Most of the chemicals that archaeologists use routinely are relatively innocuous, but all chemicals entail some level of risk, and it is important for those who use them to know the safe labeling, handling, disposal, and cleanup of chemicals. They should consult the OSHA, WHMIS, or equivalent manual or material safety data sheets (MSDS) on each of the chemicals used in the laboratory (see below). Lab activities that involve potentially hazardous chemicals range from cleaning and labeling artifacts, changing and recharging silica-gel, through ‘digesting’ sediments for pollen or phytolith analysis.
Keep chemicals away from children and high-traffic parts of the lab, and never leave unlabeled flasks or beakers around the lab. This is an extremely dangerous practice as the next person using the lab will have no way to know what they contain or how to clean or dispose of them safely. Use bilingual labels, where appropriate, and standard hazard symbols, such as those of the global harmonized system (GHS) of classification and labeling of chemicals (see ahead). Minimize the amount of acids and solvents in the work area by only taking what you need, and keep them away from the edges of counters or tables, or anywhere where someone might knock them over. In addition, ensure that you know the location of the OSHA, WHMIS, or GHS manual and how to interpret it.
Never smoke or eat while using chemicals or allow others to do so. Some chemicals are flammable and others very toxic. Keep solvents away from flames and motors or switches that might cause sparks. Work in well-ventilated areas and avoid inhaling solvents and acids.
Always wear protective clothing, such as gloves and apron or lab coat, and do not wear contact lenses when handling or using chemicals. Always wash your hands thoroughly afterward.
Always wash out beakers or jars that you have used for chemicals, especially acids, immediately after use.
One of the chemicals that archaeologists use frequently is acetone, a solvent. It is one of the key ingredients in some of the adhesives and consolidants used to conserve artifacts, such as B-72, an acrylic dissolved in acetone. At a minimum, acetone should be used only in an extremely well-ventilated space, but it is much better to use it under a fume hood, and you should try to keep your exposure as low as possible. Acetone is a significant fire hazard and a moderate explosion hazard and, if ignited, should be extinguished with a chemical or CO2 fire extinguisher and not with water. Acetone is stable under normal storage conditions.
Other chemicals that archaeologists commonly use are acids, such as acetic acid (vinegar), citric acid, and hydrochloric acid (HCl). Generally, archaeologists use these acids only at very low concentrations, such as 5%, to remove calcareous encrustations from artifacts. If a flask of acid has been sitting around for a while, however, evaporation may have caused its concentration to increase substantially over that stated on the label. Whatever the acid’s concentration, one should get into the habit of handling acids with respect.
Always wear protective clothing, including gloves and chemical splash goggles, when pouring acids, and always have a source of running water nearby. When diluting acid, always pour the acid into water; never pour water into an acid, as it may sputter and splash.
Some kinds of laboratory work in which archaeologists engage use more dangerous chemicals and procedures. For example, extracting pollen or phytoliths from sediment involves chemically digesting the sediment with rather aggressive acids, such as hydrofluoric (HF) and (HCl) acids and separating the silicates with tetra-bromide ethylene, zinc bromide, cadmium-potassium iodide, or sodium polytungstate, of which only the last is non-toxic. To prepare quartz crystals from pottery for a thermoluminescence date, similarly, may require use of HF acid and the even more dangerous aqua regia, which even eats through glass. One must have the material safety sheets on all the chemicals in use at work, post appropriate hazard labels for them, and consult the literature on their safe use.
Chemical Storage
Store chemicals in well-ventilated, cool, locked cabinets away from most people. Never store acids and bases together, or oxidizing agents with solvents, as their respective fumes will chemically react with one another. Some chemicals that are particularly flammable should be in special cabinets that prevent explosions. All chemical-storage cabinets should be labeled on their doors to indicate which is for acids, which for solvents, and which for other materials, including use of standard hazard labels. The chemicals should be in sealed containers, preferably of plastic or plastic-coated glass and in safety carriers that minimize the chance of breakage. The containers themselves should also be labeled with their contents and concentration, along with appropriate hazard symbols. Avoid reusing old containers, but remove all old labels if it is necessary to do so.
