when heating any type of crystals.

Even heating solutions in which crystal salts of certain types have been dissolved can be risky. Some alkalis tend to “bump” when heated and can spray hot caustic solution onto your skin producing severe burns or, even worse, spray into your eyes. Acids are also very dangerous to heat and can produce not only serious burns, but lethal vapors. Mixing acids and alkalis can cause extremely violent reactions. You must also pay careful attention to the sort of glassware you use to heat materials. It’s well worth investing a bit of extra money in purchasing flasks, beakers, and test tubes that are certified as “heat resistant”. It is wise to buy recognized long-standing brands as there is a great deal of laboratory glassware these days that is imported from countries that do not have the same quality control and safety standards that we have (and ours could be better!). Sometimes heat-resistant glassware is critical even when you’re not heating a reagent. A classic example is concentrated sulfuric acid. In the process of dilution, it generates very significant amounts of heat. Also rememberAAA—“ALWAYS ADD ACID” to water when diluting, adding it slowly and carefully, wearing goggles, gloves, and protective clothing.

Sometimes dissolving crystals in warm or hot water can produce supersaturated solutions which will give nice results when a drop of the material cools on the slide. But again, exercise caution and do your homework first, either by means of MSDS or a chemical handbook. Another thing that you can try with warm, NOT HOT, solutions is placing a drop on a slide that has been chilled in the freezer compartment of your refrigerator.

When you are making solutions from crystals and powders, you also need to exercise care, especially with the powders. Preparations should always be done in well-ventilated areas with appropriate precautions ranging from rubber gloves and goggles to air filter masks to ventilated fume hoods. Some of you may be skeptical that crystals or powders could be much of a risk. However, the inhalation of some chemical dusts can be extremely dangerous since they can be very quickly absorbed into the blood stream, whereas others can rapidly affect the nervous system.

Organic reagents, such as, hydrocarbons and common laboratory solvents, such as, xylene, acetone, and toluene can also be harmful if inhaled, producing liver damage, kidney damage, and brain damage.

All of this sounds quite grim and indeed, it can be if one doesn’t take the trouble to inform oneself adequately and take the proper precautions. Commonsense, information, proper procedure, and caution can save you from very real threats to your health, safety, and even your life. These investigations have led me to order a filter mask with special filters for toxic dusts, vapors, organic solvents, acids meeting the standards of NIOSH (National Institute for Occupational Safety and Health).


There are certain chemicals that amateurs should avoid completely and I am going to mention a few, because in many of the older reference and textbooks, these reagents are mentioned with little or no warning of potential risks. In some cases this was due to the fact that the dangers were not fully recognized at the time. In other instances, it was assumed that appropriate laboratory equipment and instruction would be routinely available. I’ll sort these items into two basic categories:


1) Mercury compounds. Traditionally many fixatives used mercuric chloride (also know as corrosive sublimate) as a central ingredient. This salt is corrosive and highly toxic. One of my university colleagues banned the use of mercuric compounds from his laboratory. In addition to their toxicity, they also have a nasty propensity for contaminating glassware and other laboratory apparatus.

2) Osmic Acid (Osmium tetroxide)Extremely nasty! Again a fairly common ingredient in fixatives, especially for electron microscopy, but also used for optical microscopy. Fortunately, it is expensive enough that most amateurs would not even consider using it. To give you an idea of its hazardous properties, it is usually supplied in small glass capsules which are then placed (gently!) in a flask with distilled water or the other ingredients of the fixative you are preparing. The capsule is then broken with a glass rod-in a ventilated fume hood-and the final touches can be administered in preparing the fixative. Imagine, working in an osmium tetroxide factory where your job is to seal the stuff in glass capsules!

3) Cyanide compounds The mere mention of cyanide should excite horror and conjure memories of locked room British mystery novels (of which I must confess, my wife and I are great fans). It deadly; you know that; DON’T MESS WITH IT!

4) Benzene. A very popular solvent until, relatively recently, it was discovered just how toxic it is and that it is carcinogenic (cancer-causing).

5) Strychnine. Strychnine sulfate was sometimes recommended for anesthetizing aquatic invertebrates. It is highly toxic in concentration and can induce extremely painful convulsions.

6) Ether. Highly volatile, can quickly induce unconsciousness, overdoses are lethal. Some ethers form explosive compounds as they age and must be stored in explosion-proof refrigerators.

7) Carbon tetrachloride. This reagent is now quite difficult to obtain. However, it used to be a common household item, easily obtainable from the shelves of a local drugstore. It was used as a spot remover and as a teenager, I used it in my killing jars for insects. It had a sharp, but not unpleasant odor and I’m sure I inhaled lots of fumes and spilled some of the stuff on my hands. So, what’s the problem? Well, it has since been discovered that carbon tetrachloride is a carcinogen and does liver damage, kidney damage, and, as if that weren’t enough, can also adversely affect the nervous system.

