292 



ON THB OXIDES OF LEAD. 



96 yellow oxide, 

 4 carbonic acid. 



Summary reca- 

 pitulation. 



100. 

 Probably it varies fomewhat in the proportion of its conftita- 

 ents, according to circumftances : But all my trials were made 

 on one parcel of litharge. I have obferved traces of carbonic 

 acid alfo occafionally in red lead, but too little to affed its' 

 weight. 



VI. Conclufions. 



From the preceding experiments and obfervations we are 

 entitled, I think, to draw the following conclufions : 



1. Three oxides of lead only are at prefent known. The 

 conftituents of thefe oxides may be feen in the following table: 



Oxides. 



Colour. 



Conftituents. 



Lead. j O.KijxGii. 



Protoxide. 



Yellow. 



90.5 9.5 



Deutoside. 



Red. 



88 , { 52 



Peroxide. Brown. 



80 20 



Lead. Oxigen. 

 100 -{- 10.6 — 110.6 protoxide. 

 100 -f 13.6 zz 113.6 deutoxide. 

 100 + 25. — 125. peroxide. 



2. The allies of lead are a mixture of protoxide and lead 

 in powder. 



3. White lead and litharge are combinations of protoxide 

 with carbonic acid : the firft is a carbonate, the fecond a fub- 

 carbonate of lettd. 



* As colour is a very ambiguous criterion for diftinguifliing me- 

 tallic oxides, I have been accuftomed for fome time to denote the 

 oxide with a minimum of oxigen by prefixing the Greek ordinal 

 number to the term oxide : Thus, protoxide of lead is lead united to 

 a minimum of oxigen. The oxide with a maximum of oxigen 1 

 coll peroxide : Thus, bronvn oxide of lead is the peroxide of lead, t 

 denominate the intermediate degrees of oxidizement by prefixing the 

 Greek ordinals 2d, 3d, 4th, &c. Thus, deutoxide is the fecond 

 oxide of lead, tritoxide of cobalt, the third oxide of cobalt, and fo on, 



2 4. The 



