568 APPENDIX. 



Avhen heated, so that the weight of a given bulk varies with the tempe- 

 rature. If a vessel containing, for example, a cubic inch is filled with a 

 fluid at a moderate temperature ami cooled, the liquid will shrink, and 

 more miM In- poured in to till up the space. If, on the contrary, it he 

 warmed, the liquid will run over. The weight of the cubic inch of cold 

 liquid will he greater than that of the liquid tit the original temperature 

 hv the quantity poured in. while that of the hot liquid will be less by 

 that which has run over. It is therefore absolutely necessary to coin- 

 pure the weights of bodies at the same temperature. Specific gravities 

 are in this country estimated at 1-V C. or (JO F. 



;tri(y of Liquid*. The specific gravity of a liquid maybe 

 ascertained by th'e use of the specific gravity TJUlllf, llii 1 hydrometer, or 

 specific gravity beads. 



Specific Gravity Bottle. This is a small bottle which contains a 

 known \olume of liquid ; one form of bottle (fig. 348) contains its pro- 

 per quantity when it is tilled perfectly full, another form (fig. 844) when 

 filled up to a mark on the neck, which is long and thin. The bottle hav- 

 . n charged with the liquid, of which the specific gravity is to be 

 determined, the weight of its contents is determined by the balance, for 

 which purpose it must first be counterpoised. The quotient obtained by 

 dividing the weight of the liquid by the weight of the same bulk of 

 MI the same temperature is its specific gravity. It is difficult to 

 fill an ordinary bottle completely and to put in the stopper without get- 

 ting in an air-bubble, which would of course alter the weight of the 

 its ami MI give false results. To obviate this difficulty, the stop- 

 pi r of a specific gravity bottle has a hole bored up through its middle, 

 so that when the bottle is filled and the stopper put in, any air or fluid 

 that may be present in the neck passes up through the hole, and thus 

 both the hottle and the hole in the stopper are completely filled with 

 fluid. Before weighing the empty bottle or making a counterpoise for 

 it, it must be thoroughly dried. Specific gravity bottles of this kind 

 tTUCted "to contain from .",() to !()(") grammes of distilled 

 water at 1 :> ('. Counterpoises are always sold with them. Before, 

 u-ing them, the accuracy both of the counterpoise and of the capacity 

 of the bottle mn>t be toted. For thi' latter purpose, the bottle must be 

 filled and then immersed in a beaker containing distilled water at a tem- 

 perature a few degrees higher than 1.") ('.. and allowed to remain until 

 a thermometer standing in the water indicates that the required tempe- 

 lia^ been reached. The bottle must then be removed from the 



and \\eiiihed against the counterpoise, its outside having been 

 tiiM carefully wiped dry. The weight is that of the distilled water 



contained in the bottle al \~> ('. In weighing the contents of the hot - 



tl" when charged with any liquid of which the specific gravity is to be 



determined, the same method U to be followed, with the exception that 



tie must not be completely immersed in the liquid contained in 



If then ir indicate the \\eight of the water and //' that of 

 lie volume of the other liquid at the same temperature, its specific 



iiy = v. 



times it is difficult to get a sufficient quantity of liquid to fill the 

 C gravity bottle just described. When this is the case, a specific 

 gravity hottle may be made out of a test-tube, by drawing it out, as in 

 the accompanying figure (Tig. :54.")).and then flattening the bottom so as 

 to make it stand by heating it and pressing it against a piece of iron. 

 A -eratch U to be made on the narrow part of the neck, up to which 

 the bottle is to be filled with water at 1.". C.. and weighed against a 



counterpoise as before. In all other respects the procedure is that which 



11 already described. 



