c. Procedures For Decommissioning a Perchloric Acid Hood

11.



Breysse, Peter A.,Occupational Health Newsletter, 15(2,3) 1, 1966.



INTERNET REFERENCES

1.

2.



http://www.orchs.msu.edu/chemical/safeperchloricuse.html

http://www.chem.utah.edu/MSDS/P/PERCHLORIC_ACID%2C_69-72%25



5. Ethers

Much of the concern in working with ethers is due to the problem of peroxide formation.

Chapter 4, Section V.D., already dealt with this at some length, discussing this problem in the

context of storage of ethers. If ethers are bought in small sizes, so that the containers, in use on

a given day are emptied, the concerns of peroxide formation in partially full containers in storage

should not arise. Peroxides can form in unopened containers as well, although due to the absence

of excess available air in the restricted empty space above the liquid level, the rate should be

much slower. However, the inventory of unopened containers in a laboratory should be

maintained at a reasonable level so that no ethers should be kept for extended periods. All

containers should be stamped with the date received and a schedule of disposal or testing

established. If a partially empty container is kept, a target date for testing for peroxides should

be placed on the container, as well as subsequent dates for the tests to be repeated. A centralized

computer tracking program for chemicals could take this responsibility from the individual

laboratory managers and largely eliminate the problem of outdated ethers. The effort needed to

maintain a reliable program in the laboratory to check for the presence of peroxides could almost

certainly be used to greater advantage on the basic research program. Unused portions of ethers

should not be returned to the original container. Small quantities can be allowed to evaporate

in a fume hood.

Because of the explosion risk associated with peroxides, older containers of ethers are not

normally accepted as part of an ordinary hazardous waste shipment by a commercial chemical

waste disposal firm. They would have to be disposed of as unstable explosive materials which

is much more expensive than if the materials were not outdated. Any savings in buying the “large

economy size” would be more than compensated for by the additional disposal costs. Attempting

to treat the ethers to remove the peroxides or to dispose of them by laboratory personnel carries

with it the risk of an explosion and the subsequent liability for injuries.

Although a major risk usually associated with ethers is, as noted, the problem of peroxides,

t hey also pose additional problems because of their properties as flammable solvents. Many of

them have lower explosion limits, in the range of 0.7 to 3%, and flash points at room temperature

or, in several cases, much lower. Ethyl ether, the material that most frequently comes to mind

when “ether,” otherwise unspecified, is mentioned, has a lower explosion limit of 1.85%, an upper

explosion limit of 36%, and a flash point of -45"C (-49"F). The vapors of most ethers are heavier

t han air, and hence can flow a considerable distance to a source of ignition and flash back.

Because of their flammable characteristics, many ethers, especially ethyl ether, placed in

improperly sealed containers in an ordinary refrigerator or freezer release vapors which represent

a potential “bomb” that can be ignited by sparks within the confined space and explode with

sufficient force to seriously injure or even kill someone in the vicinity. A fire is virtually certain

to result should such an incident occur which, depending upon the type of construction and the

availability of fuel in the laboratory area, could destroy an entire building. Because ethers, as well

as other flammable solvents, are used so frequently in laboratory research, it is strongly

recommended that all refrigeration units in wet chemistry laboratory environments should be

purchased without ignition sources within the confined spaces and with explosion-proof

compressors, i.e., they must meet standards for “flammable material storage,” even if the current

program does not involve any of these materials. At some time during the effective lifetime of



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most refrigeration units, it is likely that flammable liquids will be used in the facility where they

are located.

A spill should be promptly cleaned up using either a commercial solvent spill kit material to

absorb the liquid or a preparation of equal parts of soda ash, sand, and clay cat litter, which has

been recommended as an absorbent. Since the lower explosion limit concentrations are so low

for so many of the commonly used ethers, all ignition sources should be promptly turned off

following a spill and all except essential personnel required to leave the area. The personnel

performing the clean up should wear half-face respirators equipped with organic cartridges. The

resulting waste mixture from the clean up can be placed in a fume hood temporarily until removed

from the laboratory for disposal as a hazardous waste.

