TABLE IV.--_Exhibiting the_ BOILING POINTS _of Mixtures of Alcohol and Water of the given strengths._ By GRÖNING.
---------------+------------+----------------+------------ | Alcohol | | Alcohol Boiling point. | per cent. | Boiling point. | per cent. Fahr. | by volume. | Fahr. | by volume. ---------------+------------+----------------+------------ 205·34 | 5 | 179·96 | 55 199·22 | 10 | 179·42 | 60 195·8 | 15 | 178·7 | 65 192·38 | 20 | 177·62 | 70 189·50 | 25 | 176·54 | 75 187·16 | 30 | 175·46 | 80 185· | 35 | 174·92 | 85 183·38 | 40 | 174·2 | 90 182·12 | 45 | 173·14 | 95 181·58 | 50 | 172· | 100 ---------------+------------+----------------+------------
TABLE V.--_Showing the_ BOILING POINTS _of 'under proof' spirit._ By Dr URE.
----------------+-------------+--------------- Boiling points. | Per-centage | Corresponding Fahr. | strength. | Sp. Gr. ----------------+-------------+--------------- 178·5 | Proof. | ·9200 179·75 | 10· U.P. | ·9321 180·4 | 20· " | ·9420 182·1 | 30· " | ·9516 183·4 | 40· " | ·9600 185·6 | 50· " | ·9665 189· | 60· " | ·9729 191·8 | 70· " | ·9786 196·4 | 80· " | ·9850 202· | 90· " | ·9920 ----------------+-------------+---------------
_Obs._ This method does not answer well with spiritous liquor above 'proof,' owing to the variations of their boiling point being so slight as not to be easily observed with accuracy; but with liquors under 'proof,' and particularly with wines, beer, and other fermented liquors, due care being observed, it gives results closely approximating to those obtained by distillation, and sufficiently accurate for all ordinary purposes. In testing strong alcoholic solutions it is, therefore, proper to dilute them with twice their bulk of water; and commercial spirits, with an equal bulk of water; the results obtained being doubled or tripled as the case may be.
_d._ From the EXPANSION of the LIQUID when heated: Silbermann's DILATATOMETER. The expansion of alcohol between 0° and 212° Fahr. is triple that of water; and between 77° and 122° Fahr. it is much greater. Between -14° and -98° Fahr. the rate of expansion is about the ·00047th part in volume for every degree of Fahrenheit's scale. The measurement of this expansion has been proposed as a new and ready method of alcoholometry, adapted to nearly all spirituous and fermented liquors. Silbermann's instrument, which is based on it (see _engr._), simply consists of a flat brass or ivory plate (_A_), on which are fixed a mercurial thermometer (_D_) graduated from 22° to 50° Cent. (= 77° to 122° Fahr.); and the DILATATOMETER (_B_), which is a glass pipette open at both ends. A valve of cork, or vulcanised india rubber, closes the tapering end (_c_); this valve is attached to a movable rod (_C_) which is fastened to the supporting-plate, and connected with a spring (_f_) and a handle (_g_) bearing a four-threaded screw, by which the lower orifice of the pipette can be opened or closed at will. In use, the pipette is filled with the liquor under examination, to a little above the zero point (0) on the scale. This is effected by suction, by means of a little piston of leather (_i_), which fits tightly in the long and wider limb of the pipette; the valve (_d_) being previously opened by turning the knob (_h_). The proper quantity of liquor being introduced, and the lower end closed, the piston is moved up and down two or three times, for the purpose of drawing the air-bubbles and absorbed air out of the liquid, the presence of which would vitiate the results of the trial. To allow the piston to be withdrawn without any shock, or the danger of dividing the column abruptly, the rod attached to it is made hollow throughout. In using it the operator applies the ball of his forefinger to the top of the piston-rod (_E_), in order to create a vacuum as he raises it; and then withdraws it, to readmit the air when he thrusts it down or removes it from the tube. The excess of liquid (if any) in the pipette is then run off until its upper surface is exactly level with the zero (0) of the scale, at 25° C., to which it is raised by immersion in a water bath of that temperature, as observed by the thermometer; which is done by very cautiously turning the rod which depresses the valve. The whole apparatus is now again immersed in the water bath; and, held by the upper portion of the plate, kept in gentle motion with the hand, until the temperature rises to exactly 50° C., when the coefficient of expansion is obtained, and hence also the proportion of alcohol--the scale of the instrument being so graduated, from actual experiments previously made upon mixtures of known composition, as to give, at once, the per-centage of alcohol by VOLUME (nearly).[14]