Chemicals (cold pack practical): I would like use the following chemicals for a cold pack prac: ammonium chloride, ammonium nitrate, magnesium sulfate and sodium thiosulfate.
Are these available? Are there particular safety issues?
Submitted by sat on 08 October 2015
Answer reviewed 22 February 2023
Chemical/salt solids which undergo endothermic reaction with water are suitable to use in a “cold pack making” investigation. The overall process becomes endothermic when heat is absorbed from surroundings to break up the lattice structures of these salts into individual ions when dissolved in water.
The four inorganic salts mentioned, namely: ammonium chloride, ammonium nitrate, magnesium sulfate and sodium thiosulfate do produce endothermic reactions with water and are listed in Science ASSIST’s list of recommended chemicals for use in science in Australian schools.
Ammonium chloride, magnesium sulfate and sodium thiosulfate are available for purchase from any laboratory chemicals supplier.
Ammonium nitrate
“Solid ammonium nitrate is a chemical of security concern and is subject to state and territory regulations. It may require a licence to purchase and store depending on the legislation in your jurisdiction. Solutions of ammonium nitrate are permitted in all jurisdictions. Schools in New South Wales, Victoria, Western Australia and Queensland do not require a licence to store, handle or use up to 3 kg of ammonium nitrate. Schools in Tasmania can apply for an exemption for a licence to store up to 3kg of ammonium nitrate. Schools in South Australia and Australian Capital Territory require a licence to store any amount of solid ammonium nitrate. An End User Declaration may also need to be completed before purchase of ammonium nitrate.”1
Before handling any chemical, the Safety Data Sheets (SDSs) must be consulted.
Science ASSIST recommends
Please refer to individual SDSs for detailed information on each chemical.
It is recommended that the following PPE is worn for all of the above chemicals: wear safety glasses, laboratory coat and nitrile gloves and ensure that work is always conducted in a well-ventilated area.
Science ASSIST suggests substitution of ammonium nitrate with the less hazardous chemical Urea.8 This product can be purchased from any laboratory chemical supplier.
For example, Vernier have developed An Investigation of Urea-Containing Cold Packs.9
1 Science ASSIST. (2018). Chemical Management Handbook for Australian Schools – Edition 3, Retrieved from the Science ASSIST website: https://assist.asta.edu.au/resource/4193/chemical-management-handbook-au...
2 Science ASSIST. (2015). AIS: Risk Management and risk assessment, Retrieved from the Science ASSIST website: http://assist.asta.edu.au/resource/3079/ais-risk-management-and-risk-ass...
3 Science ASSIST. (2018). Risk Assessment Template, Retrieved from the Science ASSIST website: http://assist.asta.edu.au/resource/2298/risk-assessment-template
4 Sigma-Aldrich. (2021). Ammonium chloride, Safety Data Sheet. Search https://www.sigmaaldrich.com/australia.html to source the latest Safety Data Sheet via the product information page.
5 Sigma-Aldrich. (2022). Ammonium nitrate, Safety Data Sheet. Search https://www.sigmaaldrich.com/australia.html to source the latest Safety Data Sheet via the product information page.
6 Chem Supply website, (2019). Magnesium sulfate, Safety Data Sheet. Search https://www.chemsupply.com.au/ to source the latest Safety Data Sheet via the product information page.
7 Chem Supply website, (2022) Sodium thiosulfate, Safety Data Sheet. Search https://www.chemsupply.com.au/ to source the latest Safety Data Sheet via the product information page.
8 Chem Supply website, (2019) Urea, Safety Data Sheet. Search https://www.chemsupply.com.au/ to source the latest Safety Data Sheet via the product information page.
9 Vernier Science Education. (nd) An Investigation of Urea-Containing Cold Packs, Retrieved (22 February 2023) from the Vernier Science Education website: https://www.vernier.com/experiment/chem-i-3_an-investigation-of-urea-con...