设为首页收藏本站

华讯行业社区

 找回密码
 立即注册

QQ登录

只需一步,快速开始

查看: 1112|回复: 1
打印 上一主题 下一主题

二氧化钛(钛白粉)

[复制链接]
跳转到指定楼层
楼主
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) 0 n! G% E9 ]' d: x' ]3 j
  z0 W/ [1 s& D# u
$ M1 S& A  V5 c) H
CAC关于二氧化钛(钛白粉)的使用规定
" p1 l, H4 O9 m' W: \1 F" z2 o8 ]9 yGSFA Online
. S/ r% D8 c" E0 P- }6 zFood Additive Details2 {: i% e% K, l) `
Titanium Dioxide (171)6 j% b; W8 U1 I6 \2 L6 F
Number Food Category  & B8 [3 E, {( `! i9 F8 q/ i4 |
  01.1.2 Dairy-based drinks, flavoured and/or fermented (e.g., chocolate milk, cocoa, eggnog, drinking yoghurt, whey-based drinks)  
& S4 f8 i' j2 n8 i1 l! X  01.3 Condensed milk and analogues (plain)  
0 S& d' C# S7 t0 k5 r3 ~; l  01.4.3 Clotted cream (plain)  
9 K$ L, N! U) m0 ^! O# d  01.4.4 Cream analogues  
5 n5 H* [% |' D$ P2 s4 J+ _  01.5 Milk powder and cream powder and powder analogues (plain)  ' f$ L7 O( H6 c* A; Z. q
  01.6 Cheese and analogues  3 [* d! `! F, @7 U6 K# e0 B  M+ g
  01.7 Dairy-based desserts (e.g., pudding, fruit or flavoured yoghurt)  
# z( \* t* O4 J: E3 C  01.8 Whey and whey products, excluding whey cheeses  
/ P  J9 Z4 H5 A  @: y  02.2.1.2 Margarine and similar products   
/ P& G4 {0 W+ ^# a. s% A  02.2.1.3 Blends of butter and margarine  
4 A- _5 S4 O+ X6 e7 |7 ]  02.2.2 Emulsions containing less than 80% fat   9 i: r  r& o) E" L7 I
  02.3 Fat emulsions maily of type oil-in-water, including mixed and/or flavoured products based on fat emulsions   
# G- p, J" `; a* G  02.4 Fat-based desserts excluding dairy-based dessert products of food category 01.7  5 e$ G6 x8 M9 J( r/ n
  03.0 Edible ices, including sherbet and sorbet  7 X! m# l' D% Y6 q4 S/ `. n
  04.1.2 Processed fruit  
1 p" O. h( d4 V4 ]% {0 R  U6 k# @  04.2.2.2 Dried vegetables (including mushrooms and fungi, roots and tubers, pulses and legumes, and aloe vera), seaweeds, and nuts and seeds  ! T4 p* Y% X8 A
  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  - a8 V. ]2 ]$ i$ Z/ H# `* N# T
  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  
8 ]9 t! d7 _3 D! ^9 \+ _  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)  / y. `: [# J: J: @8 p' \! 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  2 K2 J$ ~/ t; l+ N! d
  04.2.2.8 Cooked or fried vegetables (including mushrooms and fungi, roots and tubers, pulses and legumes, and aloe vera), and seaweeds  / ~3 y, ]) I' X
  05.0 Confectionery  
, a: [1 l3 ]  W. L* F! \3 S) U# q5 h  06.3 Breakfast cereals, including rolled oats  
: ]% i4 j# b" o) k( h, B$ ?! p  06.4.3 Pre-cooked pastas and noodles and like products  , K, G% `0 [, ~$ ~: I! T
  06.5 Cereal and starch based desserts (e.g., rice pudding, tapioca pudding)  
: u" \: z5 T) p# C, d& H  06.6 Batters (e.g., for breading or batters for fish or poultry)  ( W( |+ I) t; t$ o/ ?
  06.7 Pre-cooked or processed rice products, including rice cakes (Oriental type only)  
7 u  q/ J& {* U  06.8 Soybean products (excluding soybean products of food category 12.9 and fermented soybean products of food category 12.10)  0 [; n9 Y" M3 b7 a
  07.0 Bakery wares  ! P& U7 x2 g  U2 R) {) R
  08.2 Processed meat, poultry, and game products in whole pieces or cuts  ; _9 S6 }. E* v. Z4 h8 f5 i
  08.3 Processed comminuted meat, poultry, and game products  
8 ~9 g$ f% ^# j9 H4 M! l9 d  08.4 Edible casings (e.g., sausage casings)  , y$ O. H9 y8 r( k) O
  09.3 Semi-preserved fish and fish products, including mollusks, crustaceans, and echinoderms  
" E) w/ K+ w( U* Z( q: U* z$ o# ~  09.4 Fully preserved, including canned or fermented fish and fish products, including mollusks, crustaceans, and echinoderms  # n2 Z# t" e, o& g6 p
  10.2.3 Dried and/or heat coagulated egg products  - H+ i. D8 p& \9 h
  10.3 Preserved eggs, including alkaline, salted, and canned eggs  - r8 R( @# a& \+ A
  10.4 Egg-based desserts (e.g., custard)  
% G. I: t$ _: ~0 F. A  11.6 Table-top sweeteners, including those containing high-intensity sweeteners  , O# d7 {  F& l; Z& V6 S
  12.2.2 Seasonings and condiments  
) C9 d: @! u3 V: @4 y  12.3 Vinegars  
, V. X3 p6 [# Q  z' J  12.4 Mustards  ( x9 c- J# D& q1 A& t
  12.5 Soups and broths  
' n( |/ t0 }7 J. ^" P+ q5 z  12.6 Sauces and like products  
# h# T3 p& L& |( z8 c; X  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  9 s6 v2 H% s  g" n3 }  L% Y
  12.8 Yeast and like products  8 Q5 r; ]' v+ J# X2 I) N. V
  12.9 Protein products  
" e( n* m- W3 ^" T  12.10 Fermented soybean products  
+ Y- }) {  \8 G  13.3 Dietetic foods intended for special medical purposes (excluding products of food category 13.1)  
* f" R) Y" F7 P& X: E  13.4 Dietetic formulae for slimming purposes and weight reduction  1 \, O1 ], b. |2 j
  13.5 Dietetic foods (e.g., supplementary foods for dietary use) excluding products of food categories 13.1 - 13.4 and 13.6  
. G6 q) X# b9 a( {" ?  13.6 Food supplements  
5 R5 m4 Q7 f7 f: H( P% H, H6 Z) m  14.1.1.2 Table waters and soda waters  
6 q4 x8 Y6 f) Y& v6 |- n  14.1.4 Water-based flavoured drinks, including "sport," "energy," or "electrolyte" drinks and particulated drinks  
' l. G1 I2 f. y" H/ b% W, Y2 s  14.2.1 Beer and malt beverages  7 i8 S' ~: E) [  t/ l2 `
  14.2.2 Cider and perry  $ _. G  _$ W9 q3 K! Y
  14.2.4 Wines (other than grape)  " [5 k. @0 \- D  a6 o
  14.2.5 Mead  
; ?  b8 K! Z3 n3 f; t! C( R3 N8 |  14.2.6 Distilled spirituous beverages containing more than 15% alcohol  
- Z8 X( o" |/ p6 c6 D  14.2.7 Aromatized alcoholic beverages (e.g., beer, wine and spirituous cooler-type beverages, low alcoholic refreshers)  
" ?, {5 v! o; C  K" ?# ?  15.0 Ready-to-eat savouries  
8 |. y; `0 h( a: k( F6 R% }  16.0 Composite foods - foods that could not be placed in categories 01 – 158 h+ B* r& V1 B/ u7 |* b

