RECTIFICATION OJF NITRIC ACID. 



135 



ieveral authors direct. The quantity of litharge muft vary 

 irom one to eight fixteenths of the weight of the acid, accord- 

 ing (o its degree of impurity. On the other hand, if difiilJed 

 lo.drynefs, tiie.Iatler portions of the nitric acid will carry over 

 with them in folution muriate of lead, or of filver. 



Four kilogrammes (lOlb. 8oz. I6dwt. troy) of nitric acid ^^'^^f "'"^^"'* 

 of the fliops, at 35^, containing muriatic aciid, and a very lit- 

 tle fulphuric, are firft diftilled in a reverberatory furnace in a 

 retort placed on an earthen veffel iiiled with fand. The fire 

 muft be fo regulated that the drops fucceed each other llowly, 

 and half the ^cid is to be thus drawn off. It will then give 

 l^*^ of Baumd's areometer. What remains In the retort is to 

 Jbe poured into a bottle. Its fpecific gravity will be expreifed 

 by 4° of the areometer. Litharge being thrown into it in fine 

 powder, and ftirred with a glafs rod, will be converted into a 

 white powder in a few hours. More litharge is then to be 

 added in the fame manner; and this is to be continued, till the 

 litharge retains its colour after feveral hours fiandihg. The 

 muriate and fulphate of lead are then to be left to fubfi'de eli- 

 tirely, and the acid is to be decanted off into a tubulated glafs 

 retort, placed on a fmall earthen plate filled with fand, in the 

 midft of a reverberatory furnace, all the parts of which are 

 retained except the dome, A receiver is to be adapted, which 

 fits clofely without luting; for, as the vapour of the acid eafily 

 defiroys every kind of lute, the product would otherwife be 

 lijtbleto become impure; and the difiillation is to be fo con- 

 dueled, as to admit a Ihort interval between the fall of each 

 drop. Great caremuft be taken not to fuifer the acid to boil, 

 for thus it would be diffipaled in incompretiib'e vapour, Tlie 

 firfl: half that comes over marks 35®, the fecond 40^. Both 

 ' portions are colourlefs, and have all the properties of a veff 

 ; pure nitric acid, if -j^ of the liquor be left in the r6t'6i*t!" " ." ' " *.j'^ 

 If a flop be put to the difliilation after the firtl portion is fe- Beautiful H 



parated, and the retort left to grow cold, you will obtain a ^^y^.^^^ °^. , ^ 

 J . , . . / murute of lead , 



beautiful cryftalHzation of muriate of Jead in large and very may be obtained 



brilliant ftriated hexaedral lamina?. This fait is a true muriate, ^i^*^? ^^^au^j 



for fulphuric acid expels from it vapours eafily diflinguithable oft', 



to be thofe of the muriatic acid. On continuing the difiilla- 



tion, thefe cryftals gradually lofe their regular figure, and at 



length fall to the bottom in a powdery preeipilate. 



Eafy 



