A spectacular firework display at Florence, Italy.
Painted by G M Terrini (1739-1811)
The artificial volcano appears to
be of conventional pyrotechnics
The seemingly innocuous artificial volcano consisting of a pile of ammonium dichromate crystals is now deemed to be hazardous. The voluminous green chromic oxide "ash" is a suspect carcinogen. The inclusion of Pharaoh`s Serpent Eggs (mercuric thiocyanate Hg(CNS)2 "pills") within the orange pile of crystals was always a bad move, and possibly explains why some chemistry teachers of yesteryear appeared as mad as hatters.
The sulphur & iron volcano must be considered highly dangerous. Small quantities of iron filings and flowers of sulphur do not work. Presumably there is a critical mass, where the heat generated by the oxidisation of the iron in the centre is not conducted away fast enough. The internal temperature then rises to the point at which the exothermic reaction between iron and sulphur begins.
One can envisage using thermocouples and a datalogger to provide useful information from a small (laboratory scale) mass of the iron filings / flowers of sulphur / water mixture. The critical mass necessary for the internal temperature to reach the ignition point could then be calculated. Here the ignition of the reaction to form ferrous sulphide is described -
From a popular science book of 1844
From a letter to Michael Faraday from Ernest Glitch dated June 1856.
Concerning the reaction of sulphur and iron in ton quantities