Class B fire extinguishing agents are to be used to combat ether fires as well as other fires

involving flammable liquids. Usually the most effective are dry chemical extinguishers which

interrupt the chemistry of a fire, while carbon dioxide units can be used to smother small fires.

Portable Halon extinguishers are also usable if the fire is such that the fuel has time to cool before

the concentration of the halogenated agents falls below the critical concentration at which it is

effective (the current extinguishing agents used in most of these, Halon-1301 and Halon-1211,

damage the ozone in the atmosphere and will be replaced with units using safer alterative agents).

It is worth pointing out once again that unless there is a reasonable chance of putting out a fire

with portable extinguishers, it is preferable to initiate an evacuation as quickly as possible and

to make sure that everyone can safely leave the building, rather than engage in a futile attempt

to put out the fire.

In general, the toxicity of ethers is low to moderate, although this generalization should be

confirmed for each different material to be used by information obtained either from the container

label or the MSDS. Prolonged exposure to some ethers has been known to cause liver damage.

Many have anesthetic properties and are capable of causing drowsiness and eventual

unconsciousness. In extreme cases of exposure, death can result. Four ethylene glycol ethers 2-methoxyethanol, 2-ethoxyethanol, 2-methoxy ethanol acetate, and 2-ethoxyethanol acetate have

been identified as causing fetal developmental problems in several animal species, including fetal

malformations and resorption and testicular damage. Studies have also shown adverse

hematologic effects and behavioral problems in the offspring of animals.

6. Flammable Solvents

Much of the concern in the literature is centered on the flammable characteristics of flammable

liquids, much of which has already been addressed in Chapter 4, Section V.G. This characteristic

will be treated in more detail in the following section. There are many other issues relating to the

health effects of these solvents which also need to be considered.

a. Flammable Hazards

The fire hazard associated with flammable liquids should be more appropriately associated

with the vapors from the liquid. It is the characteristics of the latter which determine the seriousness of the risk posed by a given solvent. In previous sections on storage of liquids, two

of the more important properties of flammable liquids were mentioned in terms of defining the

classes to which a given solvent might belong. Definitions of Class lA, lB. 1C, 2A, 3A and 3B

were based on the boiling point and flash point of the solvents. The formal definition of these

two terms will be repeated below, as well as three other important parameters relevant to fire

safety, the ignition temperature and the upper and lower explosion limits.

Boiling point (bp) - This is the temperature at which the vapor of the liquid is in equilibrium

with atmospheric pressure (defined at standard atmospheric pressure of 760 mm of mercury).

Flash point (fp) - This is the minimum temperature at which a liquid gives off vapor in

sufficient concentration to form an ignitable mixture with air near the surface of a liquid. The

experimental values for this quantity are defined in terms of specific test procedures which are



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based on certain physical properties of the liquid.

Ignition (autoignition) temperature - This is the minimum temperature which will initiate a

self-sustained combustion independent of the heat source.

Lower explosion (or flammable) limit (lel) - This is the minimum concentration by volume

percent in air below which a flame will not be propagated in the presence of an ignition source.

Upper explosion (or flammable) limit (uel ) - This is the maximum concentration by volume

percent of the vapor from a flammable liquid above which a flame will not be propagated in the

presence of an ignition source.

For a fire to occur involving a flammable liquid, three conditions must be met: (1) the

concentration of the vapor must be between the upper and lower flammable limits; (2) an oxidizing

material must be available, usually the air in the room; and (3) a source of ignition must be

present. The management strategy is usually to either maintain the concentration of the vapors

below the lower flammable limit by ventilation (such as setting the experiment up in an efficient

fume hood) or to eliminate sources of ignition. The latter is easier and more certain because the

ventilation patterns even in a hood may be uneven or be disturbed so that the concentrations

may locally fall into the flammable range. While some materials may require an open flame to

ignite, it is much easier to ignite others. For example, the ignition temperature for carbon disulfide

is low enough (80" C or 176"F) that contact with the surface of a light bulb may ignite it.

