General Distribution of Iodine. 319 



any compound of iodine, will be at once apparent. The condenser 

 (5) was intended to liquefy any watery vapour which might, during 

 the experiment, be carried from the jars (3) and (4). 



The air, under a pressure of 3 lb. on the square inch, was allowed 

 to traverse the arrangement for fully four hours, during which time 

 upwards of 4000 cubic feet had been brought in contact with the re- 

 agents employed. The apparatus was then 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 in- 

 dication of even a rose colour when moistened with distilled water. 

 The condensers (2 and 5) contained each a very small quantity of 

 liquid, which, on being tested, did not shew a trace of iodine. The 

 contents of the jar (3) were thrown on a filter and washed with cold 

 water. To the filtrate was added some drops of a solution of car- 

 bonate of potassa, and the liquid thus rendered alkaline was evapo- 

 rated to a quarter of an ounce ; no iodine was present. The car- 

 bonate of potassa used in this trial was prepared by calcining cream 

 of tartar at a white heat, and was so far free from iodine, that none 

 could be detected in two ounces of a dilute solution, of which, in 

 testing the contents of the jar, I employed less than half an ounce. 

 There was, therefore, no likelihood of a perceptible quantity of iodine 

 being added in the minute portion of alkali used, even though 

 the analysis of the contents of the jar had shewn 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 em- 

 ployment of silver, and the result was also negative. 



Notwithstanding the large scale on which this experiment was 

 conducted, I still felt disinclined to pronounce a decided opinion on 

 the subject, and resolved to make another trial on a much larger 

 scale than either of those yet referred to. Accordingly I fitted up 

 an apparatus of a larger size and more durable nature., which was 

 carried to Kinneil, and attached, as before, to the condensed air 

 receiver. At this time the air was passed through — 



1. A capacious double-necked gas bottle, about two-thirds filled 

 with distilled water. 



2. A wide tube, containing starched papers. 



3. A capacious gas bottle, containing pumice-stone, distilled water, 

 iron filings, and a little sugar. 



4. A similar bottle with pumice-stone, and solution of acetate ol 

 lead. 



The object in passing the air through the distilled water was to 

 load it with aqueous vapour, so that it should have less influence 

 in causing evaporation of the liquids in 3 and 4. The sugar added 

 to the bottle (3) w£& intended to prevent the oxidation of any pro- 

 tiodide of iron which might be formed, and which decomposition 



y 2 



