SANGER AND BLACK. — DETERMINATION OF ARSENIC IN URINE. 329 



The distillation of arsenic from organic matter by hydrochloric acid, 

 first used successfully by Schneider ^ and Fyffe,^ is a common proced- 

 ure and needs no explanation. We have not been able, however, to 

 find any instance of its application to the analysis of urine. The only 

 serious objection is the difficulty of obtaining hydrochloric acid with a 

 negligible amount of arsenic. Fortunately such an acid is obtainable 

 at low cost in this country, ^^ and one does not have to resort to the 

 troublesome methods of purification, which to some are prohibitive of 

 the use of hydrochloric acid in arsenic work. 



Not only is the distillation method more accurate, but it will also 

 be shown that, in point of time for the entire operation, the advantage 

 is greatly in its favor, particularly, as we have said before, if the careful 

 elimination of the organic matter is made a prerequisite to the intro- 

 duction of the solution into the Marsh flask. 



The Method. 



Apjjarafus. For distillation, a 300 c. c. round-bottom flask is used, 

 with a neck about 20 cm. long. The side tube, which is about half- 

 way up the neck, is 20 cm. in length, and is bent downward in the 

 middle at an obtuse angle, so that it passes into an upright condenser 

 parallel to the neck of the boiling flask, which is closed by a short glass 

 tube sealed off at each end, over which is slipped a short piece of rub- 

 ber tubing. A glass-stoppered boiling flask could advantageously be 

 used. The cooling tube is 50 cm. long, with a jacket of 35 cm. The 

 side tube of the flask passes through a rubber stopper in the neck of 

 the condenser and as far into the cooling tube as possible. The con- 

 densing tube passes at the bottom through a rubber stopper, over which 

 is slipped a wide tube 15 cm. long, similar to a chloride of calcium 

 tube, having a bulb of about 25 c.c. capacity near the lower end, which 

 terminates in a tube of ordinary bore. To this end is fused a tube of 

 equal diameter about 15 cm. long. The arrangement is practically a 

 pipette-shaped adapter, similar to that used in ammonia distillation, 

 and is intended to prevent the rise of distillate into the condenser in 

 case of back pressure. The distilling apparatus is conveniently set up 

 in duplicate, mounted on two stands (see Figure A), and is placed in 

 the hood under a strong draught. 



Distillation. 200 c.c. of urine are evaporated in a porcelain dish 

 over a low flame or on the steam bath to about 35 c.c, cooled, and in- 



8 Pogg. Ann., 85, 483 (1851). 



9 Jour. f. prakt. Chem., 55, 10-3 (18-52). 



1" Baker and Adamson Chemical Company, Easton, Pa. 



