CHEMICAL NOTATION IN THE PHARMACOPIEIA. 
217 
oxides of lead, but the name “ litharge ” and the characters given in the 
Materia Medica are only applicable to the normal plumbic oxide. The hy¬ 
drates of sodium and potassium are individualized by the familiar names 
“ caustic soda” and “ caustic potash.” The name “ red oxide of mercury ” 
satisfactorily distinguishes the officinal mercuric oxide from the unstable 
black mercurous oxide. The oxide of antimony, which is mentioned in the 
definition of “ sulphuretted antimony,” is correctly named “ teroxide of an¬ 
timony,” to distinguish it from the pentoxide. The peroxide of manganese 
is called “ black oxide,” and therefore cannot be mistaken for the green or 
the red oxide ; and the test which indicates its property of yielding oxygen 
when heated, serves to distinguish it from the normal manganic oxide. The 
formulae given for the pharmaceutic oxides and hydrates of iron do not reveal 
the exact constitution of these preparations, and are naore likely to mislead 
than inform the student. Thus the formula given for the so-called “ peroxide 
of iron ” represents ferric oxide combined with one atomic proportion of 
water; but it is doubtful whether such a product is obtainable by the Phar¬ 
macopoeia process. Again, the formulae representing the so-called “ hydrated 
peroxide of iron ” and “ magnetic oxide of iron” fail to express the relation 
which these variable hydrates bear to the normal ferric and ferroso-ferric 
hydrates. In place of the formula given under “ peroxide of iron,” some 
such definition as the following might be inserted:—“ Ferric oxide slightly 
hydrated.” For the present definition of “ hydrated peroxide of iron,” the 
following might be substituted:—“Ferric hydrate, with a variable amount 
of uncombined water.” And for that of “ magnetic oxide of iron,” the follow¬ 
ing:—“An oxide intermediate between the higher and lower oxides of iron, 
or the ferric and ferrous oxides, with combined water.” I am of opinion 
that the term “ sesquioxide,” which is used by the new as well as by the old 
chemists, is preferable to “ peroxide ” as a pharmaceutic name for the higher 
oxide of iron, as the latter term is now usually applied to an oxide in which 
part of the oxygen is in an unstable condition. 
Oxygen-Acids and Anhydrides .—The modern doctrine that acids are salts 
of hydrogen is dimly reflected by the formulae of the principal acids given in 
the Pharmacopoeia. Thus sulphuric, phosphoric, glacial acetic, benzoic, tar¬ 
taric, and tannic acids are represented as deflnite hydrates, agreeing in com¬ 
position with the bodies to which the same names are applied by the followers 
of Gerhardt. Citric and gallic acids are also formulated with constitutional 
water, besides water of crystallization. The names of all these acids, with 
the characters and tests, are therefore sufficiently distinctive without the for¬ 
mulae. The “nitric acid” of the Pharmacopoeia is represented as a definite 
compound of two combining proportions of anhydrous nitric acid with three 
of water; and according to the modern system of notation may be regarded 
as a compound of four molecules of true nitric acid, or nitrate of hydrogen, 
with one molecule of W'ater. To express the fact which the old and new 
chemists set before us in different lights, the compilers of the Pharmacopoeia 
might substitute for the present formula, the simple statement that the offi¬ 
cinal acid contains 80 per cent, of anhydrous nitric acid, or nitric anhydride. 
The true acetic acid of modern chemists is the glacial acid, which is defined 
in the Pharmacopoeia as “ monohydrated acetic acid.” This definition should, 
therefore, be excluded with the formula. The name, specific gravity, and 
volumetric test ought to suffice to distinguish this definite compound. The 
strength of the ordinary “ acetic acid,” of specific gravity 1‘044, might be ex¬ 
pressed by the intelligible statement that it contained 33 per cent, of the 
glacial acid. The sulphuric acid of the Pharmacopoeia is said to have the 
specific gravity 1'846, and is described as “ monohydrated ” acid. Accord¬ 
ing to Miller, Ure, and many other authorities, the liquid having this specific 
