TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Process Details: The cation of the ionic liquid comprises an imidazolium or pyridinium nucleus, if need be substituted by one or more 1-4C alkyl groups, more preferably a substituted imidazolium of formula (I) in which R1 and R2 are 1-4C alkyl.Cations especially preferred are 1-n-butyl-3-methylimidazolium and 1-ethyl-3-methylimidazolium or a pyridinium of formula (II).A preferred compound is 1-butyl-3-methylpyridinium.Preferred anions are halides and perfluorides, such as bis(trifluoromethylsulfonyl)imide and hexafluorophosphate. Preferred ionic liquids are 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide and 1-butyl-3-methylimidazolium hexafluoro-phosphate.The molecular precursor is a derivative of an element from groups 13, 14 or 15, or of a transition metal, or an alkoxysilane of general formula (III).R'x(RO)4-xSi (III)x = 0-3; andR, R' = 1-4C alkyl.Preferred alkoxysilanes are tetramethoxysilane, methyltrimethoxysilane or a mixture of alkoxysilanes. The molar ratio of ionic liquid/molecular precursor is 1/2. The preferred carboxylic acid is formic acid. The molar ratio of molecular precursor/carboxylic acid is 1/50. The reaction mixture is left dormant for 7-9 days at ambient atmosphere and temperature ; more preferably the mixture is aged under ultrasonics for 24 hours.Preferred Ionogel Characteristics The ionogels are monolithic solids which are transparent, stable up to 300-350 degrees C, and are ionic conductors with a conductivity of 10E-4 -10E-3 S/cm at ambient temperature and 10E-2 - 10E-1 S/cm at 230 degrees C. The products comprise an ionic liquid confined in the core of a continuous solid. They have the following mechanical characteristics: a Young's modulus of 50-100 MPa, particularly 52-75 MPa and mean of 63 MPa; and a breaking stress of 0.1-1.5 MPa, particularly 0.44-1.31 MPa and especially a mean of 0.82 MPa. EXAMPLE - Synthesis of 1-ethyl-3-methylimidazolium bis(trifluorosulfonyl)imide (EtMeIm+NTf2-) is described. Ethylmethylimidazolium bromide was first prepared from methylimidazole and ethyl bromide. The product was added dropwise at ambient temperature to a mixture of lithium bis(trifluorosulfonyl)imide and water. The mixture was then refluxed for 2 hours and the product extracted with dichloromethane. A light yellow ionic liquid was obtained (yield 86%).    Synthesis of pastilles based on tetramethoxysilane containing the ionic liquid EtMeIm+NTf2- is described. 1 ml of EtMeIm+NTf2-, 2 ml of formic acid and 1 ml of tetramethoxysilane were introduced in order into a Teflon tube. After homogenization, the mixture was left to gelify at ambient temperature and pressure. Gelification was effected after 1.5 hours and ageing was carried out for 7-9 days. A transparent product was obtained.