158 DR WILSON ON THE SOLUBILITY OF 
5. Of the presence of Fluorine in Plants. 
Comparatively few examinations of plants have yet been made, in reference 
to the occurrence of fluorine in them ; but these, on the whole, have been satis- 
factory. SPRENGEL appears to have been the first to suggest the likelihood of its 
presence in vegetables, but failed in detecting it in any of them, and referred his 
failure “to its existing in such a state of combination as caused it to be dissipated 
by the heat necessary for expelling the carbonaceous matter, so that it could not 
be detected in the ordinary method.”* 
Dr DavBeny “ascertained that no sensible action is exerted on glass by heat- 
ing, with sulphuric acid, the earthy phosphates present, in twelve pounds of 
barley.”+ Iwas equally unsuccessful with the ashes of Kanaster tobacco, and 
of peas, and with those of charcoal and of coal. I ascribe the failure, however, 
not to fiuorine existing in a peculiar state of combination in plants, but to the 
presence of silica, which, when in any quantity, makes the detection of fluorine 
very difficult. I took no measures to separate the silica in the few experiments 
I made on the subject, and SpreNGEL and DAvuBENY appear to have omitted the 
same essential preliminary. Dr Wrx1 of Giessen, who kept this point carefully 
in view, states that “ careful experiments, conducted under his own superin- 
tendence, by Messrs JAMES MULLER and BLAKE, severally, have shewn that the 
ashes of French barley, grown in Switzerland, contain very distinct traces of it ; 
both straw and grain were employed.” { 
To Witt the credit of first finding fluorine in plants is entirely due. As 
barley, however, contains a large amount of calcareous phosphates, which the 
fluoride of calcium has been supposed to accompany in a peculiar state of combi- 
nation, I thought it well to examine the ashes of a plant containing little phos- 
phate of lime, and which might be considered as having derived any fluorine it 
contained directly from the water its roots absorbed. I chose for this purpose the 
crudest American potashes, which, as they are obtained in part by burning the 
young and succulent branches of trees, should contain portions of all that is soluble 
in the sap. A pound weight of ashes was supersaturated with hydrochloric acid, 
the liquid poured off, neutralised with ammonia, and precipitated by nitrate of 
baryta. The precipitate washed and dried, when treated with Nordhausen 
sulphuric acid in a lead basin, in the way already described, etched glass dis- 
tinctly. 
Whether the fluorine found in plants is essential to them, and serves some 
purpose in their organization, or merely circulates in their sap, as other soluble 
matters do, without being appropriated by the living organism, cannot be deter- 
* Chemical Society’s Memoirs, vol. ii., p. 103. + Ibid. ¢ Ibid, p. 182. 

