Botanical Society of Edinburgh. 235 



procured from Glasgow. It is to Canada and the United States 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 recognising this substance is to heat a considerable 

 quantity of the salt with a minimum of water. On cooUng the solu- 

 tion, the greater portion of the carbonate of potash, 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 resolution 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 from 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 

 freshwater plants was now generally recognised, 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, and burn them cautiously ; indeed the 

 burning should be rather termed charring ; the ashes are reduced to 

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

 and subsequently treated like the potashes. In every case the pro- 

 cess used for the liberation of iodine is that suggested by Dr. Price, 

 viz. nitrite of potash and hydrochloric acid ; and in many cases where 

 no indications of iodine could be obtained by the ordinary methods, 

 good results were procured with Dr. Price's process. 



In the following plants, hitherto not known to contain iodine, Mr. 

 Macadam has detected that element : — 



Myosotis pnlustris Dixddingstone Loch. 



Mentha sativu Ditto. 



