Wood's metal

Wood's metal (in an ampoule)

Wood's metal, also known as Lipowitz's alloy or by the commercial names Cerrobend, Bendalloy, Pewtalloy and MCP 158, is a fusible metal alloy (having a low melting point) that is useful for soldering and making custom metal parts.[1] The alloy is named for Barnabas Wood, who invented and patented the alloy in 1860.[2][3] It is a eutectic alloy of 50% bismuth, 26.7% lead, 13.3% tin, and 10% cadmium by mass. [1] It has a melting point of approximately 70 °C (158 °F).[4][5] Its fumes are toxic, as well as being toxic on skin exposure.

Applications

Wood's metal (in a visibly solid state)

Wood's metal is used for making fusible links in the sprinkler heads of commercial building automatic fire sprinkler systems.[1] Due to the fire, ambient temperature increases enough to melt the link, releasing the water. A similar use is fusible plugs in boilers.[1]

Uses also include making custom-shaped apertures and blocks (for example, electron-beam cutouts and lung blocks) for medical radiation treatment, and making casts of keys that are hard to otherwise duplicate.[6][7]

Like other fusible alloys, e.g. Rose's metal, Wood's metal can be used as a heat-transfer medium in hot baths. Hot baths with Rose's and Wood's metals are not used routinely but are employed at temperatures above 220 °C (428 °F).[8]

At room temperature, Wood's metal has a modulus of elasticity of 12.7 GPa and a yield strength of 26.2 MPa.[9]

Toxicity

Wood's metal is toxic because it contains lead and cadmium, and contamination of bare skin is considered harmful. Vapour from cadmium-containing alloys is also known to pose a danger to humans.[10] Cadmium poisoning carries the risk[11] of cancer, anosmia (loss of sense of smell), and damage to the liver, kidneys, nerves, bones, and respiratory system. Field's metal is a non-toxic alternative.

The dust may form flammable mixtures with air.[10]

Alloy Melting point Eutectic? Bismuth
%		 Lead
%		 Tin
%		 Indium
%		 Cadmium
%		 Thallium
%		 Gallium
%		 Antimony
%
Rose's metal 98 °C (208 °F) No 50 25 25 — — — — —
Cerrosafe 74 °C (165 °F) No 42.5 37.7 11.3 — 8.5 — — —
70 °C (158 °F) Yes 50 26.7 13.3 — 10 — — —
Field's metal 62 °C (144 °F) Yes 32.5 — 16.5 51 — — — —
Cerrolow 136 58 °C (136 °F) Yes 49 18 12 21 — — — —
Cerrolow 117 47.2 °C (117 °F) Yes 44.7 22.6 8.3 19.1 5.3 — — —
Bi-Pb-Sn-Cd-In-Tl 41.5 °C (107 °F) Yes 40.3 22.2 10.7 17.7 8.1 1.1 — —
Gallium 29.8 °C (86 °F) Pure metal — — — — — — 100 —
Galinstan −19 °C (−2 °F) No <1.5 — 9.5–10.5 21–22 — — 68–69 <1.5

References

  1. ^ a b c d Moody, Bernard (2013). Comparative Inorganic Chemistry. Arnold. p. 179. ISBN 9781483280080.
  2. ^ Jensen, William B. (2010). "The Origin of the Name "Onion's Fusible Alloy"" (PDF). Journal of Chemical Education. 87 (10): 1050–1051. Bibcode:2010JChEd..87.1050J. doi:10.1021/ed100764f. Archived from the original (Archived Reprint) on 2012-04-03.
  3. ^ "Collection: Barnabas Wood Papers". SCOUT at University of Tennessee, Knoxville. Retrieved March 22, 2022.
  4. ^ G. W. A. Milne, ed. (2005). Gardner's Commercially Important Chemicals: Synonyms, Trade Names, and Properties. John Wiley & Sons. ISBN 978-0-471-73661-5.
  5. ^ Khan F. M., Gibbons J. P. "The Physics of Radiation Therapy, 5th ed". Wolters Kluwer.
  6. ^ DeviantOllam (2019-05-01), Copying Keys via a Mold and Cast Attack, archived from the original on 2021-12-22, retrieved 2019-05-04
  7. ^ The Modern Rogue (2019-10-04), Duplicating a Key Using Molten Metal (with LockPickingLawyer), archived from the original on 2021-12-22, retrieved 2020-11-09
  8. ^ Sambamurthy, K. (2007). Pharmaceutical Engineering. New Age International. ISBN 9788122411690.
  9. ^ Do-Gyoon, Kim (February 2006). "Evaluation of Filler Materials Used for Uniform Load Distribution at Boundaries During Structural Biomechanical Testing of Whole Vertebrae". Journal of Biomechanical Engineering. 128 (1): 161–165. CiteSeerX 10.1.1.721.5864. doi:10.1115/1.2133770. PMID 16532630.
  10. ^ a b "Wood's Metal Safety Data Sheet". Flinn Scientific. Retrieved 7 October 2024.
  11. ^ Genchi, Giuseppe (May 26, 2020). "The Effects of Cadmium Toxicity". NIH National Library of Medicine. Retrieved November 16, 2024.

Bibliography

  • Birchon's Dictionary of Metallurgy, London, 1965
  • Experimental techniques in low-temperature physics, G. K. White, Oxford University Press, Third Edition
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