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DOT hazard classes

The department of transportation has developed a very good system for safely handling almost any chemical.  The developers have intelligently heeded the KISS concept: Keep It Simple Stupid.  Although, as Murphy says, it is impossible to make things fool proof, because fools are so clever.

To help people handle chemicals safely, they have been divided into nine categories.  Four of these categories are discussed later: Explosives, Compressed Gas, Radioactive, and ‘Other’.  The remaining classes are based on chemical properties that help us handle these chemicals safely.

1.  Class 3, Flammable liquids.  These types of chemicals have two important issues.  The first is that they cause/fuel fires, and the second is that they are volatile (like perfume).   The vapors from these chemicals can not only feed a fire, but they are often poisonous to breathe, or, they can displace all the oxygen in the air, leaving none to breathe.

Another issue for firefighters is that putting water on a gasoline fire only spreads the gasoline around, as well as the fire.  In Cleveland, the Cuyahoga River caught fire on June 22, 1969.  The river burned for thirty minutes, not the water, but the oil-like substances floating on top of the water.  For Firemen, spraying water on a river to put out a fire doesn’t work very well.

This is why there are different kinds of fire extinguishers, you can’t use water to put out all types of fires.  You should not use water to put out a grease fire in the kitchen, use the lid of a pot, sand (if available), or baking soda, otherwise you should have “dry chemical” type fire extinguisher.

Flammable liquids are often volatile, and if the cap is left off, or there is a hole if the container, the liquid will evaporate out and can become a breathing and fire issue.  Flammable liquids should be stored in a secure location that is isolated from living spaces, to ensure fumes don’t build up or get trapped inside to be breathed.  These vapors are flammable, and they can become an explosion hazard, similar to how fuel-air explosives work.

2.  Class 4 materials are reactive, sort of like nitroglycerine.  These chemicals can react with oxygen or water, and often need special handling procedures.  For example sodium metal must be kept in oil because it will react violently with water- even the water in the air.

There are also chemicals that react with water, like sodium hydrosulfite, which is a common rust remover (a reducing agent), and bleaching agent.  It is important for fireman to be aware of these compounds, because you don’t want to pour water on these materials during a fire as it will only make the emergency worse.

At one time miners used to use the chemical calcium carbide to generated a flame for their head lamps.  When this chemical is mixed with water it releases the gas acetylene (also used in acetylene torches), which ignites to produce light.  Obviously it would be very bad for a fireman to spray water on a fire when calcium carbide is involved.

3.  Class 5 materials are oxidizers, and they can release, and so provide, oxygen for a fire.  The increased oxygen makes the fire burn better, these materials help “fan the flames”.  The most dangerous of these provide oxygen, and fuel to a fire.  Some of the worst are organic peroxides, which often come (packaged separately) with epoxy resin, they act as a “hardener”.  These materials can not only be the fuel, but provide the oxygen and heat required for a fire to start.   Often car paint patching, or filling resins, come with a separate little tube of ‘hardener’.  These should be handled with care.

4.  Class 6 materials are poisons.  These chemicals generally come from deliberately created poisons like bug killer and weed killer.  There are instances where a poison only kills the pest of interest, but it is incorrect to think that a compound which poisons one species is ok for another, like DDT, poison is poison.  History (or hind-sight) shows us that what is safe (according to those who make it) one day, is toxic the next (after it kills people).

Inhalation Hazard Materials are included within this class, and refer to any volatile chemical which is poisonous like methylene chloride.  The designation ‘IDLH’: Immediately Dangerous to life or health, is used by DOT to indicate that a compound is volatile, and dangerous.  IDLH values were originally determined for 387 substances in the mid-1970’s, and IDLH values for 85 substances like benzene and methylene chloride, were determined by NIOSH to meet the OSHA definition of “potential occupational carcinogen” as given in 29 CFR 1990.103.  Unfortunately, many of these substances can be purchased down at the corner store, and at most require labeling of ORM-D (“Other Regulated Materials-Domestic”) for consumer commodities.

5.  Class 8 materials are corrosives- both acids and bases.  These are primarily cleaners.  For example, ‘Deck Cleaner’ can be either an acid, or a strong base.  The definition of corrosive is based on how fast that chemical will corrode some metal.  An interesting experiment is to put a nail in a glass of coke, and watch the nail corrode away over time;  This is due to the phosphoric acid in the ingredients.

