76 



THE HYDROSTATIC BALANCE. 



A !\ /! !\ 



W" = W ( ?) -M it 



\S S / \S SI 



(S' - 8) S" 



_>_ rf/f 



- 



(4) 



EXAMPLES. 



1. If with 78 gallons of spirit, specific gravity 0.92, 

 22 gallons of water be mixed, what is the specific gravity of 

 the mixture? Ans. 0.9376. 



2. British standard gold contains 11 parts by weight of 

 pure gold, and 1 part of copper. Required its specific 

 gravity. Ans. 17.647. 



3. An iron vessel completely filled with mercury weighed 

 500 Ibs., and lost, when weighed in water, 40 Ibs. If the 

 specific gravity of the cast iron is 7.2 and that of the mer- 

 cury is 13.6, find (1) the weight of the empty vessel, and 

 (2) that of the mercury contained in it. 



Ans. (1) 49.5 Ibs. ; (2) 450.2 Ibs. 



36. The Hydrostatic Balance. In order to deter- 

 mine the specific gravities of bodies practically and with 

 accuracy, it is necessary to employ 

 certain instruments for weighing. 

 These are the Hydrostatic Balance 

 and Hydrometers.* 



The hydrostatic balance is an ordi- 

 nary balance, having one of the scale- 

 pans smaller than the other, and at a 

 less distance from the beam ; attached 

 to the under side of the small scale- 

 pan is a hook, from which may be suspended any body by 

 means of a thin platinum wire, horse-hair, or any delicate 

 thread. The body whose specific gravity is to be found is 



Fig. 26 



* Sometimes called Areometers. 



