Phosphorus trisulfide - "P2S3"
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.