In order to work safely with flammable liquids, there should be no sources of ignition in the

vicinity, either as part of the experimental system or simply nearby. Use nonsparking equipment.

When pouring a flammable liquid from one metal container to another, both of the containers

should be grounded, as the flowing liquid can itself generate a static spark. Flammable materials

should be heated with safe heating mantles (such as a steam mantle), heating baths, or explosionsafe heating equipment. Many ovens used in laboratories are not safe for heating flammables

because the vapors can reach the heating element, or either the controls or thermostat may cause

a spark. Any spark-emitting motors should be removed from the area. Flammable materials should

never be stored in an ordinary refrigerator or freezer because they have numerous ignition

sources in the confined volume. Placing the entire system in a hood where the flammable vapors

will be immediately exhausted aids in limiting the possibility of the vapors coming into contact

with an ignition source.

The vapors of flammable liquids are heavier than air and will flow for a considerable distance

away from the source. Should they encounter an ignition source while the concentration is in

the flammable range, a flame may be initiated and flash back all the way to the source. In at least

one instance, a fire resulted when a research worker walked by a fume hood carrying an open

beaker of a low ignition point volatile solvent. There was an open flame in the hood, and when

the fumes were pulled into the hood, the fumes ignited and flashed back to the container, which

was immediately dropped, with the result that the feet and lower legs of the worker and the entire

floor of the laboratory became engulfed in flame. Fortunately, a fire blanket and fire extinguisher

were immediately available, so that the worker escaped with only minor burns and the fire was

extinguished before anything else in the laboratory became involved. This incident clearly

illustrates the need to consider all possibilities of fire when using solvents, and that a hood does

not totally isolate a hazardous operation.



REFERENCES

1.



Armour, M.A., Browne, L.M., and Weir, G.L., Hazardous Chemicals Information and Disposal Guide,

2nd ed., University of Alberta, Edmonton, Canada, 1984.



2.

3.



Federal Register F.R. 10586, April 2, 1987.

Langan, J.P., Questions and Answers on Explosion-Proof Refrigerators, Kelmore, Newark, NJ.



4.



Prudent



Practices



for



©2000 CRC Press LLC



Handling



Hazardous



Chemicals



in



Laboratories,



National



Academy



Press,



Washington D.C., 1981, 57.

5.



Lewis, R.J., Sax Dangerous Properties of Industrial Materials, 8th ed., Van Nostrand Reinold , New York,

1993.



6.



Hazardous Chemicals Data, NFPA 49, National Fire Protection Association, Quincy, MA.



7. Reactive Metals

Lithium, potassium, and sodium are three metals that react vigorously with moisture (lithium

to a lesser extent than the other two, except in powdered form or in contact with hot water), as

well as with many other substances. In the reaction with water, the corresponding hydroxide is

formed along with hydrogen gas, which will ignite. Lithium and sodium should be stored under

mineral oil or other hydrocarbon liquids that are free of oxy gen and moisture. It is specifically

recommended in the literature that potassium be stored under dry xylene.

The chemical hazards of the three metals are similar in many ways. All three form explosive

mixtures with a number of halogenated hydrocarbons; all three react vigorously or explosively

with some metal halides, although potassium is significantly worst in this respect, and the

reaction of all three in forming a mercury amalgam is violent. They all react vigorously with

oxidizing materials. Potassium can form the peroxide and super oxide when stored under oil at

room temperature and may explode violently when cut or handled. Sodium reacts explosively with

aqueous solutions of sulfuric and hydrochloric acids. The literature provides a number of other

potentially dangerously violent or vigorous reactions for each of these three materials. It is not

the intent here to list all of the potentially dangerous reactions that may occur, but to point out

that there are many possibilities for incidents to happen. No one should plan to work with these

materials without carefully evaluating the chemistry involved for potential hazards. The materials

should be treated with the care which their properties demand at all times.

