not returned to these the less pure crystals are withdrawn from crystallizers 3a 4a and 5a through pipelines 33a 34a and 35a and are conveyed to separating means 37a through pipeline 36a the solid crystals are fed to product dryer 39a through chute or conveyor 38a the less pure product is conveyed to storage not shown by means of conveyer 40a the mother liquor leaving separating means 37a is conveyed by pipelines 41a and 42 to pipeline 2 a where it is combined with a stream of purified process solution the purge from the system is removed through pipeline 43 or from some other convenient point fig2 is a schematic flowsheet of an alternate embodiment of the process of the invention this shows one set of triple effect crystallizers two means of separating the crystals from the mother liquor and two product dryers in this alternate embodiment the pure product is produced in the first effect and the less pure product is produced in the second and third effects referring to fig2 purified pregnant sodium carbonate process solution is delivered to pipeline 1b this solution is fed to the first effect crystallizer body 3b through pipeline 6b the excess of purified solution is delivered by crystallizer bodies 4b and 5b through pipelines 7b 8b and 9b the recycled mother liquor from pipeline 42c is comingled with the purified solution in pipeline 9b before it is fed to the crystallizers 4b and 5b the purified sodium carbonate process solution is prepared as previously described and contains similar impurities steam from a boiler not shown is fed to.