Tricyanate
Tricyanate was a purple crystalline substance. It was toxic to humanoids. It was also generally considered expensive to produce. 

Tricyanate occurred naturally on the planet Beta Agni II. In 2366, some contamination was found in the water supply of Beta Agni's colony. It was found to be at a concentration of seventy grams per cubic centimeter at the source coordinates covering an affected area of thirty square kilometers; it was an indication of non-naturally-occurring tricyanate, which was later found out to be the work of Zibalian trader Kivas Fajo, who had just so happened to possess the perfect amount of hytritium to neutralize the poison. When suspecting sabotage, Beverly Crusher theorized that using tricyanate allowed the act to appear to be a natural disaster. ()

See also 
 Tetracyanate 622

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Chemical compounds