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适用范围：<p>Titration techniques using KF reagent are one of the most widely used for the determination of water.</p> <p>Although the volumetric KF titration can determine low levels of water, it is generally accepted that coulometric KF titrations (see Test Method E 1064<astmref rid="a00024">) are more accurate for routine determination of very low levels of water. As a general rule, if samples routinely contain water concentrations of 500 mg/kg or less, the coulometric technique should be considered.</p> <p>Applications can be subdivided into two sections: (<span class="italic">1</span>) organic and inorganic compounds, in which water may be determined directly, and (<span class="italic">2</span>) compounds, in which water cannot be determined directly, but in which interferences may be eliminated by suitable chemical reactions or modifications of the procedure. Further discussion of interferences is included in Section 5 and Appendix X2.</p> <p>Water can be determined directly in the presence of the following types of compounds:<br> <p id="n00001"><table summary="TABLE 1" frame="void" id="n00001" class="rules"> <tr><td align="center" valign="top" colspan="2">Organic Compounds</td></tr> <tr><td align="left" valign="top">Acetals</td><td align="left" valign="top">Ethers</td></tr> <tr><td align="left" valign="top">Acids (Note 1)</td><td align="left" valign="top">Halides</td></tr> <tr><td align="left" valign="top">Acyl halides</td><td align="left" valign="top">Hydrocarbons (saturated and unsaturated)</td></tr> <tr><td align="left" valign="top">Alcohols</td><td align="left" valign="top">Ketones, stable (Note 4)</td></tr> <tr><td align="left" valign="top">Aldehydes, stable (Note 2)</td><td align="left" valign="top">Nitriles</td></tr> <tr><td align="left" valign="top">Amides</td><td align="left" valign="top">Orthoesters</td></tr> <tr><td align="left" valign="top">Amines, weak (Note 3)</td><td align="left" valign="top">Peroxides (hydro, dialkyl)</td></tr> <tr><td align="left" valign="top">Anhydrides</td><td align="left" valign="top">Sulfides</td></tr> <tr><td align="left" valign="top">Disulfides</td><td align="left" valign="top">Thiocyanates</td></tr> <tr><td align="left" valign="top">Esters</td><td align="left" valign="top">Thioesters</td></tr> <tr><td align="center" valign="top" colspan="2">Inorganic Compounds</td></tr> <tr><td align="left" valign="top">Acids (Note 5)</td><td align="left" valign="top">Cupric oxide</td></tr> <tr><td align="left" valign="top">Acid oxides (Note 6)</td><td align="left" valign="top">Desiccants</td></tr> <tr><td align="left" valign="top">Aluminum oxides</td><td align="left" valign="top">Hydrazine sulfate</td></tr> <tr><td align="left" valign="top">Anhydrides</td><td align="left" valign="top">Salts of organic and inorganic acids (Note 6)</td></tr> <tr><td align="left" valign="top">Barium dioxide</td><td align="left" valign="top"></td></tr> <tr><td align="left" valign="top">Calcium carbonate</td><td align="left" valign="top"></td></tr></table></p></p> <p class="desc"> <span class="smallcap">Note</span> 18212;Some acids, such as formic, acetic, and adipic acid, are slowly esterified. For high accuracy with pyridine-based reagents, use 30 to 50 % pyridine in methanol as the solvent. When using pyridine-free reagents, commercially available buffer solutions can be added to the sample prior to titration. With formic acid, it may be necessary to use methanol-free solvents and titrants <span class="bold">(1)</span>. </p> <p class="desc"> <span class="smallcap">Note</span> 28212;Examples of stable aldehydes are formaldehyde, sugars, chloral, etc. Formaldehyde polymers contain water as methylol groups. This combined water is not titrated. Addition of an excess of NaOCH₃ in methanol permits release and titration of this combined water, after approximate neutralization of excess base with acetic acid (see Note 9).</p> <p class="desc"> <span class="smallcap">Note</span> 38212;Weak amines are consid.........