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Barium platinocyanide is a salt of the tetracyanoplatinate(II) anion, commonly encountered as a hydrate. Its structure contains coordinated cyanide groups around platinum rather than free cyanide ions alone.

Its visible fluorescence under irradiation made it useful as a screen in the Röntgen X-ray discovery experiment. The screen converts otherwise invisible incident radiation into an optical signal.

Wilhelm Conrad Röntgen received the award for discovering X-rays.^[ref] The Röntgen X-ray discovery experiment follows how a glowing screen led to tests of a new penetrating electromagnetic radiation.

A physicist.^[ref]

The Röntgen X-ray discovery experiment connected a covered discharge tube, a fluorescent screen and photographic exposures. The X-ray article follows those tests into modern source and attenuation models.

An X-ray tube accelerates electrons from a negative cathode to a positive target anode. A heated cathode supplies electrons by thermionic emission; the evacuated envelope limits collisions before the target. This differs from the gas-discharge tube in the Röntgen X-ray discovery experiment.^[ref]

In bremsstrahlung, an electron changes velocity in the target's electric fields, emitting a photon while losing kinetic energy. Different encounters allow a continuous range of transferred energies. This is distinct from the discrete electronic transitions producing Characteristic X-rays.

Changing the accelerating voltage changes the available kinetic energy per electron and the X-ray tube cutoff. Changing the number of arriving electrons changes the number of opportunities for photon emission. These are distinct controls: a larger electric current does not by itself give each electron more energy. For an original idealized budget, $V=50\mathrm{kV}$ and tube electric current $i=0.20\mathrm{mA}$ give electrical power $Vi=10\mathrm{W}$ and arrival rate $i/e\simeq 1.25\times 10^{15}{\mathrm{s}}^{-1}$, where $e$ is the elementary charge. This is input power, not emitted X-ray power; obtaining the latter requires a conversion efficiency.