The mob has/had a reputation for throwing acid in people’s face to blind or torture them.  The real story is that they actually used a strong base.  This is because acids are easily washed away, while bases dissolve tissue to generate soap.  Soaps are made by mixing a strong base with an oil, so a strong base turns your flesh into soap.  This is why strong bases feel ‘slimy’ and are hard to wash off because the soap created helps hold the strong base in place to dissolve more flesh.

The most notorious of these are the solid drain cleaners, like lye, or sodium hydroxide- probably the strongest base known.  The solid is ‘agroscopic’, meaning it absorbs moisture from the air, and that moisture becomes a very strong base.  It also generates a lot of heat when it dissolves in water, and a hot solution is more corrosive than a cold solution.  This is why people should not use the solid drain cleaners, especially with metal pipes.

The other Classes
Class 1 is Explosives, and these have obvious concerns.

Class 2 is the compressed gases, and they have the problem of explosively decompressing, plus, the gas itself  has properties, leading to additional class designations like flammable, corrosive, oxidizer, reactive, and sometimes radioactive.  Additionally, inert gases like helium or nitrogen can drive out, or displace, all of the oxygen in the air leading to suffocation issues- an air filter does not work if there is no ‘air’ to begin with.  This is why firefighters bring along their own compressed air tanks instead of using a filter. OSHA has a separate certification called ‘Confined Space Operation’, which deals with the issue of small spaces that may have had all of the oxygen driven out.  Many workers have been caught in, and suffocated in such a place.

Class 7 are Radioactive materials, and generally associated with the nuclear industry, and Medical ‘tracers’ and chemotherapy.

Class 9, or miscellaneous hazardous materials, or generally things like asbestos tiles, and CFLs(compact fluorescent Light bulbs), or fluorescent bulbs containing mercury.

The Next Section  is Routes of Exposure

Chemical Properties
All chemicals have unique properties that allow us to tell them apart.  These properties include color, density, solubility (oil and water don’t mix), boiling point, melting point, conductivity, and many others.

Some properties are unique, and make it easy to identify that particular chemical, like the density of gold.  Other chemicals are so similar that only very sophisticated means can be used tell them apart.  It is similar to telling different people apart: black and white people are easy tell apart, but identical twins take more effort.  Many similar chemicals are grouped together, like PCBs and dioxins, which are names given to similar groups of chemicals, not individual chemicals.  Gasoline, for example, is a mixture of thousands of different individual chemicals, ranging from alkanes (like octane) to polycyclic aromatic hydrocarbons (PAHs), but we tend to think of gasoline as one chemical.

Properties can be measured, or ‘quantified’ (given a quantity).  This gives us more specific information than ‘qualities’ like heavy, or dark.  For example, gold has a quantified density; so that while lead is ‘heavy’, it is not as heavy as gold, and we can measure the difference.  This originated with the need to distinguish counterfeit coins from real ones, someone came up with the concept of density.

In the end, there are only seven different ways we can measure something:

Length(m)
Mass(kg)
Time(s)
Temperature(K)
Amount of substance (mole)
Luminous intensity (candela)
Electric current(ampere).

We can then put these seven basic measurements together in an almost infinite variety of ways, and these are called derived units:  Speed is length per time, acceleration is length per time squared, Concentration is moles per volume (length cubed), Density is mass per volume, and Force is mass times acceleration.

States of matter
All chemicals come in a certain ‘state’ under normal conditions; it is one of their identifying properties.  Matter can be liquid, solid, gas, or plasma.  For example, mercury is in a liquid state under normal conditions, while almost all the other metals are in a solid state.  Pure ‘oxygen’ and ‘nitrogen’ are in a gas state, while water is in an in-between state; sometimes in all three states at once.  Snow, for instance, is the solid form of water, while ‘wet snow’, or slush, is part liquid.  Additionally, snow can ‘sublimate’, (solid evaporates right into a gas without becoming a liquid first), so, all three states can be present in a patch of snow at the same time.

