氨水分离EDTA容量法滴定锌

氨水分离EDTA容量法测定锌

1. 方法提要

试样用、氯酸钾溶解，使锰呈二氧化锰析出，然后用氨水沉淀分离铁、铝、铅等元素。在pH5~6的醋酸-醋酸钠缓冲溶液中，以二甲酚橙为指示剂，用EDTA标准溶液滴定锌。

Cu、Ni、Pb、Ge对测定有干扰，但Cu可在滴定前加入硫代硫酸钠来掩饰。

本方法适用于一般矿石中 ω（Zn）/10-2>1的滴定.

2. 试剂配制

1) 醋酸-醋酸钠缓冲液(pH5~6),称取200gCH3COONa·3H2O溶于水中，加10ml冰醋酸，用水稀释至1000ml，摇匀。

2) 0.2%二甲酚橙或半二甲酚橙指示剂，称取0.5g二甲酚橙或半二甲酚橙溶于1000ml水中。（有效期：一周）。

3) EDTA标准溶液：C（EDTA）=0.0500mol/L

4) 准确称取105°C干燥至恒重的乙二胺四乙酸二钠37.2240g，于1000ml烧杯中，加500ml热水，搅拌使完全溶解，转入2000ml容量瓶中，用水稀释至刻度，摇匀。此溶液每毫升相当于3.2695g的Zn。

5) 5%的氟化铵溶液：称取5g氟化铵溶于100ml水中，贮存于塑料瓶中。

6) 20%硫代硫酸钠溶液：称取20g硫代硫酸钠溶于100ml水中。

7) 洗涤液：称取5g氯化铵溶于100ml热水中，加5ml氨水，摇匀。

3. 分析步骤

称取试样0.1000~0.5000g于250ml烧杯中，用少量水润湿，加入20ml氯酸钾饱和饿，盖上表面皿，置于中温电炉上加热溶解，加入0.5g氟化铵，待试样完全溶解，取下冷却。加浓硫酸7ml，继续加热至冒三氧化硫白烟约2min，取下冷却，用水冲洗表面皿及杯壁后，加50ml水，加3~5g氯化铵，用氨水中和至氢氧化物沉淀完全并过量5~10ml。加入0.3~0.5g过硫酸铵，加热煮沸10min，破环过量的过硫酸铵。取下，趁热用快速滤纸过滤，用热的洗涤液洗烧杯3次，洗沉淀6~8次，弃去沉淀，将滤液加热蒸制体积约100ml，取下冷却。试液中加入5%氟化铵5ml，0.1g抗环血酸，搅拌均匀，加20%硫代硫酸钠10ml，加2~3滴0.5%二甲酚橙或半二甲酚橙指示剂，用硫酸（1+1）中和至溶液由紫红色变成黄色【硫酸不要滴过多，溶液红色消失即可】，再用氨水（1+1）中和至溶液由黄色变成红色，加20ml醋酸-醋酸钠缓冲液（pH5~6），加水至150ml左右，用EDTA标准溶液滴定溶液颜色由紫红色变成亮黄色即为终点。

4. 分析结果计算

TV

ω（Zn）/10-2=-------x100

m

式中：T---EDTA标准溶液对锌的滴定度（mg/ml）

V---滴定时消耗EDTA标准溶液的体积（ml）

m---称取试样的重量（g）

Ammonia water from the EDTA volumetric method for the determination of zinc

1. Summary of the method

With nitric acid, potassium chlorate of the sample dissolution, MN manganese dioxide precipitation, followed by ammonia precipitation and separation of iron, aluminum, lead, and other elements. In the pH5~6 in acetic acid-sodium acetate buffer solution, with xylenol orange as the indicator, standard solution with EDTA titration of zinc.

Cu, Ni, Pb, Ge on the determination of any interference, but Cu be joined before the titration of sodium thiosulfate to conceal.

This method applies in General ore ω (Zn)/10-2>1 titration.

2. reagent preparation

1) acetic acid-sodium acetate buffer solution (pH5~6), that take

200gCH3COONa · 3H2O in water, increase 10ml acetic acid, diluted with water to 1000ml, shake.

2) indicator of xylenol orange or semi-xylenol Orange, taking 0.5G xylenol orange or semi-xylenol Orange dissolve 1000ml water. (Validity: one week).

3) EDTA standard solution c (EDTA) =0.0500mol/L

4) accurately called get 105 ° c and dry to constant weight of ethylene diamine tetraacetic acid disodium 37.2240g, 1000ml the beaker, and 500ml hot water, stirring fully dissolved, 2000ml, volumetric flask, dilute with water to scale, shake. Per millilitre of this solution corresponds to the 3.2695g of Zn.

5) ammonium fluoride solutions: call of 5G ammonium fluoride dissolved in 100ml water, kept in plastic bottles.

6) of sodium thiosulfate solution: call of 20G thio-sulfate dissolved in 100ml water.

7) washing liquid: preparation of 5G ammonium chloride dissolves in 100ml in hot water, plus 5ml ammonia, shake.

3. the analysis steps

Preparation of 0.1000~0.5000G 250ml of the sample beaker, wetting with a

small amount of water, add 20ml nitric acid potassium chlorate saturated hungry, covered dish on the surface, placed on the temperature in the furnace heated to dissolve, add 0.5G ammonium fluoride, specimen dissolved completely, remove the cooling. Adding concentrated sulfuric acid 7ml, continue heating until white smoke about sulfur trioxide risk 2min, removed the cooling, washing dishes and cups on the surface of water after the wall, plus 50ml, and 3~5G ammonium chloride, ammonia and 5~10ml to the hydroxide precipitation and completely excessive. Join 0.3~0.5G ammonium persulfate, boiling heat 10min, breaking the excessive amounts of ammonium persulfate. Remove, at home and use the quick filter paper filter, hot washing liquid washing beakers used 3 times, wash the precipitate 6~8, discard precipitation, heat the filtrate steaming mass of about 100ml, removed the cooling. Try liquid in the joined 5% fluoride of ammonium 5ml,0.1g anti-ring blood acid, mixing uniform, plus 20% sulfur generation sodium sulfate 10ml, plus 2~3 drops 0.5% II cresol orange or half II cresol Orange indicates agent, with sulfate (1+1) in the and to solution by purple red into yellow \"sulfate don't drops too much, solution red disappear canhe and to solution by yellow into red, plus 20ml acetate-acetate sodium buffer liquid (pH5~6), plus water to 150ml around, with EDTA standard solution titration solution color by purple red into lit yellow is for end.

4. analysis results calculation

TV

ω（Zn）/10-2=-------x100

m

Type: T---EDTA standard solution for titration of zinc (mg/ml)

EDTA V---drop scheduled consumption volume of standard solution (ML)

M---take the weight of the sample (g)