Acetylene and its salts acetylides

It has long been known that acetylene explodes under the influence of compression. Experiments by Rimarski and Metz [99] showed that at a temperature below 500°C acetylene does not explode if the pressure is lower than 3 kg/cm2. An explosion may occur at 510°C under a pressure of 2.05 kg/cm2. At room temperature acetylene may explode provided it is compressed adiabatically with a pressure of 170 kg/cm2. 

Acetylene is an endothermic compound, its heat of formation —AH ) being — 54.9 kcal/mole. Its heat of explosion is therefore very great, viz. 1870kcal/kg, although the explosion is not connected with an oxidation reaction  

Solid acetylene (m.p. about — 83°C) is insensitive to impact, but at a density of 0.64 it can be detonated by a number 8 detonator, showing a rate of detonation of 2500 m/sec and a lead block expansion of 300 cm3. 

Gaseous, compressed acetylene also detonates. According to Penny [100] when compressed to 8 atm in a pipe -in. in diameter, it detonates with a rate of 1817 + 7 m/sec and in a pipe 1 in. dia. with a rate of 1870 + 22 m/sec. According to Mayes [101] when compressed to 3-6 atm in a pipe 1 in. dia., it detonates with a rate of 1848 m/sec. 

The heavy metal salts of acetylene have the properties of primary explosives, but only cuprous acetylide was found to be satisfactory for practical use. 

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