252 DEOXIDATION OP FERRIDCYANIDE OF POTASSIUM, 
covered with the glass plate, and allowed to drain quietly 
during the night. 
Whilst this extraction with water is going on, I filter the 
alcoholic solution from the waxy matter, and distil off the 
alcohol in a small steam apparatus, until only a few ounces 
remain. The fine green syrupy residue I then pour into a 
porcelain dish, and add to it the v. atery solution when eva- 
porated to a syrupy consistence, and evaporate it gently 
over the flame of a small spirit-lamp until of the proper 
consistence, by which means I procure an extract that dis- 
solves completely in water with a fine green color, and in 
point of activity leaves nothing to be desired. I proceed in 
the same manner with Belladonna, Digitalis, Conium, &c, 
and especially recommend this method to pharmaceutists in 
small places, as affording a certain and active product both 
in a quantitative and qualitative respect. 
I have always obtained 1 oz. 6 drms. of extract from 4 
oz. of coarsely-powdered Hyoscyamus. 
Ibid, from Buck. Rep. 
ART. LV. — ON THE DEOXIDATION OF FERRIDCYANIDE 
OF POTASSIUM, AND OF SALTS OF THE PEROXIDE OF 
IRON. 
By Professor Schonbein. 
When an iron wire with a clean surface is immersed in 
an aqueous solution of ferridcyanide of potassium, it be- 
comes quickly coated with a layer of prussian blue ; and if 
a number of such wires be placed in a similar solution, 
there very soon separates a considerable quantity of a 
bright blue body, which, by exposure to the atmosphere, 
