288 



ON THE OXIDl 



86 oxide, 



1 4 acid, and waters 



100. 

 The foUrtion being evaporated, depofited two fets of crys- 

 tals ; one fet confifting of common nitrate of lead, another iet 

 refembling thofe obtained by Prouft. 

 Three nitrates of 7. From liie preceding details we learn^ that there are three 



a. fuper-nitrate, or 

 an excels of acid ; the fecond is neutral ; the third 

 contains an excefs of bafe, and is, of courfe, a fub-nitrate. 

 The firft fpecies includes the common nitrate of chemifts in all 

 its varieties; the fecond, the nitrate of Proull; the third, the 

 yellow powder obtained by heating common nitrate fuffi- 

 ciently. 



III. BrOtcfi Oxide, 



lead ; -^f -.ne"- diftind fpecies of nitrated lead : The firft 



tral, and witn _ ' , . 



excefs or with cont-ains an excels of acid 

 defeft of acid 



Brown oxide ', 

 left when mini 

 urn is diffolved 

 in nitric acid> 



its habitudes } 



contains one- 

 tenth more oxi- 

 gen than yellow 



Though (his oxide contains a maximnm of oxigen, I beg 

 leave to introduce it Here, becaufe the knowledge of its com- 

 pofition is neceflary to enable iis to analyfe the red oxideoi lead. 

 It was difcovered by Scheele, and defcribed by him in his 

 diflertation on manganefe. When dilated nitric acid is poured 

 upon red lead, the greater part of the oxide is diiTolved, but 

 a brown powder remains behind, which is not adled upon by 

 the acid. This brown powder is the brown oxide of lead. 

 Prouft difcovered that it may be formed alfo by caufing a cur* 

 rent of oxl-muriatic acid gas to pafs through red lead fuf- 

 pended in water. 



1. This oxide is a taftelefs powder, of a flea-brown colour,- 

 and very fine and light, It is not a6led on by fufphuric nor 

 nitric acid. To muriatic it gives out oxigen, and converts it 

 into oxi-niuriatic acid. Oxi-muriatic acid diffolves it, and 

 forms two falts, muriate and hyper-oxl-muriale of lead. The 

 vegetable acids reduce it to the ftate of yellow oxide. Four- 

 croy, on the autliority of Vauquelin, affirms, that fulphur takes 

 lire when triturated with brown oxide of lead. With me the 

 experiment did not fucceed : I fufpeft, therefore, that the 

 oxide ufed by Vauquelin contained a portion of hyper-oxi- 

 muriate of lead mixed with it. 



2. When 100 grains of this oxide, prepared from red lead 

 by nitric acid, are expofed to a red Ijeat, they lofe nine grains 



of 

 3 



