The Students' Guide in Quantitative Analysis - Free Ebooks Library

DKTfUOI I NATION OF WA'IEK, I9
10 c.c. NI^HO, and a slight excess of IINa^PO^. (Should
a precipitate form on adding NM4HO, add NH^Cl until it
rcdissolvcs,)
Stir the contents of the beaker well, avoiding
touching the sides with the glass rod. Cover, and set aside
for 12 hours, without warming. Filter and wash with cold
water, to whicli one-fourth its volume of NH^MO has
been added, until the filtrate acidified with HNOj gives
only a slight opalescence with AgNO,. Dry thoroughly on
the filter, ignite in a platinum crucible, gradually increasing
the heat
; burn the filter on a cradle until quite white before
adding the ashes to the contents of the crucible. If the pre-
cipitate or asli is not white, moisten with a drop or two o£
cone. MNO3, evaporate, and ignite cautiously. (See Fres.,
§ 74, b and c.) Weigh the precipitate as Mg,P,Oj.
C — Determination of "Water.
Heat I to 1.5 grni. salt in a weighed platinum crucible,
and proceed exactly as in Analysis I, C.
Notes to Analysis of Maguesic SulpJmte.
On the solubility of amraonio-magnesic phosphate in
water and saline solutions. Cf. Fres. page 816, paragraphs
35-35-
One part of I 44300
f 15300 parts of pure water.
" " ammoniated ^vater
precipitate < 7548 " " strong sol. of NH.Cl.
dissolves in 15600 " " water containing NH^HO
andNH.Cl.
For a discussion of the solubility of the ammonio-magnesic
phosphate, consult Cladding's letter in Chem. News, vol.
47. P- 71 (!883).