$ c$ s# ], v. d1 Z$ X, C0 d1 ^, J7 n" X( O& z: v  `
部分译文:
0 N3 J+ P: _' n& q6 X( O( l" {0 F4 d+ N. G9 f9 s2 o  K& q$ ~
食品添加剂通用规则; P, Z3 g0 R6 m2 z$ {; O. z
食品添加剂# e; a* S. b  {# j- ?* Q7 u
                    二氧化钛(171)3 R# r) M0 i* L# T
食品类别:/ F5 Y3 U5 p: E
06.3 早餐谷类,包括燕麦片- n! G' |& V8 j! C
06.4.3面条及类似产品
3 l9 A2 P, O' N( w' F' L7 n% k4 B06.5 谷类,淀粉甜点(包括:米粉布丁,木薯布丁)+ o5 G3 L+ ]( B9 R
06.6 面团
8 H- I/ M( Z( `8 v; _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 ; J4 P* f- t# C8 D3 G
07.0 烘焙类7 U& e+ \! Y! V  m- @
07.1 面包,普通烘焙类,以及其混合物7 w! ^5 m; e- Z
07.1.1 面包,面包卷) ~! ^( _" G8 ]' ^/ ]% f
07.1.1.1 酵母发酵面包及特殊面包
! \3 H$ W" u7 ?6 K9 L; X" l07.1.1.2 苏打面包; f- D8 [# b3 b7 [8 g
$ ^1 X( Z) x* M9 W
' C3 o7 W2 w) J7 E+ R; r5 F, s
分享到:  QQ好友和群QQ好友和群 QQ空间QQ空间 腾讯微博腾讯微博 腾讯朋友腾讯朋友
收藏收藏 转播转播 分享分享 分享淘帖 支持支持 反对反对
沙发
 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)% Y: u( A9 Q6 a+ D' b. Y4 K

