Element of the Month
Each month we will explore elements of interest from the periodic table, with a brief history of discovery and development, and a review of uses and applications.
Silver - Atomic Number: 47 - Chemical Symbol: Ag
Silver is a soft white ductile metal that was used in its native form in pre-historic times. It was one of the first metals discovered and used by humans, along with copper, lead, iron, and gold.
Silver produced from refining a lead ore such as galena was used to make objects well before 2000BC
It is present in the earth’s crust at 0.08 parts per million (ppm), and is rarely found as nuggets of native metal. Most silver is produced as a by-product of refining other metals such as lead, gold, and copper.
It has the highest electrical and thermal conductivity of any metal and finds many industrial uses.
Where is Silver Used?
As a Pure Element
Pure silver is a very good conductor of heat and electricity and finds widespread use in solar and electronic applications, where electrical transmission losses must be minimised. It is also the best reflector of visible light with very low emissivity, and is used to make mirrors for telescopes.
High purity silver (99.9%) is held in the form of bullion bars and coins as part of investment portfolios
As an Alloy
Silver is alloyed with elements such as copper to produce Sterling Silver in a 92.5% to 7.5% ratio, which is the most common silver jewellery alloy. Alloys such as Argentium also contain 92.5% silver but copper and germanium are the alloying elements, which hardens the alloy and reduces tarnishing. Some alloys offered as silver from less reputable sources may contain no silver at all, and some unscrupulous sources may produce silver alloys with toxic elements such as cadmium or lead.
As a Compound
Silver compounds are extensively used in photography as light sensitive layers, but more recent digital techniques have reduced their use. There are many applications for the antibiotic qualities of silver compounds such as wound care and the purification of water. Silver cyanide and silver nitrate compounds are used in silver electroplating processes, which is one of the common uses.
As a Coating
A silver coating is typically electroplated onto a base metal substrate to improve appearance or function. It is bright and highly attractive so is widely used in costume jewellery, but also has key functional qualities such as high electrical conductivity, anti-galling, and high temperature resistance. Silver coatings are extensively used on electronic contacts and connectors, automotive exhaust fasteners, ball bearing cages, and musical instruments. Non-electrolytic immersion silver plating processes are used in printed circuit board manufacture when a very flat solderable surface is needed for surface mount component placement.
Here are some key parameters for Silver, quantifiable using instruments from Helmut Fischer GmbH
- Thickness of silver coated electrical contacts measurable by a non-destructive XRF based instrument such as the XDAL 237 to ensure compliance with functional specifications
- Composition of silver jewellery alloys, that can be verifiable in seconds using a table top XRF such as XAN 250
- Ensure compliance with jewellery safety regulations by testing for nickel, cadmium and lead in precious metal jewellery using a non-destructive XRF based XDV-SDD
- Verify thickness and ensure solderability of immersion silver coatings on PCB surface mount pads using specially designed XRF systems
- Improve quality control and reduce precious metal costs of reel-to-reel plating operations with an inline XRF system such as X-Ray 4000
- Ensure the functionality of silver coated steel ball bearing cages with a bench instrument such as the Fischerscope MMS PC2 with internal magnetic induction probe