96 
ORIGINAL COMMUNICATIONS. 
crystallizing. This may do for copper and alumina, but will 
not answer for many other impurities. 
Among the preparations into which it enters, are the com- 
pound iron mixture, and the compound iron pills of the phar- 
macopoeia; the former being similar to^the celebrated antihectic 
mixture of Dr. Griffith of England, the latter composed prin- 
cipally of the same ingredients, intended as a substitute for the 
mixture — the latter are pretty generally prescribed in this 
city. The directions given for making them are hardly ex- 
plicit enough. 
They are: Take of myrrh in powder, two drachms; carbo- 
nate of soda — sulphate of iron, each one drachm; syrup a suf- 
ficient quantity; rub the myrrh with the carbonate of soda, 
then add the sulphate of iron, and again rub them; lastly, beat 
them with the syrup so as to form a mass, to be divided into 
eighty pills. 
When the carbonate of soda and the sulphate of iron, in 
crystals, 'are mixed with the myrrh, it is very difficult to 
powder them, the sulphate more particularly; much of which, 
as the mixture becomes moist by trituration, remains in coarse 
particles, defended from the action of the pestle by the myrrh. 
I have, in making them, usually powdered the several in- 
gredients previous to mixing. In moist weather, the addition 
of syrup is unnecessary, sufficient water of crystallization be- 
ing afforded by the mutual decomposition of the salts to form 
a pillular mass. 
The Precipitated Carbonate of Iron. — When a solution 
of carbonate of soda is mixed with one of the protosulphate of 
iron, a double decomposition ensues, and a precipitate (white 
if a pure protosulphate is used, but green if the sulphate in its 
ordinary state is employed,) is formed, which is a protocarbo- 
nate of iron in combination with water. By exposure to the 
air it loses the water, and most of the carbonic acid, and ac- 
quires oxygen from the air, forming a reddish brown peroxide, 
united with a variable quantity of protocarbonate of iron. 
The formulas of the different pharmacopoeias, as in the case 
