1220
ANALYTICAL CHEMISTRY
oxidizing power of the acid is not impaired as much by dilution with the aqueous peroxide as in the original method. The hydrazine sulfate, in turn, is added in aqueous solution instead of in the solid form, presumably enabling the reagent to perform the reduction before the water boila off and the hydrazine decomposes. The following general procedure gave acceptable and reproduoible results for a variety of inorganic and nitrogen-containing organic arsenic compounds. The method is adaptable to a Bemimacro SD&IC.
PROCEDURE
Ten millilitertrs of concentrated sulfuric acid am added to the sample (100 to 200 mg.) in a Rjcldahl flask, folloired by 3 ml. of fresh 30% h diogen peroxide and then by another 10 ml. of sulfuric acid. $he solution is usually completely colorless a t this point; i t is then warmed gently, with occasional cautious addition of a few drops of hydrogen peroxide t o destroy any ye)low coloration. (The t,otal amount of hydrogen peroxide used ranged from 3 to 10 ml., while 25 to 35 ml. were used in following the original procedure.) The sohkion is heated strongly for as long a8 1 hour until heavy white fumes of sulfur trionidc are evolved. Tho flask is allowed t,o cool t o about 50" nnd then an
aqueous solution (about 10 ml.) of I50 mg. of hvdraaine sulfate is added. The mixture is heated to boiling and kept there for 0.75 t o 1hour t o ensure complete removal of sulfur dioxide from the long-necked flask. After cooling, the solution is dilutod with 20 ml. of distilled water and after the addition of 0.1 gram of potassium bromide is titrated with standard potassium bromate solut,ion. First appearance of yellow color duo to free bromine was takon BE the end point.
Results of Arsenio Determination in Various Compounds Compound Arsenious aoid Arsanilio aoid N-Gnan~l~lasnilie acid
POrln"l*
Calod., liound. % -4s (la As
75.74 76.63 34.56 34.78 27.08 27.10 27.12 CIH~oO~NaAs.CarIiOiN,15.17 15.21 15.15 .iS*08.
CaHeOIhhr
CiHmOaYa4s.ILO
A'-Gusnylarsanilia aoid picrate
LITERATURE
crrm
(1) Bogert, M. T.,and Stickler, W.C . , Science, 100, 526 (1944). (2) Gyiiry, S., 2. anal. Chern.. 32, 415 (1893). (3) Schulek, E., and Villecs. P.V., Zb
