ALCOHOLOMETEY 



59 



This process, though very accurate, is somewhat troublesome, especially to persons 

 unaccustomed to accurate chemical experiments, and it involves the possession of n 

 delicate balance. The necessity for this is, however, obviated by 

 the employment of one of the many modifications of the common 1 7 



hydrometer. This is a floating instrument, the use of which 

 depends upon the principle, that a solid body immersed into a 

 fluid is buoyed upwards with a force equal to the weight of the 

 fluid which it displaces, i.e. to its own bulk of the fluid ; conse- 

 quently, the denser the spirituous mixture, or the less alcohol 

 it contains, the higher will the instrument stand in the liquid ; 

 and the less dense, or the more spirit it contains, the lower 

 will the apparatus sink into it. 



There are two classes of hydrometers. 1st. Those which are 

 always immersed in the fluid to the same depth, and to which 

 weights are added to adjust the instrument to the density of any 

 particular fluid. Of this kind are Fahrenheit's, Nicholson's, and 

 Guyton de Morveau's hydrometers. 



2nd. Those which are always used with the same weight, but 

 which sink into the liquids to be tried, to different depths, 

 according to the density of the fluid. Of this class are most of 

 the common glass hydrometers, such as Baume's, Curteis's, 

 Gay-Lussac's, Twaddle's, &c. 



Sykes's and Dicas's combine both principles. See HYDRO- 

 METERS. 



Sykes's hydrometer, or alcoholometer, is the one employed by 

 the Board of Excise, and therefore the one most extensively ^P' ^j^ 

 used in this country. 



This instrument does not immediately indicate the density 

 or the per-centage of absolute alcohol, but the degree above or /&^ $& 

 below proof the meaning of which has been before detailed *ajP MfliP 

 (p. 45.) 



It consists of a spherical ball or float, a, with an upper and lower stem of brass, b 

 and c. The upper stem is graduated into ten principal divisions, which are each 

 subdivided into five parts. The lower stem, c, is made conical, and has a loaded 

 bulb at its extremity. There are nine moveable weights, numbered respectively by 

 tens from 10 to 90. Each of these circular weights has a slit in it, so that it can be 

 placed on the conical stem, c. The instrument is adjusted so that it floats with the 

 surface of the fluid coincident with zero on the scale, in a spirit of specific gravity 

 825 at 60 F., this being accounted by the Excise as 'standard alcohol' In weaker 

 spirit, which has therefore a greater density, the hydrometer will not sink so low ; and 

 if the density be much greater, it will be necessary to add one of the weights to 

 cause the entire immersion, of the bulb of the instrument. Each weight represents so 

 many principal divisions of the stem, as its number indicates ; thus, the heaviest weight, 

 marked 90, is equivalent to 90 divisions of the stem, and the instrument, with the 

 weight added, floats at in distilled water. As each principal division on the stem is 

 divided into five subdivisions, the instrument has a range of 500 degrees between the 

 standard alcohol (specific gravity '825) and wtiter. There is a line on one of the side 

 faces of the stem b, near division 1 of the drawing, at which line the instrument 

 with the weight 60 attached to it floats in spirit exactly of the strength of proof, at a 

 temperature of 51 F. 



In using this instrument, it is immersed in the spirit, and pressed down by 

 the hand until the whole of the graduated portion of the tipper stem is wet. The 

 force of the hand required to sink it will bo a guide to the selection of the proper 

 weight. Having taken one of the circular weights necessary for the purpose, it is 

 slipped on to the lower conical stem. The instrument is again immersed, and 

 pressed down as before to 0, and then allowed to rise and settle at any point. 

 The eye is then brought to the level of the surface of the spirit, and the part of the 

 stem cut by the surface, as seen from below, is marked. The number thus indicated 

 by the stem is added to the number of the weight, and the sum of these, together with 

 the temperature of the spirit, observed at thci same time by means of a thermometer, 

 enables the operator, by reference to a Table -which is sold to accompany the instru- 

 ment, to find the strength of the spirit tested. 



These Tables are far too voluminous to be quoted here ; and this is unnecessary, 

 since the instrument is never sold without them. 



^ A modification of Sykes's hydrometer has been adopted for testing alcoholic 

 liquors which is perhaps more convenient, as the> necessity for the loading weights 

 is done away with, the stem being sufficiontly long not to require them. It is 