In one instance, a very old can of sodium was determined by visual inspection to have

“completely” reacted to form sodium hydroxide, and the worker decided to flush it with water

to dispose of the residue. The bottom 2 inches were still sodium metal and consequently the can

exploded. The only entrance to the laboratory was blocked by an ensuing fire so that the

occupants had to escape through windows. Fortunately, they were on the first floor and the

windows were not blocked. The latter point is worth noting because shortly before this incident,

bars over the windows to prevent break-ins had been removed at the insistence of the organization's safety department. Unsubstantiated assumptions or misplaced priorities are a major cause

of injuries.

Since the three metals all react vigorously with moisture, care should be taken to avoid skin

and eye contact, which could result in burns from the evolved heat and direct action of the

hydroxides. The materials should always be used in a hood, and, as a minimum, gloves and

chemical splash and impact-resistant goggles should be worn while working. If the risk of a

violent reaction cannot be excluded, additional protection such as an explosion barrier or a face

mask should be considered. If a fire should occur involving reactive metals, appropriate class

D fire extinguishers should be available within the laboratory. These vary somewhat in their

contents, which usually are specific for a given material. Appropriate material suitable for

extinguishing fires involving these reactive materials are dry graphite, soda ash, and powdered

sodium chloride. Other materials which might be used in these class D units as extinguishing

agents are pulverized coke, pitch, vermiculite, talc, and sand. These materials will usually be mixed

with various combinations of low melting fluxing salts, resinous materials, and alkali-metal salts

which, in combination with the other material in the extinguisher, form a crust to smother the fire.

Water (obviously), carbon dioxide, or halogenated units should not be used. There are a number

of other reactive metals, which while not as active chemically as these three, once ignited, require

class D fire extinguishing agents as well. These include magnesium, thorium, titanium, uranium,

and zirconium. Other materials for which class D units should be used include metal alkyds and



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hydrides, red and white phosphorous, and organometallic compounds.

As with many other materials, one of the major considerations in using these reactive metals

is the problem associated with disposal of unneeded surplus quantities or waste materials. There

are suggestions in the literature for treating waste for each of these three materials. For example,

small amounts of potassium residues from an experiment should be treated by promptly reacting

them with tert-butyl alcohol because of the danger that they will explode (even if the potassium

is stored properly). This is appropriate for small quantities in the laboratory but disposal of

substantial quantities of unwanted material is a different matter. Recycling or transfer to another

operation needing the material should be investigated, but disposal by local treatment should

be avoided. There are limits to local treatment permitted under the RCRA Act, beyond which a

permit is required to become a treatment facility. In addition, there are safety and liability risks

associated with processing dangerously reactive materials which must be considered. Reactive

metals are among those materials that require special handling by commercial waste disposal

firms. Because special procedures are required, the cost of disposal is much higher than for

routine chemical waste. Quantities purchased and kept in stock should be limited.



REFERENCES

1.

2.

3.

4.

5.



Hazardous Chemicals Data, NFPA 49, National Fire Protection Association, Quincy, MA.

Armour, M.A., Browne, L.M., and Weir, G.L., Hazardous Chemicals Information and Disposal Guide,

2nd ed., University of Alberta, Edmonton, Canada, 1984.

Lewis, R.J., Sax’s Dangerous Properties of Industrial Materials, 8th ed., Van Nostrand Reinhold , New

York, 1993.

Sax, N.I. and Lewis, R.J., Sr., Rapid Guide to Hazardous Chemicals in the Workplace, Van Nostrand

Reinhold, New York, 1986.

Portable Fire Extinguishers, NFPA-10, National Fire Protection Association, Quincy, MA.



8. Mercury

Mercury and its compounds are widely used in the laboratory. As metallic mercury, it is often

used in instruments and laboratory apparatus. In the latter application especially, it is responsible

for one of the more common types of laboratory accidents, mercury spills. Thermometers

containing mercury are frequently broken; mercury is often spilled in working with mercury

diffusion pumps or is lost when cleaning the cold traps associated with high vacuum systems

in which mercury pumps are used. Over a period of time, the small amounts of mercury lost each

time can add up to a substantial amount. In one instance, the cold traps were always cleaned over

a sink. After a few years of this, a large amount of mercury accumulated in the sink trap which

finally eroded the metal, and spilled on the floor. Over 15 pounds of mercury were recovered.

