Introduction to the Chemical Reactivity Worksheet (CRW)
The Chemical Reactivity Worksheet (CRW) is software that you use to find out about the potential reactive hazards of substances and mixtures of substances.
To use the CRW, you select chemicals from its database, and add them to a "mixture." The software then predicts the reactivity of this mixture. (There are about 5,000 chemicals and chemical mixtures in the database; these are the same ones that you'll find in the CAMEO (Computer-Aided Management of Emergency Operations) chemical database.)
You also can use the CRW to check any chemical's intrinsic reactive properties, such as flammability, peroxidizability, polymerizability, explosivity, strong oxidizer or reducer capability, water or air reactivity, and radioactivity.
How the CRW Works
Each substance was assigned to one or more reactive groups, based on the known structure, reactivity, and chemistry of that substance. Reactive groups are categories of chemicals that are assumed to react in similar ways because they are similar in their chemical structure.
- To see descriptions of all the reactive groups we defined, from the Reactivity Mixture worksheet of the CRW, click Add Reactive Group (middle-right of screen).
- To see which reactive groups include a particular chemical, perform a search for the chemical. On the Chemical Search Results card, double-click the chemical name. On the Chemical Datasheet, click the Reactivity tab to see the reactive group(s) it's in.
To predict the reactivity of a mixture of chemicals, the CRW first identifies the reactive groups to which the chemicals belong, and then predicts the kinds of chemical reactions likely to occur when members of these groups are mixed together.
You can mix groups, rather than specific chemicals, and might wish to do so if
- you know the chemical class of a chemical, but not its exact name or CAS (Chemical Abstracts Service) registry number. For example, you may be able to tell it's a powdered metal (which would typically be used in manufacturing processes as a reducing agent or catalyst);
- it's not in the CRW's database, but its MSDS (Material Safety Data Sheet) tells you what chemical class it's in (or you happen to know its chemical class). This would be most likely for a new compound that hasn't yet been included in major chemical databases.
- you work with or store custom or proprietary chemicals that are not included in the CRW's chemical database. The CRW's "Custom Chemicals" section allows you to create records containing reactive hazard information about those chemicals.
The CRW only predicts the reactivity between two chemicals at a time. Be aware that
- sometimes, three or more chemicals can react together in ways the CRW can't predict. For example, sulfuric acid, nitric acid, and glycerine react together to produce nitroglycerine (the CRW recognizes that this mixture would be very reactive, but does not predict that nitroglycerine would be produced);
- one chemical can catalyze (speed up) the reaction between other chemicals. For example, nickel carbonyl catalyzes many polymerization reactions and other kinds of synthetic organic reactions. The CRW cannot predict when a reaction between two chemicals could be speeded up by another chemical.
However, reactions among more than two chemicals are relatively uncommon in nature (except for the catalyzed reactions that are common components of the metabolic processes of living organisms).
- CAMEO An integrated set of software modules designed to help first responders and emergency planners plan for and quickly respond to chemical accidents.
- CAMEO Chemicals An online tool that allows emergency responders and planners. to search for chemicals, get response recommendations, and find out how chemicals would react if they mixed. The same reactivity prediction functionality available in the CRW is also available in CAMEO Chemicals.