667 



furnaces. By means of a stop-cock fixed in the receiver, and a long, 

 flexible tube, the air was conducted to the following arrangement : — 



1. A wide tube, containing slips of paper dipped in starch. 



2. A condensing-worm, surrounded by a freezing mixture and 

 attached to a receiver. 



3. A tall jar, containing chips of pumice-stone and a few iron- 

 filings, with sufficient water to cover them. 



4. A similar jar, with pumice-stone, scrapings of clean lead, and a 

 solution of acetate of lead. 



5. A condensing-worm, immersed in a freezing mixture and attached 

 to a receiver. 



The air, under a pressure of three lbs. on the square inch, was 

 allowed to traverse the arrangement for fully four hours, when the 

 apparatus was taken asunder; and, the contents of the vessels being 

 placed in stoppered bottles, the whole was brought to Edinburgh for 

 examination. The slips of paper (1) were not sensibly altered in tint, 

 and did not betray the slightest indications of even arose colour w^hen 

 moistened with distilled water. The condensers (2 and 5) contained 

 each a very small quantity of liquid, which on being tested did not 

 show a trace of iodine. The small quantity of liquid in the conden- 

 sers may be accounted for by the comparatively high temperature 

 possessed by the air rushing through so quickly as it did. The con- 

 tents of the jar (.3) were thrown on a filter, and washed with cold 

 water. |: To the filtrate was added half an ounce of a solution of car- 

 bonate of potassa ; and the whole evaporated to a quarter of an ounce. 

 No iodine was present. The carbonate of potassa used in this trial 

 was prepai'ed by calcining cream of tartar, and was so far free from 

 iodine that none could be detected in two ounces of the solution, of 

 which half an ounce was employed. There was therefore no likeli- 

 hood of iodine being added in the alkali used, even though the ana- 

 lysis of the contents of the jar had shown its presence. The jar (4) 

 with the lead solution was treated in the same manner as described in 

 a former part of this paper, when referring to the employment of sil- 

 ver; and the result was also negative. Notwithstanding the large 

 scale on which this experiment was conducted, a volume of air of not 

 less than 4000 cubic feet having been forced through the arrangement, 

 Mr. Macadam has been unable to verify the results of Chatin ; yet he 

 feels disinclined to pronounce those results unwarranted, and has 

 therefore resolved to make another trial, on a still larger scale. It is 

 proposed to fit up an apparatus of a stronger and more durable 



