On Trihasic Phosphoric Acid. 1ST 



(a)— 1.1468 (b)— 1.7613 (c)— 0.8639 



V. Method hij Mercwy. (To be used when it is desirable to 

 separate alkalies from alkaline earths.) 



This method is exceedingly valuable in eases where 

 alkalies and alkaline earths have to be separated from 

 iron in phosphatic minerals. It might have been, there- 

 fore, superfluous to include it here, as this case will 

 probably never occur in iron ores; for the sake of com- 

 pleteness, however, I undertook to experiment with it in re- 

 gard to its facility and value as a method. The compound 

 has to be dissolved to this end, in a very little 1IO, NO,, as 

 a large amount renders it difficult to drive off the excess of 

 nitric acid, to wash out the alkalies and alkaline earths, and 

 to prevent the mass from coining over, in the subsequent fusion. 

 A large amount of nitric acid, besides all this, will cause a tur- 

 bulent reaction, which may easily give rise to losses by -pat- 

 tering. I will state, in this connection, that I did nol succeed 

 in any case in driving off all the nitric acid from the sesquioxide 

 of iron, as I found each time a little of it in solution, and in 

 two cases, also, traces of phosphoric acid. After heating the 

 mass with mercury on a water bath, (a wide dish being tin; 

 more suitable,) until no smell of nitric arid can be detected, 

 tin' insoluble part was completely separated by washing, the 

 filtrate (which will contain the alkali.-. &c.) gave a slight 

 precipitate with ammonia and sulphide of ammonium. Alter 

 freeing it from the mercury, this wa9 filtered .,(]', dissolved in 

 IICl,oxydized with NO,, and precipitated with Ml . 



