158 



ANALYSIS OF FLUOR- SPiR. 



f^xpeiimenU 

 on it. 



Digested in 

 ♦iitric acid. 



edly wiih car- 

 bonate of pot- 

 ash. 



■JOO grains di- 

 gested in sul- 

 j|>hurlc acid> 



which, when stronj^ly heated in a wind furnace, loses at an 

 average only ^^^th part of its weight. The obvious iu^- 

 ciiracy of the analysis' given by the authors ju8t mentioned 

 induced me, to make a set of experiments on it last sum- 

 mer (1807). I selected the purest, transparent, colourless 

 crystal, which I found by repeated trials to be very nearly 

 pure fluute of lime. When reduced to a fine powder, and 

 digested in nitric acid, I found in the acid only a little 

 lime, owing doubtless to the partial decomposition of the 

 fluate, and minute traces of iron and lead: these two me- 

 tals I detet'r^ecl, by evaporating the nitric solution to dry- 

 ness, heating it to redness, and then dissolving the residue 

 in muriatic acid. The colour of the solution showed the 

 presence of iron, and a few needlcform ciystals of muriate 

 of lead were deposited after the solution had stood for some 

 days. The fiuate, which I used, had been dug out of a 

 lead mine in Northumberland, and small crystals of sul- 

 phuret of lead were here and there to be seen in it. Proba- 

 bly some one of these had escaped my attention, and, by^ 

 being mixed with the fluate which I used, occasioned the 

 appearance of the lead, which, however, did not amount 

 to j^^th part of the salt, and therefore could not occasion 

 any sensible errour in the subsequent analysis. 



1 first tried to decompose the fluate of lime, by fusing it 

 with twice its weight of carbonate of potash in a platinum 

 crucible. Only a small portion of the fluate was decom- 

 posed. I was, therefore, obliged to repeat the fusions very 

 often, washing oflpthe alkali after each operation by means 

 of water, and then dissolving the carbonate of lime formed, 

 in muriatic acid. Fatigued with the tediousness of this 

 method, and despairing of an accurate result from the great 

 number of succcrssive solutions, I abandoned it altogethe/, 

 and adopted the following method, much more expeditious 

 and equally precise. 



. From a mass of flu or spar, which I had ascertained to 

 contain no sensible portion of foreign matter, t separated 

 100 grains, which 1 reduced to powder, and digested for 

 some hours in a platinum crucible, with rather more than 

 an ounce of pure concentrated sulphuric acid. The mix- 

 ture was then evaporated to dryness, and the crucible ex- 

 posed 



