72 BULLETIN 42, UNITED STATES NATIONAL MUSEUM. 



Per cent. 



Sulphate of leadCrbSO.,) 74.17 



Oxide of lead (PbO) 8. 52 



Sesquioxideof iron (FejOs) 0.40 



Alumina (AI-O3) 0.65 



Oxide of zinc (ZnO) 2. W! 



Lime (CaO) 4.45 



Magnesia (MgO) 0.22 



Silica (Soluble SiO^) l--'">5 



Sulphurous acid (SOi) 0.27 



99.13 



Accessories. 



(1) Bag, made of unwashed wool used to catch the fumes. (55190.) 



(2) Fire brick, glazed by the corrosive action of the fused lead compounds in the 

 furnace. (.55180.) 



The Application of Lead. 

 A single illustration of the application of lead is shown : 



THE manufacture OF WHITE LEAD BY THE DUTCH PROCESS. 



The metal is cast in small pieces and placed with the requisite 

 amount of acetic acid in crucibles with holes in the sides. The loaded 

 crucibles are then stacked up in large piles and covered with decom- 

 posing organic material. The acetic acid gradually dissolves the lead 

 and then the carbonic acid given off by the decomposing organic mate- 

 rial replaces the acetic acid, forming a basic carbonate of lead. This 

 reaction goes on until all or nearly all the metal is converted into 

 white lead, when the crucibles are taken down, the white lead removed 

 and ground in oil ready for use. 



This process is illustrated by a collection from the works of Harri- 

 son Bros. & Co., Philadelphia, Pennsylvania, including also some 

 higher oxides of lead formed from the white lead. 



(1) Buckle, ready for corrosion. (55691.) 



(2) Acetic acid, used for corroding the lead. (55683.) 



(3) Crucible containing buckles of metallic lead. (5.5690.) 



(4) Tan bark, used to cover the crucibles during the corrosion. (55684.) 



(5) Crucible containing white lead. (55692.) 



(6) Buckle, corroded. (55693.) 



(7) White lead, ground in oil. (55685.) 



(8) White lead, finished. (55686.) 



(9) Litharge. (5.5687.) 



(10) Orange mineral. (.5.5688.) 



(11) Red lead. (55689.) 



