According to Wikipedia, the solubility of Potassium Dichromate increases very significantly with the temperature.
At 20°C, 13g/100ml, and at 100°C, 104g/100ml.
Therefore, it should be possible to dissolve about 520g of potassium dichromate in 500 ml of boiling water, but only about 65g in the same water, but at room temperature.
Today, I acquired about one kg of technical potassium dichromate and tried recrystallizing it, by weighing 507g of raw dichromate and dissolving it in about 500ml of water, room temperature. I expected it to no dissolve fully until the water was heated to boiling.
However, as soon as the water got slightly warm (45°C-50°C) everything dissolved. I added more raw material, and it kept dissolving until in the end everything (~970g) was added and dissolved before reaching boiling temperature.
Now, it is very slowly cooling down, and at about 35°C I seeded some small crystals and they're growing.
What went wrong in my calculations of the solubility? Anything I should've considered and missed?
PS.: Things I've already considered and ruled out: