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that we owe our supplies of these materials. As imported into this 

 country they are contaminated with many foreign ingredients ; and 

 amongst the rest the author has detected iodine. The most ready 

 means for separating and recognizing this substance, is to heat a con- 

 siderable quantity of the salt with a minimum of water. On cooling 

 the solution, the greater portion of the carbonate of potassa, as well 

 as the impurities, falls to the bottom of the vessel ; whilst the iodide 

 of potassium remains dissolved in the water. When testing for the 

 iodine in the potashes, this solution was evaporated to dryness, treated 

 with alcohol, boiled, and filtered. The filtrate on being evaporated to 

 dryness left a residue, which on re-solution in water acted distinctly 

 with the starch test for iodine. 



The presence of this element in potashes leads the author to believe 

 that iodine will be found more generally distributed in the vegetable 

 kingdom than it has formerly been supposed to be. The potashes 

 from the States, and from Canada, are principally the dried lixivium 

 of the ashes of forest-trees ; but, whilst by much the greater portion 

 is so, the parties in charge are not very scrupulous about what plants 

 they employ; and occasionally everything which comes in the way, 

 and which will burn, is added to the pile. It may therefore be ob- 

 jected to the statement that forest-trees contain iodine, that the iodine 

 found in the ashes may be derived from the succulent herbs and 

 shrubs, and not from the trees themselves ; but this objection will be 

 at once removed when it is stated, that in the lixivium of charcoal the 

 author has obtained very distinct traces of iodine. Now the charcoal 

 sold and used in this country is principally oak, with a little birch, 

 elm, and ash. 



The amount of iodine in forest-trees must be comparatively small. 

 When experimenting with the potashes, one is apt to forget the small 

 bulk into which a large quantity of timber falls when the organic 

 matter is expelled, and the saline ingredients are alone left. So far 

 as can be estimated firom the present qualitative experiments, the 

 relative quantity of iodine in forest-trees is much less than that in 

 succulent plants growing in marshy places. 



In conclusion, it was mentioned that the presence of iodine in some 

 fresh-water plants was now generally recognized, and that the author 

 is at present engaged in testing the various plants growing in the lochs 

 in the neighbourhood of Edinburgh. The method employed in their 

 analysis is to dry the plants, burn them cautiously (indeed, the hurn- 

 ing should be rather termed charring) ; the ashes are reduced to fine 

 powder, digested in water, and filtered ; the clear liquid evaporated 