8) Phenol (Carbolic Acid). This is a chemical that gets mixed with formaldehyde to make embalming fluid! It is extremely poisonous as crystals, vapor, or liquid and is readily absorbed. It is highly caustic and can produce deep, severe burns that may not be noticed at first because of the way it attacks tissues and nerves. Many phenol compounds are carcinogenic.

Phenol has sometimes been used as a clearing agent for aqueous specimens and is indeed often effective but, in general,

the dangers of working with this reagent make it simply not worth the risk.

9) Concentrated Acids and Realgar. I have put these two under the same topic heading only because of diatoms. Some diatomists, like the alchemists, have had a touch of madness. In this quest to produce beautifully, clean, pristine, sparkling silica frustules (shells), they have gone to extraordinary measures. These beautiful objects pose a number of difficult challenges. In order to clean the frustules, diatomists have boiled them in concentrated mineral acids. A good lungful of these vapors will solve all your problems-permanently! The vapors of these acids, especially when heated, are highly corrosive to mucous membranes and, if inhaled, can be fatal! These acids should only be used in a well-equipped carefully regulated laboratory.

When you think of the classic mystery tale involving poisoning, what pops into your mind? Well probably two things: we already mentioned cyanide and the other is, of course, arsenic. Realgar is a form of arsenic that some diatomists have used in their quest to achieve a mounting medium with a high refractive index (R.I.). Part of the problem is that the diatom frustules, being composed of silica, are essentially glass, so unless you have a mountant with a significantly higher refractive index than about 1.52, the diatoms become virtually invisible. Hyrax has an R.I. of 1.822, but realgar has one of the very highest at over 2.0. All you have to do is heat the realgar until it gives off deadly vapors which you collect on a slide or cover glass to mount your diatoms on! Not my idea of fun but, hey, some people get a thrill out of going over Niagra Falls in a barrel or wrestling alligators.

Let’s go back to acids for a minute. Some people think-ah, glacial acetic acid, that’s just concentrated vinegar—WRONG! Glacial acetic acid is very nasty, has an overwhelmingly powerful odor, attacks mucous membranes and has the bizarre property of “freezing” at 63 degrees Fahrenheit or 16.6 degrees Centigrade. If this happens and it breaks the container and spills then you will have a vile, dangerous mess to clean up. One acid you NEVER, NEVER, NEVER, want to deal with is hydrofluoric acid. This stuff has to be stored in special wax-lined containers, because it is so reactive that it eats glass! Imagine what a whiff of that could do to clear out your lungs.

The second category is :


1) Picric Acid (trinitrophenol). These crystals MUST ALWAYS be kept moist, in fact, they are best kept in a saturated solution and away from metals and metal compounds. If the crystals become dry or form certain kinds of metallic picrates, they become high explosives. As you can tell from its chemical name, this compound is closely related to TNT! It is used in a classic fixative (and its variants) called Bouin’s fluid or Bouin’s fixative. It is, as you would expect from a fixative, quite toxic. In solution, it is stable but should be mixed with other reagents ONLY following proven formulas and then taking full safety precautions.

2) Concentrated Alkalis. The majority of these substances are highly caustic and, if spilled on the skin produce deep burns and ulcerations which take a long time to heal. A splash into the eyes can be disastrous and may well result in blindness. They are even more dangerous when heated since some alkalis tend to “bump” and can spray scalding, caustic liquid over you and your equipment.

3) Oxidizing Agents. All of us are familiar with hydrogen peroxide and it is a staple in many medicine chests. It can react strongly with certain chemicals and with organic material. What you usually purchase at the store is a 3% solution. If you put some on a cut or abrasion, you will notice it foaming. If you dilute some of it with an equal amount of water and use it as a mouthwash, you will feel its bubbling activity. Some health food stores sell 35% hydrogen peroxide. The label tells you to dilute it down to 3% and use it for cleaning and scrubbing vegetables. It’s always seemed simpler and more economical to me to just buy the 3% solution in the first place (not that I ever scrub vegetables with anything but water). A 35% solution is, I assure you, highly reactive, and with some other chemicals can form peroxides that are violent and even explosive.

Whenever you are considering mixing different chemicals, always consult the section in the MSDS which states the incompatibilities of a given compound.

4) Formaldehyde. A number of generations have grown up treating formaldehyde almost as casually as alcohol as a preservative, plunging their arms up to the elbow in the solutions to retrieve specimens from the bottom of shipping containers. Formaldehyde has always been obnoxious to work with due, in large part, to its pungent, irritating, and penetrating odor. However, for many purposes, it is exceptionally useful, effective, and inexpensive.

Gradually it has become known that formaldehyde is a quite dangerous reagent. Even when MSDS sheets say only “possible carcinogen” or “suspected carcinogen”, don’t kid yourself-anything so described is dangerous. In addition to the formaldehyde itself, there is always the toxicity of methyl or “wood” alcohol to take into account, since it is always a component of commercial solutions.

