Properties of Hydrogen Cyanide, HCN

Hydrogen cyanide, a colorless liquid, is similar, in many of its physical properties, to water.320 This similarity also explains the limitless solubility of HCN in water and its strong tendency towards absorption (dissolution) in water. The equilibrium concentration321 of hydrogen cyanide in water is investigated in more detail in chapter 

319 I also want to point out that I did not include all this academic, self-serving ivory tower chatter in order to impress people. I was simply advised by many friends, supporters, and adversaries to include all my material since back-references to my German original is no help to most English language speakers, of whom only a tiny fraction can read German. 

320 High polarity, low molecular mass, possibility of formation of hydrogen bonds. 

Graph 1 shows the equilibrium percentage of hydrogen cyanide in air as a function of temperature. Even at 0°C, the percentage still lies at 

Braker, A.L. Mossman, Matheson Gas Data Book, Matheson Gas Products, East Rutherford 1971, p. 301. Ihave left out some of the less interesting dimensions in this connection heat capacity (20.9°C) 2.625 J g 1 K 1 (Water 4.187 J g 1 K 1) dielectricity constant (20°C) 114 (Water=78.5) evaporation heat 28 kJ mol 1 evaporation entropy 190 J mol 1 K 1 spontaneous combustion temperature 538°C flash point -17.8°C regarding dielectricity constants, see R.C. Weast (ed.), Handbook ofChemistry and Physics, 66th Ed., CRC Press, Boca Raton, Florida 1986, E 40. However, under normal conditions (1 atm, 25°C), hydrogen cyanide is not a gas. 

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