Langenhan—The Arsenical Solutions. 
159 
LIQUOR POTASSII ARSENITIS U. S. P. 1910 
Solution of Potassium Arsenite 
Jjiq. Pot. Arsen.—-Fowler’s Solution Liquor arsenicalis Fowleri P.I. 
An aqueous solution containing potassium arsenite, correspond¬ 
ing in amount to not less than 0.975 per cent, nor more than 1.025 
per cent, of As 2 0 3 (197.92). 2 Preserve the Solution in amber-col¬ 
ored bottles. 3 
Arsenic Trioxide , 4 in fine powder, 5 ten grammes 7 .. 10 Gm. 
Potassium Bicarbonate , 6 twenty grammes T . _.... 20 Gm. 
Compound Tincture of Lavender , 11 thirty grammes . _.. 30 Gm. 
Distilled Water , 8 a sufficient quantity , 9 
To make one thousand grammes 12 . 1000 Gm. 
Boil the arsenic trioxide and potassium bicarbonate in a tared 
flask with one hundred grammes of distilled water, until solution 
has been effected, 10 and then add enough distilled water to make the 
solution weigh nine hundred and seventy grammes; then add the 
compound tincture of lavender and filter through paper. 
Solution of Potassium Arsenite is a clear or faintly opalescent liquid 
with a pink color and a slight odor of lavender. 13 It is alkaline to litmus. 14 
Acidulate strongly 10 mils of the Solution with hydrochloric acid and 
add an equal volume of hydrogen sulphide T.S.; a yellow precipitate is 
produced which dissolves in ammonium carbonate T,S. 14 
Acidulate 4 mils of Solution of Potassium Arsenite with diluted nitric 
acid, add 1 mil of silver nitrate T.S. and superimpose a layer of ammonia 
water upon this liquid; no red or reddish-brown color is observed at the 
line of contact (arsenate ). 14 
Assay—Dilute about 20 mils of Solution of Fotassium Arsenite, accur¬ 
ately weighed, with 75 mils of distilled water, acidify the mixture very 
slightly with diluted hydrochloric acid, then dissolve in the solution 2 Gm. 
of sodium bicarbonate and titrate the resulting liquid with tenth-normal 
iodine V.S., starch T.S. being used as indicator. It shows not less than 
0:975 per cent, nor more than 1.025 per cent, of As 2 0 3 . 15 
Each mil of tenth-normal iodine V.S. used corresponds to 0.004948 Gm. 
of As^Og. Each gramme of Solution of Potassium Arsenite corresponds 
to not less than 1.97 nor more than 2.07 mils of tenth-normal iodine V.S. 15 
Average dose— Metric, 0.2 mil—Apothecaries, 3 minims. 16 
