156 Austin — Double Ammo7iiu?n Phosphates in Analysis. 



Art. XIX. — The Double Ammonium Phosphates in Analy- 

 sis ; by Martha Austin. 



[Contributions from the Kent Chemical Laboratory of Yale Universitj'— CIX.] 



The function of ammonium salts in the formation of double 

 ammonium phosphates for the purposes of analysis has been 

 the subject of a good deal of study. Manganese, which tends 

 to fall as the tribasic phosphate, MUgP^Og," appears in the 

 presence of a sufficiency of ammonium salt in the form of the 

 ammonium manganese phosphate (NHjMnPO^, which gives 

 the pyrophosphate, Mn^PgO^, on ignition. Magnesium, f on 

 the other hand, tends to pass under the influence of ammonium 

 salt toward the condition of the diammonium magnesium phos- 

 phate which yields the metaphosphate on ignition. Further, 

 in the cases of zinc and cadmium:|; it has been my experience 

 that the presence of a considerable amount of ammonium salt 

 is essential to the precipitation of the ideal double ammonium 

 phosphates of both these elements, although in the case of cad- 

 mium, too large an amount of the ammonium salt prevents 

 complete precipitation and apparently occasions the formation 

 of a phosphate too rich in ammonia. The solvent effect of the 

 reagents in the case of mercury phosphate:}: is very great, 

 yielding a new salt the composition of which has not been 

 investigated in recent years. Beryllium§ is only partly con- 

 verted to that ammonium beryllium phosphate which yields 

 the pyrophosphate on ignition, even in the presence of large 

 amounts of ammonia salt. Neither an ammonium salt nor 

 ammonia in solution converts the phosphates of barium, stron- 

 tium, and calcium:}: to the double ammonium phosphates. Of 

 these three elements barium alone falls in the form of the 

 hydrogen barium orthophosphate. In certain recent articles 

 upon the precipitation of the double ammonium phosphates 

 some of the facts mentioned above have been called in question. 



In the determination of zinc and manganese Dakin|| has pro- 

 posed to substitute ammonium phosphate as the precipitant in 

 place of microcosmic salt (hydrogen ammonium sodium phos- 

 phate) in presence of a considerable amount of ammonium 

 chloride, and to wash with a one per cent solution of the pre- 

 cipitant followed by alcohol. Dakin's analytical results, taken 

 without scrutiny, would seem to show that the precipitate pro- 



* Gooch and Austin, this Journal, vi, 233. 



f Gooch and Austin, this Journal, vii, 187. Neubauer, Zeitschr. anorg. 

 Chem., ii, 45-50; iv, 251-266; x, 60-65; Zeitschr. angew. Chem., 1896, 

 435-440 ; Jour. Am. Chem. Soc, xvi, 289. 



X Austin, this Journal, viii, 206. 



^Roessler, Zeitschr. anal. Chem., xvii, 148. 



I Chem. News, Ixxxii, 101 ; Ixxxiii, 37. 



