Precipitation, maximum mutual

According to Berthellot, when substances of definite composition are formed, they are either (i) the result of a mutual saturation of an acid by a base, when the powers of each are just neutralised in a certain proportion (the change of reaction proceeding continuously) or (2) they are, exceptionally, due to the interference of other manifestations of the physical forces, such as (a) cohesion, when a precipitate of definite composition is formed because it happens to have the maximum density, or (b) elasticity, when a gaseous product is formed which escapes from the system, and as the most volatile product is favoured in the reaction. Solutions were regarded as true chemical compounds of variable composition. Salts crystallise out in a neutral state because in that neutral state the insolubility is greatest. ... 

The alkoxides are dissolved in a mutual solvent (e.g., isopropanol) and refluxed for 2 h prior to hydrolysis. While the solution is vigorously stirred, drops of deionized, triply distilled water are slowly added. The reaction is carried out in a C02-free atmosphere to prevent the precipitation of barium carbonate. After drying the precipitate at 50°C for 12 h in a helium atmosphere, a stoichiometric BaTiOs powder with a purity of more than 99.98% and a particle size of 5-15 nm (with a maximum agglomerate size of < 1 p.m) is produced. Dopants can be incorporated uniformly into the powders by adding a solution of the metal alkox-ide prior to hydrolysis. 

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