[ 9^ ] 



cake ; this cake was powdered and boiled with fix ounces 

 mcafures of diftilled water for half an hour. The filtered 

 liquor ftruck a deep black colour, with hepatic air and folution 

 of hepar fulphuris ; and depofited a white precipitate on the 

 addition of marine acid, and a folution of neutral arfenical 

 fait. From the encrcafed weight of the cake it appears probable 

 that it had attraded fixed air from the atmofphere. 



From the foregoing experiments it was inferred that lime 

 ads imperfedly, perhaps not at all, upon lead, without the aflift- 

 ancc of air to calcine the metal. 



The following experiments were made in order to afcertain 

 the adion of lime upon lead, in different ftates of calcination. 

 I took ten grains of finely powdered lithrage a, the fame quan- 

 tity of calx of lead precipitated from nitrous acid by volatile 

 alcali ^, and the fame weight of minium c ; to a and b were 

 added four ounces by meafure of lime water made by boiling lime 

 with the pureft diflilled water. The fpecific gravity of this 

 lime water at the temperature 60 was 1003; to <: were added 

 four ounces and a half of the fame lime water. 



The mixtures were all put into phials which contained them 

 cxadly ; to each of thefe ftoppers were carefully adapted, fo 

 fo as to exclude the air completely; the phials were placed 

 in fand, which, for feveral days together, was heated to one 

 hundred degrees. After they had flood for thirty days, 

 during which time they were often fhaken, the liquors 

 were filtered, and the powders that remained undiffolvcd 



were 



