Qt M.V777M 77 !7<; /;A7'A7i',U/,Y,t 77
for .sample I. Carefully remove the M«»pper, holding over beiiker I, and
pour alnmt 0.2 to 0.5 grn info the beaker. Repine*' the .stopper, u*«ing great
carol hut. no particles .shall fall outside the beaker and be lost, then re\\eigh
tho bottle, and contents. For thc.se weighings flu* zero point of the balmier
need not be. known, an explained on page ,'tH. Record the* last weight under
the* first- and subtract to obtain tin* weight of wimple used, Heeord the
laKt, weighing also at the top of \\\i\ space for sample II. Remove it. nrconti
portion to iM'ukcr II and r*«wi%h tlu* hottlr, rwordiMg un«l<*r th^pn^MMlii^
weighing, Suhtnict again for th(* weight of sample II.
Dissolve* <*:tfh wM'igtird .^ansph* in 75 re of disf ilh'd \vnt««r, inpn-«in'd with n
fair dc'grrc of arfurary in a gnuhiati'd cylindrr, and add 1 <"'" of UO-prr rriit
nitric acid. (\Vat«T an«l arid mu,Ht !»«• fn«J' from rhlorid«*:». T«'?*t. hy niuiiig
the (juantiti^ inon!iom*d al»c»v<* and adding a f«*\v dr«tp^ of rli*jir Htlvrr
nitrate .solution. ) Hi*at th«* chloride noliition nearly to boiling then pr«*ripi».
tatc* with rl«*ar «Vper cent holulion of silver nitrate, adding drop l»y drop
from a pipette and stirring continuously. Ten to 20 cc of Nolutiott may hi*
rcMjuircd. acc«»r<ling to the na,fnre and purity of the saittph*.
C*ovrr tlie heakcTH and place on th** «t**am hath or over it low- Ha»n* whirh
shows no yellow. Digest nt n««nr the hoiling ientperuture until the precipi-
tate has been well florenbtted, then test for completeness of precipitation hy
adding a drop or two of silver nitrate, solution to the clear, supernatant, hiftiid,
I hiring this process of digestion the crucibles are to be removed fr«»m the
oven and cooled in de.Nteeators for MO tninute.M_t then \veijghed accurately,
handling only with clean crucible tongn (not ruhbcr tipped), flue** i&
crucible in the holder and, if a (Jooch in tn«*d, moisten the pud with a few
drops of water from the wn^h bottle, Apply the Muctinn to either ihi<
(looch or the alundurn crucible mid filter, holding the beaker clone to I he
top of the crucible ami pouring down a gl?t.>^ rod, If a f Sooeh eruciblc w
uwd place* flit* rod ngain^t. flit* perforated plntr* c<»verinw; the n^tn^fim
Rhine- nil ioom* precipit itfi» into the filter, then clean the beaker by mean*)
of thi* jMiliceiiiiiii 61 rublx*r-tipped	rnd| ftinl wiwh hiitllf ami ftiifillv
wash tin* entire precipitate and crticible. !»y pouring itt il--per cent, chloride-
free nitric acid from u beaker until tfie witching** ?s!m»\v no eloudtnerc.t wiMi n
drop or two of dilute hydrochloric acid, thwt »howin{( that nil ;ti!ver iMfrnfe
ha« been removed. In making ^uch 11 t«**t ftrnt rin^e the ftntftnlr of Hi** |ow-ef
Mid of the funitc! fJih*% then roller!, nlmtif. I ce of the wwihtntt** from flu-
Kilvrr ehlorifie i« n cjeun ti^f. tu!i«* eontatrung is, drop of <litute hv«)ro«'htotte
acid, If an lilnndiifii rrucible is iisih!, obwrve particular cnre in wn,*s!iing the
upper portion, i» the prtrotis wall* itr<! filled with » Holuttrirt cnrtt-uininiit nil
noliihle salt h prwnt,
Finally gi%*r flu* «ilvf»r cltlorifli* mid filter » nifigli* ri«,«iiig with rrilisfilieii
alcohol, wipe the outride* f»f the crucible, if a Goorh, und dry nf th»* tempera'
ttiri! that win* efujiloyi'd for the ongiint! filter. After 30 itiiiinti*'H_4 rnn\ m fit*'
dc«ici*!itfir and weigh, Dry for uddilionnl |***rir«i.H of |5 iiiiriiit*^ itnfi! fh««
weight dt'im not vnry nwre than 0,3 rog. C!iilr.til!itf» tin* per ct*nt of chtortti*-
in the wimple.