884 STARCH 



STAMPS. See DRESSING OF ORES. 



STANItf.ft.TE AND STATJNITE OF POTASH AND SODA. Stannates 



and stannites of alkalis are valuable mordants. For the stannato of soda, 22 Ibs. of 

 caustic soda are first put into an iron crucible, heated to a low red heat, till the 

 hydrate be produced ; to which 8 Ibs. of nitrate of soda and 4 Ibs. of common salt are 

 introduced. When the mixture is at a fluxing heat, 10 Ibs. of feathered block-tin are 

 added, and it is stirred with an iron rod. The mass now becomes dark coloured and 

 pasty, and ammonia is given off (the tin decomposing the water of the hydrated soda 

 and part of the nitrate of soda). The stirring is continued, as well as the heat, till 

 deflagration takes place, and the mass becomes red hot and pasty. This product is 

 stannate of soda. It may be purified by solution and crystallisation. 



Stannite of soda is made by putting 4 Ibs. of common salt, 18 Ibs. of caustic 

 soda, and 4 Ibs. of feathered block-tin into a hot iron crucible over a fire, and stirring 

 and boiling to dryness, and as long as ammonia is given off. What remains is stan- 

 nite of soda. 



To produce the tin-preparing liquour, 3 Ibs. of stannate of soda are dissolved in 

 1 gallon of boiling water, and 3 gallons or more of cold water, to bring it to the 

 required strength. The stannite of soda is treated in the same way. 



The process of Mr. James Young is much more recent, and presents a very 

 beautiful application of science. Instead of reducing metallic tin from the ore, and 

 oxidating the metal again to form the stannic acid at the expense of nitric acid, Mr. 

 Young takes the native peroxide of tin itself, and fuses it with soda. The iron and 

 other foreign metals present in the ore are insoluble in the alkali, so that by solution 

 of the fused mass in water, a pure stannate of soda is obtained at once. It is crys- 

 tallised by evaporation, and obtained in efflorescent crystals containing nine equiva- 

 lents of water. 



STARCH (Amidon, Fecule, Fr. ; StarJce, Ger.) is a white pulverulent substance, 

 composed of microscopic spheroids, which are bags containing the amylaceous 

 matter. It exists in a great many different plants, and varies in the form and size of 

 its microscopic particles. As found in some plants, it consists of spherical particles 

 J^th of an inch in diameter ; and in others of ovoid particles, g^th or ^th of an 

 inch. It occurs : 1. In the seeds of all the acotyledonous plants, among which are 

 the several species of corn, and those of other Graminece. 2. In the round perennial 

 tap roots, which shoot up an annual stem ; in the tuberose roots, such as potatoes, the 

 Convolvulus batatas and C. edidis, the Helianthus tuberosus, the Jatropha manihot, &c., 

 which contain a great quantity of it. 3. In the stems of several monocotyledonous 

 plants, especially of the palm tribe, whence sago comes ; but it is very rarely found 

 in the stems and branches of the dicotyledonous plants. 4. It occurs in many species 

 of lichen. Three kinds of starch have been distinguished by chemists; that of 

 wheat, that called inuline, and lichen-starch. These three agree in being insoluble in 

 cold water, alcohol, ether, and oils, and in being converted into sugar by either 

 dilute sulphuric acid or diastase. The main difference between them consists in their 

 habitudes with water and iodine. The first forms with hot water a mucilaginous 

 solution, which constitutes, when cold, the paste of the laundress, and is tinged blue 

 by iodine ; the second forms a granular precipitate, when its solution in boiling-hot 

 water is suffered to cool, which is tinged yellow by iodine; the third affords, by 

 cooling the concentrated solution, a gelatinous mass, with a clear liquid floating over 

 it, that contains little starch. Its jelly becomes brown-grey with iodine. 



Ordinary Starch. This may be extracted from the following grains: Wheat, 

 rye, barley, oats, buckwheat, rice, maize, millet, spelt ; from the siliquose seeds, as 

 peas, beans, lentiles, &c. ; from tuberous and tap roots, as those of the potato, the 

 orchis, manioc, arrow-root, batata, &c. Different kinds of corn yield very variable 

 quantities of starch. Wheat differs in this respect, according to the varieties of the 

 plant, as well as the soil, manure, season, and climate. See BREAD. 



Wheat partly damaged by long keeping in granaries may be employed for the 

 manufacture of starch, as this constituent suffers less injury than the gluten; and 

 it may be used either in the ground or unground state. 



With unground wheat. The wheat being sifted clean, is to be put into cisterns, 

 covered with soft water, and left to steep till it becomes swollen and so soft as to 

 be easily crushed between the fingers. It is now to be taken out, and immersed in 

 clear water of a temperature equal to that of malting-barley, whence it is to be trans- 

 ferred into bags, which are placed in a wooden chest containing some water, and 

 exposed to strong pressure. The water rendered milky by the starch being drawn 

 off by a tap, fresh water is poured in, and the pressure is repeated. Instead of 

 putting the swollen grain into bags, some prefer to grind it under vertical edge- 

 etones, or between a ptiir of horizontal rollers, and then to lay it in a cistern, and 

 separate the starchy liquor by elutriation with successive quantities of water well 



