**M. Electroless Nickel Solution Analysis**

â– 1. Determination of nickel

1) Analysis steps

Pipette 5 ml of the solution in a 300 ml Erlenmeyer flask, add 2 ml of hydrochloric acid and 2 ml of 30% hydrogen peroxide, boil and evaporate to near dryness, add 100 ml of water. If there is salt precipitation during evaporation, shake to dissolve. Add 2 ml of triethanolamine, 12 ml of ammonia, and a little ammonium nitrate. Titrate with 0.05 M EDTA solution until the end of transition from brownish yellow to purple. The titration rate is slowed at the end point.

2) Calculation

Nickel sulfate containing NiSO4.7H2O= M Ã— V Ã— 0.2808 Ã— 1000/5 (g/L)

In the formula:

The molar concentration of M--standard EDTA solution;

V--use milliliters of standard EDTA solution.

â– 2. Determination of sodium hypophosphite and sodium phosphite

Method one: Cerium nitrate titration

2.1 Determination of sodium hypophosphite:

1) Analysis steps

Pipette 5 ml of the solution in a 250 ml Erlenmeyer flask, add 15 ml of 1:5 sulfuric acid, and test 1 drop of ferric oxide. If the solution is red, indicate that there is ferrous iron, and add 0.1N ceric ammonium nitrate dropwise. Liquid to red disappear (does not count). Then add 0.1N ammonium cerium nitrate 25 to 30 ml (containing 1 g/l of NaHPO2.H2O1/l, add 15 ml excess) from a burette, place in a 60Â°C water bath for 30 minutes, cool, and add Triathlon 1 The drop was titrated with a 0.1 N ferrous ammonium sulfate solution until the end of sudden red coloration.

2) Calculation

Contains sodium hypophosphite NaH2PO2.H2O = (N1V1-N2V2) Ã— 0.053 Ã— 1000/5 (g/L)

In the formula:

N1--standard equivalent concentration of ceric ammonium nitrate solution;

N1-- consumption of standard milli-ammonium nitrate solution in milliliters;

N2--standard equivalent concentration of iron(II) sulfate ferric ammonium solution;

N2-- consumption of standard milliliters of ammonium ferrous sulfate solution;

0.053--NaH2PO2 .H2O / 2000

2.2 Determination of sodium phosphite

1) Analysis steps

Pipette the solution into a 2.5-mL Erlenmeyer flask and add 8 mL of 1:5 sulfuric acid (15 mL) and one drop of Tritonine. If the solution is red, add 0.1N ceric ammonium nitrate solution until the red color disappears (does not count. ). Then add 0.1N ammonium cerium nitrate solution 40 to 50 ml (with each NaH2PO2.H2O1 g/l, add 1 ml; Na2HPO 31 g/l add 0.5 ml, then excess 15 ml) from the burette, and cap the flask, heating Boil, keep boiling for 30 minutes with low heat. Be careful not to evaporate excessive water. Cool, add 1 drop of ferric oxide to the end of 0.1N ferrous ammonium sulfate droplets to sudden red color.

2) Calculation

With sodium phosphite Na2HPO3 = (N1V1 - N2V2) Ã— 0.063 Ã— 1000/2.5 - 2.38A (g/L)

In the formula:

N1--standard equivalent concentration of ceric ammonium nitrate solution;

N1-- consumption of standard milli-ammonium nitrate solution in milliliters;

N2--standard equivalent concentration of ammonium ferrous sulfate solution;

N2-- consumption of standard milliliters of ammonium ferrous sulfate solution;

A--NaH2PO2.H2O content in solution (g/l);

2.38--2 x Na2HPO3 / NaH2PO2.H2O;

0.063--Na2HPO3/2000.

Note: (1) The above two methods are not applicable to solutions containing organic salts such as citrate, and the results are much higher;

(2) When measuring hypophosphite, the bath temperature should not exceed 60 Â°C, otherwise the phosphite may be oxidized, resulting in high results;

(3) This method allows the direct determination of hypophosphite in the presence of phosphite, which is fast and results are correct;

(4) Preparation and calibration of indicators and standard solution flaps.

1 Test ferrioxide indicator dissolves 1.485 g of o-filaline in 100 ml of 0.25M iron sulfate (containing 0.769 g of FeSO4Â·7H2O).

2 Standard 0.1 N ceric ammonium nitrate solution, weigh out [Ce(NO3)4Â·2NH4NO3] yttrium ammonium nitrate 56 g and concentrated sulfuric acid (specific gravity 1.84) 56 ml, carefully add 100 ml each time, stir until fully dissolved, and then Say it to one liter. If there is any, it should be filtered.

Calibration, using a pipette to absorb 25 ml of ceric ammonium nitrate standard solution in a 250 ml Erlenmeyer flask, add 25 ml of water, 15 ml of 1:5 sulfuric acid, and 1 drop of Triathlon, to use a new standard of 0.1N ferrous ammonium sulfate solution. Titrate until the end suddenly turns red.

N=N1*V1/25

Where: the equivalent concentration of N-standard ceric ammonium sulfate solution;

The equivalent concentration of N1-standard ferrous ammonium sulfate solution;

N1 - The number of ml of standard ferrous ammonium sulfate solution consumed.

Method two: Iodometric method

(a) Determination of sodium phosphite

1. Analysis steps:

Pipette 5 ml of the solution in 50 ml, iodine bottle, add water and weigh it to 50 ml, add 5% sodium bicarbonate 20 ml and 0.1N iodine solution 30-40 ml (each containing NaHPO 21 g/l, add 1 (milliliter, 15 ml excess), cover the stopper, place it for one hour, open the stopper, acidify the solution with acetic acid, lightly coloured with 0.1 N sodium thioglycolate, add 3 ml of starch, continue titration to blue Disappeared for 1 minute.

2. Calculation

With sodium phosphite Na2HPO3=(N1V1-N2V2)*0.063*1000/5(gL)

The equivalent concentration of N1--standard iodine solution in the formula;

V1-- consumption of standard iodine solution ml;

N2--normal concentration of sodium thiosulfate;

V2-- consumption of standard sodium thiosulfate in milliliters;

0.063- Na2HPO3/2000.

(b) Determination of sodium hypophosphite

1. Analysis step

Pipette 2.5 ml of the solution in a 50 ml iodine bottle, add 15 ml of 1:5 sulfuric acid and about 40 ml of 0.1 N iodine solution (each containing NaH2PO2Â·H2O1 g/l), add ml; Na2HPO3 1 g/l, Add 0.5 ml, then excess 15 ml,) Cover the stopper, let it stand for 10 hours or overnight, and cool the solution with ice water (to prevent iodine from evaporating during neutralization) Neutralization of sodium bicarbonate used for slurrying in water Then, add 5% sodium bicarbonate 20 ml, cap the stopper, place for 1 hour, acidify the solution with acetic acid, and titrate to the end point with 0.1 N sodium sulfate solution according to the previous method.

2. Calculated with sodium sulfite NaH2PO2Â·H2O=[(N1V1-N2V2)*0.0265*1000/2.5]- 0.421A (g/L):

The equivalent concentration of N1--standard iodine solution in the formula;

V1-- consumption of standard iodine solution ml;

N2--normal concentration of sodium thiosulfate;

V2-- consumption of standard sodium thiosulfate in milliliters;

A--Na2HPO3 content (grams) in solution;

0.421--NaH2PO2Â·H2O/ 2Na2HPO3

0.0256--NaH2PO2Â·H2O/4000

Source: PCB Information Network