LEAD. 397 



mixture of deutoxide and protoxide in variable 

 proportions. In some very beautiful red lead, I 

 have found the proportion of protoxide amount 

 to nearly one-half of the whole weight. If we 

 digest red lead in acetic acid, we dissolve the 

 protoxide, and leave the deutoxide untouched ; 

 it has a dark red colour, and is destitute of the 

 beauty which characterizes red lead. Various 

 experiments have been made to determine the 

 additional quantity of oxygen necessary to con- 

 vert the protoxide of lead into deutoxide. I 

 made a set of experiments on the subject about 

 twenty years ago ;* but as I was not aware at that 

 time, of the mixture of protoxide present in the 

 pigment, I did not, of course, attempt to separate 

 it, and consequently underrated the proportion of 

 oxygen which it contained. Even Berzelius, 

 though aware of the existence of the protoxide of 

 lead in red lead, does not seem to have succeeded 

 in removing the whole of it. But the proportion 

 of oxygen, which he assigns to this oxide, though 

 below the true quantity, affords a sufficient ap- 

 proximation to enable us to determine the com- 

 position of the deutoxide of lead. 



9'835 parts of deutoxide, when heated to red- 

 ness, gave out 0*29 parts of oxygen, and left 

 9 -545 parts of protoxide of lead.t According to 



* Nicholson's Jour. VIII. 289. 



f Afhandlingar, III. 168, or Ann. de Chim. LXXV.TII. 14. But 

 there is a typographical error in the French translation. 



