Page:The New International Encyclopædia 1st ed. v. 18.djvu/338

* SOAP. 284 SOAPWOBT. cate fibre and at the same time not prove so effi- cient a detergent. Theories of the DETEEsn^ Action of Soaps. Berzelius's theory formulates the dissociation and subsequent formation of an acid soap which forms the suds and free alkali uniting with any greasy matter present. This is the generally accepted theory to-day. On the other hand, Rotondi, who made a careful experimental investigation of the subject, maintained that soaps decompose in solution, not into acid soaps and free alkali, but into acid soaps and basic soaps, the latter being precipitated from solution, by common salt, with- out losing any alkali, while acid soajjs are com- pletely soluble in hot solutions of basic soaps. The basic soaps, according to Rotondi. have the power to emulsify, but not to saponify ( unite chemically) with fatty bodies, and it is to this emulsifying power that the detergent value of soaps is due. Recent experiments (1903), con- ducted with fabrics impregnated with emulsifi- able, but not saponifiable, materials — such as kerosene oil — seem to confirm Rotondi's opinions. BiBLlOGKAPHY. Sadtler, Handbook of Indus- trial Organic Chemistry (Philadelphia, 1900) ; Christiani, Soaps and Candles (London, 1881) ; Carpenter, Soaps and Candles (ib., 1885) ; Watt, The Art of Soap Making ( ib., 1887 ) ; Cameron, Soaps and Candles (ib., 1888) ; Gadd, Soap Manufacture (ib., 1893) ; Hurst, Soaps, A Practical Treatise (ib., 1899) : Thorp. Ontlines of Industrial Chemistry (ew York, 1898); Gathmann, American Soaps (Milwaukee, 1901). See Fats; Oils; Ste.rin ; Palmitix; Oleic Acid; Oleix; Stearic Acid; Pai.mitic .cid: Lairic Acid; etc. SOAPBERRY {8api)tdus Sajmnaria). A West Indian tree of the natural order Sapin- dacese, occurring in Southern Florida. Its pulpy fruit, which contains saponin, is used instead of soap in washing, a use apt to injure linen. With the exception of Sapindus marginatus, a tree 30 to 40 feet in height, found in the Southern United States, the genus is entirely trojiical. The fruits contain shining black very hard nuts, formerly used for making buttons. See Sapindace.!:. SOAP BUBBLES. Many important applica- tions of the mechanics of liquid surfaces can be studied very conveniently by means of soap bub- bles and soap films. By measuring the diameter of a bubble and the pres- sure upon the air within the elastic strength of the film can be measured. B / Xaturally the pressure in a small bubble is great- er than in a large one, because the curvature of the surface is greater. This is very prettily shown when two bulibles of different sizes are joined as in Fig. 1, when it will be observed that the partition film p is always con- vex into the larg- er bubble A. be- ing pushed to Fig. 2. that form by the greater pressure in the smaller bubble B. In air quiet and free from dust two bubbles may be rested against each other as shown in Fig. 2 a, like two elastic balls, but if a stick of sealing wax be rubbed to electrification and brought near the bubbles, they will coalesce as in Fig. 2 b. One bubble may be blown in- side of another as shown in Fig. 3 a. Then electrifica- tion will cause it to fall through the outer bubble to the form Fig. 3 6. Soap-bubble films on wire frames ar- range themselves in a manner beautifully to confirm and illustrate the laws of the composition and equilibrium of forces. A wire frame, as Fig. 4 a, with a thread Fig. 4. tied upon it, is instructive. If it is dipped in soap solution and a complete film put on it, the thread will move freely about in the film, but if the film on one side of the thread be broken, the film on the other side will pull the thread to the form 6. If the thread have a loop in it the form c may be obtained, and the 0])en ring will move freely about in the film. A good so- lution is made of fresh oleate of soda with a little glycerin, or Castile soap may be success- fully used. Great care must be exercised to keep the solution free from dust, but it must not be filtered. For complete details, consult: Boys, Soap Bubbles and the Forces Which Mold Them (London, 1895), an interesting volume describ- ing many simple and instructive experiments. See Capillarity. SOAPFISH (so called from the unctuous skin, due to smooth scales and an excessive flow of mucus). (1) A West Indian fish (Ryp- ticHS s<iponaccus), related to the sea-bass, and locally called 'jabon' and 'jaboncillo.' It is of small value. (2) See Liz.'VRD-Fish. SOAPSTONE, Steatite, or Talc Rock. A rock composed essentially of the hydro-magnesian mineral talc. Soapstones are produced by weathering agencies, are tough and durable, and often susceptible of taking a high polish. They are, however, very soft and easily marred. Soap- stones are generally produced by the alteration, through weathering, of the ultra-basic or mag- nesian igneous rocks. In the Lake Superior region and elsewhere dikes of soapstone have played an important r6le in the concentration of bodies of ore. Soapstone is used to a small extent as a building stone, for monumental work, and for sinks, etc., and when ground it is em- ployed in the manufacture of toilet powders, soaps, and as a lubricating m.aterial. See T.LC. SOAPWORT (Snponaria) . A genus of plants of the natural order Caryophyllaceie. Saponaria calabrica is a favorite garden annual. Common soapwort, bouncing Bet (Saponaria officinalis), is found on roadsides, in thickets, and on banks of streams, in many parts of Europe and Amer- ica. Both the root and the leaves contain sapo-