488 NITRATES OF EARTHS. 



It is to be broken up and preserved in tight bottles. After "being 

 exposed to the sun for a few hours, it emits in the dark a beautiful 

 white light." Henry. 



(d.) With a strong heat it is completely decomposed, and lime 

 remains. 



(e.) It contains so much water that it scarcely acts on combusti- 

 bles unless previously dried. 



(f.) .More deliquescent than any other salt.* 



(g.) Water at 60 dissolves 4 parts ; boiling water any quantity ; 

 and boiling alcohol its own weight. Although difficult to crystallize, 

 it will, when evaporated to a thickish consistence, often become solid 

 and hot by the slightest agitation. 



(h.) J^cids, and alkalies and earths decompose it in the same man- 

 ner as the other nitrates. If potassa is added to a concentrated so- 

 lution it throws down the lime nearly solid, because it absorbs the 

 water. 



4. PROPORTIONS. 



Exclusive of water, the equivalent number of nitrate of lime 

 would be 82, i. e. acid 54, lime 28, and this would give for its con- 

 stitution in the 100 parts, 



Acid 65.86 Mr. Dalton found acid 61.3 base 38.7 



Base 34.14 Philips " 65.6 34.4 



100.00 



The result of Mr. Philips is very near to the regular constitution. 

 Id. 



NITRATE OF MAGNESIA. 



(a.) Of very little importance; exists in the mother waters of 

 nitre, and it may be formed synthetically; crystallizes in minute nee- 

 dles or in rhomboidal prisms; its taste is very bitter; sp. gr. 1.73; 

 soluble in half its weight of water at 60, and in less at 212; deli- 

 quescent; suffers the aqueous fusion; by more heat is decomposed, 

 like the other nitrates, leaving magnesia. 



(b.) Emits nitrous fumes with sulphuric acid. 



(c.) The alkalies precipitate the magnesia. 



(d.) Action on combustibles very feeble; it only scintillates slightly 

 on burning charcoal. 



(e.) Composition. According to Dr. Thomson, acid 1 propor- 

 tion, 54 ; 1 of base 20 ; 6 of water 54 = 128, its equivalent, which gives 

 percent, acid 42.2, base 15.6, water 42.2=100.0. 



* Hence it is kept very dry in close vessels, and used to dry the gases ; being for 

 that purpose placed in tubes through which they are made to pass. Impure deli- 

 quescent nitre, generally contains this salt. 



