SODA 853 



Take 100 grains of the soap tinder examination, and dissolve them in about 2,000 

 grains of boiling water ; should uny insoluble matter be left, decant carefully the 

 superincumbent solution and test it with dilute sulphuric acid of the proper strength, 

 exactly as described in the article ALKALIMETRY. 



The proportion of alkali contained in soap may also be ascertained by incinerating 

 a given weight of soap in an iron or platinum spoon, crucible, or capsule, treating the 

 residue with water, filtering and submitting the filtrate to an alkalimetrical assay. 

 This method, however, cannot be resorted to when the soap contains sulphates of alkalis, 

 because the ignition would convert such salts, Or a portion thereof, into carbonates of 

 alkali, which by saturating a portion of the test-sulphuric acid would give an inac- 

 curate result. 



The proportion of oil or fat in soap is ascertained by adding 100 grains of pure 

 white wax free from water to the soap-solution, after supersaturation with an acid, 

 and heating the whole until the wax has become perfectly liquid, and has become 

 perfectly incorporated with the oil or fat which has separated by the treatment with 

 an acid. The whole is then allowed to cool, and the waxy cake obtained is removed, 

 heated in a weighed crucible or capsule to a temperature of about 220 Fahr. in 

 order to expel all the water, after which the whole is weighed ; the increase above 

 100 grains (the original weight of the wax) indicates, of course, the quantity of grease, 

 fat, or oil contained in the soap. This addition of wax is necessary only when the 

 fatty matter of the soap is too liquid to solidify well in cooling. Good soap ordinarily 

 contains from 6 to 8 per cent, of soda ; from 60 to 70 percent, of fatty acids and resin, 

 and from 30 to 35 per cent, of water. 



The nature of the fat of which a given sample of soap has been made is more 

 difficult to detect, yet by saturating the aqueous solution of the mass under examina- 

 tion with an acid, collecting the fatty acids which then float on the surface, and 

 observing their point of fusion, the operator at any rate will thus be enabled to 

 ascertain whether the soap under examination is identical with the sample from which 

 it may have been purchased, and whether it was made from tallow, or from oil, &c. 



cwts. value 



Our Soap Exports were in 1873 183,750 J243.047 



1874 219,284 277,207 



SOAP-BARK. A few years since a peculiar bark was introduced into the 

 European trade, and recommended to be employed instead of soap for washing and 

 cleaning printed goods, woollens, and silks, and especially for the delicate colours of 

 ladies' dresses, &c. This soap-bark is externally black, but internally the liber 

 consists of layers of yellowish-white. The bark is remarkable for its density, as it 

 sinks in water. The cause of this is the great quantity of mineral substances in its 

 ashes, there being 13'935 per cent, of the internal parts, dried at low temperature 

 and 18'50 per cent, when dried at 100 C. The ashes consist largely of carbonate 

 of lime, which forms 2'60 per cent, of the 13'935, and appears as small crystalline 

 needles, isolated or in groups, in the cells of the liber, not only between its concentric 

 rings but in every part of it. They glitter in the sun, resembling under the microscope, 

 the aragonite form of the crystallised carbonate of lime. 



The soap-wort (Saponaria officindle) is sometimes used for scouring and cleaning 

 dresses. Several of this family of caryophyllaceous plants (Dianthus, Lychnis, 

 G-ypsophila, Silcne) are remarkable for this property in a greater or less degree. By 

 chemical means there has been extracted from these roots the Sapomne (or Struthiine), 

 a special substance, and to this, notwithstanding the very small quantity contained in 

 the roots, the singular power is attributed of making emulsions, and of being used for 

 soap in washing. The soap- wort of the Levant ( Gypsophila) is, to this day, employed 

 in the East for washing and cleaning silks and shawls. It is generally used in the 

 Mediterranean districts of France and Spain ; the French called it herbe auxfoulons 

 (the fuller's plant). The Saponaire, or Savoniere of the French, is the root of a kind of 

 Lychnis. Saponine was found by Henry and Boutron Charland in the bark of the 

 QuUlaja saponaria, a tree of the family of rosaceous plants, and a native of Huanaco, 

 in Peru. Ferdinand Leboauf made mention of this bark in 1850 for its' richness 

 in saponine, and recommended it for pharmaceutical use in preparing emulsions of 

 oils, resins, balsams, and several other medicaments. He mentions likewise the bark 

 of the Yallhoy (Monnina polystachya) as containing saponine. The fruits of Sapindus 

 saponaria, known as ' soap-berries,' are used in America and the West Indies for 

 washing linen. 



SO APSTONE. See STEATITE. 



SODA. NaO (Na-O). This is the oxide of the metal sodium, and can only be 

 obtained in the free state by the combustion of the metal itself in dry air or oxygen 

 gas. Another oxide appears to exist, but the composition is uncertain, and it is of no 



