12 
ORIGINAL COMMUNICATIONS. 
nitric acid, and ammonia, without specifying proportions, they 
proceed: "It is necessary not to lose sight of the fact, that 
the solution of the salt of iron must be complete before add- 
ing the nitric acid in small quantities, otherwise, a consider- 
able amount of a neutral sulphate of peroxide will separate in 
the form of a yellowish powder, which is very slightly 
soluble. The chloride of iron affords a means of preparing 
this body still less eligible, because the risk is run in preci- 
pitating, by ammonia, of obtaining an admixture of a large 
quantity of subchloride of iron." 
" In order that the hydrated sesquioxide may not be de- 
prived of its water, and by this means of diminishing, in 
the least possible degree, its feeble slate of aggregation, it 
should not be filtered, but after having been suffered to 
subside for several days, the supernatant fluid being 
poured off, it must be ]jreserved under water in closed 
vessels." 
" Simple as is the process here indicated for the preparation 
of the antidote, there have been, nevertheless, modifications 
proposed, some of them so unfit that we believe it useful to 
add some remarks on this subject. First of all, there is one 
practice which ought to be rejected, that of employing another 
alkali than ammonia for the precipitation of the hydrate of the 
sesquioxide of iron, as some have done; in fact, the least 
quantity of alkali retained in the precipitate will give rise to 
the formation of an arsenite, which would abstract itself en- 
tirely beyond precipitation by the hydrate of sesquioxide 
of iron, because, although this base can prevail over the 
affinity of ammonia for arsenious acid, it could not over that 
of soda or potassa."* 
The subject is now submitted for the deliberate examina- 
tion of the two professions who are interested in its determi- 
nation, and upon whom no greater reward can be bestowed 
* This may have been the mode employed by Dr. Robson, whose pa- 
tient found himself worse after having been relieved, upon using an imper- 
fectly washed precipitate; and felt no pain after using some which had 
been well washed. See Amer. Journ., Vol. 20, page 222. 
