Titration standards for preparation of buffer solutions – рН working standards of 2 nd category
Intended for
the preparation of buffer solutions that reproduce and transmit values of the activity index of hydrogen ions (pH) in aqueous solutions.
Titration standards represent quantities of chemical substances, upon dissolution of which in a certain volume buffer solution - pH working standards are received. pH working standards of 2 category are prepared by diluting the quantity of substance with double-distilled water with specific conductivity (UEC) of not more than 2 · 10-4 Sm / m.
pH working standards of 2 category are prepared in accordance with GOST 8.135-2004. Titration standards are contained in plastic bottles. The bottle is leakproof and has a screw cap with a protective ring. Titration standards ST-pH-2 have 11 modifications, differing in the composition of the quantity of substance, the concentration of chemicals in the prepared buffer solution and reproducible pH value.
| Modifications of titration standards (modification number according to GOST 8.135- 2004) | Name of chemical substances, included in titration standards | Chemical formulas of substances | Weight of quantities of chemical substances, g | The concentration of substances, mole / kg | рН reproducible value at temperature +25°С |
|---|---|---|---|---|---|
| ST-рН-2-1(1) | Potassium tetraoxalate dihydrate | KH3(C2O4)2·2H2O | 25,219 | 0,1 | 1,48 |
| ST-рН-2-2(2) | Potassium tetraoxalate dihydrate | KH3(C2O4)2·2H2O | 12,610 | 0,05 | 1,65 |
| ST-рН-2-3(4) | Potassium hydrotartrate | KНC4H4O6 | 9,50 | saturated at temperature +25°С | 3,56 |
| ST-рН-2-4(5) | Potassium hydrogenphthalate | KНC8H4O4 | 10,120 | 0,05 | 4,01 |
| ST-рН-2-5(9) |
Potassium phosphate monosubstituted Sodium phosphate twice-substituted |
KH2PO4 Na2HPO4 |
3,3880 3,5330 |
0,025 0,025 |
6,86 |
| ST-рН-2- 6(10) |
Potassium phosphate monosubstituted Sodium phosphate twice-substituted |
KH2PO4 Na2HPO4 |
1,1790 4,3030 |
0,0087 0,0304 |
7,41 |
| ST-рН-2- 7(11) |
Potassium phosphate monosubstituted Sodium phosphate twice-substituted |
KH2PO4 Na2HPO4 |
1,3560 5,6564 |
0,1 0,04 |
7,43 |
| ST-рН-2- 8(13) | Sodium tetraborate decahydrate | Na2B4O7·10H2O | 3,8064 | 0,01 | 9,180 |
| ST-рН-2- 9(14) | Sodium tetraborate decahydrate | Na2B4O7·10H2O | 19,012 | 0,05 | 9,180 |
| ST-рН-2- 10(15) |
Sodium carbonate Sodium carbonate acid |
Na2CO3 NaHCO3 |
2,6428 2,0947 |
0,025 0,025 |
10,00 |
| ST-рН-2- 11(16) | Calcium hydroxide | Са(OH)2 | 1,75 | saturated at temperature +20°С | 12,43 |
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