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二氧化钛(钛白粉)

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发表于 2008-5-23 12:09:00 | 只看该作者 回帖奖励 |正序浏览 |阅读模式
二氧化钛(钛白粉)
' f/ X8 `- q& X! `. Q6 w3 R, z  Z3 |% t2 x5 ^% ]; L
5 x  w; h5 u; G. P8 g- y9 h, I
CAC关于二氧化钛(钛白粉)的使用规定  X, z& ]) e" O, f3 x: z( d; M
GSFA Online 5 |2 ~8 G* b( j
Food Additive Details/ f% r7 s  r- S/ A- J
Titanium Dioxide (171)
0 _9 O! _" ?; F8 yNumber Food Category  9 v5 l$ V; s: W; A6 o4 P# }- O; c
  01.1.2 Dairy-based drinks, flavoured and/or fermented (e.g., chocolate milk, cocoa, eggnog, drinking yoghurt, whey-based drinks)  
2 T" P( F( k$ g  01.3 Condensed milk and analogues (plain)  
6 ?  n2 N% ]$ P: A5 E4 X- v  01.4.3 Clotted cream (plain)  
4 u2 D) J) a0 k+ ^6 v# x: {  01.4.4 Cream analogues  
$ G; J- W  U( R+ b, b' @( E  01.5 Milk powder and cream powder and powder analogues (plain)  ! r. z9 ^, f9 ]" S6 w
  01.6 Cheese and analogues  % c  a2 y! E5 }3 o3 }6 X2 n5 X
  01.7 Dairy-based desserts (e.g., pudding, fruit or flavoured yoghurt)  ! E  v0 P% L4 ^+ |# @
  01.8 Whey and whey products, excluding whey cheeses  ) S& Z4 P6 `8 x* K
  02.2.1.2 Margarine and similar products   
2 C0 N+ o; P# B+ f  02.2.1.3 Blends of butter and margarine  
! |( G% G, I# q0 P8 [5 D  02.2.2 Emulsions containing less than 80% fat   4 M) H, M: k- ^
  02.3 Fat emulsions maily of type oil-in-water, including mixed and/or flavoured products based on fat emulsions   ; E4 o+ i. w; D4 q5 c
  02.4 Fat-based desserts excluding dairy-based dessert products of food category 01.7  5 h7 S4 K8 }. I
  03.0 Edible ices, including sherbet and sorbet  ! L" B+ ]) h: K8 p8 b+ j: F: Y
  04.1.2 Processed fruit  
) U" `$ h& e% A" G: r  I$ I, G6 i  04.2.2.2 Dried vegetables (including mushrooms and fungi, roots and tubers, pulses and legumes, and aloe vera), seaweeds, and nuts and seeds  
; A6 U) t& n# U1 u  04.2.2.3 Vegetables (including mushrooms and fungi, roots and tubers, pulses and legumes, and aloe vera) and seaweeds in vinegar, oil, brine, or soy sauce  
1 y- K+ E! e3 ^( k# J  04.2.2.4 Canned or bottled (pasteurized) or retort pouch vegetables (including mushrooms and fungi, roots and tubers, pulses and legumes, and aloe vera), and seaweeds  4 o7 g4 z0 E, X; ]# k3 T
  04.2.2.5 Vegetable (including mushrooms and fungi, roots and tubers, pulses and legumes, and aloe vera), seaweed, and nut and seed purees and spreads (e.g., peanut butter)  3 O6 T! ^2 w# H
  04.2.2.6 Vegetable (including mushrooms and fungi, roots and tubers, pulses and legumes, and aloe vera), seaweed, and nut and seed pulps and preparations (e.g., vegetable desserts and sauces, candied vegetables) other than food category 04.2.2.5  
9 p& D) I1 N. G& ~: j  04.2.2.8 Cooked or fried vegetables (including mushrooms and fungi, roots and tubers, pulses and legumes, and aloe vera), and seaweeds    a$ K+ g3 _% W  V% g( S
  05.0 Confectionery  
, `& ]- Q0 _: o+ c) E  06.3 Breakfast cereals, including rolled oats  - \) c" [: f0 \* x* [* @, c
  06.4.3 Pre-cooked pastas and noodles and like products  ! Z. k3 P* a2 j' R6 A) K
  06.5 Cereal and starch based desserts (e.g., rice pudding, tapioca pudding)  
