Laboratory hazards Drops of 98%<unk>  char a piece of tissue paper instantly. Carbon is left after the dehydration reaction staining the paper black. Superficial chemical burn caused by two 98%<unk>  splashes (forearm skin)<unk>  is capable of causing very severe burns, especially when it is at high concentrations. In common with other corrosive<unk> s and alkali, it readily decomposes proteins and lipids through amide and ester hydrolysis upon contact with living tissues, such as skin and flesh. In addition, it exhibits a strong dehydrating property on carbohydrates, liberating extra heat and causing secondary thermal burns. Accordingly, it rapidly attacks the cornea and can induce permanent blindness if splashed onto eyes. If ingested, it damages internal organs irreversibly and may even be fatal. Protective equipment should hence always be used when handling it. Moreover, its strong oxidizing property makes it highly corrosive to many metals and may extend its destruction on other materials. Because of such reasons, damage posed by<unk>  is potentially more severe than that by other comparable strong<unk> s, such as hydrochloric<unk>  and nitric<unk> . 70px 70px<unk>  must be stored carefully in containers made of nonreactive material (such as glass). Solutions equal to or stronger than 1.5 M are labeled "CORROSIVE", while solutions greater than 0.5 M but less than 1.5 M are labeled "IRRITANT". However, even the normal laboratory "dilute" grade (approximately 1 M, 10%) will char paper if left in contact for a sufficient time. The standard first aid treatment for<unk>  spills on the skin is, as for other corrosive agents, irrigation with large quantities of water. Washing is continued for at least ten to fifteen minutes to cool the tissue surrounding the<unk>  burn and to prevent secondary damage. Contaminated clothing is removed immediately and the underlying skin washed thoroughly. Dilution hazards Preparation of the diluted<unk>  can be dangerous due to the heat released in the dilution process. To avoid splattering, the concentrated<unk>  is usually added to water and not the other way around. A saying used to remember this is "Do like you oughta, add the<unk>  to the water". Water has a higher heat capacity than the<unk> , and so a vessel of cold water will absorb heat as<unk>  is added. +Comparison of<unk>  and water Physical property Water Units Density 1.84 1.0 kg/L Volumetric heat capacity 2.54 4.18 kJ/L Boiling point 337 100 °C Also, because the<unk>  is denser than water, it sinks to the bottom. Heat is generated at the interface between<unk>  and water, which is at the bottom of the vessel.<unk>  will not boil, because of its higher boiling point. Warm water near the interface rises due to convection, which cools the interface, and prevents boiling of either<unk>  or water. In contrast, addition of water to concentrated<unk>  results in a thin layer of water on top of the<unk> . Heat generated in this thin layer of water can boil, leading to the dispersal of a<unk>  aerosol or worse, an explosion. Preparation of solutions greater than 6 M (35%) in concentration is most dangerous, because the heat produced may be sufficient to boil the diluted<unk> : efficient mechanical stirring and external cooling (such as an ice bath) are essential. Reaction rates double for about every 10-degree Celsius increase in temperature. Therefore, the reaction will become more violent as dilution proceeds, unless the mixture is given time to cool. Adding<unk>  to warm water will cause a violent reaction. On a laboratory scale,<unk>  can be diluted by pouring concentrated<unk>  onto crushed ice made from de-ionized water. The ice melts in an endothermic process while dissolving the<unk> . The amount of heat needed to melt the ice in this process is greater than the amount of heat evolved by dissolving the<unk>  so the solution remains cold. After all the ice has melted, further dilution can take place using water. Industrial hazards<unk>  is non-flammable. The main occupational risks posed by this<unk>  are skin contact leading to burns (see above) and the inhalation of aerosols. Exposure to aerosols at high concentrations leads to immediate and severe irritation of the eyes, respiratory tract and mucous membranes: this ceases rapidly after exposure, although there is a risk of subsequent pulmonary edema if tissue damage has been more severe. At lower concentrations, the most commonly reported symptom of chronic exposure to<unk>  aerosols is erosion of the teeth, found in virtually all studies: indications of possible chronic damage to the respiratory tract are inconclusive as of 1997. Repeated occupational exposure to<unk>  mists may increase the chance of lung cancer by up to 64 percent. In the United States, the permissible exposure limit (PEL) for<unk>  is fixed at 1 mg/m3: limits in other countries are similar. There have been reports of<unk>  ingestion leading to vitamin B12 deficiency with subacute combined degeneration. The spinal cord is most often affected in such cases, but the optic nerves may show demyelination, loss of axons and gliosis.
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Zinc oxide
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Salicylic acid
Gadobenic acid
Tienilic acid
Silver diammine fluoride