Equal parts of tallow soap, made perfectly dry, and spirit of wine, are to be put into a copper still, which is plunged in a water-bath, and furnished with its capital and refrigeratory. The heat applied to effect the solution should be as slight as possible, to avoid evaporating too much of the alcohol. The solution being effected, must be suffered to settle; and after a few hours’ repose, the clear supernatant liquid is drawn off into tin frames, of the form desired for the cakes of soap. These bars do not acquire their proper degree of transparency till after a few weeks’ exposure to dry air. They are now planed, and subjected to the proper mechanical treatment for making cakes of any form. The soap is coloured with strong alcoholic solution of archil for the rose tint, and of turmeric for the deep yellow. Transparent soaps, however pleasing to the eye, are always of indifferent quality; they are never so detergent as ordinary soaps, and they eventually acquire a disagreeable smell.
| Soap charged with duty in | 1834. | 1835. | 1836. | |||
|---|---|---|---|---|---|---|
| lbs. | lbs. | lbs. | ||||
| Hard | 144,344,043 | 143,806,207 | 146,539,210 | |||
| Soft | 10,401,281 | 12,103,109 | 13,358,894 | |||
| Amount of duty | at 11⁄2d. | per lb. on | hard soap | £902,150 | £930,039 | £915,861 |
| do. | at 1d. | soft soap | 43,339 | 50,429 | 55,662 | |
SOAPSTONE; see [Steatite].
SODA, Caustic soda (Hydrate de soude, Fr.; Aetznatron, Germ.); is an alkaline substance, used in chemical researches, in bleaching, and in the manufacture of soap. It is prepared by boiling a solution of crystallized carbonate of soda in 4 or 5 parts of water, with half its weight of recently slaked and sifted lime. At the end of half an hour, the vessel of iron, porcelain, or preferably silver, may be removed from the fire, and covered carefully, till the calcareous matter has settled into a solid magma at the bottom. The clear supernatant lye may be then decanted into bottles for use in the liquid state, or evaporated, out of contact of air, till it assumes an oily appearance, then poured upon an iron or marble slab, broken into pieces, and put up in phials secured with greased stoppers or corks.
Caustic soda is a white brittle mass, of a fibrous texture, a specific gravity of 1·536, melting at a heat under redness, having a most corrosive taste and action upon animal matters, dissolving readily in both water and alcohol, attracting carbonic acid when exposed to the atmosphere, but hardly any water, and falling thereby into an efflorescent carbonate; it forms soaps with tallow, oils, wax, rosin; dissolves wool, hair, silk, horn, alumina, silica, sulphur, and some metallic sulphurets. It consists of 77·66 soda, and 22·34 water. A solution of caustic soda affords no precipitate with solution of chloride of platinum, or tartaric acid, as a solution of caustic potash never fails to do.
The following Table of the quantity of Caustic Soda contained in Lyes of different densities, has been given by Richter:—
| Spec. grav. | Soda per cent. |
|---|---|
| 1·00 | 0·00 |
| 1·02 | 2·07 |
| 1·04 | 4·02 |
| 1·06 | 5·89 |
| 1·08 | 7·69 |
| 1·10 | 9·43 |
| 1·12 | 11·10 |
| 1·14 | 12·81 |
| 1·16 | 14·73 |
| 1·18 | 16·73 |
| 1·20 | 18·71 |
| 1·22 | 20·66 |
| 1·24 | 22·58 |
| 1·26 | 24·47 |
| 1·28 | 26·33 |
| 1·30 | 28·16 |
| 1·32 | 29·96 |
| 1·34 | 31·67 |
| 1·35 | 32·40 |
| 1·36 | 33·08 |
| 1·38 | 34·41 |
Soda free from water, can be obtained only by the combustion of [sodium], which see.
SODA, CARBONATE OF (Kohlensaures natron, Germ.): is the soda of commerce in various states, either crystallized, in lumps, or in a crude powder called soda-ash. It exists in small quantities in certain mineral waters; as, for example, in those of Seltzer, Seydschutz, Carlsbad, and the volcanic springs of Iceland, especially the Geyser; it frequently occurs as an efflorescence in slender needles upon damp walls, being produced by the action of the lime upon the sea salt present in the mortar. The mineral soda is the sesquicarbonate, to be afterwards described.