The Prussian Class P 8 steam locomotive of the Prussian state railways (DRG Class 38.10-40 of the Deutsche Reichsbahn) was built from 1906 onwards by the Berliner Maschinenbau (previously Schwartzkopff) and the Linke-Hofmann factory in Breslau by Robert Garbe. It was intended as a successor to the Prussian P6, which was regarded as unsatisfactory.

Because Garbe was an advocate of the simplest possible designs, a straightforward, superheated steam, two-cylinder driving gear was envisaged. The P 8 benefited especially from superheated steam technology, which had just been developed by Wilhelm Schmidt (nicknamed 'hot steam Schmidt'), that led to outstanding performance for those times. The P 8 was a very economical locomotive that did not make great demands on the ability of the engine driver. At the outset Garbe even designed the P 8 as an express train locomotive, with the expectation of attaining a top speed of 110 km/h (68 mph). As a result the first units were fitted with low wind-resistance, tapered driver's cabs.

Prussian blue is a dark blue pigment with the idealized formula Fe₇(CN)₁₈. Another name for the color Prussian blue is Berlin blue or, in painting, Parisian blue. Turnbull's blue is the same substance but is made from different reagents.

Prussian blue was one of the first synthetic pigments. It is employed as a very fine colloidal dispersion, as the compound itself is not soluble in water. It is famously complex, owing to the presence of variable amounts of other ions and the sensitive dependence of its appearance on the size of the colloidal particles formed when it is made. The pigment is used in paints, and it is the traditional "blue" in blueprints.

In medicine, Prussian blue is used as an antidote for certain kinds of heavy metal poisoning (caesium and thallium).

Prussian blue lent its name to prussic acid, which was derived from it, and to ferrocyanide (originally meaning "blue compound of iron", from Latin ferrum and Greek κυανεος). As ferrocyanide is made of iron and CN ligands, reinterpreting the component "-cyanide" in the compound word, produced the word "cyanide" for compounds containing the CN radical.