, v. o& H3 j( Y- mJECFA关于二氧化钛(钛白粉)的结论
) m; |2 `. v1 I* D$ x, j% }8 n0 r; y) U0 g) O3 r& u7 u
摘要: 2006年JECFA关于二氧化钛的结论. Z% t! g! p- b# I5 L* ~
ADI值:不作限制。' ^! z( O; f2 ~2 w
功能:着色剂
# A  C  P/ `6 c- x% s# S! R: y9 {; f1 Q: S: u9 X) M
TITANIUM DIOXIDE
5 P! t9 O6 D* n3 G  U: s. uPrepared at the 67th JECFA (2006) and published in FAO JECFA6 E; `2 N* s* T* p. R0 L- z
Monographs 3 (2006), superseding specifications prepared at the 63rd
% d9 A7 g  |. G+ |9 n- mJECFA (2004) and published in FNP 52 Add 12 (2004) and in the2 t+ W9 M3 B% A! r+ s8 y
Combined Compendium of Food Additive Specifications, FAO JECFA5 t- n/ ~- h1 u' L# y- m6 @; x
Monographs 1 (2005). An ADI “not limited” was established at the 13th
% n8 N% ^6 M* S2 U  N+ ?JECFA (1969).
5 H" z' c) j( s$ A6 I7 U. ESYNONYMS
% V! ?3 V# }1 q# VTitania, CI Pigment white 6, CI (1975) No. 77891, INS No. 1713 L) r; b4 B- s3 z8 B, K
DEFINITION
4 l* x2 u; M" E" h. L4 ~' @' XTitanium dioxide is produced by either the sulfate or the chloride+ b, t! K2 K8 r- @# a
process. Processing conditions determine the form (anatase or rutile# d8 }% V: j% Y$ Y5 C$ G% ^2 u1 u
structure) of the final product.
- W& {4 s, b2 Q/ H$ a7 BIn the sulfate process, sulfuric acid is used to digest ilmenite (FeTiO3)( P4 I3 R/ `$ z# j
or ilmenite and titanium slag. After a series of purification steps, the, \4 I$ [8 G; \6 o) Q
isolated titanium dioxide is finally washed with water, calcined, and' n, \3 _4 n8 m2 N
micronized.
9 x  [1 }4 e( }% ?In the chloride process, chlorine gas is reacted with a titaniumcontaining+ B' E  R2 m) c2 I2 t
mineral under reducing conditions to form anhydrous
  W. x3 a  S. F+ Gtitanium tetrachloride, which is subsequently purified and converted to
. }) w- Q8 |! E6 G# j5 ltitanium dioxide either by direct thermal oxidation or by reaction with* ^' }" B: h2 [, ~& s) M" L8 @) b! T
steam in the vapour phase. Alternatively, concentrated hydrochloric4 O+ }- n7 \7 o* a9 {. t1 r) n* h. c
acid can be reacted with the titanium-containing mineral to form a' g3 l4 g- N2 N* S4 ~+ o
solution of titanium tetrachloride, which is then further purified and3 G' j. H$ T0 w; [
converted to titanium dioxide by hydrolysis. The titanium dioxide is9 J! _$ Q' V' u/ S
filtered, washed, and calcined.
% ?8 y% Y1 e% @Commercial titanium dioxide may be coated with small amounts of
. x1 c3 p# O- j) `7 N8 Calumina and/or silica to improve the technological properties of the
1 {" h& V# q/ p) Bproduct.
  n5 l( G" R1 C5 J- a2 u* I, J" YC.A.S. number 13463-67-7
8 `  o3 O  _1 |' a2 D8 DChemical formula TiO2
0 W* `+ I; z; OFormula weight
) R. s, \7 K' s79.88
. ?) ^% S' `2 a% zAssay
% c7 [) x: D! p7 P, f( oNot less than 99.0% on the dried basis (on an aluminium oxide and
- ]" M9 w( _1 K+ K4 [silicon dioxide-free basis)  h( D" z" Y6 ~6 o* S1 B9 m
DESCRIPTION4 U. K" `/ r6 A
White to slightly coloured powder4 g- O4 G& a5 o! I
FUNCTIONAL USES
$ }3 a( V4 E& f- F8 cColour
5 Z) {" m7 O9 B+ o! o; JCHARACTERISTICS
, F% |+ N8 Y8 ]0 gIDENTIFICATION
- I# a) X, U! V* oSolubility (Vol. 4)
0 A: f/ E3 [; Z( I0 ^, Y. G1 E) B' qInsoluble in water, hydrochloric acid, dilute sulfuric acid, and organic7 L+ b0 g; ~" c! K& @* C
solvents. Dissolves slowly in hydrofluoric acid and hot concentrated
4 `/ U- O6 q  Dsulfuric acid.
3 t( u) h  I$ P0 p; {) I0 sColour reaction0 ?( q1 |# N% y# V
Add 5 ml sulfuric acid to 0.5 g of the sample, heat gently until fumes of; v% e% c: S  ^; c4 h
sulfuric acid appear, then cool. Cautiously dilute to about 100 ml with: |* `+ A! ^+ z, [6 |- `