+ `+ R5 X" ?6 p4 J  a- X, V9 R  i  06.6 Batters (e.g., for breading or batters for fish or poultry)  
+ M6 }6 s1 n5 f9 ?9 G7 z  06.7 Pre-cooked or processed rice products, including rice cakes (Oriental type only)  
. ^* ~6 L! `+ j" l: ^* L  06.8 Soybean products (excluding soybean products of food category 12.9 and fermented soybean products of food category 12.10)  ! @& E1 E* P3 D0 _' T0 o- Q
  07.0 Bakery wares  2 u6 r  K+ C$ }- u8 W  [1 p
  08.2 Processed meat, poultry, and game products in whole pieces or cuts  
. t0 c' ?0 B, i+ K- }  08.3 Processed comminuted meat, poultry, and game products  4 [3 U+ c5 T7 C+ B( r
  08.4 Edible casings (e.g., sausage casings)  
/ L" m0 ~  Z! I$ w0 [) o+ D  09.3 Semi-preserved fish and fish products, including mollusks, crustaceans, and echinoderms  - b' v+ z2 ~; w- z/ C9 c( ~6 c
  09.4 Fully preserved, including canned or fermented fish and fish products, including mollusks, crustaceans, and echinoderms  
: \+ q: n. d5 F6 Y  10.2.3 Dried and/or heat coagulated egg products  
" S# ]; h9 v  Q2 X9 B  10.3 Preserved eggs, including alkaline, salted, and canned eggs  6 @+ m& i. q, z$ ]
  10.4 Egg-based desserts (e.g., custard)  $ a% {; f1 r  c. b
  11.6 Table-top sweeteners, including those containing high-intensity sweeteners  
$ a: G  R8 r4 d  12.2.2 Seasonings and condiments  
) [9 M% Q& y( K* w2 U  12.3 Vinegars  
2 u  u8 U8 c* B$ f; q  \  12.4 Mustards  
- n8 F) C/ f( D% j2 c+ e; {+ s  12.5 Soups and broths  6 H+ b7 k, x$ A$ o( Y% Y7 e
  12.6 Sauces and like products  
% Q, M' M9 I1 V5 F6 ?* B  12.7 Salads (e.g., macaroni salad, potato salad) and sandwich spreads excluding cocoa- and nut-based spreads of food categories 04.2.2.5 and 05.1.3  
% {8 j0 T6 m- c  12.8 Yeast and like products  
5 j" |' Z& t% m6 Y$ J  12.9 Protein products  
9 C5 m# `! M. U/ U1 u: ^1 Z' g  12.10 Fermented soybean products  / s, R: y3 `  W& N* f
  13.3 Dietetic foods intended for special medical purposes (excluding products of food category 13.1)  ! o+ {# {6 I5 g$ j& {
  13.4 Dietetic formulae for slimming purposes and weight reduction  6 Z- k& ~, F+ E9 s; N2 N
  13.5 Dietetic foods (e.g., supplementary foods for dietary use) excluding products of food categories 13.1 - 13.4 and 13.6  
9 T+ d8 n+ k1 P# ~" }" f' A  13.6 Food supplements  
' l' W5 E: f: @/ @& [5 v  14.1.1.2 Table waters and soda waters  " Z" ?) H) j/ a
  14.1.4 Water-based flavoured drinks, including "sport," "energy," or "electrolyte" drinks and particulated drinks  
/ F" @8 y4 M, T7 t2 g0 @  ~) P0 y  14.2.1 Beer and malt beverages  
8 @9 `# ]% ?4 g& C  14.2.2 Cider and perry  
0 y" }9 v* u9 Y3 g1 b* q) M  14.2.4 Wines (other than grape)  
7 V; ~0 t5 Y2 [3 |  14.2.5 Mead  ' j3 p. T. v# l" ]7 Z7 L8 B" H
  14.2.6 Distilled spirituous beverages containing more than 15% alcohol  0 ]6 D& Z$ H" Y0 I- E
  14.2.7 Aromatized alcoholic beverages (e.g., beer, wine and spirituous cooler-type beverages, low alcoholic refreshers)  
" K# k# h+ B/ g- R+ D" @) j/ [. M! r3 g4 R  15.0 Ready-to-eat savouries  
( P( f4 m* S! _! ^  16.0 Composite foods - foods that could not be placed in categories 01 – 15
" k7 O9 x. D) Z% z" h; f. B+ `' `) S* |% _4 F3 N/ ?

