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Migration Cells Assembly
Cells
The cells' migration test consists of two symmetrical chambers made of polymer materials (e.g., methyl methacrylate). Each cell is equipped with an electrode (see below) and an external connector (jack). The volume of each cell should be approximately 3 liters. The mouth of the cell should fit the connecting ring (Figures 25 and 26).
Connecting Rings
Two connecting rings are needed for the test setup. The ring should be made of polymer materials and designed to hold the specimen from one side and connected to the cell from the other side. The exposure area should be as large as possible. A typical design for the 4-in. cylindrical specimens is shown in Fig. 27.
Figure 27 – Connecting ring for 4-in. specimen (96-103 mm)
Electrodes
A rod electrode is installed on each cell. Carbon electrodes should be avoided because they tend to decompose in the electrolytic solution under the application of a DC potential. Electrodes made of titanium or ruthenium oxide with titanium coating are recommended. Each electrode should be securely connected to the external connector by the jack (Fig. 26).
Solution preparation
The following procedure describes the preparation of the aqueous solutions:
1. Accurately weigh the salt or base (e.g., NaCl or NaOH) of high purity (>99%) to at least 0.001g accuracy (refer to Table 2);
2. Completely dissolve the salt or base into a certain amount of distilled or deionised water;
3. Dilute with more distilled or deionised water to a final volume of desired range;
4. Thoroughly stir the solutions to obtain homogeneity.
Table 2 - Chemical composition of 1 liter (1,000 ml) solutions
Salt /Base (purity: 99%) |
Upstream solution (salt): 0.5M NaCl + 0.3M NaOH |
Downstream solution (base): 0.3M NaOH |
NaOH (g/liter) |
12.121 |
12.121 |
NaCl (g/liter) |
29.515 |
0 |
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