April,
1935
169
LABORATORY PREPARATION OF IODINE C. E. WHITE University of Maryland, College Park, Maryland
THE METHOD given in almost all laboratory manuals for the preparation of iodine is the oxidation of sodium iodide by manganese dioxide in concentrated sulfuric acid. With the usual procedure it is very difficult for the student to obtain any appreciable quantity of iodine with these reagents. For the past few years in the University of Maryland laboratories we have used a modification of the industrial process which
employs the reduction of sodium iodate with sodium acid sulfite and have found it very satisfactory. The following directions are used: “Mix in a small beaker 9 ml. .of 0.25 M sodium iodate with 10 ml. of 0.5 M sodium sulfite and add about 3 ml. of 2 N sulfuric acid. Shake carefully. The iodine should collect at the bottom of the beaker and the liquid may be decanted
from it."
proper quantities in this preparation, since an excess of sodium sulfite will dissolve the iodine formed. The quantities given here will make a sufficient amount for all of the tests usually employed. The method has the advantage of being simple, efficient, and illustrative of a commercial process. It is necessary to
use
