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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 |倒序浏览 |阅读模式
二氧化钛(钛白粉)
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; @& R" t0 O  [1 J" s2 W# HCAC关于二氧化钛(钛白粉)的使用规定* d9 r0 g  u0 s9 @0 A. S- B
GSFA Online
3 t/ K$ n3 N: ]7 ^Food Additive Details" s7 m6 U9 I; @) |  `
Titanium Dioxide (171)
+ H* o, d; |5 L. @) [Number Food Category  9 W( C8 ^5 x: w  r7 b
  01.1.2 Dairy-based drinks, flavoured and/or fermented (e.g., chocolate milk, cocoa, eggnog, drinking yoghurt, whey-based drinks)  $ _% ]$ U2 L4 J3 f
  01.3 Condensed milk and analogues (plain)  ) w* G/ P; e7 r# W; J1 _
  01.4.3 Clotted cream (plain)  " `7 D# E, A- b4 L! ~4 e
  01.4.4 Cream analogues  
; j# }8 m6 @2 Y# E2 o8 q( e  01.5 Milk powder and cream powder and powder analogues (plain)  
  C2 R/ I+ B0 C! \  i# l8 @, M$ R# ^  01.6 Cheese and analogues  
/ V3 h2 e* d; C4 u6 z  01.7 Dairy-based desserts (e.g., pudding, fruit or flavoured yoghurt)  
! p/ e$ L8 W4 Y# `- u7 |3 l  01.8 Whey and whey products, excluding whey cheeses  3 K3 |) ?- S( ]# }7 l/ n4 T- S
  02.2.1.2 Margarine and similar products   : z" j+ v) r0 l! s( r4 y1 G
  02.2.1.3 Blends of butter and margarine  5 T0 h9 u  a/ f1 |+ q! \0 U7 G
  02.2.2 Emulsions containing less than 80% fat   7 u$ E' l4 y6 B5 P! ]6 X- Y% }, U
  02.3 Fat emulsions maily of type oil-in-water, including mixed and/or flavoured products based on fat emulsions   
4 f- T+ t( ^$ t! o6 z  02.4 Fat-based desserts excluding dairy-based dessert products of food category 01.7  9 S9 }2 ?  \( s7 j7 L3 ?
  03.0 Edible ices, including sherbet and sorbet  , X3 u+ W& z: s/ I' u
  04.1.2 Processed fruit  
: T. G: h0 r, x4 \  04.2.2.2 Dried vegetables (including mushrooms and fungi, roots and tubers, pulses and legumes, and aloe vera), seaweeds, and nuts and seeds  
' a4 i- f% s$ |  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  * Z$ a! B. S1 V- z, d
  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  ' r( V6 X7 B2 k# v& T+ q+ _1 ?
  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)  
5 e8 j$ k$ R4 q  j  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  , T- y$ h4 g% p6 h3 P
  04.2.2.8 Cooked or fried vegetables (including mushrooms and fungi, roots and tubers, pulses and legumes, and aloe vera), and seaweeds  3 C8 x. s! ?0 y* p; R0 ~- k. x
  05.0 Confectionery  5 S, M: n* {) E% E
  06.3 Breakfast cereals, including rolled oats  
. R" s0 p7 J" H6 z6 Y  06.4.3 Pre-cooked pastas and noodles and like products  
/ H9 g: l' Z9 X6 ~: m  06.5 Cereal and starch based desserts (e.g., rice pudding, tapioca pudding)  
1 f7 A( z" B6 F  06.6 Batters (e.g., for breading or batters for fish or poultry)  
9 J- e* E! f; l) U  06.7 Pre-cooked or processed rice products, including rice cakes (Oriental type only)  1 V! j) h  w; L0 T
  06.8 Soybean products (excluding soybean products of food category 12.9 and fermented soybean products of food category 12.10)  
& G) r. s2 \1 i  Q  07.0 Bakery wares  
+ n! u0 Q; L4 K; E; s( w9 P% t  F' C! c1 i  08.2 Processed meat, poultry, and game products in whole pieces or cuts  
8 _7 B; e! G6 V" e( W3 D0 b' D  08.3 Processed comminuted meat, poultry, and game products  
/ j' o' t* N: W! }3 N7 D  08.4 Edible casings (e.g., sausage casings)  
0 D2 j- h7 r& m- }  09.3 Semi-preserved fish and fish products, including mollusks, crustaceans, and echinoderms  " d/ Z% Z, {! [9 p, W) X
  09.4 Fully preserved, including canned or fermented fish and fish products, including mollusks, crustaceans, and echinoderms  ' d7 l9 H  L. ]+ w
  10.2.3 Dried and/or heat coagulated egg products  . @. L; \6 N  P
