Masking and Demasking Agents

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1. Masking & Demasking
Agents

Pratiksha Thakur

2. Masking by Precrottation=

Many heavy metals Can be SeparateA itiaeo ho Aine forro of

foSoluble Sulgnides using Sodium Sulghide ox as insoluble. — —
exes using Anioneekamide. These dr Altened, At composed

engl

Teacher's Sign.

3. cp) sage ee © 4
% Masking agents-

|) PM control — wena,
Avery simple method op masking 15 based Ue e face shag
Me alkaline eatin merals Form ederake complexes below pr
whilst most bransihion elements form ee oo Shay,
doum to pla, Certain metal fons, such as th ston Ga),
Cobalt CE) and Ahortum (19), can be Selechvely Abrabed a
SM lower PA values.

2) Ammontum Fluoride
Lol Mask alummium, tron and Astamtur by Complex Formation,

9) Ascorbte ac

Ts a Convenient veducing agent for tron Gr) which is then
masked by complextng asthe very stable hexacyanofenrate (1)
complex: This latter ts more Stable and less intensely colewr
than ne hexacyanoPerrate (HE) complex.

NI Simecatreh = 2-0 Desert propano); (us. HSH: 09)
— Sans of mercuny Cadmium ,2mc, amsente, antimany By
lead and bismuth react tottn dimencapra in weakly act
Solution to Form precipttates which art sue In alone Sot

AN Am
ESE Complexes are Stronger he un

ar wt Copper but ot wed, art
Plexes by dimer caprel-

4. Complexes y So Mak olsen tons, Such as leads Magnesium, —

so and tae alkaline enebro mekals, can be

dekenmines foie Presence of Moe metals Mi Hae Pack: group

Meénbiontd, Zinc and Cad mtusn Can he demasked From Her

cyan

Le camplenes ly aldehydes, Such as Porrsoaldebyde or
oral Wydrate (due to Me preferential Formation Dead —

“yonninydata), and selechvely Arata —

s)

ren (disodium careohol -2,5— disipa)

KL mask alucnintuen and Hhantun as Colour ronge a

Lt Coloured comple: dis hesk Masked

as its hexacyanoferrate CE) care Qn, A —

Dr ernanal des [N (ou. ca 014]

Farms a Coloueless Complex tota alumintum ‚a yelloso comple.

fatty tron (ID), Hae colour of which ts almost d'schargel by

5. AtUtharolamme ¿Similarty y Mordant black TE canbe Used ta the
presence of kvtethavel amine aluminum Complex:

À PT indicators :
| y) Atzartn Fluorine blue — (alrzario Gomglexent) |
| This may be used to acid Soluhen ab PH Wa for tne Herahono? lead
| ane, cale AM, Mercury U), and Copper GD cohen ne Colour
| Changes from med to yalloro.

BE tS used In the determination of Alummnein Triameanolone and
Fluoamelone Acetonides and in Fluocortolone Hexanoate and
Piva Sate.

= The determination depends upon the facts that ne red Centum (DI,
Complex Changes to blue in tre Presence of fluortde tons. the |

| Organically combined Plume Is Converted Ao tnorgante uortde |
by burning Ant Compound. in oxygen and AbSowking the gases to
| Waker
~The Complex is Lovimed by Ane addttion of. alizarin Fluorine blue |
and Cerrttien GE) nibrabe in Hie presence ofa Sodium acetate- acetic
act butter and its beastly measured Spechophotometcally
at 6lo nm

2) Catcon- (mordant black IF)
TES Aves à rediish purple Colour with Calctum In alle

Solution and a blue cotour in ine absence of ree Cancomplexea)
Caletuen tons,

WSEAS used to he assay of Cadciuen carbonate | Calcium chiortie,
Calcium gluconate and Caleruen Sodtum Lackoke: |

RE

6. on
no. Yon, 4

=

caicon

BY Calcon Carbenyite act
Jos à "

Jun, giving a reddish pueple Colour, changas to blue in |

Lager absence

=| TA ts used in Me detect

= NON

Calton Camborne acid

| il catecmst voter

bte Catechol groups of Me molecule Por, weak, highly Coloured

o wol a Lote

Lux to alkaltne Solution and the more Stable ones are also blue |

ha acti Soluks cap ak: lou PH values tohen they change to |

ol eee exacnpie . tre Hpomtuem LIE) cooper is blue down to PMA and |

ne lntcenulin (IT) Complex ts blue dou to PM 15, The todicator |
is red to acid Solution helos PH LE, tien Hr Changes clou |

F
Meseta

‘Teacher's Sign, ——

7. a

nn |
Won te violek at PHC owing do \ass of a Furiher Proton Anda,

+ TeAdish~ purple sept 3 owtag to Ane loss of A Hd proton,

-Tn alkaline Solution, dear end Points ae Shown Lolth Magnesium,
Manganese y ire (it) ‚Cobalt, nkcKe, Zinc, Cadmium and calctuen

— Between PHY and, comer) lead and lanthanum give Clear end
Points ,cohiist bismutin Ahortur and antimony can be tibrated In tine
PH range VS ou and, hence, Selective Htrations may be Cacrted Out,

— Catechol violet also has ne advantage Mal (ES aqueous Soluhons arre |
highly State.

na

5) Diphenyl carbazone-

his is used as an indicator For mercuay in dhe detemmmahen of
Propyl Hnrouracil.

