Hoffman, in one of his observations, gives the history of a powder called magnesia alba, which had long been used and esteemed as a mild and tasteless purgative; but the method of preparing it was not generally known before he made it public.
It was originally obtained from a liquor called the mother of nitre, which is produced in the following manner:
Salt-petre is separated from the brine which first affords it, or from the water with which...
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