  10.3 Preserved eggs, including alkaline, salted, and canned eggs  
# u$ Z: _9 T* m  10.4 Egg-based desserts (e.g., custard)  : k. V' x* @5 y; Z' i( @! a$ m9 Q
  11.6 Table-top sweeteners, including those containing high-intensity sweeteners  
+ e& q1 b, X4 r' D1 }' C  12.2.2 Seasonings and condiments  
  e  p4 I# {, l& \: t  12.3 Vinegars  
; s: a+ T* J% A; T2 B) r  12.4 Mustards  # S& A3 Z' ~; I
  12.5 Soups and broths  
) {0 p2 M* R* F+ C: t  12.6 Sauces and like products  
# Z, Y2 ~/ S2 f( w+ h! x$ r  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  5 F3 ~  Q4 R% @, d
  12.8 Yeast and like products  1 F  |& T: F* L" A0 O
  12.9 Protein products  
0 _, u+ E( C+ k/ d6 s  12.10 Fermented soybean products  
" v1 b/ ]7 w  j2 R  13.3 Dietetic foods intended for special medical purposes (excluding products of food category 13.1)  
% T- t+ e$ s  D7 ~0 s' ?$ F  13.4 Dietetic formulae for slimming purposes and weight reduction  $ A% \' V' p; K! N  N. E8 g
  13.5 Dietetic foods (e.g., supplementary foods for dietary use) excluding products of food categories 13.1 - 13.4 and 13.6  
* y/ j0 V+ o. s6 r: }2 D0 j+ ?5 |7 S" \" I  13.6 Food supplements  
6 p$ k$ F" Z  M1 r- I  14.1.1.2 Table waters and soda waters  + V' z0 W7 J7 c3 x0 T
  14.1.4 Water-based flavoured drinks, including "sport," "energy," or "electrolyte" drinks and particulated drinks  
8 \3 v9 Q& M9 k- _  14.2.1 Beer and malt beverages  
" k" v4 ~0 T# c# f# O& O1 o' B  14.2.2 Cider and perry  ) W" _  y$ p, p' c
  14.2.4 Wines (other than grape)  7 s+ F- ^& G, R/ K: ?
  14.2.5 Mead  
( @* g8 t5 f5 i! U% t4 w' ^: C  14.2.6 Distilled spirituous beverages containing more than 15% alcohol  & }. C3 f# I. p
  14.2.7 Aromatized alcoholic beverages (e.g., beer, wine and spirituous cooler-type beverages, low alcoholic refreshers)  
/ s* u4 ^# X: y& ~$ m  15.0 Ready-to-eat savouries  
. p# ~- ^4 ~" j) E  16.0 Composite foods - foods that could not be placed in categories 01 – 15
, q( \" _' R# P% s3 F6 }
( l  `" s5 C' x. U! y3 A1 ?# b
, j5 d2 p1 o, g- ^部分译文:
5 q  y3 _" {2 k1 `! y& E( n* s) m. t; ?  _
食品添加剂通用规则
: t3 o# G* `! w( e: S" |/ }* G  ]食品添加剂; T6 O8 L3 b7 U- x/ u; z/ u; q
                    二氧化钛(171)3 T1 J% {+ ]# g8 {5 [
食品类别:# ]1 t& U' [2 \$ }
06.3 早餐谷类,包括燕麦片
$ S9 ^  P- o7 \" M& d( x! G+ A7 G06.4.3面条及类似产品
. c+ Y  ^: r. H* h- R3 q& s06.5 谷类,淀粉甜点(包括:米粉布丁,木薯布丁)  y1 j$ _' t+ y3 k7 q5 K* ?
06.6 面团
9 n1 A9 Z; ?, d$ s+ f06.7 预煮的或加工的米产品,包括年糕(只包括中式的)06.8 Soybean products
2 `  M8 r# {% H  W07.0 烘焙类
. ~- f6 [; C1 A4 K9 D3 g2 g; z07.1 面包,普通烘焙类,以及其混合物$ h& I# f6 v0 S- y5 u
07.1.1 面包,面包卷
5 S" {- m' }2 A. e6 A% d7 X4 E! ]/ h07.1.1.1 酵母发酵面包及特殊面包
% Q* F# h( l& W07.1.1.2 苏打面包
0 S0 j/ R; {* A; a+ J: [, O0 V
3 H" h$ g, U7 t/ l7 {; ^
* R! S3 Q9 j& B9 o! I# y) c
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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)$ V2 I) E' d2 F) h
7 D- e4 }- O. E* f5 {# p6 X- u, y
JECFA关于二氧化钛(钛白粉)的结论: k, {' _* D2 T& c

: |" k/ g) S# f* ?: J; H摘要: 2006年JECFA关于二氧化钛的结论2 Q* v; `) Q9 g9 D( {3 c
ADI值:不作限制。
- i, C6 p& ?- i- C8 O7 [功能:着色剂. n! R* u) Z) {( p0 I# p! e. ~4 `
% h- C8 X1 T9 o6 b7 r1 H$ ~, T" K
TITANIUM DIOXIDE! ]- C4 J4 o! a# q8 t# a
Prepared at the 67th JECFA (2006) and published in FAO JECFA) G0 t" M  J$ z. J0 X8 X9 I
Monographs 3 (2006), superseding specifications prepared at the 63rd: ], Z' T0 P/ u9 d, X
JECFA (2004) and published in FNP 52 Add 12 (2004) and in the
4 z6 N  ]+ @& ?' p2 @  o. hCombined Compendium of Food Additive Specifications, FAO JECFA
& P% l6 Q5 a5 T3 k& e+ }- `3 H' YMonographs 1 (2005). An ADI “not limited” was established at the 13th
& A. O1 B0 V! gJECFA (1969).
