ing the gluten, is decanted, and the sediment is treated in like manner with another solution of carbonate of soda of the same quantity and strength as before. The sediment is next mixed with two hundred and twenty-four gallons of water, and the mixture is pumped slowly into a long vat divided into three or more compartments. When the first compartment is full, the liquor flows over the partition into the second; and so on until the vat is filled, and the liquor runs out at the farther end. By this arrangement, the heavy gritty particles with which the starch is mixed are separated in the different compartments, and the starch passes from the vat in a pure state. The liquor is allowed to stand, and the starch is separated and boxed in the ordinary manner. An additional quantity of starch may be obtained by collecting the gritty sediments in the different compartments, and treating them in like manner with another quantity of the solution of carbonate of soda. Another method of preparing starch from rice has been devised and patented by Mr. James Colman, which consists in the application of a dilute acid as a solvent for the gluten, the starch remaining undissolved. The acid to which preference is given is hydrochloric or muriatic. The rice, having been softened by digestion in water and reduced to a pulp, is mixed with dilute muriatic acid, composed of three quarters of an ounce, or one ounce, of strong acid to a gallon of water, in the proportion of two pounds of rice to a gallon of dilute acid, and is allowed to digest during five days, being stirred every four hours. The mixture is next left to settle for eighteen hours; after which the liquor is decanted, and the sediment treated in a similar manner with another quantity of acid liquor, somewhat more dilute than the former. The starch thus obtained as the sediment is washed through sieves, and dried, as usual. § IV. PREPARATION OF STARCH FROM THE POTATOE. The manufacture of starch from potatoes is carried on to a very large extent in France; not less than twelve millions of kilogrammes, or about twenty-six millions five hundred thousand pounds, being produced there annually. In this country, also, potatoe starch has of late been manufactured in considerable quantity, and sold for food under a variety of imposing names. The basis of " Bright's Nutritive Farina" is potatoe starch, carefully prepared and slightly aromatized and coloured. The Prince of Wales' Food," prepared by the Patent Farina Company, "Anderson's Soluble Starch," and some of that sold as "Indian Corn Starch," are merely potatoe starch with various slight additions to impart a flavour. The " potatoe flour" met with in some Italian warehouses in London is the same substance (Dr. Pereira). The composition of the potatoe has often been made the subject of chemical investigation. The existence of starch in the tuber was discovered about Variety of potatoe. the middle of last century, and announced in the Swedish Transactions with a simple process for its preparation. Pearson, Lampadius, and Henry junr. have executed analyses of different kinds of potatoes; but the results which deserve most confidence are those obtained by Einhof. The different varieties contain the same ingredients, but the proportions vary considerably, as may be seen by the following table. The first six results were obtained by Einhof; the seventh by Henry, and the remainder by Lampadius. COMPOSITION OF THE POTATOE. An The potatoe contains some substances, however, which are not included in the preceding table. extended analysis by Michaëlis (in 1837) of a red potatoe, richer in starch than the ordinary varieties, gave the following results: Citrates, silicates, and phosphates of potash, soda, The starchy fibrin or amylaceous fibrin of the potatoe differs essentially from the fibrous matter of most plants. It consists for the most part of a substance analogous to common starch in many of its properties. Asparagin is a white, soluble, crystallizable substance discovered in the juice of the asparagus by Robiquet in 1805. It was first detected in the potatoe by Vauquelin. The shoots of germinating potatoes were discovered by M. Baup to contain a small quantity of solanine, an extremely poisonous substance which constitutes the active ingredient of the solanum dulcamara (deadly night-shade). It is contained in several species of solanum. The observation of Baup has been confirmed by Otto of Brunswick, who found the germs developed in the spring to contain a very sensible quantity of this poisonous principle. The tuber itself sometimes contains a small quantity, which it readily yields to water (Buchner). If germinated potatoes (with the germs remaining) are employed in the preparation of po tatoe spirit, the residue contains so large a quantity of solanine, that cattle fed with it become paralyzed in their posterior extremities. From the table inserted at page 125, it is evident that different varieties of the potatoe contain very different quantities of starch. The following table, drawn up from the experiments of Mr. W. Skrimshire, shews the proportion of starch, &c. obtained from five pounds of various kinds of fresh potatoes. The starch was separated by grating the potatoe and washing the pulp on a searce (Thomson's Organic Chemistry, Vegetables). White kidney. STARCH IN POTATOES. Total 30 90 22 0 60 60 30 52 0 3 14 3 15 4 22 3 14 3 oz. lb. oz. lb. oz. lb. 02. 06/0 820 80 8 2 0 0 0 0 0 12 610 62050 14 4 04 23 15 15 05 050 5 0 5 0 5050 5 0 *This is by no means a rare instance of the contiguity of an active poison and an amylaceous substance. In the tuber of Arum, for instance, starch is associated with an acrid principle which gives it a purgative property; and in the root of the manioc, from which tapioca and cassava are prepared, the starch is accompanied by prussic acid. But, fortunately, the poisonous matters may always be removed by |