= Tk forms avivlet- coloured Complex Gin Mercury (I) tons, buts
He meachon ts only Specific for Mercy tn O2 M nine acid,
provided Mat chromates and Molyedates are absent,

= Tn neutral oF slightly AC Solution, Copper, tron, Cobalt: and
Other tons GIVE Coloured Complexes.

chlorides reduce Sensitivity do mercury due to dine formaken of
(yey) tons.

|

gs |
ie
2 CEHENEN-CoONWINH-Cells 4H à a 5 >
> de bene

ia

8. er Aukn, lead Amtuen, Cobalt LI, Magnets
y manganese LM) can he deitrmerl using an arnes
niente = asamanta butter atole, amd do still Stange alta —
calcium, Serentiuco and home cante dtosted

Ja à » aquecs solution of Moe dye 15 Stable and it echas:
feo blue do yenoı to dort Salulico dod bine tn grey to alain
utio

rate used tn ne Mimik desk Ec Ca) Clu In Sulpnalrerme lisis

A 50; me ry (Cm: Soon),
ee er
7 aa Tue
Gone = Gan ue

9. | 9 mordante black = (Erichwome Black T, Solocrrome Black Lo)
| ts Indicator has wotde Applicaton,

| Teis blued about PH wand mast OF MES Complets ame rela
|= Qetoco M 6-2 and Above IWS, the dye tESAR is wreddish IKE Complosen
| — Bots Hrewefore ; necessary ds camry Dub Hoe biblio tn Presence,
| oR a buk er at to.

mo,
OH as
en LO a
DD a > want
, à

y

Y

Que (Pf 10)

= Magnestuen, Calera, Cadmtum, Zine, Manganest ; lead, lantiramum

and Mercury CIE) Maybe Aibrated dorechy using Hols Indicator:
= For barturo and strontium, (bis beter do add excess Sodium
| egetate and har tirate with a Standamd magnesium chlortde
| Solution.

| = Cobalt, nickel, Copper, aluminium, Silver, Panam and platinum

| Foe rome Stable Compenes in the dye Ahan with Hee edekate
and hence, Ane former Cannot be uses as am indicator.

| = Tron (I), cevtur GE) and Varadate tons oxidise Ane dye, Unit

| SOC) ana Ti GE) tons reduce it.

= AI Ahese tons inteafere and must Le removed OF masked. Fortine.

Same reason as murextde, Mordant Mack is used as a Freshy
Prepared 0:27 dispersion M Sodium chloride,

| AMordant_Llue3- (Solotmome cyantne A)

— This ges a deep purple Colour With aluminium tons tn acidic
| Solution and a gale pink Colourin He absence of Gree
| Gancomplexea) olumintum tons:

10. a PE A NUS A

Date
Soe

Murexide= Cammontum Purpurste)

“This is mainly used Por the +ibrabion of culetuen ak pri, —

Caleren ts hound ta an eight membered ing to the murextie
Chelate,

he larger cing canfers a lower Stability Hoan Mos Usual Lye

And Stix-membertd ating Chelates,

Since magnestien= ure wide ts less Skakle than the Cabot
Coples, caletuen Canke Aitraled tn the presence of _

Magnesium. Tats ts applied to water analyst

no al

1

y 3
DH

om

Murexide (Violet ai pn 12)

Ho. A
el

LES Drea

Caletuen — rouvre de

Copper, Cobal N Ce
sde t ke

Ciopunge stone Atnted ede

asa 0.2%! disperston In powdered Sodtucn Chloride, —

11. N) Sodium Alizarine Swphonate—

TMS gives a biuisn—ved lake woth aluminum and Hnomtum tons y,
about pH4 amd ts Yellow at this phin He absence oF Hrese tons,

— Ti bas been used as am Indicator for the determination of Flusnne
10 “Trtamemolone by Htrahon ibn Standard Anonum nitrate
Sub

») — Gisodium , 12 -dthydroxy Phemol- 3,5—deswphonate)

- This forms a blue colour Lolth tron CON) behoeen PH2 and 5, a
Moltt colour behoeen PM Stand Fand dred Complex fn atfkatene,
Solution.

~The blue complex tn acid Solution ts a Suitable Milcator for
oralen win disodium edetate , ne Colour changes being greenish
Vue Anrougn green to yetlow:

| — Tira bons are best carried Out at Lo to 50°C.

~The red tron GID) complex to cukaline Solution ts stable. and
Specific for Lurie Iron pte ts Sensitive te Lin 200 million.

Iris Mot used A9 an Mndiatter On ededate —tron btrations; bub

YE cam be used ds the basis ofa Colowimetrte assay for Perro

on oy

20,5 se SL
| Tem x
he so
INES eo
| EL,
| Soy Say

Sue seme Red complex

12. Fine Stabilthy OR tne Compleses, however, antes tain OM

Moss, vi ist +
Mo a m ad

Lf ond meacury tan tot drbrated.

hexamtne alone or tin Varying amounts of att:

= AGE TU

EI 7 CE u

=
mars =
manne 7, RS

y

El

Ll

Cb