6 C$ |# a1 H% e+ }1 f  D9 X! ASYNONYMS
) r! R& D8 x! G) n! CTitania, CI Pigment white 6, CI (1975) No. 77891, INS No. 171
' a8 N% N) j7 tDEFINITION0 M. h+ T  g9 l1 e9 f
Titanium dioxide is produced by either the sulfate or the chloride
  N8 N4 N+ e; W. f2 Z5 tprocess. Processing conditions determine the form (anatase or rutile' N/ Y+ a8 `% m, F
structure) of the final product.9 a- s& E7 A- v* z4 G+ U
In the sulfate process, sulfuric acid is used to digest ilmenite (FeTiO3)* M; S0 Y; g3 q4 ]2 J' T; Z# \
or ilmenite and titanium slag. After a series of purification steps, the# {! a+ G, f1 j0 F2 y, O% e7 M) V, a
isolated titanium dioxide is finally washed with water, calcined, and
0 B8 j/ f) L( U  W! m. ^micronized.
* E* A5 H5 Q* i* u, v+ P. F( O6 G% QIn the chloride process, chlorine gas is reacted with a titaniumcontaining
) O. {+ n! ?& @& q3 Emineral under reducing conditions to form anhydrous
, Q: U; i+ O( B0 [: b) B: C. `* Stitanium tetrachloride, which is subsequently purified and converted to. B) |1 Z: U" w' ^+ g
titanium dioxide either by direct thermal oxidation or by reaction with
6 H- o2 d  P/ Qsteam in the vapour phase. Alternatively, concentrated hydrochloric
" i5 e* s6 ^" e$ \; [5 lacid can be reacted with the titanium-containing mineral to form a5 \/ X3 F6 D& h3 E
solution of titanium tetrachloride, which is then further purified and5 P8 Y' A0 Q7 g# Q& k+ ~9 Q' H
converted to titanium dioxide by hydrolysis. The titanium dioxide is  E3 Z; ^4 a  E5 B* K9 ^. Q) y& Q
filtered, washed, and calcined.
% R8 P0 G* y0 R0 {: r& ]: Z7 Y2 OCommercial titanium dioxide may be coated with small amounts of
8 Z6 _% n! s6 {) x% zalumina and/or silica to improve the technological properties of the
3 h* j" B8 Z& R6 J3 s3 O; Rproduct.
! J/ \0 h0 w* H0 ]' y" W( zC.A.S. number 13463-67-77 ^6 {+ N* g- w& n# U
Chemical formula TiO2- q3 f) d* D2 [. @4 `% Z
Formula weight! L, S0 E3 w) a1 d8 W* d, j
79.88
4 K& h4 V; M* E& Z5 M0 rAssay* S( i4 n$ }( i( w/ j0 o) X
Not less than 99.0% on the dried basis (on an aluminium oxide and
! l1 y% J* |" I3 m# @4 t# {. ^( `0 tsilicon dioxide-free basis)
6 T8 v  p6 R! j* Z+ [. wDESCRIPTION
- C- L8 ]! n) J6 j9 O5 h, YWhite to slightly coloured powder
8 U$ \& c; d3 U; o$ UFUNCTIONAL USES1 Z9 h1 W* A5 W4 z! g4 J+ T/ v
Colour
5 m1 b* E& w; c! s" U7 ]3 LCHARACTERISTICS
* k7 `  B& b4 n' OIDENTIFICATION7 @$ I/ S+ {( F
Solubility (Vol. 4)
. [; Z; v$ ?* H% jInsoluble in water, hydrochloric acid, dilute sulfuric acid, and organic
. j% j* s8 V6 t0 _( O5 C9 tsolvents. Dissolves slowly in hydrofluoric acid and hot concentrated
. M, L* y8 O% V6 X1 Lsulfuric acid.
