# What is the characterstics of additives that it must posses to make any mixture hypergolic? [closed]

This is about hypergolicity of rocket propellant.Turpentine gave hard-start with RFNA and WFNA but excellent with mixed acid(mixture of HNO3 & H2SO4).Similarly,Furfuryl alcohol & WFNA(also RFNA) become hypergolic mixture.So,what properties must additives posses to ignite particular mixture at any time without requiring oxygen?

• In a mixture $HNO_3 + H_2SO_4$, there are more $NO_2^+$ ions than in pure $HNO_3$. – Maurice Mar 27 '20 at 12:35
• @Maurice So,NO2+ ion makes the mixture hypergolic? & RFNA also contain NO2.That idea seems contradicting – Auberron Mar 27 '20 at 12:39
• @ Auberron. Please don't mix up $NO_2$ which is a brown and neutral molecule, and $NO_2^+$ which a colorless ion. – Maurice Mar 27 '20 at 12:54
• @Maurice Yeah you are right. – Auberron Mar 27 '20 at 13:22
• Just use chlorine trifluoride: it is hypergolic with everything including most containers. seriously, though, there are whole books on the topic so it is unlikely you will get a good general answer. Try John D Clarke's famous "Ignition: an informal history of liquid rocket propellants" for a good overview. – matt_black Mar 27 '20 at 17:31