Lab Chemicals: Segregation and Expiration Guide

         1.      Segregation

1.1     Proper segregation must address flammables, unstable materials (including those that can form explosive peroxides), reactives and vapors from highly toxic materials. This can be achieved by arranging the materials to provide separation based on their chemical properties. MSDSs (Material Safety Data Sheets) shall be consulted for determining the characteristics of a compound.

1.2     Common Hazards Due to Chemical Reactions (Incompatibles) are:

• Generation of Heat - e.g. acid and water
• Fire - e.g. hydrogen sulfide and calcium hypochlorite
• Explosion - e.g. picric acid and sodium hydroxide
• Toxic gas or vapor production - e.g. sulfuric acid and plastic
• Flammable gas or vapor production - e.g. acid and metal
• Formation of a substance with greater toxicity than reactants - e.g. chlorine and ammonia
• Formation of shock or friction-sensitive compounds
• Solubilization of toxic substances - e.g. hydrochloric acid and chromium
• Dispersal of toxic dusts and mists
• Violent polymerization - e.g. ammonia and acrylonitrile

1.3     Sufficient space should be provided so that incompatible chemicals can be segregated.

1.4     Following are the basic principles for proper segregation of the chemicals in the laboratory:

1.4.1  Chemicals should not be stored alphabetically. Acetic acid and acetlehyde could be adjacent members on a shelf and are an incompatible pair other examples include sodium cyanide and sulfuric acid, sodium borohydride and sodium chlorate.

1.4.2  Segregations shall be based on the properties and mutual reactivities.

1.4.3  First segregates chemicals into organic and inorganic.

1.4.4  Then separate liquids from solids in the above groups because chemicals must come into contact to react and this is avoided by having liquids and solids separated.

1.4.5  Organic chemicals shall further be segregated as per following scheme:

a)       Alcohols, glycols

b)       Hydrocarbons, esters

c)       Ether, ketones

d)       Epoxy compounds, isocyanates

e)       Sulfides, polysulfides

f)        Phenols, cresols

g)       Peroxides, Azides

h)       Acids, anhydrides, peracids

i)        Miscellaneous

1.4.6  Inorganic chemicals shall further be segregated as per following scheme:

a)       Sulfur, phosphorus, arsenic, phosphorus pentoxide

b)       Halides, sulfates, sulfites, thiosulfates, phosphates

c)       Amides, nitrates, nitrites

d)       Metals and hydrides (no water)

e)       Hydroxide, oxides, silicates

f)        Arsenates, cyanides

g)       Sulfides, selenides, phosphides, carbides, nitrides

h)       Borates, chromates, manganates, permanganates

i)        Chlorates, perchlorates, chlorites, perchloric acid, peroxides

j)        Acids (not nitric acid)

Special Note:

• Perchloric acid is separated from all other substances. Perchloric acid is an extremely strong oxidising agent (especially in the concentrated form), which can react explosively with organic materials.  It should ideally be stored separately, away from organic materials or dehydrating agents such as sulphuric acid.

• Concentrated nitric acid is separated from all other substances.

• Glacial acetic acid should be stored with flammable and combustible materials since it is combustible.

• 2,4,6-trinitrophenol, also known as picric acid, is normally sold as a saturated solution containing at least 40% water, and classified as a flammable solid.

• Inorganic and organic acids are stored separately.

• Bases are stored separately.

• Explosives or potential explosives are separated. Store ammonium nitrate separately.

• Flammables shall be labeled and segregated. Flammable solvents must never be stored with oxidising agents (e.g. sodium hypochlorite – bleach, iodine and other halogens, hydrogen peroxide, nitric acid, potassium permanganate etc.) reducing agents (e.g.  sodium borohydride, lithium aluminum hydride...etc) or concentrated acids (e.g. concentrated sulphuric or hydrochloric acids).

• Chlorinated solvents are best stored separately from flammable (non-chlorinated) solvents because violent reactions can result from the mixing of certain flammable and chlorinated solvents and toxic gases such as phosgene (as well has hydrogen chloride and chlorine) can be produced. They should not be stored with alkali metals such as lithium, potassium or sodium, since any mixing can cause an explosion.

