342 Mr. P. Forbes on Phosphorite from Spain, 



facility and in larger quantity than borax-glass, and forms a clear 

 colourless glass, which, however, if supersaturated, becomes a 

 white enamel. 



A portion of the mineral in the state of powder was placed in 

 a small leaden capsule and drenched with strong sulphuric acid. 

 Hydrofluoric acid was evolved upon gently heating the capsule, 

 and etched deeply letters written through a film of wax varnish 

 coating a glass plate with which the leaden capsule was covered. 



The analysis of the mineral was conducted as follows: — 

 31*05 grains in powder were heated for some time to redness in 

 a platinum crucible; upon cooling,' the diminution in weight 

 amounted to 0*45 gr., equivalent to 1*44 per cent., which 

 loss was considered as water ; the powdered mineral had become 

 much darker in colour during ignition, and on cooling had as- 

 sumed a reddish-brown tint. 



In order to determine the amount of carbonic acid present, 

 this gas was displaced by the action of hydrochloric acid upon 

 100 grs. of the powdered mineral placed in a previously tared 

 thin glass apparatus, from which the gases were evolved after 

 passing through a tube containing chloride of calcium. The 

 loss of carbonic acid was found to be 0*45 gr., or equivalent to 

 0*98 per cent, carbonate of lime in the mineral. 



Sulphuric acid was also distinctly observed, but in quantity 

 too small for estimation unless an unusually large amount of 

 the mineral had been operated upon. 



For determining the fluorine a thin glass bulb was employed, 

 closed by a cork through which two tubes passed, the one for 

 evolving the gaseous products, and the other, reaching to the 

 bottom of the bulb, for passing a stream of air through it in 

 order to displace and drive off the hydrofluosilicic acid which 

 remained behind in the apparatus at the termination of the 

 operation; a sufficient quantity of pure strong sulphuric acid was 

 now placed in the bulb along with 10 grains pure silicic acid 

 (precipitated from hydrofluosilicic acid), and the whole boiled to 

 expel any moisture present, and weighed. 50*00 grs. phospho- 

 rite in powder were then introduced, and the whole heated and 

 weighed several times during two days ; the ultimate loss was 

 found to be 2*66, or 5*32 per cent, terfluoride of silicon ; and as, 

 according to Wohler, 100 terfluoride of silicon is equivalent to 

 72*79 fluorine, this would afford 3*87 per cent, fluorine, or 8*01 

 fluoride of calcium. 



The insoluble matter was estimated by dissolving 36*94 grs. 

 in nitrohydrochloric acid and collecting the insoluble remainder, 

 which was found to weigh 0*42 gr., or 1*41 per cent. 



20*00 grs. were now digested with strong sulphuric acid, 

 which evolved fumes of hydrofluoric acid, and the mass then 



