QTA .V777M 77 VK DNTKHMIXA T1ONN

chloride and 140 gm til" ammonium ehloridc in water, add l.'iOcc of ammo-
nium hydroxide fnpccific gravity 0.1)0) and dilute to 1000 cc. If thin .solution
Is kept in ntock for any considerable time it will acquire a floceulcnt precipi-
tate* of hydrntcd nilica, derived from notation of the. glann by the bane. The
Bolution must he clear whcm uned. Thin condition may bo innurcd by
filtering the solution or by prepanng only enough of the reagent to hint
a short time.
Weigh duplicate samples of 0.2 to 0.4 gm of the plionphate into hcakcrn
of re.nint.ance glzinn, diHsnlve and dilute* to 7/i cc. Add a. drop of methyl red
and if a basic* reaction in not shown add dilute ammonium hydroxide until
the notation beconicn yellow, avoiding an exccnn. Add 10 or. of a 10 per
rent notation of amnionittm chloride, mix and then add, very slowly, "mag-
nesia mixture" nuflicient in quantity to precipitate nil of tlu1 phonphatc.
AH the precipitate doen not form rapidly in a barely banic notation it in not
always easy to determine when enough of the wagont ban be.<»n addecl.
It in then bost f o us*- \vliat in thought to be a good exwnn and to rely upon
t«wting the fiitratf wbirh in obtained Inter.
Allow to ntand for 1.5 minutfn until it roriHidernble part of the precipitate
lion appeared, thi*n itdfl c-onrrntrated amntonimn hy<lnjxi<lct«oluti(»a (n|M*c'ifm
gravity (MXh, in nurh quantity that the solution nbull finally eon tain ammo-
nium hydroxide fqtiivulent to one-ninth of itn total volume. <..*ov(*r and
allow t<» ntattri for 3 hmirn or ntir continuounly for W minuten. A wmall
ntirritig ntachiiu* may b<* u«ed for this purpow*.
Filter the prrriftititfe on a filter of extrnHwl paper, in a weighed platitunn
GfKH'h erueible or tit an ignited and weighed altmcium crueible, and wanh
until free from rhiorideH with u nolution roritaining 2 per cent of ammonia
or 10 per eeitt of amnioinuin nitrate, iimtlly tcHting a fi*w drojin of the wanh-
iiign with nilver nitntf i* after nc*idifyiug with nitric* acid.
•Set the filtrate nwdf% nft««r lidding 5 <uit morn of magncnia mtxturi*. If
more preripituli* forms nfter ntanding an hour thin munt !>« filtered out,
Wfjwhet! ami *sid«li*cl to the main portiort.
If iiCtiwirfi rnieibli* iiji-n bi*i*ii uni*«i for filtration, plan* the rap on the bottom
and heat over tin? burwr tiist.il dr>% thini over the blant lump for 20 utimttcn.
An ahindiiiit rrueiblc* in trt*nfi*d similitrly. If n puper filter wa« un«*il remove
the paper from the fiifiiti*!, foltl and place in a weighed porrelain or platinum
crucible*, liifliiii* tbe rrueible with th<* ifovi*r leaned ngainnt it find heat
gently over fhi* burner until the paper in eonspletely burned mid. th<* pre-
cipitate in iii*iirly whiti*. After tlte preripititti! is white or light gray the
crucible in fi«*fit«*<! for 20 ittinttten over the bla«t lump, cooled in tb<*(icMtcc,at4ir
nml wctgheii. From ilw weigfit of miigncnium pyroplio«phfite calculate the
I'M*r cent «tf phonphorun, -of pliiwplioruH pentoxide or of the* phonphatf* radical,
according to the nature of the wimple imed.
Determination of Phosphorus in R0ek Phosphate.--!*repnrc» a «oJuf,lon of
nmnwuiutn Htntjifaltttr nn follows:
Difwolve ICMI gm of motvbdic acid In a mixture of Hfi cc of concentrated
ammoriiuifi hydroxide* fnporifie grnvity C?,!M)) ant! 270 ec of water, I'our
thin Koltition nlowly am! with vijcoroiiH sfirrifig into a nitNf.fft'e of -i!*<) «-e of