& b" q" n/ |# J6 _, }: u1 o6 XColour reaction
. A/ G  G3 \; `0 v1 x' mAdd 5 ml sulfuric acid to 0.5 g of the sample, heat gently until fumes of1 U9 X1 E5 ^& D9 u# _+ l
sulfuric acid appear, then cool. Cautiously dilute to about 100 ml with
# W, o9 e7 L  ]4 _. zwater and filter. To 5 ml of this clear filtrate, add a few drops of" e1 P1 D& w0 F4 }' W
hydrogen peroxide; an orange-red colour appears immediately.
; {2 U5 t; l7 Q" x* A2 P. ~( sPURITY: L# e$ m6 W5 i6 W' ]
Loss on drying (Vol. 4) Not more than 0.5% (105°, 3 h)  H' t. o" ~: a. ?$ W) I! ?
Loss on ignition (Vol. 4)
4 g$ |0 o, o* u. b' Z9 ANot more than 1.0% (800o) on the dried basis
+ o8 f! N. B+ y7 H2 v2 J- B" AAluminium oxide and/or
0 i* p) y1 D0 M' asilicon dioxide
* d. m. b# K7 i8 W7 f' ^Not more than 2%, either singly or combined
2 t0 P, j+ |" ~. F4 `. Q0 ]4 OSee descriptions under TESTS/ ]+ u! G/ e, j& |3 l: C
Acid-soluble substances Not more than 0.5%; Not more than 1.5% for products containing
: E0 j0 \9 q+ x7 M8 U4 {7 `alumina or silica.. u6 \' S0 W$ ]  M5 L* v0 Y
Suspend 5 g of the sample in 100 ml 0.5 N hydrochloric acid and
3 p& O7 r# w, M+ r7 f6 u) W$ lplace on a steam bath for 30 min with occasional stirring. Filter
+ D4 `, h: k  q3 cthrough a Gooch crucible fitted with a glass fibre filter paper. Wash
5 s; g. V* Y. _! E% Jwith three 10-ml portions of 0.5 N hydrochloric acid, evaporate the6 H7 i( \- B6 X' T
combined filtrate and washings to dryness, and ignite at a dull red
: j: z2 p' F& Eheat to constant weight.
5 E, C1 X0 B' f7 dWater-soluble matter7 k6 ^$ M8 e& i
(Vol. 4)' r1 n; |2 r9 C+ W, U) h2 Y4 [
Not more than 0.5%" ?; D# W- ~. w7 E. D6 l2 i8 g
Proceed as directed under acid-soluble substances (above), using/ x* p& q7 P0 }# _
water in place of 0.5 N hydrochloric acid.
9 Y; N8 O! |9 H% [- NImpurities soluble in 0.5 N
2 P% V% m( i! B9 Ihydrochloric acid5 y* B- A7 C. O% S, u! W
Antimony Not more than 2 mg/kg) y; c0 ~' k' m- ]7 `8 F
See description under TESTS
; \6 y: k3 \7 f1 d7 \1 e% rArsenic Not more than 1 mg/kg
% v7 i7 A4 A, C( r7 F. C. eSee description under TESTS6 z: H$ X0 h7 e# M- P. g; _
Cadmium Not more than 1 mg/kg8 `" u; x7 k. y9 v4 Q* Z
See description under TESTS
: N$ a; {& M) kLead  @, v1 c1 ^9 h/ b
Not more than 10 mg/kg
& u% R" _% t( C2 Z5 OSee description under TESTS9 C0 l6 U# x5 V1 c4 p
Mercury (Vol. 4) Not more than 1 mg/kg# s  K. Z9 X5 z$ P: N
Determine using the cold vapour atomic absorption technique. Select a) [1 }& ^# \  B, M$ G5 C
sample size appropriate to the specified level: o6 C4 A8 z* K) G
TESTS& g, X: g) W0 ]/ t# K0 P
PURITY TESTS6 w% l+ f! y# X2 b
Impurities soluble in 0.5 N/ t- R$ o! r9 D0 j8 j9 K* j2 a
hydrochloric acid4 x/ g! @/ T6 J. Z, B- Y
Antimony, arsenic,! p$ X% Y8 S2 S( S7 H
cadmium and lead
# e- r0 m. [( F  M, r' h3 i(Vol.4)3 K8 J$ M/ a! K" B* h9 x
Transfer 10.0 g of sample into a 250-ml beaker, add 50 ml of 0.5 N
3 B0 ~0 Y4 |  `8 Y3 Q0 t5 [1 F9 hhydrochloric acid, cover with a watch glass, and heat to boiling on a
% a2 T4 J+ T9 i5 Hhot plate. Boil gently for 15 min, pour the slurry into a 100- to 150-ml
# N- F8 C% W4 ?) Z# b9 H. }centrifuge bottle, and centrifuge for 10 to 15 min, or until undissolved1 y* N& r5 \. j( L7 f
material settles. Decant the supernatant extract through a Whatman
. U. ~3 D2 W, L# {1 f/ M0 fNo. 4 filter paper, or equivalent, collecting the filtrate in a 100-ml
1 [; b$ W, E  Cvolumetric flask and retaining as much as possible of the undissolved
. M4 A; f8 I) W/ v% zmaterial in the centrifuge bottle. Add 10 ml of hot water to the original. U5 X2 M4 M2 U! q+ P
beaker, washing off the watch glass with the water, and pour the
$ k3 Q- n. k$ V$ Rcontents into the centrifuge bottle. Form a slurry, using a glass stirring+ e, i) N7 o; E
rod, and centrifuge. Decant through the same filter paper, and collect/ O& v" q2 ]; ^
the washings in the volumetric flask containing the initial extract.
