IV. 
CONTENTS. 
On the presence of Tin in the Protosulphate of Iron, and the incon- 
veniences therefrom in examinations for Arsenic. By M. 
Sarzeau, of Rennes, CG 
Process for obtaining Veratria. By M. J. Righini, - 70 
Note upon the Bark of Cedrela febrifuga. By A. Richard, - 71 
Method of determining the quantity of coloring matter contained 
in Cochineal. Extracted by J. de Fontenelle, - 73 
Upon the Preparation of Essential Oils. By E. Soubeiran, - 75 
On Fluorine, By G. J. Knox and the Rev. Thomas Knox, - 79 
Miscellany, . 81 
