Rochefoucauld

See La Rochefoucauld.

Rochejaquelein

See La Rochejaquelein.

Rochelle Salt, Or Salt Of Seignette (Tartrate Of Potash And Soda

Rochelle Salt, Or Salt Of Seignette (Tartrate Of Potash And Soda, sodic-po-tassic tartrate), a double tartrate of potassium and sodium, discovered by Seignette, an apothecary of La Rochelle. By neutralizing cream of tartar (bitartrate of potash, KHC4H4O6) with carbonate of soda, its basylous atom of hydrogen may be replaced by sodium. By evaporation the tartrate of potash and soda separates in large transparent rhombic prisms of the formula KNaC4H4O6+4Aq. The crystals melt in this water of crystallization between 160° and 176° F., and dissolve in 2 parts of water at 42°, and in 0.3 part at 100°. Acids precipitate cream of tartar from the solution. The salt is a mild cooling purgative, in doses of from two drachms to an ounce. In small and repeated doses it does not purge, but is absorbed and renders the urine alkaline. It is the principal component of Seidlitz or Rochelle powders.

Rock Castle

Rock Castle, a S. E. county of Kentucky, bordered S. E. by Rock Castle river, by the branches of which and Dick's river it is drained; area, about 350 sq. m.; pop. in 1870, 7,145, of whom 369 were colored. It has an uneven surface and a not very fertile soil. It is intersected by the Louisville and Nashville and Great Southern railroad. The chief productions in 1870 were 10,539 bushels of wheat, 216,816 of Indian corn, 35,077 of oats, 23,445 lbs. of tobacco, 10,949 of wool, 92,675 of butter, and 11,702 gallons of sorghum molasses. There were 1,638 horses, 1,648 milch cows, 2,314 other cattle, 6,625 sheep, and 7,189 swine. Capital, Mount Vernon.

Rock Fish

See Bass, vol. iv., p. 368.

Rockbridge

Rockbridge, a central county of Virginia, intersected by North river, a branch of the James, and bordered S. E. by the Blue Ridge; area, about 700 sq. m.; pop. in 1870, 16,058, of whom 3,890 were colored. It has a mountainous surface and very fertile soil. The Chesapeake and Ohio railroad crosses the N. W. corner. The county derives its name from the natural bridge in the S. corner. (See Bridge, Natural.) The chief productions in 1870 were 214,800 bushels of wheat, 119,518 of Indian corn, 85,564 of oats, 6,022 tons of hay, 186,469 lbs. of tobacco, 9,156 of wool, 131,092 of butter, and 3,290 gallons of sorghum molasses. There were 2,288 horses, 2,378 milch cows, 4,493 other cattle, 3,481 sheep, and 6,986 swine; 1 manufactory of cement, 2 of tin, copper, and sheet-iron ware, 4 of tanned and 4 of curried leather, and 16 flour mills. Capital, Lexington.

Rockdale

Rockdale, a N. county of Georgia, bounded S. W. by South river, a branch of the Oc-mulgee, and drained by other branches of that stream; area, 200 sq. m. It has been formed since the census of 1870. The Georgia railroad traverses it. The surface is diversified, and the soil good. Iron, gold, and other minerals are found. Capital, Conyers.