. t, ]5 O/ \, K" L6 v" \: ZRepeat the entire washing process two more times. Finally, wash the( K7 L9 w; U" ]) X% J$ r
filter paper with 10 to 15 ml of hot water. Cool the contents of the flask9 G3 A* ?) u  O5 ^, z6 g4 I, |9 J3 s; n8 d
to room temperature, dilute to volume with water, and mix.$ [4 N1 Q% G" T: ]& ~
Determine antimony, cadmium, and lead using an AAS/ICP-AES; \+ g! d1 H- N  v7 S; g( ~0 s
technique appropriate to the specified level. Determine arsenic using the
7 D: O+ P) g" GICP-AES/AAS-hydride technique. Alternatively, determine arsenic using
" }2 S0 i4 E$ M5 S3 M' ^Method II of the Arsenic Limit Test, taking 3 g of the sample rather than
1 Y0 m* j% r- p  ]! \& ]! l1 J1 g. The selection of sample size and method of sample preparation
, ?2 U9 H3 J' \; r5 X. L& A& Q4 J4 Vmay be based on the principles of the methods described in Volume 4.3 ?6 T$ e9 `8 _% c% M: X
Aluminium oxide Reagents and sample solutions+ h0 B0 k( q8 J+ ~
0.01 N Zinc Sulfate5 X7 p/ H% W5 X, d
Dissolve 2.9 g of zinc sulfate (ZnSO4 ? 7H2O) in sufficient water to$ ^4 p2 c1 @9 n0 A& w6 e* k/ ]
make 1000 ml. Standardize the solution as follows: Dissolve 500 mg
; ^- d4 M1 A0 J& S( O. H8 Dof high-purity (99.9%) aluminium wire, accurately weighed, in 20 ml of
: |6 X) j, ]3 A+ U# q. Pconcentrated hydrochloric acid, heating gently to effect solution, then
2 s" G. b, ]( l; ]6 @, Wtransfer the solution into a 1000-ml volumetric flask, dilute to volume
& r9 Z4 _9 m) U1 \+ S  Pwith water, and mix. Transfer a 10 ml aliquot of this solution into a 500
/ a# m5 S7 a0 xml Erlenmeyer flask containing 90 ml of water and 3 ml of0 R" L( C" D2 t" ^/ o6 o/ R4 C
concentrated hydrochloric acid, add 1 drop of methyl orange TS and
6 B& B) H- o* b25 ml of 0.02 M disodium ethylenediaminetetraacetate (EDTA) Add,
- R' j( ?! @4 l% _6 q/ Q% fdropwise, ammonia solution (1 in 5) until the colour is just completely
6 v0 D' o4 o* b( r+ B2 T7 g) vchanged from red to orange-yellow. Then, add:9 {7 Q7 _1 s* y4 c
(a): 10 ml of ammonium acetate buffer solution (77 g of
2 Q9 S. q: U0 g  m6 O/ oammonium acetate plus 10 ml of glacial acetic acid, dilute to
2 f; R9 _; ~/ l4 ~8 T9 d; K1000 ml with water) and: c( w' l) k1 U/ H6 M9 r# ^* B6 S
(b): 10 ml of diammonium hydrogen phosphate solution (150 g: G9 E5 d3 I3 h5 L& Q2 W# y
of diammonium hydrogen phosphate in 700 ml of water,+ J; w" V5 F/ g2 ?7 N
adjusted to pH 5.5 with a 1 in 2 solution of hydrochloric acid,
8 u/ v% Z" C  y; x8 a* \1 uthen dilute to 1000 ml with water).
& \9 u) f3 _4 `9 {' b/ eBoil the solution for 5 min, cool it quickly to room temperature in a6 J; H1 P$ u5 o
stream of running water, add 3 drops of xylenol orange TS, and mix.
