In the Greenland fisheries, the blubber produced from whales is cut into small pieces and packed in casks, and when it arrives in England, it is in a putrid state. It is started into a large receiver, containing about twenty tons. There is a semicircular wire grating in the side of the back, close to the bottom, through which the fluid parts drain, the wires being sufficiently close to prevent the pieces of blubber from passing. The oil, as it drains through this grate, is to be conducted by means of a copper pipe into another back, containing about the same quantity. When this receiver is full, it is left two or three hours to settle, and then conducted by a sluice into a copper heated by a fire in the usual way. The oil is stirred until it has acquired heat equal to 225° Fahrenheit; this destroys the rancidity, and causes the mucilaginous matter to settle at the bottom. As soon as the oil has received the before-mentioned heat, the fire must be drawn, and about half a tun of cold water pumped upon the surface of the oil, which descending cools the bottom of the copper, and prevents the adhesion of the mucilaginous matter thereto.
The oil may then be run off into coolers, and when quite cold be drawn off into casks for use.
Whale oil may, however, be purified, by a system of filtering, without the aid of heat. For this purpose, the long cylindrical bags used by the sugar refiners are sometimes employed. These are about 40 inches long, and lb inches wide, their mouths being distended by wooden hoops. They are made of stout canvass, lined with flannel; and between these two substances a packing of powdered charcoal, or bone black, is quilted throughout in a stratum of about an inch thick, which detains the gelatinous matter, and other impurities This oil is received in a cistern, containing water at the bottom to the depth of about 6 inches, in each 20 gallons of which is dissolved about an ounce of blue vitriol, which nearly divests it of the impurities that escaped the filter, and of the unpleasant odour it had before. But it is further cleansed by a second washing, in another cistern of water, wherein it is allowed to remain for several days, and then filtered several times through charcoal; and lastly, by filtering through canvass and flannel without charcoal.
Amongst the numerous papers on this subject that have appeared in the scientific journals, we select the following process, recommended by Mr. Dossie, where the utmost purity is required, and particularly for the woollen manufacture.
"Take a gallon of crude stinking oil, and mix with it a quarter of an ounce of lime slaked in the air, and half a pint of water; stir them together, and when they have stood some hours, add a pint of water, and two ounces of pearl ashes, and place them over a fire that will just keep them simmering, till the oil appears of a light amber colour, and has lost all smell, except a hot, greasy, soaplike scent. Then superadd half a pint of water, in which an ounce of salt has been dissolved; and having boiled them half an hour, pour them into a proper vessel, and let them stand till the separation of the oil, water, and lime be made, as in the preceding process. Where this operation is performed to prepare oil for the woollen manufacture, the salt may be omitted; but the separation of the lime from the oil will be slower, and a longer boiling will be necessary. If the oil be required yet more pure, treat it after it is separated from the water, etc. according to the second process, with an ounce of chalk, a quarter of an ounce of pearl ashes, and half an ounce of salt."
In the South-Sea fishery, the whalers bring home their oil in casks. In consequence, however, of the wasteful and dangerous nature of the process adopted for obtaining the oil from the blubber, some presses have lately been sent out by the ships to express the oil from the pieces of the blubber that have been boiled, but in which a great quantity of oil still remains. All this oil was formerly allowed to remain in these pieces, called "scraps," and was with them made use of merely as fuel, and burned under the "try-pots " or boilers; but in consequence of the extreme inflammability of the oil, and its great superabundance, serious accidents occurred by the flames issuing from the furnace, and catching the oil in the try-pots. By the use of the subjoined machine (in p. 204) we understand that the danger beforementioned has been obviated, and the oil contained in the scraps, which was before wasted, now forms a sensible portion of a ship's cargo. It is the invention of Mr. John Blythe, an intelligent engineer, of Limehouse.
a a a a a is the frame of the press, consisting of a strong cast-iron bed and head, and wrought-iron jambs, secured at each end by nuts and screws; b is a hollow cylinder, with an iron plate perforated with small holes, resting upon ribs in the bottom of the cast-iron cylinder, as shown at e; c is a snout for allowing the oil to run off; d is a follower, also made of cast iron; / a screw made of wrought iron, and fitted into an internal screw in the wheel g; h is a lever for screwing down the follower, when great speed and hut little pressure is required, i is a bolt which is put in to prevent the wheel g from turning round, which then becomes a box for the screw to work through; when greater pressure is necessary, this bolt is withdrawn, and the power of one or more men applied to the handles j j, which turn an endless screw, and give motion to the wheel, as shown at o; the wheel in its revolution bites upon the underside of the head of the press, and consequently forces the screw downwards, with the increased power of the endless screw and wheel and main screw. The scraps Are put into the cylinder warm, with a mattress, (wicker basket,) ¾ of an inch thick in the bottom, to prevent the hard substance from filling up the holes at e.
After the press is charged, it is set to work by first screwing down with the single power of the screw and lever, and finished by adding the power of the wheel and endless screw.