21. The practical colors included Prussian blues and graphite grays. 22. The new colour was first called Berlin blue, but later became known as Prussian blue . 23. In other words, Prussian blue is considered as an integral part of precision tool making. 24. Painted surfaces could be scraped, while floors were treated with acid and Prussian blue mixtures. 25. "The Stonemason's Yard " is a very early example of using Prussian blue in oil painting. 26. But until now, national stockpiles of Prussian blue pills have been limited, and bought from overseas. 27. Hg ( CN ) 2 can also be prepared by mixing HgO, finely powdered Prussian blue . 28. Prussian blue was the first modern synthetic pigment.29. They also provided backing on two tracks for Richard Clapton's debut album " Prussian Blue ". 30. The standard is coated with a very thin coating of a material such as Prussian blue .
