NITRIC ACID. 44Q 



Jlny acid, either weaker or stronger, boils at a lower temperature; if 

 weaker, it is strengthened, if stronger, it is weakened by boiling ; and 

 acids of all degrees of strength come, by continued boiling to sp. gr. 

 1.42, which seems to be the strongest combination of acid and water. 

 Acid of sp. gr. 1.369, contains half its weight of water ; that of sp. 

 gr. 1.30, has acid 40 and water 60, and boils at 236.* 



(/.) Frozen at 2 below 0, Fah. if of sp. gr. 1.3. When either 

 stronger or weaker, it requires a much more intense cold, as much, in 

 some cases, as to freeze mercury. f 



(g.) Exposure to light, colors it red, while oxygen gas is given 

 out, provided it be strong ; and this happpens when it is weak, if it 

 be previously mixed with sulphuric acid. 



(A.) Decomposed into oxygen and nitrogen gases, or nitric oxide 

 gas, by being passed in vapor through a red hot earthen tube, and 

 the stronger the acid the more readily it is decomposed. A pendent 

 candle just blown out, is promptly relighted by being plunged into the 

 mixed oxygen and nitrogen ; these may be analyzed by any of the 

 eudiometrical methods, and their proportion ascertained. They will 

 be found to be in nearly the reversed proportions of the atmosphere. 

 Some nitric oxide gas usually comes over and produces red fumes of 

 nitrous acid, which are soon absorbed by the water, and leave the ox- 



(gen and nitrogen mixed. The decomposition of the solid nitrates 

 y ignition affords similar results ; nitrate of ammonia, is however an 

 exception, as will appear in its proper place. 



(i.) Causes ice and snow to melt, producing cold ; 4 parts strong- 

 est nitric acid with 7 of snow, sink the mercury from -f 32 to 30 , 

 see tables of freezing mixtures. 



(j.) Attracts water from the air and becomes weaker, but not in 

 an equal degree with sulphuric acid. 



(/c.) Acid 2, -f- water 1, at common temperature, raise the therm. 

 112, but if more water is added, this mixture lowers the tempera- 

 ture. Nitric acid, 58 measures, of sp. gr. 1.5, mixed with 42 of 

 water, raises the temperature from 60 to 140, Fahr. and on cool- 

 ing, the 100 measures occupy 92.65.J 



(I.) More or less affected and decomposed by all combustibles, and 

 by most metals. 



(m.) It explodes with hydrogen at a high degree of heat ; 

 caution is required ; it is best shown by passing the hydrogen gas 

 from a flask, by means of a tube bent twice at right angles, through 

 nitre melted in a crucible, when there is a slight explosion, and a 

 flash at the passage of every bubble of gas ; some caution is requisite. 



Dalton. Thomson. Henry. t Cavendish, Phil. Trans. 1788. 



Ure, quoted by Turner. 



57 



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