NITRITES. 489 



NITRATE OF MAGNESIA AND AMMONIA. 



1. PREPARATION. Formed by a partial decomposition of nitrate 

 of magnesia by ammonia, or of nitrate of ammonia by magnesia, or 

 better by a mixture of the two nitrates. 



2. PROPERTIES. 



Slender acicular crystals; Utter. 



Little deliquescent; soluble in 11 parts of water at 60, in 

 less at 212, and the solution deposits crystals as it cools.* 



NITRATE OP ALUMINA. 



1. PREPARATION. The fresh precipitated earth is washed and 

 heated with dilute nitric acid. 



2. PROPERTIES. 



(a.) The solution, which is always acid, deposits, after evapora- 

 tion, thin crystalline ductile plates. 



(b.) Taste sour and astringent ; extremely soluble and deliques- 

 cent; decomposed by heat without decomposing the acid. 



(c.) Decomposed by most alkalies and earths. 



3. COMPOSITION. Nitrate of alumina, when dried between folds 

 of blotting paper, is composed of acid 1 proportion, base 2, water 10, 

 and by a stronger heat it loses a portion of its acid. Thomson. 



The nitrates of the other earths are unimportant. 



NITRITES. 



They cannot be formed synthetically, and the only distinct one is 

 that of potassa. 



1. PREPARATION. Fuse nitre in a crucible till one proportion of 

 its oxygen has escaped, or partially deflagrate it with charcoal. 



2. PROPERTIES. Deliquescent, and emits red fumes of nitrous 

 acid even with vinegar, and very strikingly with a strong acid. 



It is not certain whether this salt is a nitrite or hypo-nitrite. 



RECAPITULATION 



Of some principal facts relating to oxygen and nitrogen. 

 1 . Remark. Even a limited acquaintance with chemistry is suffi- 

 cient to enable us to see that the properties resulting from chemical 

 combination are such as we cannot always foresee, nor account for 

 when known ; and that the different results, obtained from combina- 

 tions of the same elements in different proportions and in various de- 

 grees of condensation, are very surprising. 



* See Thenard, 2d ed. Vol. Ill, p. 240. 

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