Wells's principles and applications of chemistry; . Uugrometer, from the Greek words vypo^ (moist) and fterpov (measure). Questions.—When is air said to be saturated Avith moisture ? What arc hygrometers ?Explain the liair hygrometer and its principle of construction ? 94 TRINCIPLES OF CHEMISTRT. comes shorter; so that the index is of course turned alternately from one sideto the other. The instrument is graduated by first placing it in air artificially made asdry as possible, and the point on the scale at which the index stops underthese circumstances, is the point of greatest dryness, and is
Wells's principles and applications of chemistry; . Uugrometer, from the Greek words vypo^ (moist) and fterpov (measure). Questions.—When is air said to be saturated Avith moisture ? What arc hygrometers ?Explain the liair hygrometer and its principle of construction ? 94 TRINCIPLES OF CHEMISTRT. comes shorter; so that the index is of course turned alternately from one sideto the other. The instrument is graduated by first placing it in air artificially made asdry as possible, and the point on the scale at which the index stops underthese circumstances, is the point of greatest dryness, and is marked 0. Thohygrometer is then placed in a confined space of air, which is completelysaturated with vapor, and under these circumstances the index moves to theoLher end of the scale: this point, which is that of greatest moisture, ismarked 100. The intervening space is then divided into 100 equal parts,which indicate different degrees of moisture. Fig. 144. Daniels Hygrometer. — Anotherform of hygrometer, known as Daniels Hygrom-eter, determines the moisture in the air by indicat-ing the dew point, or the temperature at whichmoisture is deposited from the air. It consists of abent tube of glass. Fig. 40, at the extremities ofwhich two bulbs, a and &, are blown. The bulb &is made of black glass, and contains a little ether,into which dips the ball of a small and delicatethermometer, contained in the cavity of the whole instrument contains only the vapor ofether, the air having been removed. The bulb a iscovered over with a piece of muslin. The supportof the tube sustains another thermometer, by whichwe can observe the temperature of the air. Whenan observation is to be made with this instrument,a little ether is poured on the muslin of tho bulb a; this evaporates rapidly,and by so doing reduces the temperature of the other bulb, &. As soon asthis has cooled sufficiently to condense the moisture of the atmospher
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Keywords: ., bookcentury1800, bookdecade1860, booksubjectchemistry, bookyear18
