电镀产品上电镀金精确计算产品上金含量分析方法

Gravimetric analysis for different Au solutions

重量分析方法计算电镀金用量

1.0 Purpose

1.1 The purpose of this document is to describe the gravimetric methods to analyze different Au

solutions including Acid Au bath, Aqua regia refining Au solution & Cyanide stripping Au refining solution etc. It’s not recommended to use gravimetric method if Au concentration is less than 0.5g/L.

2.0 Associated Procedures & Materials

2.1MSDS of H2SO4, HNO3, HCl, Na2SO3, PGC & Pd salt

3.0Jig and Fixture Used

3.1 N.A

4.0 S afety Requirements

4.1 Follow Area Safety Rules

4.2Goggles

4.3Safety shoes

4.4Rubber Gloves & disposal plastic gloves

4.5 Chemical Resistant Uniform,

4.6 Chemical resistance apron

5.0Equipment

5.1Fume ‘ cupboard ‘

5.225ml transfer pipette

5.3Gooch Crucible

5.4500ml Conical flask, 250ml, 500ml & 1 liter beaker with watch glass

5.5High temperature furnace.(900 oC)

5.6Normal oven up to 250°

5.7100ml measuring cylinder

5.8Hot Plate(2~3kw)

5.9Ashless filter paper

5.10Funnel

5.11Desiccator

5.12Balance, accuracy is 0.0001gram

6.0 R eagent

6.1 Sulfuric acid (98%)

6.2 Nitric acid (>65%)

6.3 HCl concentrated & HCl(50v/v%);

Address：16 Collyer Quay, #26-01 Income@Raffles, Singapore 049318 Tel:+ 65-6589 8045 Fax:+65- 6589 8041

6.4 Sodium sulfite, anhydrous, Na2SO3

6.5 Aqua regia (HNO3:HCl=1:3)

7.0 C leanliness

7.1 All beakers & volumetric flask used for analysis must be carefully cleaned with D.I. water

before being used.

8. Procedure

8.1. Procedure for citric acid Au bath & cyanide stripping refining solution

8.1.0 Clean crucible with Aqua Regia & thoroughly wash with DI water,

and then dry up in 110°C clean oven for 2 hrs. Store clean & dried

crucible in desiccator.

8.1.1. Pipette 25ml sample(filtrate first if necessary) into a 500ml beaker

8.1.2. Slowly add about 40ml Sulfuric acid (98%), and then cover with

Watch glass

8.1.3. Heat up the mixed solution until it becomes clear(but still in deep

brown color) on Heater, which will take 20~40min.The gold will

form sponge.

8.1.4. Cool down, slowly & carefully add DI water to dilute left Sulfu ric

Acid;

8.1.5. Use boiled hot DI water to wash sponge 2 times, and carefully pour

out washing water to make sure no Au particle lost.

8.1.6. Add concentrated Nitric Acid 20ml to boil sponge 10min., and then

cool down.

8.1.7. Use boiled hot DI water to wash for a few times.

8.1.8 Transfer Au sponge & particles into weighted crucible(W1), and then

dry for 2hrs@150°C in a clean oven;

8.1.9. Switch off oven, and then cool down;

8.1.10 Put crucible into disccator for 20min., and then weight crucible

Again(W2)

Calculation:

Gold (g/L)=(W2-W1)x40

Note:

?Keep all washing solution & rinsing water in a big beaker, and mix well to verify Au concentration with AA machine after completion of

gravimetric analysis.

?To minimize possible big analysis error, normally total Au attracted by gravimetric method should be more than 0.2g. Thus, the sampling volume can be more or less than 25ml.

? A correlation in 900°C furnace >20min. show that there is no difference compared to 150°C oven dry 2hrs results.

8.2. Procedure for gold refining aqua regia solution

8.2.0 Prepare cleaned crucible same as 8.1.0

8.2.1 Pipette 25ml sample(filtrate first if necessary) into a 500ml beaker

8.2.2 Add 10ml concentrated HCl, and then add DI water to about 150ml,

mix well

8.2.3Slowly add total 5grams Sodium Sulfite anhydrous, and m ix well

with glass rod agitation;

8.2.4Solution become turbid, which indicates Au ion is reduced

And Au is precipitated.

8.2.5Put on watch glass cover, and heat up on oven to just boiling, and then

switch off hotplate to keep warm about 40min so as to Au particles

can completely settle down

8.2.6Carefully pour out clear solution through ashless filter paper & funnel

and try the best not to pour out Au particles. The solution should be

collected by 1 liter beaker

8.2.7Use DI water(washing bottle) to wash watch glass & beaker& Au

particles, and keep for 20~40min. until Au particles completely settle

down & water become clear.

8.2.8Repeat 8.2.6 to carefully pour out clear solution.

8.2.9Slowly add 30ml concentrated Sulfuric Acid into beaker, and put on

the hotplate to boil until white smoke coming out. Au particles will

form sponge. This may take 20~40min.

8.2.10C ool down beaker on asbestos mes h, and then carefully & slowly add

DI water to dilute left solution, and then pour into 1 liter beaker

through ashless filter paper.

8.2.11W ash beaker, watch glass & sponge for a few times to neutral, and

pour all of washing water through ashless filter paper.

8.2.12T ransfer ashless paper & sponge to weighted crucible(W1), and put

into clean furnace & heat up to 150°C for 10~20min., and then up

temperature to 900°C for at least 30min.

8.2.13S witch off furnace and cool down to about 100°C,and then take out

the crucible from the furnace to put into desiccator to store for half

hour;

8.2.14W eight the dry crucible for (W2)

Calculation:

Gold (g/L)=(W2-W1)x40

Note:

?Keep all washing solution & rinsing water in a big beaker, and mix well to verify Au concentration with AA machine after completion of

gravimetric analysis.

?To minimize possible big analysis error, normally total Au attracted by gravimetric method should be more than 0.2g. Thus, the sampling volume can be more or less than 25ml.