148

ALCOHOL. —SlLBERMANN'S ALCOHOLOMETER.

Water 100 parts,.Alcohol 0 parts ;

do. 99 “ . do. 1 “

do. 98 “ . do. 2 “

and so on up to pure alcohol; and their several pointsof elevation at the respective temperatures (25° to50° 0.), be carefully marked on the tube, a completecentesimal alcoholometric scale will be produced,which will indicate the quantity of alcohol containedin any mixture of alcohol and water, by introducingit at 25° C. and heating it to 50° C.

The same process may be employed with regard toany other two liquids having points of dilatationdiffering between those of alcohol and water; butit will be understood that the same scale will notserve for more than one mixture. To adapt this

principle to the ordinary purposes of alcoholometricmeasurement, Silbermanu constructed a thermometerin a peculiar manner, thereby forming an instrumentwhich he named a dilatometer , Fig 58.

The form and arrangement of this apparatus arethese:—A large bulb tube, A, of the form of a hydro-meter, but tapering at the bottom and open at thetop, is fixed to a metal plate, to which a thermometer,C, is also attached. The thermometer is graduatedfrom 77° to 122° Fahr. (25° to 50° C.). Both thethermometer and bulb of the apparatus, A, are im-mersed in the liquor to be tested; the former toshow the temperature, and the latter to ascertain theexpansion of the liquid when it is heated from 25° to50° C. The expansion of distilled water between

Fig. 52.

COMPARISON OF MEAN AND ACTUAL SPECIFIC GRAVITIES OF VARIOUS MIXTURES OF ALCOHOL AND WATER.

1000 -

the extreme degrees of the thermometer is marhedon the stem of A by the figures 25 and 50 ; from thelatter the scale of degrees from 1 to 100 appended tothe stem of the apparatus commences, and by it theexpansion of the alcoholic liquors is ascertained, whensuch liquors are heated from 25° to 50° C. A valveof cork or india-rubber closes the tapering end of a ;this valve is attached to a rod, b b, fastened to thesupporting plate and connected to a spring, B. Tocause the liquid under examination to flow, the springvalve is depressed by turning a screw of four threadsfor the purpose of giving a quick motion, fitting inthe upper part of the rod, and by reversing the mo-tion of the screw the thermometer is closed; some-times the rod may be made to terminate in a flattened

end or cap, as the figure represents, and is moved bypressing it with the finger. As the liquids are oftenimpregnated with air or gas, it is found necessary,before testing, to remove it; the best method ofeffecting this is by means of a vacuum, which may beproduced by the use of a small leather piston, e,working in the tube of the thermometer. This pistonserves first, by suction, to fill the thermometer frombelow; and then, the lower part being closed, by twoor three strokes to separate the air from the liquid.To effect the withdrawal of the piston without anyshock, so as not to divide the column abruptly, thepiston-rod is made hollow throughout; the operator,having wetted his finger, applies it to the top of thepiston-rod, in order to create a vacuum as lie draws