Chemical Disposal
Never pour laboratory chemicals down the drain. This is not only illegal in most jurisdictions and polluting, but also could lead to nasty chemical reactions in the drain, some of which might corrode through the pipes or even cause an explosion. It is best to have leftover chemicals removed by specialists in chemical waste disposal, as are found at universities and hospitals, but small amounts of less dangerous chemicals can sometimes be disposed as follows.
When disposing of a small amount of acid, dilute it by adding it to a large volume of water and neutralize it with baking soda (sodium bicarbonate) or soda ash (sodium carbonate). The solution will give off heat and effervesce until the acid is neutralized, so be sure that it is in a large, open container. It is then safe to dispose of it on carbonaceous soil in an isolated area along with large amounts of water. Tissues or towels containing acid should be washed out with lots of water before disposal.
Small amounts of solvent, such as acetone, can be left to evaporate in a shallow, labeled bowl under a fume hood, away from any source of flame or sparks. The solvent in resins and acryloid B72 can similarly be allowed to evaporate, leaving a container with a hardened block of resin or B72 inside. It can then simply be disposed of in the garbage. Preferably the container should be one that no one would be tempted to reuse, such as the cut-out base of a plastic water bottle or a damaged beaker. Tissues or towels that might contain traces of solvent should also be left in a glass container under a fume hood for evaporation before disposal.
Any glass vessels that contained chemicals should be washed thoroughly before disposal, while plastic containers should be holed to prevent their reuse.
Chemical Spills
Any lab that uses chemicals should have a spill kit. A spill kit is a set of labeled boxes containing material that you can use to absorb and neutralize spilled chemicals safely, each box meant for a different category of spill or a particular kind of chemical.
If you spill an acid, you should wear rubber gloves and splash goggles, then spread the contents of the appropriate box from the spill kit, or soda ash or sodium bicarbonate over the spill to neutralize the acid. Slowly add enough water and mix it with a shovel or dust-pan. The effervescence will stop once the acid is neutralized. Mop up the spill using lots of water, and use a great deal of running water to rinse out the mop.
If you spill acetone, alcohol or other chemicals that dissolve in water, shut off any potential source of flame or sparks and mop up the spill with large volumes of water. Ventilate the area thoroughly afterward to evaporate any remaining traces.
If you spill a solvent that does not dissolve in water, such as toluene, again shut off any potential source of flame or spark, and sprinkle the appropriate box from the spill kit, or vermiculite, sand, or ‘kitty litter’ over the spill. Once this has absorbed the spill, shovel the mixture into a metal bucket and put it under a fume hood or in an isolated, well-ventilated place where the solvent can evaporate. Ventilate the room where the spill occurred until all traces of solvent have evaporated and the smell is gone.
Other Chemical Emergencies
Sometimes, in spite of protective clothing, you may splash a hazardous chemical on your skin or in your eyes, or accidentally inhale or ingest something dangerous.
For splashes on skin, rinse the exposed skin with large amounts of running water until the chemical is completely removed. For chemicals that do not dissolve in water, use soap and water. Remove any clothing on which the chemical splashed and do not wear it again until it has been thoroughly washed. If the splash has caused burning or corrosion to your skin, you will need medical attention, and should inform healthcare workers what chemical was involved and what first aid was given.
Splashes in the eye also require irrigation with large amounts of running water, and many labs have special eye-wash stations for this purpose. Hold eyelids open to wash the entire eye, and then seek immediate medical attention, providing information on the chemical and first aid to the healthcare workers.
If someone in the lab inhales a dangerous vapor, you should remove the victim from the affected area, loosen his or her clothing and, if breathing stops, give artificial respiration. Seek medical attention and report the chemical involved and any first aid given.
If someone ingests a chemical, rinse out the mouth with large amounts of water, which the victim should not swallow. If any of the chemical was swallowed, the victim should also drink a large amount of water to dilute the contents of the stomach. Do not induce vomiting. Get immediate medical attention and tell the healthcare workers the quantity, concentration, and type of chemical that was ingested.
World History
