Tbe 1877 crop of dammar exported from Java was distributed as follows :-8272 piculs (of 135:i lb.) to Holland, 3674 to Singapore, 1050 to France, 736 to the Chaunel for orders, 615 to America, 14 to Italy ; total, 14,361 piculs. The 1878 crop :-4161 to Holland, 2375 to France, 1721 to America, 1345 t,o Singapore, 410 to England, 213 to the Channel for orders ; total, 10,225 piculs. The 1879 crop :-6820 piculs to France, 4413 to England, 2968 to Holland, 1957 to Singapore,1887 to America, 814 to the Chanuel for ordera, 343 to Italy, 262 to Port for orders ; total, 19,464 piculs. The ata,te of Sarawak, in 1879, exported 407 dollars' worth (of 4s. 2d.) to foreign countries. The approximate London market values of the dammars are as follows :— Manilla (called "copal"), 16-65s. a cwt. ; Batavian, 70-115q. ; Singapore, 55-105s.
It rnust be acknowledged that our information concerning the darnmars of the E. Archipelago and their soureca is far from being comprehensive. There are many similar products of that region of which we know practically nothing.
Dextrine, British Gum, Starch-gum, Fruit-gum (Fa., Gommc d' Alsace, Leiogomme, Gommlinc ; GER., _Dextrin, Leiwwn, Sttirkegummi, Starkemeklgummi).—This substance, whose formula, C,211,00,o, is homologous with that of starch, occurs aparsely in many plants, and seems to play an important part in the development of those parts of plants in which a new formation of cells takea place. Its preaenee in various grains (air-dried) amounts to the following percentages :—Wheat, 1.5 ; wheat-bran, 5.52; barley, 6.55; rye-bran. 7.79; malt, 8.23. It is more abundant as a transformation-product of grain-starch in bread, beer, and other substances manufactured from grain ; and is found also in the blood, muscle, spleen, and liver of' animals, particularly graminivorous.
Pure dextrine is a white, amorphous, flavourless and odourless powder, ap. gr. 1.52. It is com pletely soluble iu cold water, forming a glutinous mucilage. Co:nmercial dextrine usually leaves a residue of 12 per cent. or more of unchanged or burnt stare:. It is insoluble in absolute alcohol and in ether. Heated with dilute acids (sulphuric, hydrochloric, or acetic), it is partially trans formed into grepe-sugar. Alone, it is unfermeutable. Heated in the presence of an inert vapour laden with moisture, it is converted into sugar, the amount of glucose thus formed increasing as the starch used is more acetone.
Commercially, the term "dextrine" is restricted to starch-dextrine prepared by the artificial transformation of starch. This may he effected in 3 ways:—(1) By the prolonged roasting of dry starch at a temperature of 200°-275° (392°-527° F.); (2) by heating starch with dilute acids
for short period ; (3) by treating starch with a solution of diastase (malt-extract) at a tempera ture of 60°-75° (140°-167° F.). In all these cases, the formation of a certain quantity of glucose is a necessary accompaniment of the operation. In the industrial manufacture of dextrine, the dual object aimed at is the most complete transformation of the starch into dextriue, with the least possible co-production of glueose. Absolute purity is a matter of minor consideration, the technical application of the material demanding chiefly an article that will paste and thicken well. The stareh employed may be of any origin, and such as is most cheaply and readily pro curable on the spot (see Starch).
In manufacturing dextrine by the roasting process, it is essential that the transformation shall go on evenly and at one temperature. The limits of temperature commonly adopted are 212° and 250° (413r-482° F.), though Payen says that a temperature of 200°-210° (392°-410° F.) produces the most perfectly soluble dextrine. Several methods are adopted for conducting the manufacture at an equable temperature, one of the best being based on the principle of an oil-bath.
This form, adopted by Proudfoot & Co., Manchester, who produce nearly 4 tons daily of dextrine, is shown in Fig. 1171. It is suited to the treatment of wheat-, rice-, and potato-starch, but only produces the article in powder form, not in transparent pieces. The starch is first dried at 80° (176° F.) in an apartment for the purpose; its subseqnent loss of weight in roasting is small, 220 lb. of starch giving 176 lb. of finished dextrine of good quality. The starch is fed in through the oval hopper a. The double-jacketed cylinder b is supplied with well-refined rape-oil up to a gange-cock. A fire is then kindled in the furnace c, the stirrer in the inner receptacle of the cylinder b is put in motion, and the starch, in charges of about 5 cwt., is introduced from the hopper a. The oil rapidly expands by the heat, so as to completely surround the inner cylinder of b. The temperature to which the oil is heated varies with the grade of dextrine required. The roasting is known to be complete when a peculiar decided odonr is emitted at the hopper. The material is then withdrawn into the metallic dish d, about 81 ft. long and 4 ft. wide; the larger pieces are crushed and sifted before being pulverized in the mill e. It is finally placed in a sieve drum or gange-cylinder f, and is then ready for packing.