. N2 {; A4 g5 c: _+ V/ ]! lUsing the zinc sulfate solution as titrant, titrate the solution to the first
2 d7 @* x$ Y) ~6 z6 J6 g4 ~% eyellow-brown or pink end-point colour that persists for 5-10 sec. (Note:
  w$ |( k) r( }# aThis titration should be performed quickly near the end-point by
! B( r5 U9 s4 L3 t0 gadding rapidly 0.2 ml increments of the titrant until the first colour
& L- j$ [0 }/ C0 pchange occurs; although the colour will fade in 5-10 sec, it is the true" e0 g3 k3 e+ |5 `& S
end-point. Failure to observe the first colour change will result in an
3 v2 w2 C% U: O9 L& bincorrect titration. The fading end-point does not occur at the second5 @" i2 q! b& n9 o, _) L) a
end-point.)% J7 G/ C( T& f# R. x- }
Add 2 g of sodium fluoride, boil the mixture for 2-5 min, and cool in a+ O& w! q) A; P" h! r
stream of running water. Titrate this solution, using the zinc sulfate
+ Z8 D" g* L4 R" U" Psolution as titrant, to the same fugitive yellow-brown or pink end-point
, ~( S3 O2 c9 n+ R( h8 a0 bas described above.
; K+ E% }! t2 h( MCalculate the titre T of zinc sulfate solution by the formula:# _; @9 O: C; N0 Z1 q
T = 18.896 W / V
' Q: n$ K9 |; ~' l+ Bwhere% v: B. e# c/ c, \+ {) h* n* y, x
T is the mass (mg) of Al2O3 per ml of zinc sulfate solution
) f7 K- g0 T; UW is the mass (g) of aluminium wire
8 H. ~: D& i: O  L" V, t' CV is the ml of the zinc sulfate solution consumed in the
, Z1 C: A% ^7 ?7 \second titration; q4 b& D1 c1 D; O+ b
18.896 = (R × 1000 mg/g × 10 ml/2)/1000 ml and
+ e3 m, U- v# s+ k3 w* p) ~R is the ratio of the formula weight of aluminium oxide to0 L( k) y: R9 D7 m6 M, F. C
that of elemental aluminium.* q. N- t8 U. Z( |' k* M
Sample Solution A
: @- @/ B5 z8 n( H& wAccurately weigh 1 g of the sample and transfer to a 250-ml high-silica1 ~/ p& a  B, T/ F1 w
glass Erlenmeyer flask. Add 10 g of sodium bisulfate (NaHSO4 ? H2O)., |5 i8 \, g$ J" Y- C
(Note: Do not use more sodium bisulfate than specified, as an excess
) d/ N( O4 F& g5 Q# W( E6 _concentration of salt will interfere with the EDTA titration later on in the# A. Y9 n: ]  f5 U& c
procedure.) Begin heating the flask at low heat on a hot plate, and* \! `& Y) ]! V7 _5 w% j( R
then gradually raise the temperature until full heat is reached.
# R: ~" F" {& Q' |+ P  C8 f: v(Caution: perform this procedure in a well ventilated area. ) When
6 f7 }0 q; H( t4 r0 Espattering has stopped and light fumes of SO3 appear, heat in the full/ t$ v0 F' {) p- Y
flame of a Meeker burner, with the flask tilted so that the fusion of the
* C& z0 @: r; Y3 zsample and sodium bisulfate is concentrated at one end of the flask.+ l. M2 |' H3 H0 y8 U; S6 P
Swirl constantly until the melt is clear (except for silica content), but
! f$ ^0 x6 n: M0 C- |guard against prolonged heating to avoid precipitation of titanium
2 l2 o5 x, O( v/ ]. ?dioxide. Cool, add 25 ml sulfuric acid solution (1 in 2), and heat until
$ S7 \) D% U1 a/ \4 T: Lthe mass has dissolved and a clear solution results. Cool, and dilute to
8 l. ~4 k8 N& |- A  a120 ml with water. Introduce a magnetic stir bar into the flask.* |2 u4 E9 Q. O
Sample Solution B
; S0 L& p+ E+ C6 l3 r! DPrepare 200 ml of an approximately 6.25 M solution of sodium: r; l9 Y$ V/ B* u+ L( U
hydroxide. Add 65 ml of this solution to Sample Solution A, while) J+ C9 n' B8 B) A
stirring with the magnetic stirrer; pour the remaining 135 ml of the
0 j; g1 v2 z! E" J5 r8 ralkali solution into a 500-ml volumetric flask.
