OXIDES AND NITRATES OF LEAD. 



133 



tact with melted caustic soda. In this case there is 

 only the influence of a given temperature, to vvhich the 

 oxide is instantly carried by the heated caustic soda, to ac- 

 count for the production of the red colour. In further 

 proof of the correctness of these views, massicot put into 

 melted caustic soda acquires nearly the same red tint. 



I am therefore led to think, that the molecular change 

 which is instantly produced in this experiment, takes place 

 slowly in the oven where massicot is changed into red lead 

 for commercial purposes. 



Chemistry already possesses some examples, of a per- 

 manent molecular change being eifected by the action of heat 

 only. For example, the black phosphorus obtained by Mr. 

 Thenard, and the red amorphous phosphorus lately dis- 

 covered. 



RED CRYSTALLINE OXIDE — ACTION OP CAUSTIC POTASH 

 ON THE HYDRATED OXIDE OF LEAD, 



When a solution of boiling caustic potash is saturated 

 with hydrate of oxide of lead and left to cool, the pink 

 oxide of lead is not produced as with soda, but a beautiful 

 red crystalline one, which was discovered nearly at the 

 same period by Mr. Mitscherlich and myself. This oxide 

 has several of the characters of the pink oxide, but is in 

 smaller crystals, and more soluble in acids. 



By throwing into melted caustic potash some hydrate of 

 protoxide of lead, the red amorphous oxide above described 

 is produced. 



CRYSTALLINE OLIVE OXIDE. 



To prepare this new oxide, a warm solution of nitrate of 

 lead, having 1-114 specific gravity at 60° Fahrenheit, was 

 poured into a warm solution of concentrated potash, indi- 

 cating 1-162 specific gravity at 60° Fahrenheit. The sub- 

 nitrate of lead thus formed, was decomposed by boiling the 