water and filter. To 5 ml of this clear filtrate, add a few drops of9 r" D- g/ X1 T8 Z& N$ J
hydrogen peroxide; an orange-red colour appears immediately.
. s# c0 e  L6 B) u1 o6 h& HPURITY
$ p1 d- \& }" O; Q4 I5 \Loss on drying (Vol. 4) Not more than 0.5% (105°, 3 h)
: r* K3 t* ]: x* l; G: O0 kLoss on ignition (Vol. 4)
2 p: K/ y' J4 \& mNot more than 1.0% (800o) on the dried basis
8 f) G) R' @1 L0 K$ VAluminium oxide and/or
) {) S' E+ y8 G% w8 Usilicon dioxide5 K' P6 o* L% o$ [2 l
Not more than 2%, either singly or combined" G# o) g" ?7 P7 d4 z9 y7 |
See descriptions under TESTS/ S1 T2 Y+ ^. v* H. b% {5 c
Acid-soluble substances Not more than 0.5%; Not more than 1.5% for products containing
& n( S$ h: |8 ~* m1 Oalumina or silica.. ]0 H$ K, p8 [* y+ m, Z" J$ I. ?
Suspend 5 g of the sample in 100 ml 0.5 N hydrochloric acid and3 H1 B8 o+ L5 c+ ^
place on a steam bath for 30 min with occasional stirring. Filter! o  z$ ~  h% I6 ~  f
through a Gooch crucible fitted with a glass fibre filter paper. Wash* ]' X! o* ^; K
with three 10-ml portions of 0.5 N hydrochloric acid, evaporate the
: L# W; ]2 r: {; Gcombined filtrate and washings to dryness, and ignite at a dull red; [# v, U. d; J! B' P7 f
heat to constant weight.
, x0 S' m$ x: K' tWater-soluble matter
( J" B; R4 t+ ^4 ~& Q3 A. ~(Vol. 4)
' F6 }: Z# a8 U- H. mNot more than 0.5%- F% Q( R! q, Z% d8 R
Proceed as directed under acid-soluble substances (above), using
% W- P+ `5 r- B% W1 U" Hwater in place of 0.5 N hydrochloric acid.6 T0 S5 n  g( \" d% \
Impurities soluble in 0.5 N% h9 L4 n5 m/ C9 F" L
hydrochloric acid4 c, |/ Z9 B6 n* C9 D
Antimony Not more than 2 mg/kg
! F) M7 l/ X: }9 ZSee description under TESTS' t# w: b0 x; F! }/ \
Arsenic Not more than 1 mg/kg$ v# s8 S) J( _( c
See description under TESTS* B' [' e* u/ d! ?4 T
Cadmium Not more than 1 mg/kg0 S7 x( E4 J7 P6 A* r( g
See description under TESTS! d- Q: F2 R! q. k4 O  {
Lead
5 f2 G$ V. T& b& X& ~Not more than 10 mg/kg
( B" r3 J& c) c- W& GSee description under TESTS# h0 S. X, p1 S  x1 U  B$ _) o
Mercury (Vol. 4) Not more than 1 mg/kg
, T* g+ E8 W+ ~( t& m( BDetermine using the cold vapour atomic absorption technique. Select a
5 u+ X1 l8 g: T# f0 z9 zsample size appropriate to the specified level1 J' p/ S7 k' [. ^# w# L2 [
TESTS  Q# Y; L9 U5 I! W; d( G
PURITY TESTS
+ y2 U" w7 G$ v& J" n, c" l* d: ZImpurities soluble in 0.5 N
% K) ]  {4 U2 c7 Q0 o) z2 t8 s$ dhydrochloric acid" s- l# g6 h, `" W2 b9 H* t4 s
Antimony, arsenic,
+ O! Q. \( _% R; L# Scadmium and lead
/ u0 G5 P8 ]6 l) B(Vol.4)& {5 Y! g/ C  z4 S) V
Transfer 10.0 g of sample into a 250-ml beaker, add 50 ml of 0.5 N
2 h( k. c0 E- [5 ehydrochloric acid, cover with a watch glass, and heat to boiling on a' v" f4 p$ K& z" J0 U+ K
hot plate. Boil gently for 15 min, pour the slurry into a 100- to 150-ml
( f# F) q3 P* F; ~5 e9 E: ~* rcentrifuge bottle, and centrifuge for 10 to 15 min, or until undissolved
" C4 F- s7 U2 A( C6 a, Jmaterial settles. Decant the supernatant extract through a Whatman
# t# H/ w9 ~# [  X; j/ N' O* U# ENo. 4 filter paper, or equivalent, collecting the filtrate in a 100-ml
& o; s5 ~4 v/ W6 `7 Rvolumetric flask and retaining as much as possible of the undissolved
4 {* \( y; Z3 j- b8 w; Pmaterial in the centrifuge bottle. Add 10 ml of hot water to the original4 v; f% y' w" }2 A
beaker, washing off the watch glass with the water, and pour the  I7 ?5 D7 l7 U- R5 \
contents into the centrifuge bottle. Form a slurry, using a glass stirring+ g3 M# l: \: _  ~2 o8 T
