SOAP-TEST. This test, for which science is indebted to prof. Clark of Aberdeen, is now universally employed for determining the degree of hardness of water. Every one knows how much more readily a lather is formed—as, for example, in washing the hands —with soft than with hard water. This is accounted for by the earthy bases of the hard water displacing the alkaline bases of the soap, and forming compounds insoluble in water. This is the foundation of the soap-test. A hard water of known strength is first prepared by dissolving 16-galins of pure carbonate of lime in pure hydrochloric acid, evaporating. to dryness, and dissolving the resulting chloride of calcium in a gallon of distilled water. This gallon of chloride of calcium solution accurately represents a natural water whose hardness is due to 10 grains of carbonate of lime in a gallon. A solution of soap in proof-spirit is next prepared of such strength as that a quantity of it which will fill 32 measures of a volumetric tube, each measure of which contains 10 grains, will be exactly able to convert 1000 grains' measure of the standard solution of hard water into the cart hy soap described. This point is thus ascertained; The hard water is placed in a stoppered bottle', and the soap solution added to it by degrees. the bottle being shaken after each addition, when a but hie will form, which rapidly disappears so long as any lime is present; but when at last it is all used up, a froth of soap bubbles remains after hard shaking, such as to last unbroken for three minutes. If, now, a given sample of water be examined, and this point. is reached at. the expense of the entire 32 measures, it is a water of 16 degrees of hardness. Now, perfectly soft water consumes 2 measures of the soap solution before permanent bubbles arc formed, so that a water of 16 degrees of 6 1 hardness has in reality only consumed 30 measures of the soap solution. But so = 0.53; hence, if any given measures of the soap-test be used in estimating the hardness of a water, we must first subtract 2 from the amount, and then multiply by 0.53; and the result will give us the degree of hardness. For example, let a given sample require 27 measures of the soap test. On subtracting 2 and multiplying by 0.53, we find its hard ness to be 12.25. Clark's Soap•test Table for Hardness of Water is given in time article " Soap-test" in Knight's English Cgclopcedia; and full details regarding the mode of work ing the test, to determine the amount of lime, magnesia, soda, sulphuric acid, and pure carbonic acid, are given in Dr. Parkes's .3lan-ual of Practical Hygiene (Loud. 1864).
SOAPWORT,Sapowirria, a genus of plants of the natural order caryophyllacem, having a cylindrical or ventricose 5-toadied calyx, without any outer calyx or attendant hractem, five undivided petals with long claws, ten stamens, two stigmas, and a capsule opening at the top by four valves. Some of the species have very beautiful flowers. S. calabrica has of late become one of the most favorite annuals pf our flower-gardens.—COMMON SOAPWORT (S. otficinalis) is found on waysides, in thickets, and on the banks of streams, in most parts of Europe, although it is a somewhat doubtful native of Britain. Both the root and the leaves contain saponine (q.v.). in consequence of which they are sometimes employed for washing. The brownish-red color of the balk of the root. however, is apt to tinge white articles. The root of this plant has also medicinal properties, being aperi ent, resolvent, and alterative. IL is sometimes sold as RED SoAr-noor.
Nearly allied to the genus .saponaria, but having an angular calyx and a 5-valved capsule, is the genus pypsophi/a, some species of which are called SOAP-ROOT, and con• lain much saponin. Thus, time EGYPTIAN SOAP-ROOT.(G. Strialthilii), and the SPANISII SOAP-floor (0. Hispanica), called Jabonera in Spain, have been employed for washing from time immemorial, and the roots not having a dark rind can be used for washing white articles. and are to some extent an article of commerce, being used for silken and other stuffs, the colors of which will not bear the application of soap. The roots of lychnis dioica, One of the most common British plants, possess the same properties in an inferior degree.—The bark of guillaja soponaria, a Chilian tree of the natural order Rosace,x, contains much saponin. is generally used for washing in Chili and Peru, and there forms a considerable article of commerce.—Some of the tropical South Sea islands produce a species of vine (ritis saponaria), the stem of which, especially the thicker part, cut into pieces, and softened by cooking on hot stones, produces in water a rich lather almost equal to that of soap. See also SoLANUM.
is merely a modification of the ordinary movements of respiration excited by nient,..1 emotions. It is the consequence of a series of short convulsive contractions of the diaphragm, and' is usually accompanied by a closure of the glottis, temporarily preventing the entrance of air into the lungs.