In a mineral state soda has hitherto been found only in combination with some acid.
Common salt ([202]) is a compound of soda with muriatic acid ([29]).
The soda of commerce is obtained from sea-water; and from the ashes of different kinds of plants that grow on the sea-shores, but particularly from that called salsola soda, which is found in great abundance on the coasts of the southern parts of Europe; and from which it has its name. It is sometimes called barilla, from the salsola soda being so denominated in Spain.
This alkali is of essential use in the arts. When melted with flint or sand, it forms glass, and answers much better for this purpose than potash. In conjunction with oil and lime, it is employed in the manufacture of soap; and it is used as a substitute for soap in the cleaning and bleaching of linen, flannels, and worsted goods. If a weak solution of soda be poured into foul bottles, or casks in which wine has long been kept, it will cleanse them. It may also be successfully used for the cleansing of vessels in which milk has become acid. Saddles, bridles, or boot-tops, may be effectually cleaned by means of this liquor, and restored nearly to their original colour and appearance.
The art of soap-boiling may easily be illustrated by the following experiment. Take a piece of quick-lime, slake it gradually by sprinkling on it a sufficient quantity of water. When it is completely slaked, add to it about twenty times its weight of water. To this mixture add two parts, by weight, of common subcarbonat of soda, previously dissolved in a sufficient quantity of water. Boil the whole for about half an hour, strain it through a cloth, and boil it till so much of the water is evaporated that a phial that will contain an ounce of water will hold one ounce, seven pennyweights and a half, of this ley. Then mix in an earthenware pipkin or basin, one part of the ley, with two parts of olive oil. Place the mixture in a gentle heat, capable only of making the liquor simmer, and allow it to simmer, stirring the liquor continually, with a wooden stick, till, by letting a few drops of it fall on a plate, the soap will be found to coagulate, and the water become speedily separated from it. After which, pour out the contents into a cup, and suffer it to cool.—Soap may also be prepared without heat. If one part of the ley be mixed with two parts of olive oil, in a glass or stone ware vessel, and the mixture be stirred, from time to time, with a wooden spoon or spatula, it will become thick, and white; in seven or eight days afterwards the combination will be completed, and a white and firm soap will be obtained.
White soap is formed of ingredients similar to those that have just been mentioned. Yellow soap is made with tallow, resin, and soda. Soap may be formed by boiling shreds of woollen cloth with ley till the whole has acquired a certain consistence. This kind of soap has been made, and applied with success, in several manufactories in France.—The combination of oil and other ingredients with potash ([205]), instead of soda, affords what is called soft soap.
201. NATRON, or CARBONAT of SODA, is a salt which consists of soda ([200]) in combination with carbonic acid ([26]). It is massive, of greyish colour, soluble in water, and has a disagreeable alkaline taste.
This salt is found in Egypt, on the surface of the earth, and particularly near the margins of certain lakes called natron lakes. In the summer season the water of these lakes is evaporated by the heat of the sun, leaving a bed of natron generally about two feet in thickness. This is broken with wedges and hammers; and packed up for sale in the European markets. The waters of some of the lakes contain both common salt and natron; and these, on evaporation, crystallize in successive beds. Natron is found in considerable quantity under the form of an efflorescence, on the surface of the earth, in the plains of Debreczin in Hungary. It is likewise found in small quantity in the ashes of most vegetables, but particularly in those of salsoda and salicornia.
The ancient Egyptians are said to have made great use of natron for the preservation of dead bodies, by macerating them in it for several months previously to their being embalmed. Large quantities of this salt are sometimes imported into England, by the East India Company’s ships, from China, and other parts of the East. It is employed in the manufacture of soap, and for the washing of linen. Glass-makers mix it with sand for the formation of glass. On the continent it is administered as a medicine in complaints of the bowels and liver. The ancients sometimes employed a mixture of natron for soaking their seed corn, under an impression, that, when afterwards committed to the earth, it would thereby be rendered more fertile.
202. COMMON SALT, or MURIAT of SODA, though found in some countries in a solid and massive state, is for the most part an artificial preparation from sea-water, and from the water of salt lakes and brine springs. It consists of soda ([200]) in combination with muriatic acid ([29]).