. Q. @- H# `3 K" h2 qSlowly, with constant stirring, add the sample mixture to the alkali- n- i, T6 n$ _3 j
solution in the 500-ml volumetric flask; dilute to volume with water,- m8 k9 z. ?1 @
and mix. (Note: If the procedure is delayed at this point for more than- Q) q% O* n. `1 K+ _, Y" M4 s
2 hours, store the contents of the volumetric flask in a polyethylene
+ t8 E3 R! i7 t( @bottle.) Allow most of the precipitate to settle (or centrifuge for 5 min),, ~% B6 ^7 s  J( P+ h! m
then filter the supernatant liquid through a very fine filter paper. Label7 [% S0 A& a% J/ j; j& l
the filtrate Sample Solution B.: O" `7 S2 X. S
Sample Solution C3 C9 u" n, r. A7 o5 P
Transfer 100 ml of the Sample Solution B into a 500-ml Erlenmeyer2 Y" Q3 E/ e$ @8 @3 L
flask, add 1 drop of methyl orange TS, acidify with hydrochloric acid* ~/ a1 s: E& y0 ?3 R
solution (1 in 2), and then add about 3 ml in excess. Add 25 ml of 0.02
; ]! i( b! r- c* _! W& G  D( L  }& H' L$ nM disodium EDTA, and mix. [Note: If the approximate Al2O3 content is- w* }3 }" V& e7 j
known, calculate the optimum volume of EDTA solution to be added/ M& h* G9 v2 ^' A1 \/ g
by the formula: (4 x % Al2O3) + 5.]+ f- b  I/ f7 G* L3 ]6 Z
Add, dropwise, ammonia solution (1 in 5) until the colour is just6 x" e4 F* k( s8 L, c1 |% w
completely changed from red to orange-yellow. Then add10 ml each6 j9 F8 @/ W" ?# R4 e
of Solutions 1 and 2 (see above) and boil for 5 min. Cool quickly to
( }+ Y! {4 e7 Z: {5 ]5 c# Jroom temperature in a stream of running water, add 3 drops of xylenol
- k. ^8 @0 F4 f$ y$ W" j' Horange TS, and mix. If the solution is purple, yellow-brown, or pink,
3 M: q! C5 I2 w2 cbring the pH to 5.3 - 5.7 by the addition of acetic acid. At the desired
- j8 f$ e* \- Q2 y, ypH, a pink colour indicates that not enough of the EDTA solution has& o, O+ ]. ^+ I/ U$ Y
been added, in which case, discard the solution and repeat this
+ |' a: t& @# a8 s  n8 Zprocedure with another 100 ml of Sample Solution B, using 50 ml,
/ W0 |4 I" M9 [5 Crather than 25 ml, of 0.02 M disodium EDTA.
- T2 i( y0 t3 V& i, u* n7 `Procedure# W  |& R! i; ]
Using the standardized zinc sulfate solution as titrant, titrate Sample3 S2 I4 q, Y& A5 M. v3 z6 ~
Solution C to the first yellow-brown or pink end-point that persists for- b# U4 U& \  Q9 j4 ~* r( _" \) l
5-10 sec. (Important: See Note under “0.01 Zinc sulfate”.) This first- ^+ \) u( r. f* p: M
titration should require more than 8 ml of titrant, but for more accurate
- t: `9 b; N& R# {/ M7 Xwork a titration of 10-15 ml is desirable.
: R: Y# _2 F3 ]3 k6 ~# KAdd 2 g of sodium fluoride to the titration flask, boil the mixture for 2-5
5 W- y1 ?+ [3 T3 `+ x  l6 O& D' cmin, and cool in a stream of running water. Titrate this solution, using7 k; E- _& L$ l% `# G# H3 E
the standardized zinc sulfate solution as titrant, to the same fugitive7 d" J+ B& ?' I% P
yellow-brown or pink end-point as described above.) V. }$ l$ m' n/ ?9 m* d
Calculation:. j) k) ~  q- ]- S
Calculate the percentage of aluminium oxide (Al2O3) in the sample
3 e! I' _6 a2 I) q/ V7 G# h% Gtaken by the formula:5 W; m( w' e4 Q! h
% Al2O3 = 100 × (0.005VT)/S
. s7 v/ K6 z* J6 `7 ^* q* Iwhere& K. u  l2 @# K3 e. `: f+ Y9 z
V is the number of ml of 0.01 N zinc sulfate consumed in- v, X8 b% u8 R+ u
the second titration,
6 P) h$ B: p+ [: l2 K  ZT is the titre of the zinc sulfate solution,$ X; V0 L" _% ~# O; g: M
S is the mass (g) of the sample taken, and
; d6 a; }, s. B0.005 = 500 ml / (1000mg/g × 100 ml).) ~9 M3 w; u& f( r3 J+ K
Silicon dioxide Accurately weigh 1 g of the sample and transfer to a 250-ml high-silica# _) p' p# w3 c, u* k
glass Erlenmeyer flask. Add 10 g of sodium bisulfate (NaHSO4 ? H2O).# d: F3 d! _: {8 E: q6 w  j2 X, D! P
Heat gently over a Meeker burner, while swirling the flask, until5 L0 Q; R  x% x: o
decomposition and fusion are complete and the melt is clear, except& {9 m5 b" ]$ S
for the silica content, and then cool. (Caution: Do not overheat the
# B! N& v; H; R, ~: v9 [contents of the flask at the beginning, and heat cautiously during
. h/ p# U7 N  Z6 H; U; k7 e) Nfusion to avoid spattering.)
