166 The Phosphates of America. 



DETERMINATION OF THE SPECIFIC GRAVITY OF SOLIDS. 



Solids heavier than, and insoluble in, water, 

 a. By weighing in air and water. 



(weight in air) 



Sp. gr. = 



(loss of weight in water) 



b. By Nicholson's hydrometer. 



Let w 1 be the weight required to sink the instrument to the mark 

 on the stem, the weight of the instrument being W ; to take the 

 specific gravity of any solid substance, place a portion of it weigh- 

 ing less than w in the upper pan, with such additional weight, say 

 ty 3 ,aswill cause the instrument to sink to the zero-mark. The 

 weight of the substance is then w^ w s . Next transfer the sub- 

 stance to the lower pan, and again adjust with weight w^ to the 

 zero-mark. 



Bp.gr.. 4?!-=^. 



c. By the specific-gravity bottle (applicable to powders). 



Weigh the flask filled to the mark with water, then place the 

 substance, of known weight in the flask, fill *o the mark with 

 water and weigh again. 



(weight of substance in air) -f- (weight of flask and water) 

 o _ (weight of flask and water and substance) 



(weight of substance in air) 



Solids lighter than, and insoluble in, water. 



The solid is weighted by a piece of lead of known specific gravity 

 and weighed in water. 



g _ (weight of substance in air) 



~ (weight of lead in water) (weight of lead and substance in* 

 water) + (weight of substance in air) 



Solids heavier than, and insoluble in, water. 



Proceed as in a, using instead of water some liquid without 

 action on the solid. 



(weight of bulk of liquid equal to substance) = 

 (weight of substance in air) (weight of substance in liquid). 



(weight of bulk of liquid equal to substance) 

 (weight of bulk of water x (gp gp of water) 



equal to substance) (sp. gr. of liquid)" 



(wpjght of substance in air) 



P- S r > = (weight of bulk of water equal to substance)' 