Mercury is frequently ejected from simple manometers consisting of mercury in plastic tubing,

connected to a system under vacuum. As an example of the consequences of this last type of

accident, an employee, working in a room previously used for years as an undergraduate biology

laboratory, was diagnosed as having a somewhat severe case of mercury poisoning, although

he did not use mercury. Upon investigation, more than 50 pounds of mercury were retrieved from

under the wooden floorboards in the room. Although the instructors had “cleaned up the

mercury” when spills had occurred, over the years a substantial amount had obviously not been

recovered, but had worked its way through the cracks in the floor. No measurements of the

airborne concentration were made at the time, but the normal equilibrium vapor pressure of

mercury in air at normal room temperatures is between 100 and 200 times the current permissible

levels of mercury in the workplace. It should also be noted that the vapor pressure rises rapidly



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with temperature. At the temperature of boiling water at standard atmospheric pressure, the vapor

pressure is more than 225 times higher than at 20 " C (68"F) (0.273 mm Hg) and reaches 1 mm Hg

at 126.2"C (259.2"F). Clearly, mercury always should be heated in a functioning fume hood instead

of an open bench, yet this is not always done.

Mercury poisoning has been known to affect many individuals, among them such prominent

scientists as Pascal and Faraday as well as workers in various industries, such as those exposed

to mercury as an occupational hazard while using mercuric nitrate in the hat industry in making

felt. A frequently cited example of the effects of mercury poisoning is the “Mad Hatter” in Lewis

Carroll's Alice in Wonderland. In the 1950s, many Japanese in a small fishing village suffered

serious permanent damage to their central nervous system and, in many cases, death or

permanent disability due to eating fish containing methyl mercury as a result of the industrial

discharge of mercury compounds into the sea near their village. In the 1970s, fish taken from some

of the common waters of Canada and the U.S. were found to be contaminated with mercury, and

fishing was banned in some areas. Some commercial swordfish and tuna were found to be

contaminated with mercury and had to be withdrawn from the market In at least one instance,

fish in a river in the southeastern United States were found to be contaminated by mercurycontaining waste from a chemical plant. Eventually the plant closed down its operations because

the expense of modifying its operation to eliminate the discharge would have been too high.

Mercury compounds were at one time used as fungicides and many individuals died from

mistakenly eating seed corn treated with these materials. Probably the worse such incident

occurred in 1972 when at least 500 persons died in Iraq from consuming treated grain mistakenly

issued to them as food. Mercury, once it enters the biosphere is slow to biodegrade. As a result

of the dangers inherent in materials containing mercury, the use of mercury for most agricultural

purposes has been banned, and dumping wastes containing mercury compounds in such a way

as to be able to contaminate the environment is no longer permitted. Currently it is difficult to

dispose of compounds containing mercury. Waste liquid mercury metal, on the other hand, can

be recycled. Small batteries containing mercury should not be disposed of in common trash.

Elemental mercury is probably not absorbed significantly in the gastrointestinal tract,but many

of its compounds are. Poisoning due to inhalation and absorption of mercury vapors results in

a number of symp toms. Among these are personality and physiological changes such as

nervousness, insomnia, irritability, depression, memory loss, fatigue, and headaches. Physical

effects may be manifested as tremors of the hands and general unsteadiness. Prolonged exposure

may result in loosening of the teeth and excessive salivation. Kidney damage or even failure may

result. In some cases the effects are reversible if the exposure ceases, but, as noted in the

previous paragraph, ingestion of some organic mercury compounds may be cumulative and result

in irreversible damage to the central nervous system. Alkyl mercury compounds have very high

toxicity. Aryl compounds, and specifically phenyl compounds, are much less toxic (in the latter

case comparable to metallic mercury) and therapeutic compounds of mercury are less toxic still.