rod, and centrifuge. Decant through the same filter paper, and collect  m' g! s+ O, J$ Q/ S3 ~+ q( S" c
the washings in the volumetric flask containing the initial extract.0 v. W! e. b; r' A2 v& H
Repeat the entire washing process two more times. Finally, wash the
4 B, \$ H' p3 ]" _* u3 Hfilter paper with 10 to 15 ml of hot water. Cool the contents of the flask
3 b) y# ?# I$ ~, q' M/ |( @9 a- Uto room temperature, dilute to volume with water, and mix.- X# N9 _8 X2 `2 i# M
Determine antimony, cadmium, and lead using an AAS/ICP-AES
/ \. f; b) b) a" J2 l( g; a% e$ g  ztechnique appropriate to the specified level. Determine arsenic using the5 t5 r$ h  _2 A1 h, B+ D
ICP-AES/AAS-hydride technique. Alternatively, determine arsenic using6 h) q  v5 U# c1 V8 j% r/ ^
Method II of the Arsenic Limit Test, taking 3 g of the sample rather than
2 e& ~) Y) y* U" C- j, T: y; C1 g. The selection of sample size and method of sample preparation8 O+ u7 x8 g4 I* j+ t
may be based on the principles of the methods described in Volume 4.
! E6 V8 K# F( z4 G( s! xAluminium oxide Reagents and sample solutions6 W( P2 _0 Y% z! \1 H2 v
0.01 N Zinc Sulfate- p# s5 B8 J$ I) t( K- `# ]
Dissolve 2.9 g of zinc sulfate (ZnSO4 ? 7H2O) in sufficient water to
: U0 T% Y0 x: q/ w9 Kmake 1000 ml. Standardize the solution as follows: Dissolve 500 mg
/ r; O/ X8 i! e* \0 ]8 ?of high-purity (99.9%) aluminium wire, accurately weighed, in 20 ml of' k* w7 h/ F1 h5 q5 ^
concentrated hydrochloric acid, heating gently to effect solution, then
6 ]: O: f4 i0 @* Ytransfer the solution into a 1000-ml volumetric flask, dilute to volume. g  B! Z" v6 E2 t
with water, and mix. Transfer a 10 ml aliquot of this solution into a 500
8 ?- T- s5 k  U7 p7 W: Iml Erlenmeyer flask containing 90 ml of water and 3 ml of
9 R* v+ M1 [2 [; R1 `) Yconcentrated hydrochloric acid, add 1 drop of methyl orange TS and
: w5 P; n9 C/ D( O6 \25 ml of 0.02 M disodium ethylenediaminetetraacetate (EDTA) Add,
6 x: P2 O4 @& I% B5 ?2 sdropwise, ammonia solution (1 in 5) until the colour is just completely& H' n: k! D1 e$ N7 K" e. {
changed from red to orange-yellow. Then, add:; p/ y7 T* w3 Y" I1 u
(a): 10 ml of ammonium acetate buffer solution (77 g of6 O- `. D8 Q# I$ H& o
ammonium acetate plus 10 ml of glacial acetic acid, dilute to9 K# M9 @2 Z" Q+ r! \5 ?, u% {
1000 ml with water) and
) b# g2 _2 @- K1 E; ~(b): 10 ml of diammonium hydrogen phosphate solution (150 g8 t2 V. O/ G8 q# e7 \: a) J) i# f
of diammonium hydrogen phosphate in 700 ml of water,, W5 P. G4 A- N- F0 j+ J
adjusted to pH 5.5 with a 1 in 2 solution of hydrochloric acid,
% V1 `3 x  r- C' xthen dilute to 1000 ml with water).% Q* Y& z3 W4 d
Boil the solution for 5 min, cool it quickly to room temperature in a; Y) F9 U) _0 n- u5 I$ |3 N" F
stream of running water, add 3 drops of xylenol orange TS, and mix.
9 u. x* [+ I  K- ~Using the zinc sulfate solution as titrant, titrate the solution to the first
/ S( Q5 F1 C0 g9 B1 V: c* Gyellow-brown or pink end-point colour that persists for 5-10 sec. (Note:3 D2 a) }1 \' f* `" k; k+ o  a
This titration should be performed quickly near the end-point by* U' R9 N9 v5 A$ G
adding rapidly 0.2 ml increments of the titrant until the first colour
; z' Y* f$ V; T' ochange occurs; although the colour will fade in 5-10 sec, it is the true+ l& @8 K+ W) C' T: R6 x3 u  y+ v, {
end-point. Failure to observe the first colour change will result in an
% n, X% {  M, D7 kincorrect titration. The fading end-point does not occur at the second; C1 g1 b- ^; c5 T8 x: g
end-point.)) x" u; e; x$ Y" O5 ?
