Falls refpiil'tng Nitric ^cid. — Indigt, , 32^ 



XII. 



Dtlachcd FalJs or Notices on chemical SubjeSls — Nitric Acid — Oxide of Azote — Indigt — Ni' 

 trite of Potajh — Refidue of Ether — Inflammation of Oils by Nitric Acid — Ammoniac — Fu- 

 trid Ifater at Sea. By CITIZEN P ROUST, ProfeJJor of Chemijlry at Madrid.* 



Nitric Acid. 



w> 



ITH very dry nitre and fulphuric acid I prepared nitric acid, which was pure, and 

 fupported the proof of barytes. After it had been deprived of gas, by careful diftillation, 

 it continued yellow, and had a fpecific gravity of 152. — When again diftilled, the firft pro- 

 du£l had the fpecific gravity of 151, and w^as lefs yellow; the fecond, though lefs coloured, 

 was only of the fame denfity; but I was furprlzed to find the refidue, which was perfedily 

 colourlefs, weighed only 147. This being alfo diftilled over, the firft: portion was of 149, 

 and the reft did not exceed 144. 



In another experiment the a«d obtained from very dry nitre had the denfity 155. It was 

 firft cleared of gas, and afterward diftilled. Its firft produdl had the denfity 162. The fecond 

 paler, 153 ; and the colourlefs refidue weighed no more than 149. Hence we may obfervc 

 that the acid in its concentration is affeded very differently from what we might fuppofe f , 

 and that it is the reverfe of other acids. I have remarked on thefe occafions, that the 

 ftronger the acid the eafier the diftillation, and that it is not neceflary to boil it, in order that 

 it may evaporate with more rapidity. A notion of the force which concentrated acid exerts 

 upon its own parts may be formed by pouring the acid of 148 upon pulverized tin. It pro- 

 duces no more efFedl than upon fand. This, however, is not the cafe with zinc J. 



Oxide of Azote. 



To obtain this gas with certainty, the acid made ufe of muft have the /pecific gravity of 15* 

 of the areometer of Baume (1,114) to be applied to zinc. An acid at 18 or 20 afford a mix- 

 ture of nitrous gas, and no doubt azote. 



Indigo, 



An acid of 148 diflblves this fubftance, and turns it yellow by oxidation. It is a refin 

 foluble in alcohol and fcparable by water. It was with furprize that I found, by means 

 of weak acids, magnefia even abundantly in indigos, befides the extradlive matter which they 

 are known to contain. 



An acid of 151 or 152 inflames indigo, as Sage has publifllcd, and as Woulf likewife 

 (hewed to Hillare Rouellc, who ftiev/ed itin his ledtures. 



♦ Journal de Phyfique, Meflidor VII. 



f The fame fafts have been obferved by Chaptal and other French chcmifts. 



} The majority of chemifts afcribc this diS'erence of effeft to the decompoCti<m of witer, which, from 

 many fafts, appears to be the true folutiun. 



Vol. III. — October 1799. U u Nitrite 



