In respect of David Starley's XRF analysis of the WWII gasmask clip, 
which he notes 'showed high levels of cadmium as well as iron and 
zinc and traces of nickel and copper', I would be particularly 
interested to know the following:

1. Does the clip respond to a magnet, suggesting an iron or steel 
core?

2. If not under vacuum is the analysis qualitative rather than 
quantitative? Are the results likely to represent the metallic 
elements at the surface of the clip (i.e. would you detect a higher 
peak for a thin cadmium/zinc plating and a lesser peak for an iron 
core). 

3. Are there any signs of surface peeling or bubbling which may 
suggest a plated surface? 

4. Does the clip appear to have been fabricated from sheet or cast 
metal?

As others have suggested (Northover, Scott and Seeley) the clip may 
very well be plated with cadmium. Perhaps you are looking at several 
layers of platings; as with chrome objects, where steel (for example) 
has a copper plating, and sometimes also nickel, between the steel 
and chrome (G. Bailey, 23/1/99, CoOL). As to whether plating 
technology was this complex in the 1930s, does anyone know? I think 
it is interesting, however, that works published towards the end of 
the 19th century included Electro-metallurgy (10th ed. by 1897), 
Electro-deposition (3rd ed. by c. 1897 ), and Electroplating (4th ed. 
by c. 1897) which included the deposition of aluminium and nickel 
amongst other metals.

Is it also possible that you could be detecting a zinc which contains 
cadmium? Percy, writing in 1861, noted that the analysis of one 
carbonate of zinc deposit (calamine) contained 3.36% Cd; and sulphide 
of zinc (blende) deposits, up to 3.2% (pp. 548 -9). He also noted 
that, 'zinc in the state in which it is condensed in the process of 
reduction [rough zinc] always contains Cadmium'; and that 'commercial 
zinc is rarely free from iron'. (Percy 1861: 548-9, 590). Whilst 
early zinc plating produced by dipping (e.g galvanised iron) has the 
familiar blue-grey large crystalline appearance, apparently, 
electrolytically deposited zinc is harder to identify, and can be 
mistaken (visually) for dulled chrome (Child and Townsend 1988).

I would also like to add to the general discussion on the use of 
cadmium and note some alloy compositions. Experimental work by Metzel 
(as early as 1829), on the effect of cadmium on the malleability of 
zinc, found that an alloy of 85% Zn and 15% Cd could be rolled to a 
thickness of 1/12 inch without cracking (Percy 1861: 590). Cadmium 
(m.p. 320 0C) was used in the manufacture of 'fusible alloys', alloys 
of low melting point, such as 'Wood's metal' and 'Lipowitz' alloy' 
(bismuth, lead, tin, and cadmium in varying proportions), of which 
both have a melting point of around 70 0C (Uvarov 1979: 58, 174). 
Smith (1956) lists a range binary alloys of cadmium with aluminium, 
antimony, bismuth, copper, magnesium, silver, and tin. (For a 
micrograph of an 84% Cd, 16% Cu alloy see p. 133; a cadmium-tin phase 
diagram is illustrated on page 150.). Hoyt (1952: 457) notes that in 
addition to the use of cadmium as a coating on steel for resistance 
to seizure and corrosion (particularly in alkaline solutions), it was 
also used extensively in the manufacture of solders (binary examples 
given are 82.5% Cd, 17.5% Zn; 95% Cd, 5% Ag; and a quaternary alloy 
of 50% Ag, 18% Cd, 16.5% Zn, 15.5% Cu). Cd-Ag solder, for example, 
was found to stronger than Pb-Sn solder at all temperatures. However, 
according to Hoyt (1952: 456-7) one of its main applications was in 
the manufacture of bearings. The Cd-base 'Babbitt' (an alloy named 
after I. Babbitt AD 1799-1862, which originally had a Sn, Cu, Sb 
composition (Uvarov, 1979: 36)), was utilised in the manufacture of 
automomtive engines as this alloy could operate at a higher 
temperature than with Sn-base Babbitt bearings. Much of Hoyt's work 
appears to be based on earlier publications of the 1930-40s. A Cd-Cu 
alloy was also used in the manufacture of tramway wires (Sharp, 1990: 
73).

The above suggests that the gasmask clip could also manufactured from 
a number of 'exotic alloys', or re-melted scrap, rather than a 
plating. 

Finally, I do not have a copy to hand, but it may also be worth 
consulting: Child, R.E. and Townsend, J. M. ed.s (1988) Modern Metals 
in Museums. Institute of Archaeology Publications. (Particularly the 
chapter on 'Properties and Applications of Electroplated Coating'.)

References:
Hoyt, S. L. (1952) Metal Data. New York: Reinhold Publishing 
Corporation.
Percy, J.. (1861) Metallurgy, vol. 1 part 2. London: John Murray.
Sharp (1990) Dictionary of Chemistry. Penguin.
Smith, M. C. (1956) Alloy series in Physical Metallurgy Series. USA: 
Harper Brothers.
Watt, A. (1897 10th ed.) Electro-metallurgy. Crosby Lockwood & Sons.
Watt, A. (1897 3rd ed.) Electro-deposition. Crosby Lockwood & Sons.
Uvarov, E. B. (1979) The Penguin Dictionary of Science. Penguin.
Urquhart, J. W. (1897 4th ed.) Electroplating. Crosby Lockwood & 
Sons. 

----------------------
Diane Charlton
Honarary Research Assistant
University of Bradford





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