Nitroglycerine

Nitroglycerine

Nitroglycerine is a poisonous, colorless, oily liquid, insoluble in water. It usually burns quietly when ignited, but when heated, rapidly struck or detonated, it explodes violently. Noble (1867) found that nitroglycerine could be stabilized by absorbing it in kieselguhr. This was dynamite, which is now, however, usually manufactured by using wood pulp as the absorbent, and adding solid ammonium nitrate. Blasting gelatin or gelignite is made by mixing nitroglycerine with gun-cotton (cellulose nitrate). The smokeless powder, cordite, is a mixture of nitroglycerine, gun-cotton and Vaseline. Nitroglycerine is also used in the treatment of angina pectoris.

Nitroglycerine is manufactured by adding glycerol in a thin stream to a cold mixture of concentrated nitric and sulphuric acids:

CH2OH                                  CH2ONO2

丨                                           丨

CHOH   +   3HNO3  ⟶      CHONO2  +  3H2O

丨                                           丨

CH2OH                                  CH2ONO2

Nitroglycerine is an ester, not a nitro-compound; it is glyceryl trinitrate. The incorrect name appears to have been introduced due to the use of ‘mixed acid’ which is normally used for nitration.

 When heated with formic acid or oxalic acid at 260^oC, glycerol is converted into allyl alcohol. With dibasic glycerol forms condensation polymers known as alkyd resins, the commonest of which is glyptal, formed by heating glycerol with phthalic anhydride.