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.Mt 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*'H4 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.