Gum, British

Starch pyrodextrins and British gums have the abiUty, in aqueous dispersion, to form films capable of bonding like or unlike materials. Thus, they have uses as adhesives for envelopes, postage stamps, and other products. These dextrins are used in glass-fiber siting to protect the extmded fiber from abrasion, and as binders for metal core castings, water color paints, briquettes, and many other composite materials (qv). 

Britischgummi, n. British gum, dextrin, Brockchen, n. small bit, small piece, crumb, brockelig, a. brittle, friable, crumbly, fragile. Brdckeligkeit, /. brittleness, friability, brbckeln, v.t. crumble. 

BRITISH GUM. — Artificial Gum—Torrefied Starch—Dextrin,—Under theso names a modification of stsroh Is known, which is often prepared in the following manner —... 

British gum or dextrin is now mot with in commerce in three distinct forms namely, as a white, brilliant, and pearly powder as a sirapy solution and in the form of exotic gum, in greater or less perfection, either broken into small fragments, or made into rolls of various sizes. 

British gum may he prepared by many other processes than the ono just described. Besides being procured by torre ction, it is also obtainable, either by the use of acids, or by means of diastase. 

A patent was granted in May, 1845, to J. F. Finel, for improvements in the method of treating farinaceous matters for the production of British gum. The modus oper/mdi is as follows —... 

The last-named authority has remarked with reference to British gum prepared by sulphuric acid, that it possesses the disadvantageous property of being deliquescent. This method is, therefore, never employed, as besides this, the products are often colored. He also states that when nitric arid is employed in the preparation of dextrin, it must be perfectly pwe. Commercial nitrio acid, as obtained by the action of oil of vitriol upon nitrats of Soda, always contains a small amount of chlorine and although this element is contained in diminished proportion in the dextrin, it is nevertheless sufficient to considerably lessen the brilliancy of the colors prepared with the dextrin. Several printers upon paper and vegetal tissues have observed this, but have been unable to account for it otherwise than by attributing it to the iaferior quality of the gum. 

Dextrins (pyrodextrins) are made by heating dry starch with or without acid. Since it is a dry process, recovery of water-soluble materials is simpler than with aqueous fluidity and oxidized starches. Depending on reaction conditions, greater or lesser amounts of three reactions will occur (a) hydrolysis (b) transglycosidation and (c) repolymerization. According to which predominates, the product is a white dextrin, a yellow dextrin or a British gum. Like other converted materials, these products offer a way to use higher solids to increase performance. 

Commercial dextrins are specifically the oligomers of starch. White dextrins, so called because of their visual appearance, are produced from a 30-40% suspension under the mildest possible hydrolysis conditions (79-120°C for 3-8 h in 0.2-2% H2S04 or HC1). Yellow dextrins and British gums are the partial hydrolysates at higher time-temperature integrals. Maltodextrins, dextrose equivalent20 5-19, derive from controlled enzyme or acid partial hydrolysis of gelatinized corn starch. The 20-24 dextrose equivalent hydrolysates tire com syrups (Appi, 1991). 

The British gum was made by stripping off water at 140° C. and then heating for 1 hour at 200° C. under nitrogen with strong agitation. 

Avedex British gum Caloreen canary dextrin C Pharm Crystal Gum dextrinum album Primogran W starch gum yellow dextrin white dextrin. 

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