ALCOHOLOMETRY 



63 



Thus, ten glasses of cider or porter, six glasses of claret, five glasses of Burgundy, 

 four glasses of champagne, three glasses of port, sherry, or Marsala, are equivalent 

 to one glass of brandy. 



M. 1'Abbe Brossard-Vidal, of Toulon, 1 has proposed to estimate the strength of 

 alcoholic liquors by determining their boiling point. Since water boils at 100 C. 

 (212 F.),and absolute alcohol at 78 -4 (1 73 F.), it is evident that a mixture of water 

 and alcohol will have a higher boiling point the larger the quantity of water present 

 in it. This method is even applicable to mixtures containing other bodies in solution 

 besides spirit and water, since it has been shown that sugar and salts, when present 

 (in moderate quantities), have only a very trifling effect in raising the boiling point, 

 and the process has the great advantage of facility and rapidity of execution, though 

 of course not comparable to the method by distillation, for accuracy. 



Mr. Field's patent (1847) alcoholometer is likewise founded upon the eame prin- 

 ciple. The instrument was subsequently improved by Dr. Ure. 



The apparatus consists simply of a spirit-lamp placed under a little boiler containing 

 the alcoholic liquor, into which fits a thermometer of very fine bore. 



When the liquor is stronger than proof spirit, the variation in the boiling point ia 

 so small that an accurate result cannot possibly be obtained ; and, in fact, spirit 

 approaching this strength should be diluted with an equal volume of water before 

 submitting it to ebullition, and then the result doubled. 



Another source of error is the elevation of the boiling point, when the liquor is kept 

 heated for any length of time ; it is, however, nearly obviated by the addition of 

 common salt to the solution in the boiler of the apparatus, in the proportion of 35 or 

 40 grains. In order to correct the difference arising from higher or lower pressure 

 of the atmosphere, the scale on which the thermometric and other divisions are 

 marked is made moveable up and down the thermometer tube ; and every time, 

 before commencing a set of experiments, a preliminary experiment is made of boiling 

 some pure distilled water in the apparatus, and the zero point on the scale (which 

 indicates the boiling point of water) is adjusted at the level of the surface of the 

 mercury. On p. 55 will be found a Table showing the boiling point of alcohol of 

 different specific gravities. 



But even when performed with the utmost care, this process is 18 



still liable to very considerable errors, for it is extremely difficult to 

 observe the boiling point to within a degree ; and after all, the fixed 

 ingredients present undoubtedly do seriously raise the boiling point 

 of the mixture in fact, to the extent of from half to a whole degree, 

 according to the amount present. 



SUbermann's Method, M. Silbermann 2 has proposed another 

 method of estimating the strength of alcoholic liquors based upon 

 their expansion by heat. It is well known that, between zero 

 and 100 0. (212 F.), the dilatation of alcohol is triple that of 

 water, and this difference of expansion is even greater between 

 25 C. (77 F.) and 50 C. (122 F.); it is evident, therefore, that 

 the expansion between these two temperatures becomes a measure 

 of the amount of alcohol present in any mixture. The presence of 

 salts and organic substances, such as sugar, colouring, and extractive 

 matters, in solution or suspension in the liquid, is said not materi- 

 ally to affect the accuracy of the result ; and M. Silbermann has 

 devised an apparatus for applying this principle, in a ready and 

 expeditious manner, to the estimation of the strength of alcoholic 

 liquors. The instrument may be obtained of the philosophical in- 

 strument makers of London and of Liverpool. 



It consists of a brass plate, on which are fixed 1st, an ordinary 

 mercurial thermometer graduated from 22 to 50 C. (77 to 122 

 F.), these being the working temperatures of the dilatatometer ; and 

 2ndly, the dilatatometer itself, which consists of a glass pipette, open 

 at both ends, and of the shape shown in the : figure. A valve of cork 

 or india-rubber closes the tapering end A, which valve is attached to 

 a rod, b b, fastened to the supporting plate, and. connected with a 

 spring, , by which the lower orifice of the pipette can be opened 

 or closed at will. The pipette is filled, exactly up to the zero point, 

 with the mixture to be examined this being accomplished by the 

 aid of a piston working tightly in the long and wide limb of the pipette ; the 

 action of which serves also another valuable purpose viz. that of drawing any 



1 Comptes Rendus, xxvil. 874. 



Hid. xxvil. 418. 



