CARBONATE OF LEAD. 591 



Carbonate of lead, Ceruse, White lead ; PbO, CO 2 ; 1670.9 or 

 133.89. Occurs in nature well crystallized, in the form of car- 

 bonate of barytes. It is precipitated as a white powder, of 

 which the grains although very minute are crystalline, when an 

 alkaline carbonate is added to the acetate or nitrate of lead. 

 The precipitate is anhydrous. When oxide of lead is left covered 

 with water in an open vessel, it absorbs carbonic acid, and be- 

 comes white, forming the subcarbonate PbO, CO 2 -}-PbO, HO. 



The carbonate of lead is invaluable as a white pigment from 

 its great opacity, which gives it that property, called body by 

 painters, and enables it to cover well. As precipitated by an 

 alkaline carbonate, it is deficient in body, owing to the transpa- 

 rency of the crystalline grains composing the precipitate. It is 

 also a neutral carbonate, as thus prepared, and differs in compo- 

 sition from the ceruse of commerce, which Mulder finds always 

 to contain hydrated oxide of lead in combination with the car- 

 bonate of lead. The result of Mulder's analyses of numerous 

 specimens of white lead, is, that there are three varieties of that 

 substance, the composition of which is expressed by the three 

 following formulae : 



2(PbO,CO 2 )+PbO, HO; 



5(PbO,CO 2 ) + 2(PbO, HO); and 



3(PbO,CO 2 ) + PbO,HO. 



Mr. T. Richardson, who has also been engaged with a che- 

 mical examination of the varieties of white lead, finds all of 

 them to contain a portion of oxide of lead, in addition to the 

 carbonate, and so far confirms the conclusions of Mulder.* 



* The following are Mr. Richardson's results, which he has communicated 

 to me. The specimens were all dried at a temperature of about 300 for 24 

 hours, previous to analysis. No. 1, was made by the French plan, (by trans- 

 mitting carbonic acid through subacetate of lead) ; No. 2 is Kremner white, 

 No. 3, 4, 5, were made by causing small pieces of lead to be agitated in a 

 tub, into which carbonic acid was passed, as practised in London ; Nos. fi, 7, 

 8, 9, 10, were made by the old Dutch plan, but each of the specimens was 

 from a different manufacturer : 



12 3 45 7 8 9 10 



Carbonic Acid. 13.70 15.83 13.70 13.03 13.24 14.61 13.71 13.99 12.99 U.!*. 



Protox. Lead. 86.00 83,4'J a r ).66 85.98 86.40 84.83 8(5.02 86.09 86,45 H5.UL'. 



99.70 99.32 99.3(5 99.01 9D.70 99.44 99.73 100.08 99.44 99.97. 



"While the neutral carbonate of lead consists in 100 parts of 

 Carbonic acid. . . . 16.54 

 Oxide of lead. 83.46 



100.00 



Q Q 