# W$ Q0 u5 M; ^) n$ Z部分译文:9 O+ K' C; A! P1 R) v
# r9 b/ z2 i, A! e) b' o
食品添加剂通用规则/ S: @+ s& h, C) @$ I& [8 E
食品添加剂
. {. Z$ u! k3 J1 e  u1 d                    二氧化钛(171)
. b% F) y5 U. v/ W# V食品类别:" k5 n; _8 v2 O2 I6 f/ P2 _
06.3 早餐谷类,包括燕麦片
5 I8 ~% H( ]% H4 M& m& \2 b: H* W06.4.3面条及类似产品% y. Q$ m( [" e4 p
06.5 谷类,淀粉甜点(包括:米粉布丁,木薯布丁)- {2 a( e1 D9 p' r! `6 _0 c
06.6 面团. R' _/ z8 p! E1 O
06.7 预煮的或加工的米产品,包括年糕(只包括中式的)06.8 Soybean products * q/ `3 f4 |, {% B' l
07.0 烘焙类
; {, Z3 ~' q( q, _- ]07.1 面包,普通烘焙类,以及其混合物
1 H! U# n; E, N  ]4 D9 B5 k07.1.1 面包,面包卷
% D+ L7 D+ G1 }3 O+ u" e- }; a07.1.1.1 酵母发酵面包及特殊面包- [2 \# l2 ]& K, `% N% c; f; ^
07.1.1.2 苏打面包& m/ N% y, {) Z. z, m! e
4 B+ H- ?0 _0 J$ C, \& Q$ P/ i
3 F/ d  u& G0 g9 ]
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 楼主| 发表于 2008-5-23 12:10:00 | 只看该作者

二氧化钛(钛白粉)

二氧化钛(钛白粉)
+ d  F, U/ O4 \! Y4 r! L1 s0 J5 {
6 k, {* I: k- g% CJECFA关于二氧化钛(钛白粉)的结论4 z7 L' c  v5 }/ V8 e0 R& S& ~

1 N5 J# h# U# H5 X, l, |) [$ `* e摘要: 2006年JECFA关于二氧化钛的结论
7 [/ F( Y- i2 s! VADI值:不作限制。
& N6 T, j- @7 l4 @& e# y功能:着色剂
/ `! `& u( {" z  r* M4 h- K
& g. b: j4 a1 ?6 vTITANIUM DIOXIDE/ m0 m5 V: Q* O
Prepared at the 67th JECFA (2006) and published in FAO JECFA
' W9 a; l, T- z8 \Monographs 3 (2006), superseding specifications prepared at the 63rd6 D& t3 t6 S: j" ?" v# W
JECFA (2004) and published in FNP 52 Add 12 (2004) and in the
$ K; @$ h" g9 b  x/ R' [Combined Compendium of Food Additive Specifications, FAO JECFA
' N$ w9 {+ s2 e9 a( ~Monographs 1 (2005). An ADI “not limited” was established at the 13th$ R* p: ~4 m6 U' L3 Q& ~
JECFA (1969).' R' Q7 r9 u* d- ?: Y$ L4 {
SYNONYMS5 a* E9 \, b% F+ D/ U
Titania, CI Pigment white 6, CI (1975) No. 77891, INS No. 171
1 a- Z4 b& ^# K* kDEFINITION
' ~) S3 h( }" ^  V5 y1 HTitanium dioxide is produced by either the sulfate or the chloride
; _1 P# v3 V/ o* g  P' z" Kprocess. Processing conditions determine the form (anatase or rutile8 U9 V& n( J) r1 V/ {2 O( _7 s
structure) of the final product.; O& R; E$ [" ]! r% C
In the sulfate process, sulfuric acid is used to digest ilmenite (FeTiO3)
$ J5 w0 W* E% Y. {" D. Oor ilmenite and titanium slag. After a series of purification steps, the
+ G% z1 `4 m) }  X4 {" q& t" n( |8 }isolated titanium dioxide is finally washed with water, calcined, and- ?& |) H" f8 G
micronized.
3 ^2 `) u0 }1 MIn the chloride process, chlorine gas is reacted with a titaniumcontaining
: i/ U- [! p7 c  |/ S7 Q! Ymineral under reducing conditions to form anhydrous. F3 i7 u' U; p! ~' c4 p2 h
titanium tetrachloride, which is subsequently purified and converted to
! ~, I* a' \& c7 I1 R# {titanium dioxide either by direct thermal oxidation or by reaction with
5 u" X% |! l) a: _, q+ Lsteam in the vapour phase. Alternatively, concentrated hydrochloric+ W0 d2 w; D$ E  A; n" N5 l
acid can be reacted with the titanium-containing mineral to form a
, u/ l6 a+ U0 L" u3 M# M8 E$ Ysolution of titanium tetrachloride, which is then further purified and
9 \# e! Z- j/ f1 n+ K6 hconverted to titanium dioxide by hydrolysis. The titanium dioxide is& q* t' y1 C  Q4 t$ {: Y) m8 f* Q, s
filtered, washed, and calcined.  o$ r7 F, s2 {) H  Z: v
Commercial titanium dioxide may be coated with small amounts of
" M% C6 H7 U2 L* j0 b. `* calumina and/or silica to improve the technological properties of the* O( l6 n# ]9 [2 n. u) _! h
product.
% `  j. B0 _. v3 B* y0 L( p$ |C.A.S. number 13463-67-71 ~7 U2 o: E& K
Chemical formula TiO2
4 Q9 G  ]8 F1 ?) O* oFormula weight
, @, r7 @  c. N79.880 f0 o8 e" z9 ?$ m5 @/ D6 x' x
Assay1 I/ [* p) P0 X( ?& `
Not less than 99.0% on the dried basis (on an aluminium oxide and
- J3 {2 x6 z6 ^4 P1 y( osilicon dioxide-free basis)
( p; N5 M& `, W/ a( O0 PDESCRIPTION. C  q- t8 ^, K5 L
White to slightly coloured powder
. f8 _) I0 R. J* LFUNCTIONAL USES
# |* Y$ ~3 V3 O+ DColour4 f) r1 P* I8 y2 L& x
CHARACTERISTICS- J1 L' c% s- x
IDENTIFICATION
  b; i' N( A/ @# TSolubility (Vol. 4)
6 X4 t6 J4 `+ \( H& \# R/ _% eInsoluble in water, hydrochloric acid, dilute sulfuric acid, and organic
1 }/ k  @+ h5 t) E& F8 d; w/ u$ @solvents. Dissolves slowly in hydrofluoric acid and hot concentrated. b1 D2 B: o; G5 V" D. ^5 }
sulfuric acid.
