. A treatise on pharmacy for students and pharmacists. avity beads, also known as Lovis beads, are small,sealed, pear-shaped glass bulbs of various specific weights, whichhave been carefully ascertained and are marked on them; thesebeads will float indifferently in any liquid having the same specificgravity, and may be used in reducing liquids to a fixed specificgravity by dilution or evaporation. If a bead marked beplaced in ajar of alcohol it will sink—unless the liquid happens tobe official diluted alcohol—but will slowly rise upon the additionof water, until a sufficient quantity has
. A treatise on pharmacy for students and pharmacists. avity beads, also known as Lovis beads, are small,sealed, pear-shaped glass bulbs of various specific weights, whichhave been carefully ascertained and are marked on them; thesebeads will float indifferently in any liquid having the same specificgravity, and may be used in reducing liquids to a fixed specificgravity by dilution or evaporation. If a bead marked beplaced in ajar of alcohol it will sink—unless the liquid happens tobe official diluted alcohol—but will slowly rise upon the additionof water, until a sufficient quantity has been added to increasethe specific gravity of the mixture to that indicated on the bead,when it will float about midway in the liquid. Eesults obtained SPECIFIC GRAVITY. 53 with specific gravity beads are never so accurate as with othermethods. Hydrometers, or areometers, are instruments intended to indicateeither the density or specific gravity of liquids, and in some casesalso the perceutage by volume or weight of certain liquids. They Fig. 13683 .5522 .0460 Showing the manner of reading the specific gravities. consist of a glass tube having a bulb blown at one end, a littleabove which the tube is usually expanded cylindrically for a shortdistance, and then terminates in a long stem in which is securely fast-ened a graduated paper scale (see Fig. 33). The bulb is filled withmercury or small shot, so as to enable the instrument to assume avertical position when floated in any liquid. Hydrometers, like allfloating bodies, displace their own weight of a liquid and sink in itto a depth proportional to the volume of liquid displaced, whichvolume is equal in weight to the weight of the instrument; thus, by 54 GENERAL PHARMACY. Fig 33. comparison of volumes displaced, the densities and specific gravitiesof various liquids can be ascertained. While the great majority ofhydrometers are so constructed that with constant weightthey will sink to varying depths in d
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Keywords: ., bookcentury1800, bookdecade189, booksubjectpharmacy, bookyear1895