% N* t' S4 ~4 O. O. P9 oTo the cooled melt add 25 ml of sulfuric acid solution (1 in 2) and heat) k1 d' X& G+ F( Z+ x! X
carefully and slowly until the melt is dissolved. Cool, and carefully add: a3 L9 u3 a+ ^5 Y# a
150 ml of water by pouring very small portions down the sides of the
9 Y1 E5 A+ `% N9 N+ ~+ D; dflask, with frequent swirling to avoid over-heating and spattering. Allow3 @  K* [7 F# Z& S  j
the contents of the flask to cool, and filter through fine ashless filter! Z6 S1 E3 n+ J$ i/ C
paper, using a 60 degree gravity funnel. Rinse out all the silica from
# I0 h$ o' {0 A+ w, D6 p( Kthe flask onto the filter paper with sulfuric acid solution (1 in 10).& r, f8 x$ z7 u1 E! h+ c8 A
Transfer the filter paper and its contents into a platinum crucible, dry in+ A# T! C3 s7 r* f
an oven at 1200, and heat the partly covered crucible over a Bunsen7 G3 K, A4 P- P% P. `
burner. To prevent flaming of the filter paper, first heat the cover from% l4 a, D3 n6 ]# f" ?+ x
above, and then the crucible from below., E: D6 A& X# b
When the filter paper is consumed, transfer the crucible to a muffle
# T* d! Q9 _8 h( x5 Q& O% V6 Tfurnace and ignite at 1000o for 30 min. Cool in a desiccator, and
$ @# \, `5 f/ Y2 Oweigh. Add 2 drops of sulfuric acid (1 in 2) and 5 ml of concentrated6 p% p2 r9 A0 G, ~/ c5 D  y
hydrofluoric acid (sp.gr. 1.15), and carefully evaporate to dryness, first0 j7 Z! F  A3 Z, A  z
on a low-heat hot plate (to remove the HF) and then over a Bunsen
! A1 J$ [$ u5 e9 W: @burner (to remove the H2SO4). Take precautions to avoid spattering,7 u! o7 |2 t. d1 J* `0 V
especially after removal of the HF. Ignite at 1000o for 10 min, cool in a7 m+ Y  g0 ~/ Y2 x
desiccator, and weigh again. Record the difference between the two, X( y8 |' |3 j
weights as the content of SiO2 in the sample.
: F5 x' i# h, r1 R* ]8 KMETHOD OF ASSAY) o+ w" i2 a: K3 _0 Z
Accurately weigh about 150 mg of the sample, previously dried at 105o7 u; F, o& r4 q% n& J+ Q
for 3 hours, and transfer into a 500-ml conical flask. Add 5 ml of water
) i1 j, K7 B' C4 \. |6 N1 U+ B- Pand shake until a homogeneous, milky suspension is obtained. Add 30
1 e3 d3 w+ t( y$ Nml of sulfuric acid and 12 g of ammonium sulfate, and mix. Initially
- p+ k7 W" o" W4 W& zheat gently, then heat strongly until a clear solution is obtained. Cool,/ r0 e) d! c! x# J
then cautiously dilute with 120 ml of water and 40 ml of hydrochloric
! ]; B# D0 ]7 c( I6 Q7 y+ Vacid, and stir. Add 3 g of aluminium metal, and immediately insert a" n& m6 P( I$ ]& Q* S
rubber stopper fitted with a U-shaped glass tube while immersing the* ]% c; p$ S. o" A( C* i
other end of the U-tube into a saturated solution of sodium/ ]  N, m" G' h% U. i( c5 a
bicarbonate contained in a 500-ml wide-mouth bottle, and generate
# D5 n: }- o! _8 g3 V! K& Uhydrogen. Allow to stand for a few minutes after the aluminium metal$ }! p3 W  s5 e) Q0 C4 Q
has dissolved completely to produce a transparent purple solution.* @8 W7 ^# P8 a
Cool to below 50o in running water, and remove the rubber stopper: r" l# _) s0 `/ ^9 ~
carrying the U-tube. Add 3 ml of a saturated potassium thiocyanate
& \. {7 W8 ^) _( d# F1 `. ?( }% Ssolution as an indicator, and immediately titrate with 0.2 N ferric
& v" r, o5 n! L" h& |ammonium sulfate until a faint brown colour that persists for 306 n' S2 E& c  E) c% K
seconds is obtained. Perform a blank determination and make any0 G+ C2 a+ T' D# i3 H9 `2 }
necessary correction. Each ml of 0.2 N ferric ammonium sulfate is
# C8 I( m  q( x7 K5 D0 requivalent to 7.990 mg of TiO2.& F. g/ s3 Q& q; R/ p
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