284 
Original Communications. 
driodate of ammonia, over a water bath. The crystals ob- 
tained are of a yellow colour, very deliquescent and require 
to be kept in a close stoppered bottle. They are soluble in 
alcohol and in water. The preparation of it most in use is 
the ointment. The following is the recipe : — 
Take of hydriodate ammonia Bl. 
Cerat. Simp, vel axungia gi. 
M. ft. ung. s. a. 
It has been found highly useful in glandular indurations 
and for other purposes, to which iodine is generally applied. 
The product which I obtained in using 20 drachms of iodine, 
was only 8 drachms of the salt. Charles Ellis. 
Emplastrum Plumbi. — In the preparation of Emplastrum 
Plumbi, it is well known that water enters into chemical com- 
bination with sweet oil and litharge, and is essential to the 
formation of the plaster. 
The following is a statement showing the exact increase 
in weight, derived from the addition of the water, beyond that 
of the other ingredients. The quantities given are those 
taken at the time the plaster was manufactured. 
Olei olivarum 36 lbs. 6 oz. 
Lythargyri 24 " 8 " 
60 14 oz. 
Aquae ad libitum, 
Increase in weight, 6 2 
Product lbs. 67 
Showing an increase of 10 per cent, in weight; the plas- 
ter being well worked with the hands, and thus deprived of 
any water that might otherwise remain uncombined with it. 
C. E. 
Resin of Jalap. — The following mode of obtaining the Re- 
sin of Jalap, devised by M. Planche, although it does not af- 
ford as large a product as some others, gives a purer article 
and is less expensive. 