• Highly toxic and carcinogenic chemicals are stored separately.

List of chemical incompatibilities is attached.

1.4.7  Separate each group from the other groups by a barrier. Store incompatible chemicals by segregating the chemicals according to their hazard class and store them in tubs, trays, or buckets.

1.4.8  Polypropylene or polyethylene plastic containers should be used to provide both segregation and secondary containment. 

1.4.9  Secondary containment should be provided for liquids that are flammable, corrosive, highly toxic, or highly volatile.  (Solids do not require secondary containment.)

(Secondary containment is defined as a chemically resistant container that will hold 110% of the volume stored within that container. A closed container is not required for secondary containment)

          2.    Expiration dates:

2.1     Upon receipt of a new chemical it should be labeled with the date received.

2.2     If the chemical is one that degrades in quality or becomes unsafe after prolonged storage, the shelf-life expiration date should also be included.

2.3     The chemicals then need to be placed upright, in a proper storage area with compatible chemicals.

2.4     Once the chemical is opened it shall be labeled with date of opening.

2.5     A current chemical inventory must be maintained and MSDS kept current.

2.6     Storage area should be inspected regularly for leaking or defective containers and chemicals that have been put in the wrong place.

2.7     Visual inspection of the material and its container should be conducted routinely. Indications for disposal include:

• cloudiness in liquids

• material changing color

• evidence of liquids in solids or solids in liquids

• "puddling" of material around outside of container

• pressure build-up within bottle

• obvious deterioration of container

2.8     Not all chemicals are assigned expiration dates by the manufacturers. In this case follow the following guidance for disposal of chemicals which has been stored for longer time:

2.8.1  Solvents: Most solvents in their pure state have an indefinite shelf life if stored in unopened containers under proper conditions. These solvents can be stored for three years. However, solvents with shorter shelf life shall be disposed earlier e.g., formaldehyde has a shorter shelf life and shall be disposed in 18 months.

2.8.2  Alcohols: Ethanol has a labeled shelf life of 36 months from the date of manufacture. However, few denatured alcohols can have longer shelf life.

2.8.3  Acids: In general, most acids have a shelf life of three years. Additional care must be taken with Nitric and Sulfuric Acid, as exposure to sun and heat will accelerate decomposition.

2.8.4  Purchased Laboratory Reagents: If the manufacturer has issued an expiration date for a product, that date will be noted as the expiration date. If the manufacturer has not issued an expiration date for a product, the date the product is received by the laboratory will be noted. The product will be issued an expiration date of 4 years after the product was received.

2.8.5  Peroxide-forming chemicals should be properly disposed of before the date of expected peroxide formation (typically 6-12 months after opening). Examples, Diethyl ether, tetrahydrofuran, dioxane, sec-butyl alcohol.

2.8.6  Chemicals in solid or powder form: Chemicals have varied shelf life. They are stable if container is sealed and unopened. Shelf life directions of the manufacturer shall be followed. If chemicals are stored in prescribed environment they can be stored for 5 years. However few chemicals are reactive and lesser shelf life (less than 2 years) the examples are as follows:

Chemicals which react with air and water:

-        Alkali and alkaline earths metals and finely divided metal powders (aluminum, iron, zinc dust).

-        Acid anhydrides and acid chlorides

-        Alkaline earth metal hydroxides and oxides

-        Acetaldehyde, benzaldehyde, and oxidizable organic compounds

-        Low-valent transition metal salts [tin(II), iron(II), copper(I)]

Light-sensitive chemicals:

-        Potassium iodide, iodine, iron(II) and iron(III) citrates and oxalates

-        Benzoyl peroxide

Moisture-sensitive compounds:

-        Anhydrous salts: Aluminum chloride, calcium chloride, copper(II) chloride,           phosphorus pentoxide; potassium acetate, bisulfate, bicarbonate,   bromide, and thiocyanate; sodium bisulfite and meta-bisulfite

Deliquescent and Low-Melting Hydrates:

