242

STARCH.

silver may be first added, and then solution of gold in aqua regia , in proper p r jpor-tions. The precipitate to he mixed with flux and fused.

STARCH. In January, 1839, M. Pierre Isidore Verduer obtained " patent formaking starch, the chief object of which was to obtain the gluten of the wher.t in a purestate, as a suitable ingredient in making bread, biscuits, &c. He works wheat flourinto dough by a machine, kneads it, washes out the starch by streams of cold water,a process long known to the chemist, and purifies the starch by fermentation of thesuperjacent water. I can see nothing new in his specification.

Mr. Jones’s patent, of date April, 1840, is based upon the purification of the starchof rice and other farinaceous matters, by means of caustic alkali. He macerates 100lbs. of ground rice in 100 gallons of a solution composed of 200 grains of caustic sodaor potash to a gallon of water, stirs it gradually, till the whole be well mixed ; after 24hours, draws off the superjacent liquid solution of gluten in alkali, treats the starchydeposite with a fresh quantity of weak caustic ley, and thus repeatedly, till the starchbecomes white and pure. The rice before being ground is steeped for sometime in alike caustic ley, drained, dried, and sent to the mill.

Starch is made from wheat flour in a like way. The gluten may be recovered for use, bysaturating the alkaline solution with sulphuric acid, washing and drying the precipitate.

In June, 1841, Mr. W. T. Berger obtained a patent for manufacturing starch by theagency of an alkaline salt upon rice. He prefers the carbonates of potash and soda.

Mr. James Colman, by his patent invention of December, 1841, makes starch fromground maize or Indian corn, by the agency either of the ordinary process of steepingand fermenting, or of caustic or carbonated alkaline leys. He also proposes to em-ploy dilute muriatic acid to purify the starchy matter from gluten, &c .—See Newton’sJournal , C. S. xix. 246 ; xx. 184? 188; and xxi. 173.

The manufacture of potato flour ( fecule ) or starch in France and Holland has beeneconomized to such a degree that they supply this country with it, at the rate of 8s. or10s. a hundredweight. Fig. 158 represents in section the powerful and ingenious

mechanical grater, or rasp (rape),.now used in France : a a, is the canal, or Palong which the previously well-washed potatoes descend; b 6, is the grater, ^^g^ortof a wooden cylinder, on whose round surface circular saw rings of steel, wi ^sharp teeth, are planted pretty close together. The greater the velocity ° te0 fcylinder the finer is the pulp. A cylinder 20 inches in diameter revolves at tne {0 _from 600 to 900 times in a minute, and it will convert into pulp from 14 to