Chemists often use ‘phase diagrams’ to determine what state a chemical will be in under certain temperatures and pressures.  For example, water will boil at very low temperatures if the pressure is low enough, or, it will boil at higher temperatures if the pressure is higher; Pressure Cookers utilize this property.  Phase diagrams also help engineers design materials for various applications, like which materials will make the best ‘heat shields’ for space craft.

Solutions
Most of the chemicals we use are in the form of a solution.  Orange juice is a good example of a solution, it consists of water, plus a whole lot of other stuff like pulp, vitamins, and minerals.  Our bodies are big bags of solution, and according to aliens on Star Trek, we are ‘ugly bags of mostly water’.

The stuff mixed in water is said to be dissolved in the water, like dissolving sugar into coffee.  Water is called the universal solvent because it will dissolve anything.  Further, water dissolves different amounts of different substances, and how much it dissolves often depends on what the temperature is.  For example, Rock candy is made by pouring sugar into boiling water, and then letting the water cool.  As the water cools, it cannot hold as much of the sugar any longer, so the sugar must come out of the solution.  It does this by forming crystals, and we can evaporate off the water to leave the crystals.  On the other hand, oxygen dissolves to the maximum amount when water is near freezing,  less can be dissolved as the temperature is raised.

This is how stalagtites and stalagmites are formed in caves. The water seeping through the earth dissolves the most ‘soluble’ mineral parts of the bedrock, and leaves the rest. This solution can  enter a cave where the minerals crystalize out of solution as the water evaporates away inside the cave.

Solubility: Oil and water don’t mix

The use of this property is a good way to identify compounds like gasoline: if we put some gasoline in a glass of water it will float on top of the water.  It does not appear that the ‘oil-like’ gasoline and the water mix, they ‘separate’.  Technically, water will dissolve even oil, but it does not dissolve enough to matter for Identification; a tiny amount of gasoline will dissolve into water,  not enough to fuel a fire, but it will make the water taste like crap (our senses are very sensitive to compounds like gasoline), and kill fish.  Similarly, compounds like ‘dry-cleaning’ solvents don’t mix with water either, however, they sink to the bottom of a glass of water instead of floating on top.   Another ‘sinker’, is the heavy part of petroleum, called DNAPL, or Dense Non-Aqueous Phase Liquid.

This is why if you step in tar at the beach, washing it off with water will not help.  What is needed is a substance that allows oil and water to mix, like soap or alcohol.  ‘Like dissolves Like’ is a concept chemists use, and is similar to saying oil and water don’t mix.   Soap, and alcohol, are chemicals that act like a bridge; they have a water like end(hydrophilic), and an oil like end(lipophilic).  The oil like end dissolves oil-like compounds(like dirt and tar), while the other end dissolves in water allowing the substance to be ‘washed out’.  This is the principal behind washing clothes, with no soap you only get the clothes wet.

Reactions
There are two  types of reactions chemicals can undergo.  A physical reaction leaves the chemical unchanged, like evaporation.  A chemical reaction leads to new chemicals, like burning meat versus cooking it.

Another way we can tell chemicals apart is by how they react with (or interact with) other chemicals: Gasoline will react with air and a spark to create fire; Acids will react with bases (but not usually other acids) releasing heat and sometimes hazardous gases;  Sodium metal will react violently with water, and crystals like picric acid can explode with friction (like unscrewing a cap with some crystals in the threads (a major hazard when dealing with old bottles in a chemistry lab).  The DOT ‘hazard classes’ are based on the types of reactions certain chemicals will undergo so that they may be handled more safely.

The Science of Chemistry

Our chemical knowledge is derived from science, and science requires that something be measured; it does not rely on ‘clever thinking’.  Measured results are repeatable, and they can be made by anyone, anywhere, at anytime.  Galileo is a testament to the result of allowing entrenched clever thinking to deny real measurements; the church forgave Galileo for reporting  his observations that the Earth was not the center of the Universe 400 years later.

There are things that we can’t measure, like the origin of life, the origin of the universe, UFO’s, and Ghosts. While these topics can provide entertainment, they can’t kill you, but chemicals can- particularly if they are not handled properly.   The knowledge of how to handle chemicals properly comes after many years of direct experience.  Inductive reasoning tells us that after many observations of a behavior, like flammability, we can ‘infer’ that all similar chemicals are flammable.  This is how theories are built, from specific observations to general principles.

