134 PEOFBSSOK CALTERT ON THK 



whole for one hour, when the olive crystalline oxide was 

 produced. It must be well washed in cold water which 

 has been deprived of its air and carboffic acid by boiling* 

 This oxide, when heated, decrepitates and gives off one per 

 cent, of water. If the heat be then carried to redness, it as- 

 sumes a beautiful yellow colour, and will not then melt evea 

 at a high temperature. It is entirely soluble in acids. 



HYDRATE OF PROTOXIDE OP LEAD. 



Requiring for my experiments some pure hydrate of prot- 

 oxide of lead, I tried the methods known, and was astonished 

 to find, that by whatever means I precipitated nitrate of 

 lead with ammonia, I obtained not the hydrate, but sub* 

 salts of lead. Neither was I more successful when I poured 

 a great excess of potash into nitrate of lead, as I then pro- 

 duced sub-nitrates. To prepare this hydrate, a solution of 

 nitrate of lead, of 1'114 specific gravity at 60° Fahrenheit, 

 was poured gently into a solution of caustic potash, having a 

 specific gravity of 1*315°, and the whole boiled for some time. 

 Chemists not agreeing as to the real composition of this 

 hydrate, it was examined, and found to be zz PbO -f- 2 HO. 



ACTION OF AMMONIA ON THE HYDRATE OF PROTOXIDE 

 OF LEAD. 



In enquiring into the action of ammonia on the above 

 hydrate, I was fortunate enough to discover a new com- 

 pound, which I obtained by taking some hydrate, previously 

 dried between filtering paper, and boiling it for several days 

 in often renewed caustic ammonia. It slowly changes itself 

 into a greenish olive crystalline compound, which, after being 

 separated by decantation from a white powder, well washed 

 in close vessels, and dried in vacuo, is the plumbate of 

 ammonia, with one equivalent of water. This compound 

 is crystallized, but in such small crystals as not to be deter- 

 mined ; the salt may be kept from decomposition for 



