856 SALTPETRE, NITRATE OF SODA, &c. The terms saltpetre and nitrate are occasionally used by masters of vessels and others as if they were the same. ...
Saltpetre, nitre, or nitrate of potash, is a species of salt found on the surface of the earth. It seldom comes from anywhere except India, usually Calcutta, where the best and purest is shipped; Bombay saltpetre is less pure, has a much smaller crystal, and is of a darker colour. ... It is slightly deliquescent, as much almost as common salt, but is easily "sweated," and becomes damp and liable to damage other cargo through the dampness of a ship's hold, or if stowed with moist goods, such as sugar. ... It is used in the composition of gunpowder, and should not be stowed with inflammable materials, such as oil, tallow, &c.; it is perfectly harmless of itself, but in case of fire, when combined with those articles, produces a compound having all the dangerous properties of gunpowder. The same contingency occurs with sulphur or brimstone; see jute, combustion, general cargo, and sugar. Care should be taken that drainage of saltpetre should not be absorbed by any of the materials mentioned. By steeping fibrous matter, &c. in a solution of this salt, a powerful kind of gunpowder is made. The stains caused by the leakage from saltpetre will continue in the skin of a ship many months after. Dunnage 9 to 12 inches each side of the keelson, and 12 to 15 inches in the bilges, carried well up. When saltpetre, sugar, and rice form the dead-weight, it is recommended to stow the saltpetre in the after hold, to keep the ship in trim and the cabins free from the exhalations of the sugar, which should go in the main hold; rice in the fore hold. Saltpetre ought to be covered with masts to receive bales or cases. At Trieste, when saltpetre appears on the bills of lading as merchandize, the vessel is liable to confiscation and a heavy penalty. Saltpetre is considered one of the most risky articles to deal with in the long list of imported goods, owing to its liability to be washed away by sea-water, while other goods are more or less damaged by it. The underwriters, who will assure against almost any casualty, halt at saltpetre, and will usually assure only against total loss, thus avoiding average of any kind. Saltpetre is generally sold on a guarantee of a "repreaction" not exceeding say 5 per cent; the remainder, say 95 per cent, is pure nitrate of soda. When refined, the refuse of the 5 per cent, is termed petersalt. There is some difficulty in determining the weight of a cubic foot of saltpetre. By experiment good dry 5 per cent. saltpetre weights 25 per cent. more than water, and the English refined saltpetre of commerce 30 per cent; a cubic foot of 5 per cent. rough as imported 75 to 80 lb. when well shaken down. Nitrate of soda is rather heavier than saltpetre.
Transcribed by Lars Bruzelius
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