EARTHS. 



will precipitate the magnesia and alumina, and not the lime ; we then 

 decompose the filtered solution by carbonate of potash, and the pre- 

 cipitated carbonate of lime, after being washed and dried, is decom- 

 posed by a strong heat. Common good quick lime, that has not 

 been air slacked, answers every purpose for demonstrating the pro- 

 perties of lime. 



3. PROPERTIES. 



(a.) Color, white, and the masses recently from the furnace are 

 rather hard, but brittle. When dry, not active on the animal organs, 

 but if moistened, lime acts as a caustic ; taste astringent and alkaline. 



(6.) Specific gravity 2.3. 



(c.) Soluble in water: writers vary in stating the proportion, be- 

 tween 450 and 778 parts of water for the solution of 1 part of lime, 

 or 558 for the hydrate : 500 is the number heretofore adopted ; pro- 

 bably 700 may be near the truth ; but it appears that only a weak 

 lime water is obtained by using water at 212, which dissolves only 

 TTTTF f ^ e H me ana " JT f th e hydrate, while at 32. Accor- 

 ding to Mr. Dalton* and Mr. R. Phillips, it takes up i^, or nearly 

 double, and when the solution is heated, it becomes troubled, and 

 lime is deposited. These facts are not in accordance with the gen- 

 eral laws of solution when it is aided by heat. 



(c?.) Lime water: its taste is acrid and disagreeable, and it produ- 

 ces upon test colors the effects of alkalies ; it is not however caustic, 

 and there is so little of it contained in the water that it may be swal- 

 lowed with safety, and often with advantage. It is a valuable reagent 

 and medicine ; it is prepared by simple solution of lime, in w r ater ; it 

 must be preserved in close bottles from the atmosphere, } otherwise 

 it precipitates as a carbonate. 



(e.) Lime water^ is made to afford crystals, if placed in a vacu- 

 um, under the receiver of an air pump, the evaporation being aided 

 by sulphuric acid, contained in another vessel; the process is gradual, 

 and depends on the same principle as the congelation of water by 

 the same means, (see page 116.) The crystals are transparent 

 hexahedra, and are true hydrates, containing lime, 76.26, water, 

 23.74=100.00.J Lime water forms an imperfect soap with oil. 



* Ann. Phil. N. S. I. 107. 



t Place in a clean carboy, a quantity of good hydrate of lime ; fill the vessel with 

 rain water ; agitate it, and allow the lime to subside over night ; it will be dissolved 

 in one fourth of an hour, and in the morning it may be drawn off clear by a syphon, 

 or filtered through paper if it is wanted immediately ; if the cork be good, and the 

 water is not allowed to freeze, the same arrangement, adding water from time to 

 time, will answer for years. 



t Ann. de Chim. et de Phys. I. 335. 



