Solubility of Sodium Sulphate

Perusing my CRC the other day, I noticed that sodium sulphate heptahydrate has a solubility of 19.5g/100cc. The anhydrite has a
solubility of 4.76g/100cc. At a concentration of say 18 g/100cc why doesn't the heptahydrate crystallise out as the anhydrite then reabsorb water into its structure to become the heptahydrate and then redissolve? The respective MWs of 142 and 268 don't account for the discrepancy. Any ideas?
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snipped-for-privacy@hotmail.com wrote:

The last time I needed to know a solubility I found that the CRC had taken its data from an ancient reference and it was out by a factor of more than 10.
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