/ a* I4 s; g0 `0 I1 {Colour reaction" ]& ^$ ^) l4 R" L9 Q. ^3 ^4 ~3 ]
Add 5 ml sulfuric acid to 0.5 g of the sample, heat gently until fumes of
& n; O6 G# D! l! w- X$ Xsulfuric acid appear, then cool. Cautiously dilute to about 100 ml with
8 _9 [5 }: j, Z( Ywater and filter. To 5 ml of this clear filtrate, add a few drops of
  i. p  J+ D) B' P+ Qhydrogen peroxide; an orange-red colour appears immediately.& J0 g5 b/ R$ I8 t, r; y* t+ E
PURITY
, b9 x2 g, w; Q; Q$ |/ iLoss on drying (Vol. 4) Not more than 0.5% (105°, 3 h)
: q/ ]4 @5 {) t5 l# K4 ^) fLoss on ignition (Vol. 4)7 L  y# B  U7 A3 _
Not more than 1.0% (800o) on the dried basis
- z0 R; w% }5 T6 n1 V8 N4 }Aluminium oxide and/or
8 Z8 D( w1 B. y# msilicon dioxide0 V% c% G! m# T; b/ V
Not more than 2%, either singly or combined
" S& s9 o# |: c+ WSee descriptions under TESTS) i2 @1 k; k& |$ M/ `
Acid-soluble substances Not more than 0.5%; Not more than 1.5% for products containing
0 ~' R1 N0 p# L! N3 [5 aalumina or silica.# X6 _7 E- y5 x& B1 n" Z
Suspend 5 g of the sample in 100 ml 0.5 N hydrochloric acid and
: M* {) p& w: ]) e3 L  m3 e; S* uplace on a steam bath for 30 min with occasional stirring. Filter
4 m) H5 I# @& g5 t' z- `8 F" othrough a Gooch crucible fitted with a glass fibre filter paper. Wash8 a* n  T2 y6 _& c
with three 10-ml portions of 0.5 N hydrochloric acid, evaporate the, V' V% ]6 I1 M' D3 p
combined filtrate and washings to dryness, and ignite at a dull red0 J$ P6 x! w8 I+ H  s$ s
heat to constant weight.
3 k9 J4 _* |! e9 ?, GWater-soluble matter1 L) A7 h- {. I/ C: o
(Vol. 4); Z2 T" V2 {8 P  f' e7 ~
Not more than 0.5%
+ H; c/ c: n8 G' Z9 e+ PProceed as directed under acid-soluble substances (above), using
" Y5 D3 k) k4 B8 Z; Nwater in place of 0.5 N hydrochloric acid.
; J6 O9 H& d+ Q7 L7 L4 E0 h+ EImpurities soluble in 0.5 N
  ?( \; V3 n0 E, \' }hydrochloric acid
$ w2 _7 H0 I- ?1 n( d9 I  [3 pAntimony Not more than 2 mg/kg
- y0 M# a) L9 u8 Z) ~2 OSee description under TESTS: B+ z7 ?; x% v1 m
Arsenic Not more than 1 mg/kg8 ~! X3 S+ H4 j' \3 C  u
See description under TESTS  {3 u6 I4 d% a; s+ o" D9 e
Cadmium Not more than 1 mg/kg
" B3 Q' d, Y7 ^See description under TESTS
6 x) |4 ^6 q. e% J! ~Lead3 P& E9 ]1 b- f: Z# o, V
Not more than 10 mg/kg
( ^9 C! ]' t  SSee description under TESTS
4 q8 i- D6 `/ E* B9 vMercury (Vol. 4) Not more than 1 mg/kg
$ o9 a6 E6 t8 j9 yDetermine using the cold vapour atomic absorption technique. Select a
4 @: [3 [1 Q4 C: t, G( X. a5 n4 Hsample size appropriate to the specified level+ P& s. P8 \( V+ D
TESTS
' Z: c# N8 g. KPURITY TESTS
2 m; h4 M8 C$ R7 XImpurities soluble in 0.5 N1 s2 e8 y/ T0 j8 Q( A
hydrochloric acid
. A4 D# i4 h- B- Y; zAntimony, arsenic,
% c* ^7 u  U  S0 N  Q$ P$ Kcadmium and lead
. [% x7 H. v+ S1 S(Vol.4)
2 @0 f6 B) @8 j& x$ N, wTransfer 10.0 g of sample into a 250-ml beaker, add 50 ml of 0.5 N
. A* c; d- f3 |0 V$ n6 ohydrochloric acid, cover with a watch glass, and heat to boiling on a1 R9 M/ T2 b2 K; H
hot plate. Boil gently for 15 min, pour the slurry into a 100- to 150-ml
" \% M* R, C  q1 Ecentrifuge bottle, and centrifuge for 10 to 15 min, or until undissolved* u0 O0 |8 c8 }
material settles. Decant the supernatant extract through a Whatman
" e0 E5 {: Q& ~  O. lNo. 4 filter paper, or equivalent, collecting the filtrate in a 100-ml
) S8 E2 x. N& ]0 {4 evolumetric flask and retaining as much as possible of the undissolved+ D3 e" ]. \. [7 R9 l+ F
material in the centrifuge bottle. Add 10 ml of hot water to the original
, D- S. X- V1 |/ xbeaker, washing off the watch glass with the water, and pour the3 X- ?3 ~, R+ Z2 C  t
contents into the centrifuge bottle. Form a slurry, using a glass stirring( r* J9 [$ M7 r# B9 ]
rod, and centrifuge. Decant through the same filter paper, and collect
% ]7 E. w# ]7 @8 B+ @the washings in the volumetric flask containing the initial extract.