Additives have been produced to “deodorize” formaldehyde, but don’t forget that the fact that because it smells less noxious, doesn’t make it any less toxic. Some biological supply houses have developed substitutes in which to ship and store specimens. Nonetheless, formaldehyde is generally still used as the primary fixative and then the specimens are transferred to the “less toxic and less noxious” fluid.

So now we know that there are some basic precautions that one needs to take.

a) Work in a very well-ventilated area and/or use a ventilated mask designed for use with such chemicals.

b) Wear goggles to protect your eyes both from the possibility of accidental splash and also from the vapors.

c) Wear the proper sort of heavy-duty gloves. The thin latex surgical gloves are not sufficient protection.

d) Limit exposure as much as possible. When feasible transfer specimens to 70% alcohol. Plankton samples are virtually invariably preserved in formaldehyde. When you wish to examine such material with a dissecting microscope, transfer the sample through several changes of distilled water.

e) Don’t mix with Scotch; it tastes terrible! Hey, I’m just kidding!

5) Silver nitrate. This is a caustic and reactive substance and like many nitrates can form explosive compounds. Many men are acquainted with a form of silver nitrate in the form of a “styptic pencil” used to retard bleeding when one nicks oneself while shaving. Be extremely careful what you mix this with (or for that matter any other compound) and always inform yourself about the possibility of dangerous reactive properties or dangerous decomposition products from heating either the solution or the crystals or powder. Silver compounds have played a crucial role in, among other things, photography. I have used a dilute solution of silver nitrate to deposit a metallic coating on forams and other micro-shells. [LINK] Very dilute solutions are, of course, almost always safer to work with, but that doesn’t mean that they are without risk and one should always exercise care. Even ordinary table salt can produce toxic chlorine and sodium oxide vapors when it reaches its decomposition temperature and ordinary sugar at decomposition temperature can produce carbon monoxide. So, never assume that because something is common and readily available that it is safe under all conditions.

I want to thank Dave Walker for being generous enough to read this article and make some important suggestions which I will include here.

1) In addition to my comments on hydrofluoric acid see: http://www.palynology.org/content/nl/1995-V28No1.pdf page 15

2) Dave pointed out quite rightly that melts of certain chemicals can be made safely if there is adequate ventilation along with and electric hotplate with thermostatic control. I certainly agree, but one must be very careful about controlling this in such a manner than one does not reach decomposition temperatures.

3) Dave also pointed out that I said nothing about the disposal of chemicals. Here again the Material Safety Data Sheets are very valuable as they provide a special section presenting the types of recommended procedures for disposal. Regulations regarding the disposal of chemicals vary from country to country and community to community so, if you are unsure of the approved procedures, you should consult local experts. Remember that what you dump into a sink or toilet, could end up later in your drinking water.

4) Dave also reminded me that a significant number of amateurs, not having a dedicated lab space, may carry out their investigations either in their kitchens or bathrooms. This means that you must be very careful not to leave any chemicals in areas where they might be accessible to children. Also, if you work in a kitchen area, you need to take suitable precautions to avoid contamination of any food or dishware used in the preparation of food or drink. In fact, it is also a basic rule of laboratory safety that you should never have food or drink in the area where you are working. Imagine picking up a glass which you thought was iced tea and it turned out to be a nice rich sample from a barnyard pond that you had just collected. Enough said!


Neither the author nor anyone associated with Micscape makes any claims to completeness or final authoritative accuracy in the material presented above and can accept no responsibility for accidents, misuse of materials, or misunderstandings which may result regarding any individual or group of individuals. It cannot be emphasized too strongly that the person or persons involved in such experimentation have the obligation to adequately inform themselves and follow appropriate procedures.

Finally, I cannot emphasize enough that commonsense (which seems a rare commodity these days, especially amongst politicians), adequate information, proper protective gear and/or apparatus, and caution are essential. If you pay attention to these items, you will minimize the risks and be able to conduct interesting and productive experiments. There are no guarantees; virtually no human activity is risk-free; so much depends on the individual’s own willingness to take risks and his or her sense (or lack thereof) regarding acceptable consequences. A former student of mine bicycled from Vladivostok to Moscow, kayaked down the Niger river to seek out the real Timbuktu, has made assaults on Mount McKinley and Mount Everest and is still alive and writing about his experiences. To me exploring the micro-world is filled with adventure and I realize that there are risks from chemicals, pollution in samples I collect, and dangerous micro-organisms that can be debilitating or even life-threatening, but I do what I can to minimize the risks and maximize my pleasure. For me the great adventures are not Everest or McKinley, but the micro-mountains that I explore everyday which produce an incomparable sense of wonder.

All comments to the author Richard Howey are welcomed.



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