jYo. XIIL 



wj-w^taM,.rw.^-^-^.^..»^-,-,.y.,p„^,,j^,y^j,^^-y :ji.M^K| 



ON THE DECOMPOSITION OF 

 WHITE LEAD PAINT. 



To Mr. Benjamin Silliman, Secretary of the Con- 

 necticut Academy of Arts and Sciences, 



SIR, 



IT is well kno^vn, that a white paint, formed by mix- 

 ing oil, and usually vegetable oil, with the white 

 oxyd of lead, is very expensive, and not very durable. 

 Within a few years after this paint is laid upon a build- 

 ing, it is observed that the oil has been separated from 

 the lead, and the latter may be rubbed off with the hand, 

 being reduced to a state in which it is easily pulverized. 

 It is observable also, that the like paint on inside work, 

 not exposed to water, is not liable to the same change. 

 From these facts, it is probable that the oil, when expos- 

 ed to water, undergoes a slow decomposition. 



Oil is proved, by chemical analysis, to be composed 

 of carbon, or pure charcoal, and hydrogene, or the base 

 of inflammable air, in the proportion of nearly four parts 

 of the former, with one of the latter. Now carbon has 

 a very strong affinity for oxygene, one of the constituent 

 elements of water. Is it not probable that the decompo- 

 sition of the oil of paints is owing to that affi^nity — the 



