Langenhan—The Arsenical Solutions. 
195 
Observations p. 81. 
The first medicine is a chemical Preparation as simple as conld 
be wished for, and if proper Care be taken that the Solution of the 
Mineral is complete, it will be found of a certain and uniform 
Degree of Strength. Its being also (p. 82) in a liquid Form, 
renders it convenient, for administration by Drops, and thereby 
nicely varying the Doses, according to the Exigencies of the Case; 
a matter of some Importance, where the Activity of the Medicine 
is so great. 
The small Proportion of Compound Spirits of Lavender is added, 
merely for the Sake of giving a medicinal Appearance, lest, from 
its being colourless and tasteless, those Patients who may happen 
to be intrusted to drop it for themselves, should be tempted to use 
it with too great Freedom; the Consequences of which might fre¬ 
quently prove troublesome, if not sometimes dangerous. 
To a Pint of the Solution, sixty-four Grains were added, for the 
purpose of a more ready Calculation; therefore one Ounce of the 
Solution contains exactly four Grains of the Mineral and conse¬ 
quently each Dram, just half a Grain; I have found by repeated 
Trials of dropping the Solution, from a two Ounce Vial (with a 
broad Margin) little more than half full, that each Dram, by a two 
Ounce graduated Glass Measure, contains about eighty Drops. 
We ought to be well assured, that the fixed vegetable Alkali we 
make Use of is perfectly pure; for that which is bought of the 
Druggists is frequently so impure, as to be inadequate for the 
Purpose of producing a perfect Solution of the Mineral; a Cir¬ 
cumstance which would occasion great Confusion and Uncertainty, 
in the Doses (p. 83) of the Medicine, if therefore any One desirous 
of preparing the Mineral Solution, should not be provided with the 
pure alkali; and would not choose to be at the Trouble of purifying 
it, a double Proportion of purified Nitre (which is a preparation of 
some certainty, and supposed to be always at Hand), may be sub¬ 
stituted; for the Arsenic having the Property of discharging the 
nitrous acid, will unite with the Alkali. 
The Formula which I have given with the Alkali, contains my 
own preparation, alluded to in the Preface, and is that on which 
my experience is chiefly founded. 
Mr. Hughes has likewise used it prepared with Nitre, and on 
trial found it equally efficacious. I have also used it a Number of 