In the case of the Minemata Bay exposure in Japan in 1953 and in Nigata in 1960, it was found

that the fetus was especially vulnerable to the exposure. Mercury passes readily through the

placenta from mother to child. In recognition of the seriousness of the potential toxic effects, the

permissible ceiling exposure level for metallic mercury is currently set by OSHA at 0.01 mg/M 3,

and for alkyl organomercury compounds, an 8-hour time weighted average of 0.01 mg/M 3 has

been established by OSHA with a ceiling average of four (current ACGIH recommendation is

three times that level).

The first four paragraphs in the next section are taken directly from the article by Steere from

the second edition of this handbook.

a. Absorption of Mercury by the Body

In occupational studies, the primary intake is by mercury vapor in the lungs, with up to 90%



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of the mercury taken in by this route being absorbed. A relatively minor amount is absorbed by

the skin or large droplets reaching the gastrointestinal track, perhaps 15%, although when

exposures by this route occur, the exposure level is likely to be high. Inorganic mercury is

transformed to some extent by microorganisms in the mouth and gut to short-chain alkyl(methyl

and ethyl) forms, which are readily absorbed. Further distribution of absorbed mercury is

facilitated by the blood.

Inorganic and organic mercury compounds have a strong affinity for thiol chemical groups.

Most proteins and all enzymes contain these groups so that mercury readily is bound to body

tissues. Most mercury compounds are potent enzyme inhibitors which affects membrane

permeability, which in turn affects nerve conduction and tissue respiration.

The biological half-life of mercury in the blood is approximately three days, following an

exposure but the mercury bound to body tissues clears much more slowly with a half-life of about

90 days. Thus the end of an exposure will have long lasting effects. The levels in tissue will not

fall below 10% of the peak level until somewhat more than four half-lives have passed.

The kidney plays a key roll in the absorption of mercury in the body. Kidney tissue contains

a thiol-rich protein called metallothionein. Exposure of the kidney to mercury and other toxic

metals causes production of this protein which binds the metals tightly, and retains it in the

kidney in a relatively harmless form. As long as the kidney is not overwhelmed by the influx of

the toxic metal, the excretion of mercury will eventually balance intake so that worsening of

adverse symptoms will be limited. However, acute levels can lead to renal failure.

Chronic mercury exposure can seriously affect fertility and the outcome of pregnancy.

Mercury passes readily through the placenta and the concentration in the cord blood is elevated

above the maternal blood. In men, organic forms of mercury can cause hypospermia, and a

reduction in libido and cause impotence in some men. For some men, there has been an increase

in the rate of spontaneous abortion in their partners.

b. Excretion of Mercury

Mercury is excreted by the body through the feces and urine, with a minute amount by the

respiration. The liver excretes some in bile, which is partially reabsorbed but is eventually

disposed of by the kidney. Some mercury passes directly by the body in the urine instead of

being bound by proteins. For a steady state exposure, the urine level reflects body burden of

mercury. Another indicator of mercury intake is the concentration of mercury in the hair. As the

hair grows the mercury levels can be measured along the length of the hair by such techniques

as neutron activation analysis.

c. Control Measures

Mercury is dense (specific gravity of just under 13.6 a t 4"C (39.2"F)) and has a high surface

tension and low viscosity. As a result, it tends to break up into small droplets when it is poured

or spilled. Anyone who has tried to pick up small droplets using a stiff piece of paper can attest

to the appropriateness of the alternate name “quicksilver.” As the droplets are disturbed as, for

example, when walked upon on the laboratory floor, they tend to break up into smaller and smaller

droplets, eventually becoming too small to see. In a laboratory where mercury has been in use

for an extended period of time, it is instructive to run a pen knife in the cracks in a tile floor or in

the seams where cabinets and bench tops fit together. Invariably, small droplets of mercury will

be found.

Although a thin film of oxide will form on the skin of mercury droplets, it is very fragile and

w ill break. Similarly, sprinkling flowers of sulfur on the location of a mercury spill has been

suggested as a control measure but the surface film which forms also apparently is also very

fragile and will allow the mercury underneath the film to be readily exposed.



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