354 Dv George Wilson on the Detection of Fluorine 



converted into sulphuric acid by the cautious addition of 

 nitric acid, and then its presence is quite immaterial. But 

 in several quite successful trials no steps were adopted to 

 separate the sulphurous acid. 



The specimen laid upon the table, of glass etched by fluorine 

 from barley-straw, will illustrate the applicability of the pro- 

 cess to plant-ashes largely charged with silica, and which 

 yielded with oil of vitriol, carbonic and hydrochloric acid, 

 besides much sulphurous acid. 



The glass etched by the fluorine of charcoal-ashes is still 

 more deeply corroded, although they were subjected to no 

 preliminary process to remove the volatile acids which they 

 contained, or to set free or separate the sulphurous acid 

 which they yielded. 



In truth, the ammonia process has succeeded with every 

 substance upon which I have tried it. The worst result has 

 been with the ashes of hay, but they had been washed with 

 water and hydrochloric acid to remove chlorides and car- 

 bonates ; and in former papers I have shewn that such 

 washings remove fluorides. Notwithstanding this, the evi- 

 dence of the presence of fluorine in hay, afforded by the 

 specimen, is such as has not hitherto (so far as I am aware) 

 been afforded by any analyst, and the omission of the wash- 

 ings will, I have no doubt, yield a still more satisfactory 

 result on a repetition of the analysis. The same remark 

 applies to coal-ashes, by the fluorine of which I have only 

 one etching to shew. It is not a favourable specimen; the 

 ashes were washed with a considerable volume of hydrochlo- 

 ric acid and water ; the product of distillation was tested by 

 the less perfect potassium-process ; and the lines etched by 

 the hydrofluoric acid were drawn too fine. Experience has 

 taught my assistants that the wax should be spread thin, and 

 the lines through it be made with a broad point, if a distinct 

 etching is to be obtained. But, withal, the results with coal- 

 ashes are sufficiently marked. 



I have further tested the sufficiency of the ammonia pro- 

 cess in the following stringent way. A fossil bone from the 

 Himalayas, which I had already ascertained to contain a 

 fluoride, and which was full of crystals of carbonate of lime, 