6 U# h+ v1 }/ D$ w" l: ZRepeat the entire washing process two more times. Finally, wash the: m! g6 o3 v- n1 x1 y) y2 S
filter paper with 10 to 15 ml of hot water. Cool the contents of the flask! i5 q& S9 P, I) I5 c/ n
to room temperature, dilute to volume with water, and mix.6 p: V+ J+ H7 ?" A, D
Determine antimony, cadmium, and lead using an AAS/ICP-AES: ~4 ^/ d& I- l8 [9 P* |4 u3 t
technique appropriate to the specified level. Determine arsenic using the
! b, t7 y) ^3 h) aICP-AES/AAS-hydride technique. Alternatively, determine arsenic using
; w  {# O# u' z  gMethod II of the Arsenic Limit Test, taking 3 g of the sample rather than
, E; B. z5 J( M  y' i) E: a1 g. The selection of sample size and method of sample preparation
7 f# d# q0 l6 _may be based on the principles of the methods described in Volume 4.' |9 r( Y& ?, O
Aluminium oxide Reagents and sample solutions2 ?  E8 p" Q  m  e0 y) E0 n
0.01 N Zinc Sulfate
$ s' ]1 |" J) ?4 k, [Dissolve 2.9 g of zinc sulfate (ZnSO4 ? 7H2O) in sufficient water to$ @* z% ^, @5 J* A2 r- i
make 1000 ml. Standardize the solution as follows: Dissolve 500 mg
$ L$ C. N7 o+ Z. _7 j) Pof high-purity (99.9%) aluminium wire, accurately weighed, in 20 ml of
6 ~# f) G# W9 p3 [" Yconcentrated hydrochloric acid, heating gently to effect solution, then
2 S0 l; _! H/ u$ Ttransfer the solution into a 1000-ml volumetric flask, dilute to volume" u# k7 J: B$ j7 L6 K" A! }) A
with water, and mix. Transfer a 10 ml aliquot of this solution into a 500
% c1 c1 r- k4 w" E- g" ?7 k3 Tml Erlenmeyer flask containing 90 ml of water and 3 ml of' P' w1 K2 s9 |5 e
concentrated hydrochloric acid, add 1 drop of methyl orange TS and
7 i3 P. [$ U* i8 T  U; l25 ml of 0.02 M disodium ethylenediaminetetraacetate (EDTA) Add,5 W# g3 d+ L. Z7 U
dropwise, ammonia solution (1 in 5) until the colour is just completely
* m3 D: a  |9 x- K# i7 F* S1 gchanged from red to orange-yellow. Then, add:
" _3 Y4 r# J7 J/ ?* s3 R(a): 10 ml of ammonium acetate buffer solution (77 g of
3 `; t" D! z# y- E9 bammonium acetate plus 10 ml of glacial acetic acid, dilute to
9 \+ [9 h% c$ U) ?1000 ml with water) and( x+ I9 J# n: x9 y
(b): 10 ml of diammonium hydrogen phosphate solution (150 g' V0 h+ F+ J8 X7 G$ I# C" {* M
of diammonium hydrogen phosphate in 700 ml of water,) I8 d' _" T% n: o" {& x
adjusted to pH 5.5 with a 1 in 2 solution of hydrochloric acid,
/ Y2 u  c2 ~# j( ]: w3 gthen dilute to 1000 ml with water).* V: f( E+ H1 P
Boil the solution for 5 min, cool it quickly to room temperature in a
, @5 {  E+ x0 L% Z& w0 k" R8 _0 estream of running water, add 3 drops of xylenol orange TS, and mix.
