Table 1: The cost, acute toxicity, and melting point of thiourea, dicyandiamide, melamine, and urea [16].

PrecursorsCost ($/t)Acute toxicity
LD50 (oral, rat)
Melting point (°C)

Thiourea3906125 mg/kg182
Dicyandiamide15384000 mg/kg209
Melamine20253248 mg/kg345
Urea4508500 mg/kg133