Mr. J). Forbes on Phosphorite from Spain. 343 



extracted with alcohol to dissolve the phosphoric and excess of 

 sulphuric acid, and afterwards well washed with a saturated 

 aqueous solution of sulphate of lime, after which the sulphate of 

 lime was dried, incinerated, and weighed 23*03 grs. • deducting 

 from this weight 015 for the insoluble matter contained in it, 

 gives 22*88 grs. sulphate of lime, equivalent to 9*44 lime, or 

 47*29 per cent. Jime. From the wash-water 0*07 gr. pyrophos- 

 phate of magnesia was obtained by the usual method, repre- 

 senting 0*025 gr. magnesia, or 0*12 per cent. 



20*01 grs. were dissolved in NO 5 , filtered from the inso- 

 luble residue, and the filtrate precipitated by a solution of nitrate 

 of silver, which produced a minute precipitate, which on ignition 

 gave 0*08 chloride of silver, equivalent to 0*02 chlorine, or 0*10 

 per cent, corresponding to 0*16 chloride of lime in the mineral. 

 The excess of silver was removed as chloride from the filtrate, 

 which now only gave, with chloride of barium, indications of 

 sulphuric acid too small for accurate determination. The solu- 

 tion was now boiled and neutralized by carbonate of baryta, a 

 solution of soda added in excess, and then a solution of carbo- 

 nate of soda to precipitate all excess of baryta. The precipitate, 

 which was now filtered off, evidently from its colour contained 

 all the iron present, which was demonstrated when, on boiling 

 the filtrate (previously acidified with a little hydrochloric acid) 

 with a little chlorate of potash and precipitating with ammonia, 

 no iron was obtained, and only pure alumina fell, which was col- 

 lected, and, on ignition, gave 0*35 gr., or 1*75 per cent, in the 

 phosphorite. 



In order to determine the phosphoric acid, 14*28 grs. were 

 dissolved in nitric acid filtered from insoluble matter, and a solu- 

 tion of molybdate of ammonia, previously supersaturated with 

 nitric acid, added in great excess, and allowed to stand two days, 

 taking the precaution to test whether sufficient molybdate of 

 ammonia had been added. The beautiful yellow precipitate of 

 phosphomolybdate of ammonia, after separation, was then dis- 

 solved off the filter by addition of ammonia, and this solution 

 precipitated by chloride of magnesium. The precipitated phos- 

 phate of ammonia and magnesia was now collected and inci- 

 nerated with the usual precautions, and gave 9*74 pyrophos- 

 phate of magnesia =6*303 phosphoric acid, or 44*12 per cent. ; 

 the filtrate, which, after having separated the phosphoric acid 

 by the molybdate of ammonia, still contained the bases, was 

 placed in a corked flask with ammonia in excess and sulphide 

 of ammonium also in excess, and allowed to stand some twelve 

 hours. The insoluble matter containing the iron and alumina 

 was then filtered off, washed with water containing sulphide of 

 ammonium, and then dissolved in nitrohydrochloric acid ; a little 



