8 
Original Communications. 
uses in his own practice. It is, however, to be hoped that 
the doctor's sweeping suspicions are for the most part in- 
correct. I have myself subjected several parcels to the ordi- 
nary chemical tests, and have discovered minute portions of 
corrosive sublimate in the proportion of one in four specimens. 
The difficulty of divesting calomel entirely of corrosive 
sublimate, I attribute to the impossibility of reducing calomel, 
made in the ordinary way, to a sufficiently fine powder, and 
consequently corrosive sublimate adheres to it with great 
tenacity. 
I have recently made, in conjunction with Professor Ellet, 
of Columbia College, a most excellent article, by a process 
similar to that of Messrs. Howard and Jewel, and somewhat 
varied from the usual method, which possesses the important 
advantage of reducing the calomel to the minutest possible 
division. It consists in subliming calomel into an atmosphere 
of steam. The ingredients are put into a short necked earthen 
retort, which is attached to a receiver, having an aperture at 
opposite sides and one at the top. # A retort containing wa- 
ter is fitted to the opposite opening, and heat is applied si- 
multaneously to both retorts, when the vapour of calomel and 
the steam come in contact before they are condensed, which 
prevents the mass from becoming solid. Calomel made by 
this process is perfectly pulverulent, of a pearly whiteness, 
and very pure. 
To determine the presence of corrosive sublimate in calo- 
mel, digest in ten times its weight of boiling water, and filter; 
of the filtered solution, a drop or two may be placed on a 
gold coin, and its upper surface touched with one extremity 
of an iron or zinc wire, whose other extremity is in contact 
with some other part of the gold, so as to form a galvanic 
circle. If the solution contain mercury, its presence will be 
determined by its deposition on the surface of the gold, which 
it whitens. As no other soluble preparation of mercury is 
likely to be present in calomel, the above experiment may be 
generally considered as indicating corrosive sublimate. To 
insure absolute certainty another portion of the liquid may be 
* The opening at the top is for vent. 
