The building owner who has chosen to use a radioactive exit sign never has to worry about its failure to keep glowing for a very long time. It uses a source of perpetual light. Years ago there must have been serious thought to using radium in such signage. Every second one hundred and thirty six thousand million atoms disintegrate from inside of a single gram of radium. Yet that substance has not been used to produce the glow found in present-day radioactive exit signs.
A great deal of time and effort must take place during any effort focused on the extraction of radium. Moreover, only a tiny amount of that powerful material can be obtained from a huge amount of ore. Those facts became evident to the Curies, as that couple sought to isolate from pitchblende the substance that so fascinated them. That couple also discovered another important fact.
That discovery was made late one night, when that man and wife team decided to return to their lab/shed, one located close to their home. The purpose of their visit related to an apparatus then in use, one that was supposed to carry out a fractional crystallization on what had, up to that point, been extract from the pitchblende.
Extraction of Tritium
When the Curies opened the door of their lab, their eyes saw something for which neither of them was prepared. Their apparatus, along with all the surrounding glassware was glowing. That glow suggested the existence of a new source of power, one that had, until then, remained absent from mankind’s many other advances. In fact, one scientist, a man named Rutherford chose to investigate the source of that power.
He ended up examining three different cascades. After comparing those three different cascades, he found that each produced evidence of what Rutherford determined to be disintegration. Each cascade’s disintegration had resulted in creation of certain breakdown products.
Rutherford’s comparison of three different cascades showed that in each case all of the breakdown products came from one particular element. More importantly, each such product could be viewed as a unique version of that original element. Rutherford’s associate wanted to assign a name to such products; he called them isotopes. Due to the chemical nature of each isotope, it belongs within a particular spot, one located within its specific cascade.
That spot is determined by how much further that isotope can disintegrate, before taking on the chemical characteristics of a substance that will never disintegrate. In the case of radium, each isotope represents a material within a cascading series of disintegrations. Each such isotope represents a stage in an ongoing disintegration, one that eventually yields production of the element known as lead.
During any disintegration, a quantum of energy has been released. That energy represents the power that produces a glow, the glow that surprised and fascinated the Curies. When first discovered, that glow was viewed as a something that might possess healing powers.
Overtime however, its anticipated healing powers had to be compared with those of recognized treatments. Today no one finds a radioactive substance in any medicine on the shelves of virtual or brick and mortar stores. Still, that fact has not diminished society’s desire to utilize the glow of a radioactive substance. That is why such substances have been used in exit signs.