Nonferrous
Metal
Sodium Hydroxide for Alumite
Acidxbase titration by
Automatic Potentiometric Titrator
Standard
1.Abstract
Sodium hydroxide of anodizing solution for Alumite is measured by titration with
1mol/L Hydrochloric acid up to the endpoint, which is the maximum inflexion on titration
curve.
The concentration of Sodium hydroxide is calculated from titration volume of
Hydrochloric acid.
2.Reference
1) Experiment and Calculation for Quantitative Analysis Vol.2 by Seiji Takagi from
Kyoritsu Publication
3.Cautions in measurement
1) Handle with care when you work on chemicals.
2) Sample liquid though diluted with pure water is still alkali, and corrodes
response membrane of glass electrode. Therefore, remove residual sample liquid
of electrode completely by stirring in a beaker filled with pure water.
TIO-94004 Ver.01 1/4
4.Post-measurement care
1） As noted above, sample liquid is alkali, and corrodes response membrane of
glass electrode. Therefore, remove residual sample liquid of electrode completely
by stirring in a beaker filled with pure water.
2） Keep the electrode in a beaker filled with pure water after rinsed well.
5.Test equipment
Main unit : Automatic potentiometric titrator （Standard preamplifier: STD－）
Electrode： Option Glass electrode
Option Ceramic type reference electrode
Standard
Temperature compensation electrode
6.Reagent
Titrant
：
Solvent ：
Additive ：
l mo1/L Hydrochloric acid ( f=1.001 )
Pure water
10W/V% Potassium fluoride
7.Measurement procedure
―Measurement―
1) Prepare 5.0mL sample in a 200ｍL beaker, and add 100ｍL of pure water.
2) Titrate with 1mol/L Hydrochloric acid to obtain concentration of total
concentration of Sodium hydroxide.
3) Add 30mL of 10W/V% Potassium fluoride.
4) Again titrate with 1mol/L Hydrochloric acid to obtain concentration of free
Sodium hydroxide.
8.Formula
Total Sodium hydroxide ( g/L ) = EP1×FA1×C1×K1 / SIZE
Free Sodium hydroxide ( g/L ) = ( EP1－( EP2－EP1) / K2 )×FA1×C1×K1 / SIZE
EP1 ： Titration volume at EP1 ( mL )
EP2 ： Titration volume at EP2 ( mL )
FA1 ： Factor of titrant ( 1.001 )
C1
： Concentration conversion coefficient ( 40mg/mL )
( 1mo1/L HCl 1mL ≡ 40mg NaOH )
K1
： Unite conversion coefficient ( 1 )
K2
： Unite conversion coefficient ( 3 )
SIZE ： Sample size ( mL )
TIO-94004 Ver.01 2/4
9.Example of measurement
－Ambient condition－
Room temperature：25 ℃
Humidity ：
- Titration parameter ［Titration parameter］
Titration mode
Titration form
Titration burette
Reagent name
Detector number
： Auto control
： EP Stop
：
01
：
HCl
：
1
［Control parameter］
Number of EPs
Auto simulation
EP sense （Potential）
EP sense (Differential）
Over titration
Gain
Control speed
：
：
：
：
：
：
：
2
Off
50.0
150.0
0.0mL
1
2.0
50 ％
Weather ：
Fair
Preamplifier unit
Max. volume of burette
Auto stirrer
Wait time before titration
Titration direction
：
：
：
：
：
pH
40.0mL
Off
0s
Auto
Data sampling potential
Data sampling volume
Separate potential setup
Separate potential
EP potential setup
EP potential
：
：
：
：
：
：
4.0mV
0.5mL
Off
0.0pH
Off
0.0pH
-Titration curve-
(The above printout data are obtained from titration by AT-410)
TIO-94004 Ver.01 3/4
－Measurement results－
Batch calculated results
Sample Total NaOH Free NaOH
N
( mL )
(g/L)
(g/L)
Total NaOH Free NaOH
5.0
99.855
141.69
98.902
140.83
Mean (g/L)
1
5.0
SD (g/L)
2
0.997
0.83
100.89
142.49
5.0
RSD (%)
3
0.121
0.59
99.774
141.76
＊The above results were obtained by 3 tests of the same sample.
10.Summary
Alumite is generic term of Aluminum coating of oxidizing surface as anode by water
electrolysis in strong acidity. It is also called Anodizing process.
Sodium hydroxide is an inorganic compound with chemical formula NaOH, and is
one of the most important basic chemicals for industries. It is designated as
deleterious substance by Poisonous and Deleterious Substances Control Law.
The sample measurement shows a good repeatability with 0.6% relative standard
deviation. Precise and reliable measurement is assured by the automated
potentiometry.
The concentration of anodizing solution for alumite can be perfectly analyzed by any
of the following titration systems manufactured by Kyoto Electronics (KEM).
【AT-610】
Awarded Product of Supreme
Technology from Kyoto City
• Easy key entry by touch panel of
large color LCD （8-inch wide）
• Simultaneous titration in parallel
• Both potentiometric and Karl
Fischer
moisture
titration
(coulometric・volumetric） can be
performed at a time.
【AT-510】
• Compact and cost performance
model
• PC card expands data memory for
convenience and versatility.
【AT-500N-1】
• Low cost and high performance
• Easy view with back light LCD
• GLP/GMP conformed model
TIO-94004 Ver.01 4/4