) S9 C8 j, @, w4 j- BUsing the zinc sulfate solution as titrant, titrate the solution to the first
# `* {4 ]1 ^' t3 G! H; syellow-brown or pink end-point colour that persists for 5-10 sec. (Note:8 `- @4 s9 L- B2 X- c! d9 I* `: T
This titration should be performed quickly near the end-point by. d8 ]4 h0 ]/ X$ h, }
adding rapidly 0.2 ml increments of the titrant until the first colour
1 `# w" J3 V8 n1 V' t% d5 @, Pchange occurs; although the colour will fade in 5-10 sec, it is the true
) S5 t$ j% V# z  s0 nend-point. Failure to observe the first colour change will result in an
" ?5 i$ h; s: E* A3 ~$ t- w$ x2 Qincorrect titration. The fading end-point does not occur at the second
6 o) u) }3 O7 K/ }" |( X) iend-point.)
$ x* ]& t3 Y' |7 ~% B* cAdd 2 g of sodium fluoride, boil the mixture for 2-5 min, and cool in a
  r( a8 b) t* x! h$ }' h. y, Ustream of running water. Titrate this solution, using the zinc sulfate
. h  o) Z3 a1 o2 Z% Psolution as titrant, to the same fugitive yellow-brown or pink end-point
3 o- v3 i2 I, b# v6 T9 fas described above.
) s, ~+ M9 b) v. p) F( K0 GCalculate the titre T of zinc sulfate solution by the formula:
9 f+ D* `7 l5 @2 J: {1 C( j* w, ^T = 18.896 W / V9 d+ _- ~8 l# _4 a" @
where
% R4 {3 a: f- oT is the mass (mg) of Al2O3 per ml of zinc sulfate solution7 F9 c1 z- U5 M; N. B0 e- V
W is the mass (g) of aluminium wire9 [- {4 z- F: K/ z" r1 h* L
V is the ml of the zinc sulfate solution consumed in the* ]" J/ V0 N! M% N* z
second titration0 K' B# D! x0 c7 |9 m
18.896 = (R × 1000 mg/g × 10 ml/2)/1000 ml and
6 d+ \0 z: W- j3 l. h% j, w4 Z$ QR is the ratio of the formula weight of aluminium oxide to
5 N  y3 {' O5 Hthat of elemental aluminium., a/ B+ {) I& |: I$ f* o; d2 Z
Sample Solution A! }. ^! ]" f& N
Accurately weigh 1 g of the sample and transfer to a 250-ml high-silica
/ r1 B0 k& D5 c9 p0 N9 k, mglass Erlenmeyer flask. Add 10 g of sodium bisulfate (NaHSO4 ? H2O).
! v' n) D0 w8 n6 B  T+ _(Note: Do not use more sodium bisulfate than specified, as an excess
* w! H2 X8 n2 U3 h7 d! Hconcentration of salt will interfere with the EDTA titration later on in the% \& x, d0 C! S/ G/ d, q
procedure.) Begin heating the flask at low heat on a hot plate, and
8 p  u( Q# o0 c: C0 h) @then gradually raise the temperature until full heat is reached.% p5 w. l" w1 Q1 B
(Caution: perform this procedure in a well ventilated area. ) When2 ^/ \6 @2 q. a
spattering has stopped and light fumes of SO3 appear, heat in the full
. y6 S9 }# ]+ L, Cflame of a Meeker burner, with the flask tilted so that the fusion of the; g! r3 U( \, S. J( }9 M( y, A
sample and sodium bisulfate is concentrated at one end of the flask.
* b% ~, T) e0 f) t0 a* oSwirl constantly until the melt is clear (except for silica content), but
; |% @& N5 Q- O" D& G1 Xguard against prolonged heating to avoid precipitation of titanium
) a3 H8 _( O8 K1 U% [1 J! ^dioxide. Cool, add 25 ml sulfuric acid solution (1 in 2), and heat until
# k' }7 W7 S& j& Kthe mass has dissolved and a clear solution results. Cool, and dilute to
! v+ C  O2 O& ^  ?120 ml with water. Introduce a magnetic stir bar into the flask.; k1 g. z' f- S! c1 s" {  f* Z
Sample Solution B$ Q. p) \3 [4 a/ F
Prepare 200 ml of an approximately 6.25 M solution of sodium$ ~, E, e3 x/ Q3 a' d" M9 ?' F
hydroxide. Add 65 ml of this solution to Sample Solution A, while5 u/ w( ]/ ~$ ?, L# \/ a
stirring with the magnetic stirrer; pour the remaining 135 ml of the7 Z# m" [- ~; o( D  ]! T/ P
alkali solution into a 500-ml volumetric flask./ _9 ?* o- J6 q+ y9 H. ]9 S
Slowly, with constant stirring, add the sample mixture to the alkali5 R# s5 X+ ]( h0 d, q
