EARLY METHODS OF SALTPETER PRODUCTION PAUL C. ZIEMKE Oak Ridge, Tennessee
r
H I S T O R Y is repeating itself in the present plan to stock-pile scarce minerals received from foreign nations through the Xarshall Plan. World War I1 taught us an expensive lesson as we found ourselves cut off from strat,egic items of many kinds, including the precious uranium ores. If the War Emergency Board has its way, we will not be caught napping again. Our pioneer forefathers also learned the hard way. The War of 1812 and it,s drastic embargo was forced on them t,hrough the hitter struggle between Napoleon and Great Britain. Britain, when hostilities broke out, quickly used her age-old weapon of embargo against us before we drove up prices and depleted the market of scarce materials. Warfare of that early day was strictly a blackpowder operation, an important ingredient of which was saltpeter (sodium nitrate). We had a fair supply of sulfur and an excellent source of charcoal in the form of limitless hardwood forests, yet our saltpeter supply had come from abroad, primarily as ship ballast. The search was on in full force for salt springs or deposits of nitrous earth from which the valuable chemical could be extracted in quantity. Just ~ h found o the saltpeter in the Great Mammoth Cave in Kentucky is not definitely known, but early notes disclose t,hat its presence there zoomed up the price of the land to almost astronomical figures. When war broke out the property changed hands three times in one day. The first sale of 200 acres brought $116; the second, $400; and the final deal of the day, a purchase involving only 156 acres of the orginal tract, was closed for $3000. A bit of work with the pencil
up through countless ages by swarms of hats that nnmbered well into the millions. The large openings in the cave made possible the use of oxcarts for the hauling of the peter dirt from the larger rooms to the refining vats, also located in the cave. The smaller caves xere exploited by the use of crude, wooden--!T-heeledharrow t.hat brought the dirt to the main haulage avenues. Cumbersome, inefficient lighting was used in the form of pine knots, whale oil lamps, and tallow candles. Since the caves mere chilly to sit in during meal time or rest periods, the miners huddled around wood fires in their slreatdampened clothes. Wierd indeed must. have been the sight of the miners, mostly xegroes, as they drove the oxcart,s, xheds squealing, through the dimly lit suhterranean passages and tortuous turns. Just a short distance from the entrance, pits mere dug for the leachers, constructed ~vithleaching tanks of pitch-jointed plank. The trunks of cedar or tamarack trees, approximately six inches in diameter, were bored through half-way from opposite ends to form pipes having hell joints, not unlike our present castiron water and gas mains. Considering that these crude pipes measured 20 feet in length, it is most remarkable horn straight the early craftsmen were able t,o guide their long, hand-made augers to have the two bores meet exactly in lines. The thin ends, occasioned by the removal of wood to shape the bell and spigot ends, were reinforced wit,h bands of strap iron, shrunk on while hot. These effective mood pipes were laid to surface springs to supply water for the leaching tanks farther
later. Early records indicate that two promoters from Philadelphia, Messrs. Gratz and Wilkins, were reported to have accumulated a fortune through the sale of Mammot,h Cave salt~eter. Their resident r e ~ r e sentative was Mr. ~ r c h i b a l dMiller who managed'the reduction plant for the elimination of undesired minerals present in the crude deposit. Visitors to the cave may still see the well-preserved installations where with the crudest of implements the
I
entirely the result of gradual decomposition of the native minerals inherent in the limestone hut, like the vast guano beds off the coast of Chile, &as built
I
466
I A
~M
. ~ ~ skeleton ~ L ~ ' round ~~ crushed ~ ~ In cave
SEPTEMBER, 1952
vats Used in Leachins operation
down in the cave. Main supports consisted of pillars of limestone piled in "dry wall" fashion without the use of mortar. Each pillar was arranged to support two wood lines, one below the other. The upper line pitched down hill to the leaching operations and the lower one was on a grade to return the saline solution to the surface. The feat was accomplished by hand pumping the solution to an elevated tank, establishing the static head required to force it to the evaporators. Today's visitors to this National Park may still see the well defined ox-cart ruts in the cave floor, since the unchanging temperature has preserved them through the gradual hardening of the spent or lixiviated slimes removed from the leaching tanks. The smoke-smudged walls and ceiling, too, remain to indicate the scene of the feverish activities carried on. The chemist and engineer will marvel a t the ingenuity displayed by the craftsmen in developing the maze of drainage troughs under the vats. They con-
sist of several layers of bored wood pipes, carefully split into halves, or what appears to be natural hollom logs with dry rot scooped out to form troughs by careful splitting. The top layer appears to he a layer of upper-half circles, while the succeeding layer was a row of lower-half circles. The clever feature about this unique construction was the fact that their centers were off the vertical which permitted the lixiviated dirt to settle out of the solution and remain behind. The saline solution upon arrival at the surface (cave entrance) was handled by a bucket brigade to raise it to an elevated wood tank. From there it flowed to concent,rators consisting of open iron vats set up on stone piers above wood fires. The enriched solut,ion Tvas drawn off through a series of troughs filled with wood ashes which added the desired quantity of potassium, an essential ingredient in the making of gun powder. Secondary boiling further concentrated the liquid, after which it was allowed t o cool and crystallize. Shipment was made in light cooperage. Horse and ox-drawn wagons hauled it to the warehouse at Green River for evenha1 transfer to the Ohio River and thence to Pittsburgh and the black powder industry of the Atlantic coast. With the cessation of hostilities the operations soon fell into decline as foreign salt,peter again Tvas available, especially vast shipments of nitrates from the open pits of Chile. Although more than a century has elapsed since those pioneers labored by the light of pine knots and flickering grease lamps to produce a strategic war material, their installations still remain intact as if they had been left there only yesterday. As though to guard them from vandalism, not far removed is the mumified form of yet another miner, an aborigine, the "Warrior Mummy" of untold centuries ago, caught in t,he fall of a huge boulder as he labored to chip out a bit of decorative gypsum from the all ~vith a crude mussel-shell spoon.
A recently designed French medal in bronze (68 mm.) on Energie atomique by the French medalist A. Galtie. It may be purchased from the Administration des Monnaies et MBdailles, Paris.-Herbert S. Klielcstein, Edgar Fahs Smzth Collection in the History of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania.