Science begins with a hypothesis, this is an ‘educated guess’ that can then be ‘tested’.  A hypothesis tries to relate specific observations to general principles, and these principles are called theories.  It is like picking out produce at the grocery store; we guess which ones are the best, and then we test our hypothesis by ‘feeling’ them.   With time, we form theories about which items are the best to buy; no one wants to pay for a rotten apple.

Theories
A Theory is a way to connect, or relate, information based on what currently known.  In effect, a theory provides a ‘Data Table’ in which all of the known information can be entered into categories based on certain characteristics.  For example, Evolution provides a way to categorize animals based on similar characteristics like mammals versus reptiles.   We use this process in our daily lives, when shopping for produce we avoid fruit with ‘soft spots’, these can indicate that it won’t taste right; the theory being rotten fruit tastes nasty.

When a theory is proven repeatedly, it becomes a law.  There are no exceptions to a law, and until a theory has no exceptions, it can’t be a law.  Recently, ‘Atomic Theory’ is becoming accepted as a law.  The theory of atoms was first considered by the ancient Greeks, and today we can actually take ‘pictures’ of atoms.  Even so,  Atomic Theory has not ‘officially’ become a law, even after a couple of thousand years of observations.  Proponents of evolution want Evolution to be considered a law, but many of their arguments still contain inconsistencies,  for example, chemicals do not ‘evolve’, no matter how forceful the arguments,  evolution only applies to living systems;  it does not say where life came from, only what it does.   There would have been a lot of time and effort saved if evolution and religion did not squabble over imagined, and unknowable issues.  Students should be taught about one of the central theories of biology; not given someone’s unmeasurable opinion about where life came from, be it science or religion.

Theories must  be applied to their application;  gravity does not apply to business, nor does evolution apply to chemistry.  Unfortunately, theories are often used as a justification for groups trying to gain advantage,  like businesses using evolution’s ‘survival of the fittest’ to justify their hostile take overs of other companies.  Theories are a way to organize information, not justify behavior.

Orbital theory, practical knowledge versus theoretical knowledge

There is a huge difference between doing something verses reading about it.  Chemistry can be interesting because you can do things with it, unlike math which abstract.  The problem with most chemistry classes is that they spend too much time on abstractions rather than real world applications, like hazardous properties.  However, the overemphasis of the theoretical side can confuse people, preventing them from getting the knowledge needed to handle chemicals safely.   Most people will say how they ‘never understood’, or ‘did not like’ chemistry, even though the modern world is based on chemistry, or as the add goes: “better living through chemistry”.  There are parts of chemistry that we must all understand to live safely in this world, and there are parts that only chemists need to understand.

For example, most school curriculums require lessons on ‘orbital mechanics’; that is the s,p,d, and f orbitals that most students are forced to memorize.  Unfortunately for students, these concepts are barley relevant to reality, and most high school chemistry teachers do not understand this concept well enough to know when not to teach it.   Additionally, these concepts are derived from a form of math called ‘differential equations’; a type of math way beyond high school algebra, and even most college math classes.    If professional chemists don’t know if an electron is a particle or a wave, how can anyone possibly say what its ‘orbit’ looks like?  We are interpreting what the math is interpreting about the reality.  For example, chemists use polynomial equations (having two solutions) for interpreting things like the multiple equilibrium of polyprotic acids (sulfuric acid, H2SO4, can release two hydrogen ions, or protons, per molecule).  The ‘math’ gives two solutions, but we must understand that one of these solutions is nonsense- you can’t have a negative concentration.

Orbital mechanics is useful for chemists, but it does explain to most people why chemicals behave the way they do.  The “octet rule” is a good simplification that can make some sense out of the patterns we see in chemical behavior, like the eight main columns of the periodic table, or the reason atoms connect the way they do.  The shape of those orbitals do not become relevant until grad school if you are a chemist.  Basic chemistry needs to give people the knowledge to deal with the chemicals that are in their lives.  There are more advanced concepts to be learned in chemistry, but the world around us can serve as a good foundation as a stepping stone for more advanced topics.

Chemical properties next.