History of the Confederate Powder Works

by George Washington Rains

The centre space of the floor, about thirty-six feet square, was sunk four feet to allow water from the canal to pass around the bottoms of two of the large evaporating pans, which were placed therein near the centre of this area, and nine feet apart; these were used for a special purpose.

The best quality of gunpowder can only be made from the purest [p13] saltpetre; the impurities of the crude material are mainly deliquescent salts, which rapidly deteriorate the strength of the powder by the moisture absorbed. To refine more or less the rough saltpetre of commerce is then a necessity even in producing an inferior article.

To carry the refining process to the extent of nearly absolute purity, required several successive crystallizations and washings, involving a large amount of manual labor in the manipulation, and consuming much time. This was particularly the case in the very large amount of saltpetre, eight to ten thousand pounds per day, used by the Works, the refining of which would demand extended buildings and apparatus, as well as requiring a large number of operatives. Hence, it became desirable to devise methods by which hand labor could be superseded by motive power and machinery; in this I was entirely successful. Thus, in the operations of filling the various boiling pans with water or mother-liquor; the transference of the boiling solution of saltpetre to the draining trough, and thence to the crystallizing machines; the cooling down of the solutions, and their constant agitation to break up the forming crystals into fine particles, and transferring of these to an adjoining tank; the washing of the crystallized mass, and the subsequent removal of the mother-liquor and wash-waters, were all accomplished by machinery, with the assistance of two or three workmen only.

The saving of time and labor was thus manifest, and the rapidity with which these operations were performed, permitted a double and triple process in a single day; thus allowing a degree of purity in the product of refined saltpetre not attained in any other refinery. Its purity was such generally, that there was not the one-hundred-thousandth part of chlorides left in the salt.

Of the machinery used, the most important was a bronze revolving wheel with buckets attached to the periphery, which worked into an iron pan or kettle, whose section was an arc of a circle; the buckets grazed the surface of the bottom and sides of this kettle, the bottom of the latter being immersed in a current of cold water. The hot filtered solution of the crude saltpetre was received into this kettle, and thus kept into a state of rapid agitation, the effect being to produce a wet mass of minute crystals, which, as fast as formed, were taken up by the sharp edged buckets, and lifted sufficiently high to pour into a receiving vat; this permitted the liquid part to flow back [p14] into the kettle. By this means in a short time the entire mass of fine deposited crystals from the rapidly cooled liquid, were removed to the vat. When the operation was completed the remaining liquid in the kettle was by the revolutions of the bronze wheel, discharged into one of the eight capacious cisterns below the floor; there were two of these machines employed.

The facility for work which this apparatus, with the other mechanical appliances afforded, enabled the refinery to carry the purification of the saltpetre beyond that of the most celebrated powder factories.

Adjoining this part of the Works was the Sulphur Refinery, where this material was prepared from the crude stock, and made ready for the incorporating process. About one hundred and thirty tons of very impure sulphur had been received from Louisiana, for the use of the Powder Works; it had been purchased before the war by the planters for use in the making of sugar, and was bought up by the Confederate officers. The best quality of gunpowder has its sulphur chemically pure, which could be demonstrated by showing no trace of acid when powdered and boiled in water, and should entirely evaporate on a piece of glass when heated, leaving no stain. This can only be accomplished practically by distillation. The crude article was melted and poured into upright, thick wooden boxes five feet high and ten inches square at the bottom, tapering upwards; when cold the earthy matters would be found in the lower portion by subsidence, leaving about three feet apparently pure. This was broken off and placed into two kettles of suitable form and dimensions, having furnaces; the tops of these kettles were connected by a bent iron pipe to an enlarged portion, which was surrounded with water. On the application of heat the sulphur vaporized, and passing over through the pipe was condensed in the cooled portion, whence it trickled in a thick stream into a receiving vessel below; the first portions being rejected, the remainder was of a beautiful citron yellow when cold, and entirely pure.

Unlike the refined saltpetre, the purified sulphur had to be pulverized and bolted like flour before being used. The former was done by two iron wheels of twelve inches face and five feet diameter, weighing six hundred pounds each, revolving on a bed circle of iron like the incorporating rollers; the later was accomplished by bolters, but when these were worn out and could not be replaced, for want [p15] of the silk cloth, which was not to be found in the South, necessity compelled me to devise a different, and as it proved, a superior method.

The pulverized sulphur was placed in barrels or cylinders, with hollow axles, which were made to revolve slowly by machinery; there were ledges on the interior which caused the sulphur to be lifted and poured over as the cylinders revolved; a light current of air was blown through each, entering the hollow axle at one end, and passing out through the axle at the other end, which led into an adjoining room; there the impalpable sulphur dust was deposited, much finer than by the usual bolting process.

Adjoining this Refinery was the department in which charcoal was made and pulverized. Charcoal for gunpowder has to be made of a porous fine-grained wood, having very little ashes when burned; willow is generally preferred, and was used at first in the Powder Works, but the exigencies of the war taking away those who would ordinarily have supplied it, rendered it impracticable to procure a sufficient quantity. Recourse was had to the cotton wood, which was abundant; on trial its charcoal was found fully equal to that of the willow for the purpose, and was, thereafter always used.