Langenhan—The Arsenical Solutions. 163 
oxidation. A. N. Cook 72 attributes the oxidation to the atmospheric 
oxygen which is introduced every time the container is opened to 
remove some of the liquid. E’we and Vanderkleed 73 state that, 
4 ‘ One sample of liquor potassium arsenite U. S. P. suffered an oxi¬ 
dation of 1.9 p. c. of its As 2 0 3 as arsenite to arsenate in two years 
and three months. Another sample had 1.8 p. c. of As 2 0 3 as ar¬ 
senite oxidized to arsenate in one year and five months”. Engel- 
hardt and Winters, 74 after determining the amounts of arsenate 
and arsenite respectively during a period of 14 months conclude 
that only a slight amount of oxidation takes place in the solution. 
4. ) Arsenic Trioxide as an Ingredient. The original formula of 
Fowler calls for arsenicum album or “white arsenic”, in which 
manner the arsenic trioxide was distinguished from the yellow and 
red sulphides. The London Pharmacopoeia of 1808 calls for Ar- 
senici oxidum sublimatum. The U. S. P. of 1820 adopted the desig¬ 
nation arsenious acid in accordance with the new antiphlogistic- 
nomenclature. For other changes, see Names and Synonyms. 
5. ) The Form in Which it is Used. Fowler directs the “ white 
arsenic” to be used “in pulverum subtilissimum triti, i. e. “tritu¬ 
rated to a very fine powder”. The U. S. P. of 1820 directs that 
the “arsenious acid” be used in form of a “fine powder”; the 
Philadelphia edition of 1830 directs a “very fine powder”. 
“Small fragments” are suggested by the New York edition of 
1830, also by the editions of 1840, 1850,1860 and 1870. From 1880 
on a “fine powder” is again directed. 
The explanation for this is found in the following statement made 
by the editors of the U. S. Dispensatory, 13th ed. (1872), p. 1267: 
“In making this preparation, care should be taken that the arseni¬ 
ous acid is pure. This object is best secured by using the acid in 
small pieces instead of in powder. Sulphate of lime is a common 
impurity in the powdered acid, and if present will remain undis¬ 
solved, and cause the solution to be weaker than it should be”. 
Although the U. S. P. of 1870 directs a qualitative test (com¬ 
plete volatilization) to be made, that would bar such an impurity 
as sulphate of lime, the U. S. P. of 1880 is the first to direct the 
assay of “arsenious acid”. It is, no doubt, due to this difference 
in the requirements of the 1880 edition and its precursors from 
72 Rep. So. Dak. P. & D. Com., 1912, p. 75 (1912.) 
73 Proc. Pa. Ph. Assn., 37, p. 277 '(1914.) 
74 Jour. A. Ph. A., 6, p. 134 (1917.) 