Add 2 g of sodium fluoride, boil the mixture for 2-5 min, and cool in a
# P+ t1 F5 ]# {$ N+ L9 T% ystream of running water. Titrate this solution, using the zinc sulfate* `6 }7 H! }( _* Z
solution as titrant, to the same fugitive yellow-brown or pink end-point4 I: |7 i/ C4 x
as described above.
$ K1 u8 j! o1 cCalculate the titre T of zinc sulfate solution by the formula:6 |8 {% L) x. s- ~5 a6 B2 {
T = 18.896 W / V
9 ]- U# i8 K/ Wwhere. u) @6 W3 @9 c! V! w8 {
T is the mass (mg) of Al2O3 per ml of zinc sulfate solution
- a5 ]5 _2 I( Z2 L* {W is the mass (g) of aluminium wire) Y+ `7 R) o. C2 i: {
V is the ml of the zinc sulfate solution consumed in the3 [" O. G; W, t  Y2 L: H* |+ n; W6 v
second titration
; w8 ~/ g% `% b1 u$ `18.896 = (R × 1000 mg/g × 10 ml/2)/1000 ml and' W7 m" d: k* v0 a( y
R is the ratio of the formula weight of aluminium oxide to% i& T9 U" N, V; l; q0 {
that of elemental aluminium.
9 u3 I% L. {1 j6 lSample Solution A- W1 f) u# N( ~0 ?! x8 h  p- s
Accurately weigh 1 g of the sample and transfer to a 250-ml high-silica0 S4 b6 w$ Q% _0 X7 C; Q
glass Erlenmeyer flask. Add 10 g of sodium bisulfate (NaHSO4 ? H2O).
$ C: y0 }2 w  @4 d) l" N(Note: Do not use more sodium bisulfate than specified, as an excess" z+ W8 B& e4 V' f4 o/ M
concentration of salt will interfere with the EDTA titration later on in the
2 R, l0 w+ x. ?& Q- Oprocedure.) Begin heating the flask at low heat on a hot plate, and
4 f0 M& Z- L( v7 }. u2 b" |then gradually raise the temperature until full heat is reached.& [  L; X& o/ f
(Caution: perform this procedure in a well ventilated area. ) When
7 m& X( p, V1 ^" G# mspattering has stopped and light fumes of SO3 appear, heat in the full
5 {4 H/ W/ i7 [9 H- wflame of a Meeker burner, with the flask tilted so that the fusion of the
7 C. A7 A$ _3 Y: V, m  c2 R; Fsample and sodium bisulfate is concentrated at one end of the flask.
8 `& a7 k+ s1 R) ySwirl constantly until the melt is clear (except for silica content), but4 Y: b/ s) M4 {$ V2 N8 R* V
guard against prolonged heating to avoid precipitation of titanium. l+ B# E+ ?7 y
dioxide. Cool, add 25 ml sulfuric acid solution (1 in 2), and heat until- O, t# Y+ l; n+ A" I
the mass has dissolved and a clear solution results. Cool, and dilute to0 s" [( Z9 P  {3 W  Q& K1 V
120 ml with water. Introduce a magnetic stir bar into the flask.' t3 R: |1 k& O6 x; E) P* {
Sample Solution B
+ R2 s. Z: g  I: \Prepare 200 ml of an approximately 6.25 M solution of sodium3 `; b7 r( ?% a& }5 s; [! V) ]
hydroxide. Add 65 ml of this solution to Sample Solution A, while
3 b8 n. G: \& t! g; T  Istirring with the magnetic stirrer; pour the remaining 135 ml of the
! L7 M9 h* x. I3 _alkali solution into a 500-ml volumetric flask.
# \& l8 ?3 ^& }* g" h2 W: VSlowly, with constant stirring, add the sample mixture to the alkali2 L2 i6 J# U/ V% n
solution in the 500-ml volumetric flask; dilute to volume with water,
- _. }1 {  f# ~and mix. (Note: If the procedure is delayed at this point for more than
8 J. J. c9 t2 t& m5 r0 g# y% p3 P2 hours, store the contents of the volumetric flask in a polyethylene+ w' q% I% t% X7 m( K8 b" \, g
bottle.) Allow most of the precipitate to settle (or centrifuge for 5 min),9 `: J& @" ~) C! F9 ]: ~* E3 p" F
then filter the supernatant liquid through a very fine filter paper. Label) Y9 {6 p( v, F% E$ O
the filtrate Sample Solution B.* s5 K# \. v/ r# \
Sample Solution C- q7 v6 y2 L6 k) v- j, @
Transfer 100 ml of the Sample Solution B into a 500-ml Erlenmeyer7 S7 U1 K  e( t" b
flask, add 1 drop of methyl orange TS, acidify with hydrochloric acid
