Sentence:  Lately, in France, they stopped the boiling process in the preparation of brown sugar a few degrees before the point of crystallization, which is 243°, or 244°; and then spreading their syrup over their copper pans, placed round a stove or bake house, leave the syrup to <WSD>desiccate</WSD> slowly, and to crystallize in what they call the natural way; ... 
Meaning of the word marked with <WSD> tags:  To become dry; to dry up.