Ammonium Magnesium Phosphate of Analysis. 189 



-containing also eighteen grams of ammonium chloride, is 

 practically insoluble in the latter mixture if an excess of 

 magnesia mixture be added ; and Heintz * showed that the 

 effect of adding an excess of sodium phosphate in the solution 

 is similar. 



So far as appears, no quantitative experiments have been 

 recorded in which the behavior of a mixture of ammonium 

 chloride and magnesium salt and an insoluble phosphate in a 

 solution only slightly ammoniacal has been tested, though as a 

 matter of convenience the use of faintly ammoniacal solutions 

 and faintly ammoniacal wash water is to be preferred to the 

 mixture of strong ammonia and water [1 : 3] ordinarily 

 employed. As a preliminary step, therefore, in the work to be 

 described, experiments were made to find how small an amount 

 of magnesium could be detected in solution by precipitating with 

 microcosmic salt, either alone or in presence of ammonium 

 chloride in faintly ammoniacal solutions. The ammonium 

 chloride used for these tests (as well as in the similar quanti- 

 tative work following) was purified by boiling with a faint 

 excess of ammonia, filtering, digesting twelve hours with 

 microcosmic salt, and filtering again. The results are given 

 in Table II. 







Table II. 







Weight of 

 MgO taken as 

 the nitrate. 



H(NH 4 )N"aP0 4 • 

 4H 2 taken. 



Volume. 



NH 4 C1 taken 



Opalescent 



grm. 



grm. 



cm 3 



grm. 



precipitation 



J 0*0003 



1-75 



100 



.. 



marked 



( 0*0003 



(( 



500 



_- 



(C 



( 0-0003 



a 



100 



10 



it 



\ 0-0003 



u 



500 



10 



u 



( 0-0003 



tt 



500 



30 



faint 



o-oooi 



a 



100 



_. 



marked 



( o-oooi 



t( 



100 



10 



a 



\ o-oooi 



u 



500 



10 



faint 



( o-oooi 



It 



500 



60 



u 



The results of these tests show that even so little as 0*0001 

 grm. of magnesium oxide may be detected in Rye hundred 

 cubic centimeters of faintly ammoniacal water containing as 

 much as sixty grams of ammonium chloride. f It is plain that 

 strongly ammoniacal liquids are entirely unnecessary in the 

 precipitation of the ammonium magnesium phosphate under 



*Zeitschr. fur Analyt. Chemie, ix, 16. 



fit was found also, incidentally, that the presence of reasonable amounts of 

 ammonium oxalate (100 cm3 of the saturated solution) does not interfere with the 

 precipitation of the ammonium magnesium phosphate by microcosmic salt. 



