On this day in 1913 Francis I. DuPont was granted the patent for Method of Gravity Liquid Separation of Solids. U.S. Patent No. 1,064,459.
In this improved method a liquid other than water which is capable of being vaporized so that any liquid carried off in the separated ingredients may be vaporized and thus removed from the ore and may be condensed and returned to the separating vessel. The liquid may either be of greater density than one of the ingredients and less than that of the other, or of greater density than water, but of less density than either ingredient to be separated. Speaking generally, the ore to be separated, for example, limonite, in a divided condition is conveyed into a vessel containing this liquid -which may be stannic chlorid which -has a specific gravity of 2.27, is liquid at ordinary temperature, and vaporizes at 114° C. If the specific gravity of the liquid is greater than one ingredient, the silicious material and the iron ore containing iron oxid and silicious material, and the specific gravity of the liquid being. less than the purer iron oxid it, the purer iron oxid, will sink, or tend to sink, to the bottom, and the other ingredients named, the silicious material, and the iron ore, containing iron oxid and silicious material, will rise or tend to rise to the surface. If the liquid be of greater specific gravity than water, but less specific gravity than either ingredient, the increase of the lessening of the tendency of the lighter ingredient to sink as the specific gravity of the liquid becomes greater, increases faster than does the corresponding tendency of the heavier ingredient. Hence the lighter ingredients rise more readily to. the surface than the heavier ingredients. While in this vessel containing this liquid the-upper portion of the liquid is caused to flow in one direction and the lower portion of the liquid in the other direction, thus there is a continuous flow of the liquid in the apparatus. Agitation is also produced therein. The ingredients in the upper portion of the liquid pass to one end of the apparatus, and the ingredients in the lower portion to the other end of the apparatus. The material at each end being carried free from the liquid, except from such as . adheres to the particles, into and through a heating chamber where any liquid carried off is vaporized, the vapors are returned to the separating vessel where they are condensed to as great an extent as possible, the excess not condensed being condensed in a condenser and returned to the separating vessel.
