Faculty of Science

Department of Chemistry

For safety and environmental reasons, regulations make the disposal of chemical waste difficult and costly. It is a matter of sensible economics as well as good practice to generate as little waste as possible and, wherever practicable, substances should be recovered and recycled.

At the end of research projects it is necessary to dispose of all unwanted products or other chemicals and researchers are required to follow the instruction for laboratory clearance described in the Safety Manual.

Waste Chemicals

The PI of the individual research project is to make arrangements with a chemical waste disposal company for disposal of unwanted chemicals. A list of such companies can be obtained from the Chemistry Safety Office.

All substances to be disposed of should, if possible, be identified by chemical name and molecular formula. If this is very difficult because there is a mixed waste, then the character of the mixture must be accurately defined, e.g. categorizations such as a mixture of organic amines and their salts but with no compound boiling below 100oC; some are suspect carcinogens would be helpful and acceptable (provided it is true) but a categorization such as mixture of organic liquids, smells of nitrobenzene will not be acceptable and some work will have to be done by the originators of the waste to determine what else is with the nitrobenzene before it can be accepted. It is very important that if there are known hazards associated with the waste, these should be stated on the label (see below) including for example the inclusion of hazardous drying agents.

All substances to be disposed of must be put into leak-proof containers that are clearly labelled with the identity or categorization of the contents, any known hazards, and some indication of boiling point range. Substances identified only by a trade name will also not be accepted - there has to be some indication of the chemical nature.

General: If material is packed into used boxes, ensure that old labels are obliterated and the container is marked "this way up". The total weight should not exceed 5 kg and the dimensions should be about one foot cube. Organic or aqueous liquids should be in glass or plastic containers, solids in metal drums or plastic tubs.


Waste Solvents

The Department has a weekly arrangement to dispose of waste solvents. Prior to disposal, you are to submit a form listing the type and quantity of waste to be disposed. At present, the waste solvents are categorized into “chlorinated” and “non-chlorinated” waste. Waste solvent containers are not dumps and may contain only approved waste organic solvents with limited amounts of solute. Reaction mixtures, oxidants or solutions of oxidants must never be put into the waste solvent containers.

No substances that are category 1 or 2 carcinogens 
may be put in the waste solvents in any form.


Organic liquids acceptable as Waste Solvents


  • hydrocarbons: alkanes C5-C12, cyclohexane, toluene, xylene
  • alcohols, ethylene glycol
  • diethyl ether and tetrahydrofuran
  • acetone,ethyl and n-butyl acetate


  • C1: dichloromethane, chloroform, carbon tetrachloride
  • C2: trichloroethylene, tetrachloroethylene, 1,2-dichloroethane, 1,1,1-trichloroethane,
  • C3: 1-chlorobutane plus small amounts of non-chlorinated materials but no water.


The accepted container for transfer of waste solvent to the Lab Supplies is a screw-capped 5 L polythene bottle. No other containers are acceptable. Before use, the chlorinated or non-chlorinated label must be pasted on the canister with the date of first use and intended wastes listed. The containers must be filled only to the 80% level with approved solvents, sealed with their original caps, not leaking vapour or liquid or contaminated on the outside. Stores staff are not allowed to accept over-full, leaking or externally contaminated containers.



Prior to collection, information about the solvent to be disposed must be recorded in the log book at Lab Supplies. The cut-off time for registering disposal is 1:00 pm. The container must be uniquely numbered and accurately labelled Chlorinated or non-Chlorinated. Under no circumstances may this label be altered by laboratory users:- Stores Staff are not allowed to accept containers where the label has been altered. Labels are to be obtained from Lab Supplies.



Separate containers for Chlorinated and non-Chlorinated solvents should ideally be kept in a fume-hood. Large polythene containers of flammable solvents are extremely vulnerable in case of fire and must be kept in a closed cupboard when not being used to receive waste solvent. Secondary containers are required for the waste canisters.


Special Disposal

For disposal of other chemicals such as waste silica gel, solids, waste sulfuric acid, waste HF, waste nitric acid, waste hydrochloric acid, waste mixed acids, waste mixed alkalis, waste pump oils, please store them separately and arrange via Lab Supplies for disposal by the waste vendor. Be aware that concentrated acids especially nitric acid, being an oxidizer, can attack plastics over time. Therefore, do timely disposal.
If you have small quantities of acids or bases, you should dilute and neutralize the solution before drain disposal. This is strictly for acids/alkalis that do not contain heavy metals including copper, zinc, silver. These wastes should be sent for disposal.

Drain disposal of acids and bases

Acids and bases must be rendered neutral before being disposed down a lab sink with copious amounts of water. Neutralization should be done in small quantities (i.e., no larger than 500 ml. You should not collect a quantity of the acid/base wastes from different experiments and do a batch neutralization. Do neutralizations in a fume hood as fumes and heat may be generated.
a.   Slowly add the acid to a large amount of ice-cooled water to dilute to about 5 %.
b.   For acid neutralization, prepare a 5 % basic solution of sodium carbonate, calcium hydroxide or sodium hydroxide. (For base neutralization, add 5 % hydrochloric acid solution.)
c.   Slowly add the base solution to the diluted acid from (a).
d.   Check that the pH is between 6 to 9 before turning on the tap.
e.   Pour the solution down the drain keeping the tap on. Let the tap run for another 3 - 5 minutes after the container has been emptied.



Waste solvents should be transported only in designated lifts. These lifts are closed to the general public for the exclusive transport of wastes from 2:30 – 2:35 pm. No one should enter the designated lifts when waste transportation is being carried out.




Waste solvent is to be disposed twice weekly between 2:45 p.m. – 3:00 p.m. outside the Solvent Store. Stores Staff are not allowed to accept containers which do not meet the criteria described under "Containers" above.