300 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



plane in the form of a cz. To this is fastened by means of a rubber 

 stopper a short bulb tube about 12 mm. in diameter, terminating in a 

 longer tube which has a bore of slightly over 4 mm. The bulb of this 

 tube (deposition tube) is loosely filled with clean absorbent cotton 

 which has been kept over sulphuric acid to insure uniform dryness. 

 Instead of the bulb tube, the rubber stopper of the exit tube may 

 carry a short piece of glass tubing of about 12 mm. diameter, in which 

 is placed the absorbent cotton, and to which, by means of another 

 rubber stopper, is attached the deposition tube. 



Figure A. 



The simplicity and compactness of this apparatus allow a number of 

 determinations to be carried on at the same time by the use of several 

 pieces. It is important, however, that the bottles be of the same size, 

 and it is also advisable to have the rest of the apparatus of as nearly 

 definite size as possible. 



Beagenfs. "We have used zinc and hydrochloric acid in preference 

 to zinc and sulphuric acid, as the action goes on more regularly and 

 without the addition of a sensitizer. The chance for the formation of 

 hydrogen sulphide is also less. The zinc, known as Bertha spelter, is 

 from the New Jersey Zinc Company of New York, and has been proved 

 by exhaustive tests to be free from arsenic. It contains not over 0.019 