solution in the 500-ml volumetric flask; dilute to volume with water,
5 C+ t7 f) n0 |$ q7 L2 Hand mix. (Note: If the procedure is delayed at this point for more than
8 U1 J9 p* \+ S% l2 hours, store the contents of the volumetric flask in a polyethylene( x0 G' m5 K  N) h- T) \
bottle.) Allow most of the precipitate to settle (or centrifuge for 5 min),( T) Q) }+ X: h
then filter the supernatant liquid through a very fine filter paper. Label* `8 H% E0 c6 G1 s, S9 K8 E. s. [
the filtrate Sample Solution B.- o; }8 Z1 _& n8 s- I
Sample Solution C
. q7 {3 i% s- b9 @Transfer 100 ml of the Sample Solution B into a 500-ml Erlenmeyer5 ^4 E$ m( b8 `1 E, {, o
flask, add 1 drop of methyl orange TS, acidify with hydrochloric acid. `5 |- z7 A6 z; L" t( _" F
solution (1 in 2), and then add about 3 ml in excess. Add 25 ml of 0.02
- J1 D1 w& q* {/ ~5 MM disodium EDTA, and mix. [Note: If the approximate Al2O3 content is
) N) a8 _; ^* y% @# dknown, calculate the optimum volume of EDTA solution to be added' [* x* G1 E; r
by the formula: (4 x % Al2O3) + 5.]5 \) X/ @6 D6 e! N# C
Add, dropwise, ammonia solution (1 in 5) until the colour is just
) H: N7 F$ D' Z+ e6 o4 f  Q# xcompletely changed from red to orange-yellow. Then add10 ml each
, t7 S' D" u8 B$ c5 Cof Solutions 1 and 2 (see above) and boil for 5 min. Cool quickly to* W. Q; s, n& c5 x  [( \
room temperature in a stream of running water, add 3 drops of xylenol
7 W; M7 A* Y; B9 \0 @orange TS, and mix. If the solution is purple, yellow-brown, or pink,
8 B/ `6 I' v& S% F+ C: O5 |1 ]bring the pH to 5.3 - 5.7 by the addition of acetic acid. At the desired# I. t( S  ?4 \2 O
pH, a pink colour indicates that not enough of the EDTA solution has$ w( A8 ?  k. p
been added, in which case, discard the solution and repeat this- g) p! {% l( K: t
procedure with another 100 ml of Sample Solution B, using 50 ml,0 w# x) j8 U+ J$ Q
rather than 25 ml, of 0.02 M disodium EDTA.
+ z- I# M6 l; E. _* z) YProcedure
7 A/ [9 B2 z: N" S# H$ E+ _Using the standardized zinc sulfate solution as titrant, titrate Sample
( U8 {, h8 Y! ?2 x, P$ H6 SSolution C to the first yellow-brown or pink end-point that persists for
( i+ I4 A; i1 I5 j+ x  ]2 f5-10 sec. (Important: See Note under “0.01 Zinc sulfate”.) This first
% Y6 G& l8 c# `; f# W$ c5 etitration should require more than 8 ml of titrant, but for more accurate
8 ^! _! Z9 N9 B2 nwork a titration of 10-15 ml is desirable.
0 i2 ?5 a. I6 c. ^0 ?, Q! C0 VAdd 2 g of sodium fluoride to the titration flask, boil the mixture for 2-5! u+ d) B  G. M6 H( Z6 W* \5 I- L
min, and cool in a stream of running water. Titrate this solution, using
' A- F+ t1 q1 t; N0 U! lthe standardized zinc sulfate solution as titrant, to the same fugitive3 O4 R" C4 p! U& s6 X& I3 q
yellow-brown or pink end-point as described above.+ E' _" c, ]3 u3 d+ X
Calculation:# h! C5 _1 }8 \
Calculate the percentage of aluminium oxide (Al2O3) in the sample7 r+ ?- ~" M  a* p/ `, j
taken by the formula:
& }" I+ ?; S# [( R+ O% Al2O3 = 100 × (0.005VT)/S
0 k0 b  I! U5 a4 I& x$ Mwhere5 a6 Z1 l6 l# F, D/ o: R
V is the number of ml of 0.01 N zinc sulfate consumed in! }- O4 x4 q8 V% \
the second titration,
& g5 q+ E9 i7 M7 ?T is the titre of the zinc sulfate solution,
! J1 n7 r& p9 ~& p3 C, l* `S is the mass (g) of the sample taken, and
! n4 M0 v) b% [0 ~! ~! Q0.005 = 500 ml / (1000mg/g × 100 ml).
+ Z6 {0 ~" H+ L: {Silicon dioxide Accurately weigh 1 g of the sample and transfer to a 250-ml high-silica
* [6 |2 i. Z  Z& Q( n8 J# Kglass Erlenmeyer flask. Add 10 g of sodium bisulfate (NaHSO4 ? H2O).
