SPECIFIC GRAYITY, OR WEIGHT. 



39 



Tlo-w do we ob- 

 tain the Spe- 

 cific Gravity 

 of Liquid 

 bodies 1 



heavier than water. These numbers, therefore, are the specific gravities of +he 

 spirits, ice, iron, and quicksilver. 



For obtaining the specific gravity of Liquids the method 

 above described is substantially the one usually adopted in the 

 arts. A bottle capable of holding exactly 1,000 grains of 

 distilled water, at a temperature of 60° Fahrenheit, is ob- 

 tained, filled with water, and balanced upon the scales. The 

 water is then removed, and its place supphed with the fluid whose specific 

 gravity we wish to determine, and the bottle and contents agaui weighed. 

 The weight of the fluid, divided by the weight of the water, gives the specific 

 gravity required. Thus a bottle holding 1,000 grains of distilled watpr, will 

 hold 1,845 grains of sulphuric acid; 1,845-^1,000 = 1.845, or, the sulphuric 

 acid is 1.845 times heavier than an equal bulk of water. 



. For obtainino: the specific gravity of sohd bodies, a different 



When we im- , ^ , ^ ^^, " . u j • * 



merse a body method 13 adopted. When we unmerse a body m water, 



in water, what j^ displaces a quantity of water equal to its own bulk. (In 



occurs? ^ 1 .,, , ,.-r.-i,-l 



Fig. 7, the space occupied by the cube A B is obviously 



equal to a cube of water of the same size.) The Fig. T. 



water that before occupied the space which the 



body now fills was supported by the pressure of the 



other particles of water around it. The same 



pressure is exerted on the substance which we 



have immersed in the water, and, consequcnth", it 



will be supported in a like degree. 



.„ If the body weighs less than an 



When will a , , „ %. 



body sink, and equal bulk of water, the pressure 



when float, in ^f ^]^Q ^.^ter will sustain it entirely, 

 ♦rater ? 



and the body will float ; if, on the 



contrary, it is heavier than an equal bulk of water, 

 the pressure of the particles of water will bo un- 

 able wholly to sustain it, and, yielding to the at- 

 traction of gravitation, it descends, or sinks. 



But to whatever extent a body may be supported in water, to the same 

 extent it will cease to press downward, or its weight will diminish. TTe ac- 

 cordingly find, that a solid body, when immersed in water and weighed, will 

 weigh less than when weighed in air, and the difference between these two 

 Weights wUl be equal to the weight of a quantity of water of the same size or 

 bulk as the solid body ; all bodies of the same size, therefore, lose the sam9 

 quantity of tlieir weight in water. To find the Specific Gravity of SoUds 

 heavier tlian water, or their weight compared with the weight of an equal 

 bulk of water, we have the following rule : 



75. Ascertain the wei^rht of the body in 



Divide the weight in 



and the 



How do we de- 

 terming the 

 Specific Grav- 

 ity of SoUds 

 heavier than 

 WAter? 



water, and also in air. 



air by the loss of weio;ht in water, 



quotient will be the specific gravity required. 



