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BRITISH PHARMACEUTICAL CONFERENCE. 
Witli strychnia, the most insoluble of the iodohydrargyrates, I have not 
been more successful. When carbonate of baryta or of lime are used, the 
indication is below the mark ; when carbonate of potass in slight excess, the 
same result; when in considerable excess, or when slightly acidulated with 
acetic acid, the iodohydrargyrate is wholly decomposed, as in the case of 
morphia. Between these extremes may be ranged the remaining iodohydrar¬ 
gyrates, whose destructibility by nitrate of silver will be in direct proportion 
to their solubility. I have found that it matters nothing, whether the alka¬ 
loid has been dissolved in sulphuric or in nitric acid. 
I am therefore of opinion that the process cannot be applied with anything 
like, accuracy, and anything short of that would be worse than useless. Could 
it be applied, the following formula would separate the total of silver into that 
required by the excess of precipitant, and that by the iodine and chlorine 
belonging to the combined portion— 
—— XS 
5 
where (a) is the silver solution, ( b ) the iodohydrargyrate, and ( x ) the excess. 
I am of course sorry to be obliged to differ so completely from the con¬ 
clusions of Professor Mayer’s paper, “ On the Assay of Alkaloids, Pure and 
in Preparations,” but I certainly cannot admit either his formulae or mode 
of conducting the assay. Something may of course be said as to the degree 
of dilution, but I believe the solutions I used are as strong as can safely be 
employed for volumetric purposes, more especially when one considers the 
clottiness of the precipitates produced in strong solutions, and the consequent 
danger of the fluid not being brought completely into contact with tho pre¬ 
cipitant. 
It occurred to me that the iodohydrargyrates being all soluble in the liquids 
that dissolve their respective alkaloids, it would only be necessary to add to 
the liquid containing them in suspension the proper ethereal solvent, shake 
well and decant, to get the iodohydrargyrate in a condition to be weighed. 
The error occasioned by solubility would thus have been overcome. The al¬ 
kaloid moreover having been increased three or four times, or even more in 
weight, might have been safely subjected to the balance in cases when the 
pure alkaloid, owing to its minuteness, could not have been so estimated. 
But as both ether and acetic ether (especially the latter) dissolve iodide of 
mercury in proportions that vary in accordance with circumstances not at all 
times controllable, I could not bring the method to bear. 
I will now proceed to the other branch of the subject—the preliminar}’- 
processes for getting the active principles into a state adapted for estimation. 
The degree of purification necessary for volumetric estimation by iodohydrar¬ 
gyrate of potass, a process which, though not strictly accurate nor generally 
practicable, may have admirers, depends entirely on the nature of the extract 
containing the alkaloids we are in search of. It seems that the only bodies 
besides the alkaloids it is capable of precipitating, are those of the albuminous 
series when in acid solution, and certain extractive matters. These must in 
all cases be got rid of, as well as sulphides. Chlorides also, if the residuary 
iodine and chlorine are to be estimated, must be eliminated as well as every 
other substance incompatible with nitrate of silver. 
It is doubtless best in all cases to effect as complete an isolation as possi¬ 
ble, and for this purpose no general process can answer better than that of 
Stas. It is not necessary minutely to describe it. It is well known to con¬ 
sist in treating the substance with alcohol at about 150° F., and an organic 
acid (oxalic or tartaric), evaporating the tincture to dryness and exhausting 
the extract with the least possible quantity of water. This fluid which, if the 
operation has been carefully conducted, contains all the alkaloids present in 