" ~0 s6 P3 ~3 Z, r7 o7 `' S) t" HHeat gently over a Meeker burner, while swirling the flask, until
* F! ?3 [1 i" z3 v. `decomposition and fusion are complete and the melt is clear, except
" C6 m4 b3 q1 F/ s! Qfor the silica content, and then cool. (Caution: Do not overheat the3 P0 Z! c8 w+ j% W
contents of the flask at the beginning, and heat cautiously during
2 c: `! k5 x  O" o' d. ~% Pfusion to avoid spattering.): ~2 k) P3 l- f9 r6 f. S7 q
To the cooled melt add 25 ml of sulfuric acid solution (1 in 2) and heat3 a# n1 D: ]4 n! A( Q
carefully and slowly until the melt is dissolved. Cool, and carefully add
! c; D" G- I8 S0 X) V* N. q150 ml of water by pouring very small portions down the sides of the
9 L: `& p; M4 p# Q1 U( `9 C- G2 qflask, with frequent swirling to avoid over-heating and spattering. Allow( w. f* O' |0 p) Z. q0 r
the contents of the flask to cool, and filter through fine ashless filter
  T6 V/ ?0 N$ b/ _+ n1 h+ Q. hpaper, using a 60 degree gravity funnel. Rinse out all the silica from
+ B3 V6 k! \* Z  K( \3 P+ F/ [the flask onto the filter paper with sulfuric acid solution (1 in 10)., U8 D0 M0 C( s
Transfer the filter paper and its contents into a platinum crucible, dry in
) Z0 ?  u# a6 e6 V) X$ \an oven at 1200, and heat the partly covered crucible over a Bunsen
7 w" b( t5 z6 U8 a( O+ P' n* ?' ]burner. To prevent flaming of the filter paper, first heat the cover from0 c& o- ]4 U$ o! Y& A
above, and then the crucible from below.
, w/ X& |5 F9 gWhen the filter paper is consumed, transfer the crucible to a muffle
+ @, e- E8 Y* P& Sfurnace and ignite at 1000o for 30 min. Cool in a desiccator, and
& R5 v! C$ E0 g6 m% Iweigh. Add 2 drops of sulfuric acid (1 in 2) and 5 ml of concentrated
1 ]! m6 Y& ^8 \, I$ Khydrofluoric acid (sp.gr. 1.15), and carefully evaporate to dryness, first; j  d$ h5 g5 z' A) t, v& j3 ^! `" s
on a low-heat hot plate (to remove the HF) and then over a Bunsen6 m1 [; V+ V; C+ t% I. Z* n8 y
burner (to remove the H2SO4). Take precautions to avoid spattering,
1 n/ S" i8 H/ w" I( l, ^5 b( k0 Uespecially after removal of the HF. Ignite at 1000o for 10 min, cool in a! O& C# @% P& b
desiccator, and weigh again. Record the difference between the two% Z5 H. _5 g/ B" C( Y
weights as the content of SiO2 in the sample.9 ?  V8 L+ N: f
METHOD OF ASSAY$ B4 T) \7 S2 `; w5 n' b
Accurately weigh about 150 mg of the sample, previously dried at 105o
+ L1 Q; \' a7 N# |) K9 X$ ^) qfor 3 hours, and transfer into a 500-ml conical flask. Add 5 ml of water
. y% w% r# O) d# U  Xand shake until a homogeneous, milky suspension is obtained. Add 30' S/ F. t8 k' `0 ^
ml of sulfuric acid and 12 g of ammonium sulfate, and mix. Initially
) o# T" [4 P: ^' ~- H" k1 K: Iheat gently, then heat strongly until a clear solution is obtained. Cool,
9 s* E1 ?$ f* w% ]( Tthen cautiously dilute with 120 ml of water and 40 ml of hydrochloric( \' q: P% }  z& ]/ y6 \2 Z4 u
acid, and stir. Add 3 g of aluminium metal, and immediately insert a
  H7 m2 G. K# f# K+ C; N% brubber stopper fitted with a U-shaped glass tube while immersing the0 U! X# n! q4 c4 [7 ~+ b
other end of the U-tube into a saturated solution of sodium
5 x. X# p6 ~, Abicarbonate contained in a 500-ml wide-mouth bottle, and generate4 v! j* }. d# ]2 s
hydrogen. Allow to stand for a few minutes after the aluminium metal% ?# u4 p7 ]9 ^* q& Q# Y1 o
has dissolved completely to produce a transparent purple solution.: q9 z) p  ]( F* U  ]+ C  F/ x
Cool to below 50o in running water, and remove the rubber stopper
1 X( w0 r. H/ Y7 z! {carrying the U-tube. Add 3 ml of a saturated potassium thiocyanate. \" v# N4 M9 m( h" b
solution as an indicator, and immediately titrate with 0.2 N ferric7 [1 i, {, M; V- {# E; h
ammonium sulfate until a faint brown colour that persists for 300 g1 |! p$ [+ h8 |9 t, B4 [: Q
seconds is obtained. Perform a blank determination and make any4 G$ q, L+ l1 N. X
necessary correction. Each ml of 0.2 N ferric ammonium sulfate is2 n0 r* q& v) A
equivalent to 7.990 mg of TiO2.
* X" @9 L) z+ [! Y+ T0 }
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