- O) W, K4 ?, Psolution (1 in 2), and then add about 3 ml in excess. Add 25 ml of 0.02
: r# y  a9 d/ D, b& Z: Z* mM disodium EDTA, and mix. [Note: If the approximate Al2O3 content is
4 \2 l0 e6 Q. A! zknown, calculate the optimum volume of EDTA solution to be added' X5 A( u8 P4 I/ _
by the formula: (4 x % Al2O3) + 5.]
) K1 a( ]0 T, N# c& J; K2 LAdd, dropwise, ammonia solution (1 in 5) until the colour is just  l. @( d5 B- P& B6 X. D" O
completely changed from red to orange-yellow. Then add10 ml each3 b4 ~. Z- j$ P
of Solutions 1 and 2 (see above) and boil for 5 min. Cool quickly to
- p  L! w5 o! C9 qroom temperature in a stream of running water, add 3 drops of xylenol+ W% e: ^: P. k" y8 C" G
orange TS, and mix. If the solution is purple, yellow-brown, or pink,- F3 `  i8 S  ?
bring the pH to 5.3 - 5.7 by the addition of acetic acid. At the desired3 F6 E) k( |' d4 s6 z2 ^8 |4 E
pH, a pink colour indicates that not enough of the EDTA solution has% J; a8 t. X2 d
been added, in which case, discard the solution and repeat this0 _9 J1 ~. C1 J) o" ^+ i& a% b( p
procedure with another 100 ml of Sample Solution B, using 50 ml,3 V# \* b1 T( W4 w
rather than 25 ml, of 0.02 M disodium EDTA.5 {6 g! W( A6 k' [; K3 I
Procedure( S: A( \0 P5 F7 z: T
Using the standardized zinc sulfate solution as titrant, titrate Sample
9 d: `7 W+ d1 H4 n6 oSolution C to the first yellow-brown or pink end-point that persists for
9 b: f- U( ^$ F3 Q0 S5-10 sec. (Important: See Note under “0.01 Zinc sulfate”.) This first7 C2 F9 M' Z' K- l' J8 Z9 t
titration should require more than 8 ml of titrant, but for more accurate
- t  Q. k+ t$ swork a titration of 10-15 ml is desirable.
; `1 ?0 t# K# f' EAdd 2 g of sodium fluoride to the titration flask, boil the mixture for 2-5; j2 A0 l4 J6 ^0 B" f7 [# f9 d; t
min, and cool in a stream of running water. Titrate this solution, using
: G! o  o- C- M, G& Q+ Mthe standardized zinc sulfate solution as titrant, to the same fugitive
9 v+ m) V* Q4 I- Xyellow-brown or pink end-point as described above.2 I3 P( [4 V0 j& b; h9 M$ b8 f
Calculation:
$ A8 j( _& T9 A+ e+ ACalculate the percentage of aluminium oxide (Al2O3) in the sample
1 K1 u7 `6 F; M* b# X* m5 Ataken by the formula:/ }+ y7 j- D) o
% Al2O3 = 100 × (0.005VT)/S
5 k/ U. [. P9 twhere$ O# e4 U1 v( Y! T
V is the number of ml of 0.01 N zinc sulfate consumed in
7 F' k) A. M3 a! a% d/ m9 q, H0 }the second titration," g$ P( }; t8 T4 e8 e% f) U
T is the titre of the zinc sulfate solution,
( v/ U/ ]2 G/ j' J. U# X5 mS is the mass (g) of the sample taken, and
7 T8 P5 U" O( x( j) t7 B) E0.005 = 500 ml / (1000mg/g × 100 ml).* }# J6 \  M; M/ x# P' M
Silicon dioxide Accurately weigh 1 g of the sample and transfer to a 250-ml high-silica
/ x" B6 t$ E# ]; y- Wglass Erlenmeyer flask. Add 10 g of sodium bisulfate (NaHSO4 ? H2O).9 U7 ]0 d2 u* d
Heat gently over a Meeker burner, while swirling the flask, until9 g) y7 O6 \- o# A
decomposition and fusion are complete and the melt is clear, except
3 ^5 b/ r7 Z5 x) wfor the silica content, and then cool. (Caution: Do not overheat the
/ K0 E$ @$ M# A$ @contents of the flask at the beginning, and heat cautiously during
1 B! c; ]" Z. j3 t% Z) kfusion to avoid spattering.)3 a6 k( z  ~3 W7 O! N! @
To the cooled melt add 25 ml of sulfuric acid solution (1 in 2) and heat2 q4 e8 K( M6 s3 }: @/ n7 T8 Y
carefully and slowly until the melt is dissolved. Cool, and carefully add* A. L; d1 c! x1 {0 r2 k
150 ml of water by pouring very small portions down the sides of the
