In fact this reaction is not possible; hence an intermediate reaction is necessary which delivers sodiumbicarbonate. The letter has to be calcined to obtain anhydrous sodium carbonate = soda ash. This materials is very fine grained and therefor is call “light soda ash” (0.6 kg/l). Because of the possible damage to refractories by soda dust, we prefer the so called “heavy soda ash” which is produced by recrystallizing and recalcining “light soda ash” (price). This material has a bulk density of about 1.1 kg/l. Whereas the grain of “light soda” ranges within < 0.04 to 0.16 mm, the “grain size distribution of “heavy soda” is in the range of 0.1 to 0.5mm. The theoretic content of