-        Iron(III) chloride hexahydrate and iron(III) nitrate nonahydrate

List of chemical incompatibilities

Chemical	Incompatible with
Acetic acid	Chromic acid, nitric acid, hydroxyl compounds, ethylene glycol, perchloric acid, peroxides, permanganates
Acetylene	Chlorine, bromine, copper, fluorine, silver, mercury
Acetone	Concentrated nitric acid and sulphuric acid mixtures
Alkali and alkaline earth metals	Water, carbon tetrachloride or other chlorinated hydrocarbons, carbon dioxide, halogens
Ammonia (anhydrous)	Mercury(e.g., in manometers), chlorine, calcium hypochlorite, iodine, bromine, hydrofluoric acid (anhydrous)
Ammonium nitrate	Acids, powered metals, flammable liquids, chlorates, nitrites, sulphur, finely divided organic combustible materials
Aniline	Nitric acid, hydrogen peroxide
Arsenical materials	Any reducing agent
Azides	Acids
Bromine	See chlorine
Calcium oxide	Water
Carbon (activated)	Calcium hypochlorite, all oxidizing agents
Chlorates	Ammonium salts, acids, powered metals, sulphur, finely divided organic or combustible materials
Chromic acid and chromium trioxide	Acetic acid, naphthalene, camphor, glycerol. Alcohol, flammable liquids in general
Chlorine	Ammonia, acetylene, butadiene, butane, methane, propane (or other petroleum gases), hydrogen, sodium carbide, benzene, finely divided metals, turpentine
Chlorine dioxide	Ammonia, methane, phosphine, hydrogen sulphide
Copper	Acetylene, hydrogen peroxide
Cumene hydroperoxide	Acids (organic and inorganic)
Cyanides	acids
Flammable liquids	Ammonium nitrate, chromic acid, hydrogen peroxide, nitric acid, sodium peroxide, halogens
Fluorine	All other chemicals
Hydrocarbons (such as butane, propane, benzene)	Fluorine, chlorine, bromine, chromic acid, sodium peroxide
Hydrocyanic acid	Nitric acid, alkali
Hydrofluoric acid (anhydrous)	Ammonia (aqueous or anhydrous)
Hydrogen sulphide	Fuming nitric acid, oxidizing gases
Hypochlorites	Acids, activated carbon
Iodine	Acetylene, ammonia (aqueous or anhydrous), hydrogen
Mercury	Acetylene, fulminic acid, ammonia
Nitrates	Acids
Nitric acid (concentrated)	Acetic acid, aniline, chromic acid, hydrocyanic acid, hydrogen sulphide, flammable liquids and gases, copper, brass, any heavy metals
Nitrites	Acids
Nitroparaffins	Inorganic bases, amines
Oxalic acid	Silver, mercury
Oxygen	Oils, grease, hydrogen, flammable liquids, solids, and gases
Perchloric acid	Acetic acid, anhydride, bismuth and its alloys, alcohols, paper, wood, grease, oils
Peroxides, organic	Acids (organic or mineral), avoid friction, store cold
Phosphorus (white)	Air, oxygen, alkalies, reducing agents
Potassium chlorate	Sulphuric and other acids
Potassium perchlorate (see also chlorates)	Sulphuric and other acids
Potassium permanganate	Glycerol, ethylene glycol, benzaldehyde, sulphuric acid
Selenides	Reducing agents
Silver	Acetylene, oxalic acid, tartaric acid, ammonium compounds, fulminic acid
Sodium	Carbon tetrachloride, carbon dioxide, water
Sodium nitrite	Ammonium nitrate and other ammonium salts
Sodium peroxide	Ethyl and methyl alcohol, glacial acetic acid, acetic anhydride, benzaldehyde, carbon disulfide, glycerin, ethylene glycol, ethyl acetate, methyl acetate, furfural
Sulphides	Acids
Sulphuric acid	Potassium chlorate, potassium perchlorate, potassium permanganate (similar compounds of light metal, such as sodium, lithium)
Tellurides	Reducing agents

Table 4.4: CRC Handbook of Laboratory Safety, 5th Edition