SrECIFIC GRAVITY. 485 



The i:)rinciple upon wliicli all of these instrument are constructed is, 

 that Avheuever a body floats in any liquid, it displaces exactly a vol- 

 ume of that liquid equal in weight to the floating body. 



These hydrometers are glass bulbs, with a long, slender spindle, 

 made by means of a little mercury at the lower end to maintain an 

 erect position in the liquid. The lighter the liquid the deeper the in- 

 strument sinks, and the heavier the liquid the more of the spindle ap- 

 pears above the liquid. Within the glass spiudle is a scale, so that a 

 glance enables the ojierator to determine the specific gravity or density. 

 For convenience, the scale is such as to enable the operator to deter- 

 mine either the specific gravity or per cent of any substance presumed 

 to be present, etc.; and therefore these mstruments have been prepared 

 with scales adapted to any special purpose. We will explain those 

 only which are in use for the determination of saccharine liquids. 

 These are : 



The scale of Beaume, which is determined by marking as the 

 point on the spindle of the hydrometer to which it sinks when float- 

 ing in pure water, and as 15° the point to which it sinks in a solution 

 of 15 parts by weight of salt in 85 of water. The interval between 

 these points is divided into 15 equal parts, and the scale is continued 

 to any number of degrees beyond. 



The scale of Brix, or Balling, as it is also called, gives the per 

 cent of sugar jiresent in any given solution ; for example, a solution 

 marking 10° Brix contains 10 per cent of sugar, etc. 



The scale of Twaddle is graduated in such a manner that the num- 

 ber of degrees given, multiplied by 5 and added to 1000, will give the 

 specific gravity, as compared with water taken at 1000. Thus: 10° 

 Twaddle=:1050 specific gravity. 



To convert Beaume degrees into specific gravity, divide 144 by 144 

 less the degrees of Beaume; thus, 17° Beauuie equals 144 divided by 

 144 less 17— that is, 1.133. 



