292 Mr. R. Tuson on a Carbonate of Lead from Leaden Coffins. 
moisture and carbonic acid evolved during the decay of the 
animal remains, acting, conjointly with the oxygen of the air, on 
the leaden coffins in which the bodies were placed. 
If one might venture to assign a formula to this mixture of 
carbonate and oxide of lead, its composition would be represented 
by PbO+15(PbO, CO%), as the following numbers clearly 
indicate :— 
Calculation. Experiment. 
16PbO=1785'6 . . 84°41 84°45 
IS GOr ess ns. Lodo 15:55 
160:00 100°00 
The interesting points in connexion with this substance are, 
that it is anhydrous, that it contams but a small excess of oxide, 
and that it consequently differs in composition from any of the 
carbonates of lead hitherto described as being produced by the 
united action of air and water on metallic lead; or by the influ- 
ences concerned in the well-known Dutch method for manufac- 
turing “ white lead,’ and which, it is believed, approximate in 
character to those under which the material forming the subject 
of this cominunication was developed. 
The difference in composition of the various carbonates of lead 
formed under the circumstances referred to, will be seen by 
glancing at the subjoined Table :— 
Source. Composition. 
Air and water on lead . PbO, HO+PbO, CO?. 
Dutch method . . . PbO, HO+2(PbO, CO’), 
and sometimes 
PbO, HO+3(PbO, CO?). 
Leaden coffins. . . . PbO+15(PbO, CO*). 
Were any of these hydrated and basic carbonates of lead ex- 
posed sufficiently long to the action of carbonic acid, they would 
in all probability be transformed into perfectly neutral and anhy- 
drous carbonates. 
Lastly, it is most likely that the lead of the coffins was first 
converted into hydrated oxide, then into hydrated and basic car- 
bonate, and finally into the anhydrous carbonate of the compo- 
sition already given. 
March 21, 1860. 
