The refining of camphor in Europe was loug confined to Venice ; but it is now carried on largely in England, Holland, Hamburg, and Paris, the product being much finer and purer than that obtained by the crude processes of the East. In England, the operation is performed as follows:— The impure camphor is broken up, mixed with 3 to 5 per cent. of highly slaked lime, and 1 to 2 per cent. of iron filings. These are well sifted, and introduced through a funnel into the necks of a series of bomboloes, flasks of thin flint glass, with flat bottoms and short necks, the name being of Venetian origin. These are placed in sand baths, which aro heated by dishes of fusible metal, kept at the proper temperature by means of a furnace outside the room. The object of this is to avoid the necessity for bringing fire into the presence of the very inflammable vapour given off by the camphor. When filled and in place, the flasks are covered with sand to the neck, and rapidly heated to 120°-190° (248°-371° F.) for half an hour, to expel the water. The temperature is then gradually raised to about 201° (400° F.), and maintained at this point for about twenty-four hours. As the temperature increases, the camphor softens, and at last melts. When the mass has become fluid, the sand is removed from the upper part of the flask, and a paper stopper is put into the neck to partially close it. The heat is then carefully preserved at a point sufficient to sublime the camphor, but not to remelt it, so that it re-solidifies on the interior upper part of the flask as a semi-transparent cako, leaving all impurities behind. The temperature of the refining room is about 65° (150° F.), the air being very dry, and highly charged with camphor. To diminish the escape of camphor vapour during the process, each bombolo is covered with a glass shade; another use of this is to exclude the air, whose presence would make the sublimed camphor opaque instead of translucent. The whole process lasts about forty-eight hours; it requires the greatest attention and experience, on account of the inflammability of the substance, and the necessity for regulating the temperature very nicely, so that the sublimate may be deposited, not merely in loose crystals, but in compact cakes. When the sublimation is completed, the flasks are taken out, and cold wat,er is sprinkled on them. This causes them to break, and the now pure camphor is removed from them in the form of large bowls or concave cakes, like gigantic quoits, about 10 or 12 in. in diameter, 3 in. thick, and weighing 9 to 121b. The bomboloes weigh about 1 lb. each, and measure about 12 iu. across. Sometimes a little charcoal or sand is added to the lime, and, when sulphur is present, iron filings are a useful adjunct.
Following is an account of the Dutch method of purifying. To every pound of camphor, is added about 2 oz. of lime ; the two are well mixed in a mortar or small mill, and about lb. of the mixture is put into each still. These consist of black glass flasks of round form and with long necks, a certain number being placed in a row on sand baths heated by a furnace beneath. They are buried some inches in the sand, and tightly stoppered with cotton or tow. Under each sand bath is a furnace and ashpit. To commence with, a gentle fire is made so as to liquefy the camphor. The steam rises into the neck, and would condense aud fall back into the still in drops if it were not prevented. Each still is furnished with a conical hood or cap of tinned iron, which is covered with warm sand, and in which the vapour collects. In this way, all danger of breaking the still, by drops of camphor falling back, is avoided. When the camphor is fluid enough, and all the moisture has been eliminated from it, the sand is removed from the hood, or the latter is replaced by another, having a hole in the middle, to admit an frau implement for stirring up the mas.s in the still. As the camphor evaporates, it condenses again on the sides of the cap, and there
forms a transparent mass. All outer air must be rigidly excluded. When the hoods have been exchanged, and the moment the sublimation begins, the fire is reduced. The temperature is maintained at the proper degree for a whole day. From time to time, the workman removes the cap and the cotton stopper, in order to stir up the stuff at the bottom of the still with an iron tool, and to keep the passage of the neck open, as ihe condensing camphor has a tendency to choke it up. Towards the end of the operation, the cap is altogether removed. The end is known to have arrived when the camphor collected on the sides begins to melt. The flasks are then taken from the sand baths, cooled and broken, to extract the mass of camphor ; this is then wrapped up in blue paper. Much camphor still remains in the fragments of the flasks, and as it would be too troublesome to scrape it off, the pieces are thrown into a very deep copper still, which is covered, with a circular copper hood, and placed over a fire. The camphor collects as before around the hood, and is then easily removed. During the sublimation in the flasks, the temperature is maintained at 120° 248° F.) for half an hour, and is then raised to 190° (374° F.) ; at this point, the neck viill be coated with moisture, which must be removed by inserting a sponge on a flexible stick. A temperature of 190° to 196° (371° to 385° F.) will melt all the camphor in three and a half hours. The residue is sublimed in a cast-iron vessel, and the little product obtained is thrown in with the next lot of raw camphor.
Uses.—The applications of common camphor are restricted almost solely to medicinal and antiseptic purposes.
Borneo Camphor; Malay Camphor ; Borneole ; Camphyl Alcohol; or Kapur Barus.—Thie is quite distinct from the camphor of western commerce. It is expressed by the formula C20 HIs 0,, or two additional equivalents of hydrogen. It fuses and boils at higher tem peratures than common camphor, is harder and more brittle, of greater specific gravity (1'009), less volatile, and doos not crystallize on the interior of a bottle when kept. Its crystals are coarse and resinous looking, about in. broad on the faces, and of different form from the ordinary drug. In the chief feature, viz. aroma, it closely resembles common camphor, but is less pungent.
It is the product of a magnificent forest tree, the Dryobalanops °amphora, or aromatica, which often reaches a height of 90 or 100 ft. to the first branches, overtopping all its neighbours, and presenting a handsome head of dense foliage. The trunk often attains a girth of 17 to 18 ft. According to the natives of the Malay Archipelago, there are three kinds of this tree, named respectively mailanguan, marbin tungan, and marbin targan, from the outward colour of the bark, which is sometimes yellow, sometimes black, and often red. The bark is rough and grooved, and overgrown with moss. The leaves are dark-green, oblong-oval, and pointed ; they smell of camphor, and are hard and tough. The exterior form of the fruit is very like the acorn ; but it has around it five petals, placed somewhat apart, and the whole much resembles a lily. The tree flourishes to greatest perfection between the altitudes of 250 aud 400 ft. above sea level ; but is also found in dry (that is, not marshy) places near the sea coast, and rarely at an elevation of 1000 ft. Its chief habitat appears to be the extensive bush of the Bette country, on the west coast of Sumatra, north of Ayer Bangie ; it is also found, in the mountains of Santubong, 1Vlarang Sundu, and Sugony; in Lahuan ; in all the northern parts of Borneo, and it is said to be particularly abundant in the country of the Kyans, on the upper reaches of the Bintulu and Rejang rivers.