Final answer:
The term 'Eindhoven's triangle' does not appear to be related to lead or recognized in Chemistry. Lead has been used in paint, pipes, and various products, but due to health risks, its usage is now limited. Refined lead can reach high levels of purity but is less commonly used.
Step-by-step explanation:
The question seems to be misinformed or contains a typographical error, as 'Eindhoven's triangle' is not a recognized term in the context of Chemistry or any other subject related to lead. However, focusing on the use of lead, it is commonly known that lead was widely used in various applications such as in paint, water pipes, toys, and jewelry due to its malleability and low melting point. Over time, health hazards associated with lead exposure have led to a decrease in its use in consumer products and a switch to safer alternatives.
It is also known that electrolytically refined lead can achieve very high levels of purity, as indicated by the 99.989% pure lead nodule and 1 cm³ lead cube reference provided. Despite the high purity achievable, the dangers of lead mean that its use is now heavily regulated, and it is commonly substituted in many applications where it was once prevalent.