22 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



The Method. 



The procedure does not vary greatly from that used in the determi- 

 nation of arsenic as described by Sanger and Black 1 . Some details, 

 therefore, of that method are necessarily repeated here. 



Sensitized Mercuric Chloride Paper. A smooth filter paper of close 

 texture, or a Whatman drawing paper of about 160 grams per square 

 meter, is cut into strips of a uniform width of 4 millimeters- The 

 strips are sensitized by drawing them repeatedly through a five per 

 cent solution of recrystallized mercuric chloride until thoroughly 

 soaked. They are then dried on a horizontal rack of glass tubing, and, 



when dry, are at once cut into lengths 

 of six to seven centimeters. The small 

 pieces are kept in the dark until 

 > needed, in a stoppered bottle over 

 calcic chloride. 

 The Reduction Apparatus. (See Figure.) For rea- 

 sons that will be explained later, the construction of this 

 differs slightly from that used in the arsenic method. 

 It will be easily seen from the figure. The bottle is 

 of 30 c.c. capacity, closed by a pure rubber stopper with 

 two holes. The thistle tube, which is constricted at its 

 lower end to an opening of about 2 mm., passes to the 

 bottom of the bottle and has a length of 17 to 18 cm. 

 In the second hole of the stopper is inserted a straight- 

 walled funuel tube of 1 7 to 20 mm. bore, carrying a pure 

 rubber stopper, through which passes a right angle depo- 

 sition tube, 9 to 10 cm. in length, the inner diameter of 

 which should be as near 4 mm. as possible, but not less. 

 Reagents. These are exactly the same as in the arsenic method, and 

 are entirely free from antimony. The zinc, Bertha spelter, is from the 

 New Jersey Zinc Company of New York, and has been proved by re- 

 peated tests to be free from arsenic. The hydrochloric acid, from the Ba- 

 ker and Adamson Company of Easton, Pennsylvania, contains not over 

 0.02 milligram of arsenious oxide per liter. The quantity of diluted 

 acid (one part to six of water) used in the analysis would not contain 

 over 0.00004 milligram of arsenious oxide, an amount beyond the ab- 

 solute delicacy of the method as applied to arsenic and hence of no 

 influence in the determination of antimony. 



Moisture Conditions in the Deposition Tube. As in the arsenic 

 method, the moisture of the evolved hydrogen has an important bearing 

 on the uniformity of the color bands. While excess of moisture must 



