STARCH 887 



Starch from certain foreign plants. 1. From the pith of the Sago Palm. See SAGO. 



2. From the roots of the Maranta arundinacea, of Jamaica, the Bahamas, and other 

 West India Islands, the powder called arrow-root is obtained, by a process analogous 

 to that for making potato-starch. See ARROW-ROOT. 



3. From the roots of the manioc, which also grows in the West Indies, as well as in 

 Africa, the cassava is procured, by a similar process. The juice of this plant is 

 poisonous, from which the wholesome starch is deposited. When dried with stirring 

 upon hot iron plates, it agglomerates into small lumps, called tapioca ; being a gummy 

 fecula. See CASSAVA. 



The characters of the different varieties of starch can be learnt only from micro- 

 scopic observation ; by which means also their sophistication or admixture may be 

 readily ascertained. 



Starch, from whatever source obtained, is a white soft powder, which feels crispy, 

 like flowers of sulphur, when pressed between the fingers ; it is destitute of taste and 

 smell, unchangeable in the atmosphere, and has a specific gravity of 1'53. 



For the saccharine changes which starch undergoes by the action of diastase, see 

 FERMENTATION. 



Lichcnine, a species of starch obtained from Iceland moss (Cetraria islandica), as 

 well as Inuline, from elecampane (Imda Helenium), are rather objects of chemical 

 curiosity than of manufactures. See LICHENS. 



There is a kind of starch made in order to be converted into gum for the calico- 

 printer. This conversion having been first made upon the great scale in this country, 

 has occasioned the product to be called British gum. The following is the process 

 pursued in a large and well-conducted establishment near Manchester : A range of 

 four wooden cisterns, each about 7 or 8 feet square and 4 feet deep, is provided. 

 Into each of them 2,000 gallons of water being introduced, 12^ loads of flour are 

 stirred in. The mixture is set to ferment upon old leaven left at the bottom of the 

 backs, during 2 or 3 days. The contents are then stirred up, and pumped off into 

 3 stone cisterns, 7 feet square and 4 feet deep ; as much water being added, with 

 agitation, as will fill the cisterns to the brim. In the course of 24 hours the starch 

 forms a firm deposit at the bottom ; and the water, is then syphoned off. The gluten 

 is next scraped from the surface, and the starch is transferred into wooden boxes, 

 pierced with holes, which may be lined with coarse cloth, or not, at the pleasure of 

 the operator. 



The starch, cut into cubical masses, is put into iron trays, and set to dry in a large 

 apartment, two stories high, heated by a horizontal cylinder of cast iron traversed by 

 the flame of a furnace. The drying occupies two days. It is now ready for con- 

 version into gum, for which purpose it is put into oblong trays of sheet iron, and 

 heated to the temperature of 300 Fahr. in a cast-iron oven, which holds four of these 

 trays. Here it concretes into irregular semi-transparent yellow-brown lumps, which 

 are ground into fine flour between mill-stones, and in this state brought to the 

 market. In this roasted starch, the vesicles being burst, their contents become 

 soluble in cold water. British gum is not convertible into sugar, as starch is, by the 

 action of dilute sulphuric acid ; nor into mucic acid, by nitric acid ; but into the 

 oxalic; and it is tinged purple red by iodine. It is composed, in 100 parts, of 35'7 

 carbon, 6'2 hydrogen, and 58 - l oxygen ; while starch is composed of 43'5 carbon, 

 6'8 hydrogen, and 49'7 oxygen. See DEXTRINE. 



Manufacture of Starch from Rice, $c. Starch prepared from rice or maize by alkali 

 is said not to require boiling a point of great importance in its use; and, being less 

 hygrometric than wheat-starch, retains a more permanent stiffness and glazn. The rough 

 starch obtained in the process is valuable for feeding purposes, and for stiffening coarse 

 fabrics. 



Fig. 1894 represents in section the powerful and ingenious mechanical grater, or 

 rasp (rape], now used in France, a a is the canal, or spout, along which the 

 previously well-washed potatoes descend ; b b is the grater, composed of a wooden 

 cylinder, on whose round surface circular saw rings of steel, with short sharp teeth, 

 are planted pretty close together. The greater the velocity of the cylinder, the 

 finer is the pulp. A cylinder 20 inches in diameter revolves at the rate of from 600 

 to 900 times a minute, and it will convert into pulp from 14 to 15 hectolitres (about 

 300 imperial gallons) of potatoes in an hour. Potatoes contain from 15 to 22 percent, 

 of dry fecula. The pulp, after leaving the rasp, passes directly into the apparatus 

 for the preparation of the starch, c is a wooden hopper for receiving the falling 

 pulp, with a trap-door, d, at bottom. K, is the cylinder-sieve of M. St.-Etienne ; /, a 

 pipe ending in a rose-spout, which delivers the water requisite for washing the pulp, 

 and extracting the starch from it ; g g, a diaphragm of wire-cloth, with small 

 meshes, on which the pulp is exposed to the action of the brushes, i i, moving with 

 great speed, whereby it gives out its starchy matter, which is thrown out by a side 



