This is a sample of 100 grams of a compound, called phosphorus trisulfide. Analysis has shown that its empirical formula is P₂S₃. It is a compound which slowly reacts with humid air, giving a smell of hydrogen sulfide, so it must be stored in a tightly closed bottle. In a warm concentrated solution of NaOH the highly flammable and toxic phosphine is produced. This material is very flammable and it burns with a typical flame with dense white smoke, very reminiscent of the flame of burning phosphorus. Many places use the formula P₄S₆ for this compound, but according to modern insights, this most likely is not a chemical identity. The only known sulfides of phosphorus are P₄S₃, P₄S₅, P₄S₇ and P₄S₁₀. This probably is a mix of P₄S₃, P₄S₅ and P₄S₇.