184 Wisconsin Academy of Sciences, Arts, and Letters. 
pure”, ten grams, the amount directed to be used to make 1000 cc. 
of the Liquor, would represent 0.9700 gm. As 2 0 3 to 100 cc. of the 
solution. Hence, unless the “arsenious acid” used assayed slightly 
higher than the minimum U. S. P. requirement, the finished prod¬ 
uct would fall short by a very slight amount (within the limits of 
experimental error) of the given standard. 
The U. S. P. of 1890 states that 24.7 cc. of the solution “ should 
require from 49.4 to 50. cc. of decinormal iodine Y. S.”—“ (cor¬ 
responding to 1 gm. of arsenous acid in 100 cc. of the solution) ”. 
The As 2 0 3 equivalents of 49.4 cc. and 50. cc. N/10 I. Y. S. ac¬ 
cording to this revision represent 0.9883 gm. and 1.004 gm. respec¬ 
tively of As 2 0 3 in 100 cc. of the solution. As the purity rubric 
for “arsenous acid” in this revision is “at least 98.8 percent of 
arsenic trioxide”, ten grams, the amount prescribed to make 1000 
cc. of the Liquor, would represent 0.988 gm. to 100 cc. of the solu¬ 
tion. In this case the minimum requirement would be met with. 
The U. S. P. of 1900 states that 24.6 gm. of the solution “should 
require not less than 50 cc. of tenth-normal iodine Y. S.—” “ (cor¬ 
responding to 1 gm. of arsenic trioxide in 100 gm. of the solution) ”. 
The As 2 0 3 equivalent of 50 cc. N/100 I. Y. S. according to this re¬ 
vision represents 0.9981 gm. of As 2 0 3 in 100 gm. of the solution. 
The new purity rubric for arsenic trioxide is “not less than 99.8 
per cent, of pure Arsenic TrioxideY Hence ten grams of arsenic 
trioxide, as directed to be used for the preparation of 1000 grams 
of the Liquor, would represent only 0.998 gm. of As 2 0 3 to 100 gm. 
of the solution. In this instance the conditions meet the require¬ 
ment of 10 gm. of arsenic trioxide, which represents 9.98 gm. of 
As 2 0 3 . 
The U. S. P. of 1910 merely demands a definite percentage 
strength, viz. “not less than 0.975 nor more than 1.025 gm. As 2 0 3 
in 100 gm. of the solution, ’ ’ and makes no mention of the amounts 
of N/10 I. Y. S. to be used. The purity rubric for arsenic trioxide 
for this revision is “not less than 99.8 per cent, of As 2 0 3 .” It is 
quite evident however, that the maximum limit of As 2 0 3 content 
of the solution will probably not result when the prescribed ten 
grams of arsenic trioxide are used, as this represents only 0.998 gm. 
of As 2 0 3 to 100 gm. of the solution. The lower limit of the rubric 
viz. 0.975 gm. to 100 gm. of solution, is undoubtedly to allow for a 
slight loss of arsenic trioxide, as determined by the assay process, 
due to the oxidation of the trivalent arsenic to the pentavalent ar¬ 
senic. 
