THE CHEMICAL BALANCE

(AFTER ROSCOE AND SCHORL EMMER.) drostatic b. Fr., b. hydrostat i que. Ger., hydrostat is che Wage. A b. designed for weighing substances in water, in order to ascertain their lo of weight when supported by the laiter, and hence their specific gravity. [B.]—In duet i on b. Fr.,b, @’induction. Ger., Inductions wage. An instrument invented by Hughes for testing variations in the structure or composition of etalaiby the currents which they generate. It consists of two primary coils, through which a current is sent, each connected with a secondary coil. The two secondary coils, which are so arranged that the currents in them pa in opposite directions, are connected with a telephone. If the currents are of exactly the same strength, they neutralize each other and no sound is heard in the telephone. Connected with each seccndary coil there is a box. One of these boxes contains the metal to be tested, and the other contains a standard piece with which the former is to be compared. If, now, there is even a slight difference in the character of the two pieces, the equilibrium of the opposing currents is disturbed and the telephone sounds. The apparatus has been used for detecting the situation of pieces of metal, such as bullets, imbedded in the body. [B; J. H. Girdner, “* N. Y. Med. Jour.,” Apr. 9, 1887, p. 393.]—Michell’s torsion b.’ An apparatus consisting of à light horizontal rod having at each extremity a small leaden ball, and suspended by its centre by a light wire so as to turn freely in a horizontal plane. Beneath the rod there is a horizontal bar of equal length, loaded at each extremity with large leaden balls, and turning freely upon a central pivot directly beneath the suspending wire of the rod. The amount of torsion phedibed in the wire by the movements of the rod is observed with a telescope. The b. is used for determining the attraction which the leaden spheres exert upon the leaden balls, and hence for determining the specific gravity of the earth. [B. Mohr’s b. A form of hydrostatic b. for determining the specific gravity of liquids. It consists of a b. to one arm of which is attached a closed gla ve el filled with mercury, which serves as a weight, and which is exactly counterbalanced by a weight attached to the other arm. The arm of the b. is divided into ten equal parts, Tn using it, the mercurial weight is submerged in the liquid to be tested, and the arm of the b. is succe ively loaded with three riders, one of which has a weight precisely equal to the lo of weight of the mercurial sinker when submerged in water, and the two others weigh respectively yy and ty as much. When the riders are so adjusted that the b. is in equilibrium, their combined weight is equal to that which the sinker loses by being submerged in the liquid, i. e., it is the specific gravity of that liquid compared with water as a standard. If, for example, the first weight stands at 8, .the second at 6, and the third at 3, the sp. gr. of the liquid is 0°863, [B.|—Pharmaceutical b. A b! used by apothecaries. B, = Physical b. See Chemical b.—Prechtl’s adhesion b. A b. for demonstrating the laws of adhesion, It consists of an ordinary b. from one arm of which is weet a horizontal plate having its lower surface flat and polished, which is brought into contact with a similar polished surface, to which it adheres. The weight required to be placed in the pan suspended from the other arm of the b. in order to effect a peperetion of the plates is a measure of the adhesive force existing between the latter. [B.]—Roman b. Fr., b. romaine. Ger., römisc he Wage. See STEELYARD—Spring b. An instrument for weighing, consisting of a coil of wire which is stretched by the substance to be weighed, and to which is attached an index showing the amount of tension, and hence the weight of PRECHTL'S ADHESION BALANCE, [A, 827.] the substance. [B.]—Torsion b. Fr., b. de torsion (ou de Coulamb). Ger., Drehwage. An et devised by Coulomb for determining the laws of magnetic and electric attraction and reporn and used also for demonstrating the effects of torsion on he suspending thread or wire. It consists of a cylindrical gla case, AAAA, from the upper end of which rises another gla . cylinder, DD, of much smaller diameter, the latter being fitted at its top with a bra cap, a, carrying an index. ©. Ontside of this, and capable of turning upon it, is another cap, 6, divided at its top into 360 equal parts. In the centre of the cap, b, is an opening through which pa es a small metal rod, d, capable of turning freely and having at its lower end a notch to which is attached a very fine wire. At the lower end of the wire there is a small pee of metal pierced y a horizontal needle of shellac, f, having a small gilt ball, g, at one end. Running round the large cylinder, in the same horizontal plane as the shellac needle, a scale is marked, Opposite the zero mark of the scale, within the cylinder, there is a fixed ball of some conducting material, g’, suspended by a rod of shellac, /’, pa ing up through the cover of the cylinder. [A, 376; B. See also Michell’s torsion b.—Wheat stone’s b. See Wheat stone’s BRIDGE.