SIGNIFICATION OF FLUORIN 26 1 



abundant in mineral phosphates. In case the samples are pyritif- 

 erous, however, considerable quantities of sulfuric acid may be 

 found after treatment with aqua regia. 



The acid is precipitated with barium chlorid, in the usual way, 

 in an aliquot portion of the filtrate first obtained. The precipi- 

 tate of barium sulfate is washed with hot water until clean, dried, 

 ignited, and weighed. If the portion of the filtrate used repre- 

 sents half a gram of the original material, then the weight of 

 barium sulfate obtained multiplied by 0.6858 will give the quan- 

 tity of sulfur trioxid in one gram. 



OCCURRENCE OF FLUORIN IN PHOSPHATES 



225. Signification of Fluorin. Fluorin is quite a constant con- 

 stituent of organic phosphates of lime, as, for instance, bones and 

 teeth, and occurs in considerable quantities in many deposits of 

 such phosphates used for commercial purposes. It is the cause 

 of much discomfort and annoyance in fertilizer factories. 



The phosphates of pure mineral origin, and also sedimentary 

 phosphates, contain uniformly considerable quantities of fluorin, 

 in fact, in quite a definite proportion, and generally correspond 

 in composition to apatite. Under the influence of living organs, 

 of plants and animals, the fluorin tends to disappear. 22 



The exact determination of fluorin, therefore, in phosphates, is 

 of more than usual interest because its amount will throw much 

 light on the origin of the sample under examination. 



Free coproliths, that is, nodules of organic phosphates, are 

 very rarely found. What are so called, preserve only the form. 

 The original materials have been replaced by the fluoi phosphates 

 of more distinctly mineral nature. The fossil bones sometimes 

 found in sedimentary phosphate deposits are only bones in form, 

 just as fossil trees are only so in form. The analysis of the 

 phosphatic material composing them shows them to be different 

 from true bone. Only fossil phosphates unmetamorphosed exist 

 in recent geological epochs and in guano deposits. 



The almost universal presence of fluorin in natural phosphates 

 makes of especial interest the methods for its exact estimation. 

 The presence of fluorin is of little consequence from a practical 

 Lasne, L'Engrais, 1896, 11 : 1145, 1168. 



