Wood's metal

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. The alloy is named for Barnabas Wood, who invented and patented the alloy in 1860.[1][2] It is a eutectic alloy of 50% bismuth, 26.7% lead, 13.3% tin, and 10% cadmium by mass. It has a melting point of approximately 70 °C (158 °F).[3][4] Its fumes are toxic, as well as being toxic on skin exposure.

Applications

Uses 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.[5][6]

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).[7]

At room temperature, Wood's metal has a modulus of elasticity of 12.7 GPa and a yield strength of 26.2 MPa.[8]

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.[9] Cadmium poisoning carries the risk[10] 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.[9]

AlloyMelting pointEutectic?Bismuth
%
Lead
%
Tin
%
Indium
%
Cadmium
%
Thallium
%
Gallium
%
Antimony
%
Rose's metal98 °C (208 °F)No502525
Cerrosafe74 °C (165 °F)No42.537.711.38.5
Wood's metal70 °C (158 °F)Yes5026.713.310
Field's metal62 °C (144 °F)Yes32.516.551
Cerrolow 13658 °C (136 °F)Yes49181221
Cerrolow 11747.2 °C (117 °F)Yes44.722.68.319.15.3
Bi-Pb-Sn-Cd-In-Tl41.5 °C (107 °F)Yes40.322.210.717.78.11.1
Gallium29.8 °C (86 °F)Pure metal100
Galinstan−19 °C (−2 °F)No<1.59.5–10.521–2268–69<1.5

References

  1. 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.
  2. "Collection: Barnabas Wood Papers". SCOUT at University of Tennessee, Knoxville. Retrieved March 22, 2022.
  3. 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.
  4. Khan F. M., Gibbons J. P. "The Physics of Radiation Therapy, 5th ed". Wolters Kluwer.
  5. DeviantOllam (2019-05-01), Copying Keys via a Mold and Cast Attack, archived from the original on 2021-12-22, retrieved 2019-05-04
  6. 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
  7. Sambamurthy, K. (2007). Pharmaceutical Engineering. New Age International. ISBN 9788122411690.
  8. 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.
  9. 1 2 "Wood's Metal Safety Data Sheet". Flinn Scientific. Retrieved 7 October 2024.
  10. 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