& M" P) B0 H( B2 g: o, X8 K  Q9 ]flask, with frequent swirling to avoid over-heating and spattering. Allow
# o: v+ E) ^' w6 Qthe contents of the flask to cool, and filter through fine ashless filter% m! W5 d) z" Y. l
paper, using a 60 degree gravity funnel. Rinse out all the silica from
/ D1 u+ G3 e0 ?, }' _, e7 E  Gthe flask onto the filter paper with sulfuric acid solution (1 in 10).. W5 [1 ]) [7 o. Y$ s* V
Transfer the filter paper and its contents into a platinum crucible, dry in, c* E& c+ b# C  c$ `1 J8 K9 g
an oven at 1200, and heat the partly covered crucible over a Bunsen' E* a% Y7 b& Y7 B. I* L- M
burner. To prevent flaming of the filter paper, first heat the cover from, D, k+ O/ b- H! Z" {6 z0 Z
above, and then the crucible from below.  D1 G' i. ]' _/ `/ K! ]
When the filter paper is consumed, transfer the crucible to a muffle
3 A( o' H) n& qfurnace and ignite at 1000o for 30 min. Cool in a desiccator, and
2 v, I& f! {( {0 Eweigh. Add 2 drops of sulfuric acid (1 in 2) and 5 ml of concentrated
. b3 u' V# [8 `8 _2 p' q5 E) V2 [; v' {hydrofluoric acid (sp.gr. 1.15), and carefully evaporate to dryness, first! Z$ w0 p2 W- n- L
on a low-heat hot plate (to remove the HF) and then over a Bunsen3 {1 B6 P5 e/ v4 K: J
burner (to remove the H2SO4). Take precautions to avoid spattering,  M; H: a8 {! ]
especially after removal of the HF. Ignite at 1000o for 10 min, cool in a
3 o) D4 Q- \' d& P* U. F! sdesiccator, and weigh again. Record the difference between the two- @9 a$ D: [% G6 l" x. S0 @
weights as the content of SiO2 in the sample.
- o7 I! u! e( E0 D. m: {% hMETHOD OF ASSAY
3 J) d' N3 U8 C/ a4 E9 \Accurately weigh about 150 mg of the sample, previously dried at 105o
# K) ]$ s0 b- P+ L3 Ifor 3 hours, and transfer into a 500-ml conical flask. Add 5 ml of water
  ]. e+ C) ]9 }- |& h+ fand shake until a homogeneous, milky suspension is obtained. Add 30
- E! V# t6 y& l9 B  ^ml of sulfuric acid and 12 g of ammonium sulfate, and mix. Initially4 u) d! M( D' K4 d1 `0 a  k
heat gently, then heat strongly until a clear solution is obtained. Cool,
2 S0 ~, v( Q/ B6 r, Ythen cautiously dilute with 120 ml of water and 40 ml of hydrochloric
% O7 M: u4 Y4 r  ]0 T' g1 }. @acid, and stir. Add 3 g of aluminium metal, and immediately insert a
# F: l3 ~* j9 Crubber stopper fitted with a U-shaped glass tube while immersing the
. F9 @& d! A5 Q% E: [! i& L+ `# Kother end of the U-tube into a saturated solution of sodium
& }9 Q1 W) w' j$ l( qbicarbonate contained in a 500-ml wide-mouth bottle, and generate
7 p8 F: z5 ^, ]1 R" Xhydrogen. Allow to stand for a few minutes after the aluminium metal( d1 j$ M8 U7 {8 w2 O$ A4 U
has dissolved completely to produce a transparent purple solution.
1 u( ~) y3 L  o" sCool to below 50o in running water, and remove the rubber stopper
" J1 A1 [- }+ a4 y0 icarrying the U-tube. Add 3 ml of a saturated potassium thiocyanate
% K# l7 m3 N8 T# P4 \solution as an indicator, and immediately titrate with 0.2 N ferric
/ L0 W+ {- U3 aammonium sulfate until a faint brown colour that persists for 30
. H4 l& Z6 ~& B/ c! \seconds is obtained. Perform a blank determination and make any
# ?4 e1 N% T4 N3 K8 I' A8 _0 _+ Rnecessary correction. Each ml of 0.2 N ferric ammonium sulfate is
" y9 s* F4 t6 U2 w# c6 |+ gequivalent to 7.990 mg of TiO2.' n  g: O3 E3 W6 ~6 e
您需要登录后才可以回帖 登录 | 立即注册

本版积分规则

QQ|申请友链|手机版|华讯行业网 ( 桂B2-20030027  

GMT+8, 2025-4-2 09:24 , Processed in 0.051335 second(s), 23 queries .

Powered by Discuz! X3.2

© 2001-2013 Comsenz Inc.

快速回复 返回顶部 返回列表