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--- chemical:hf [2013/05/21 20:25] – mcmaster
+++ chemical:hf [2025/08/04 21:23] (current) – external edit 127.0.0.1
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+Although strictly speaking "HF" is the gas form (hydrogen fluoride), typically when people say "HF" they really mean HF(aq), that is hydrofluoric acid.
 ====== Applications ======
 Dissolves SiO2.
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-===== Lab notes =====
+====== Lab notes ======
 Sometime before 05/21/2013 I have tried two distillations.  One using a HDPE wash bottle and the other using a Polypropylene volumetric flask.  The first was simply too fragile and collapsed too easily.  The second was working but I got too aggressive with the vacuum/pressure and the flask eventually collapsed.  I had it around maybe 80C which jives with [Ultrapurification HF, 1 per Coppola/Hughes] which suggests 70-85C (under 1 atm?).  Although PP doesn't melt until 115C or so it does soften a little before then which must have been enough with the vacuum.
+====== Isothermal distillation ======
+[Ultrapurification HF] describes a simple technique to basically force HF(gas) from HF(aq) at room temperature.  They say to basically put one beaker with 35 M HF and then place a second beaker with equal volume distilled water.  After two days the second beaker should have 12 M acid.  If the acid in the first beaker is replenished it should get the second beaker to 25M after another 2 days.
+I've concentrated HCl(aq) by adding NaCl to weak mixture to force out HCl(gas) and I imagine that I could do similar using NaF.  I have a couple of PP flasks and PFA tubing would should be good for experimenting.
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   * The Ultrapurification of Hydrofluoric Acid (Ultrapurification HF).  W. KWESTROO, J. VISSER.
+  * Polyethylene Still for Preparation of Pure Hydrofluoric Acid.  P. P. Coppola , R. C. Hughes.
   * Sulfuric acid extractive distillation process for the recovery of anhydrous hydrofluoric acid from by-product aqueous hydrofluoric acid: Preliminary process design and economic study (Extractive distillation): http://www.amazon.com/Sulfuric-extractive-distillation-anhydrous-hydrofluoric/dp/B0007HL7VW
   * US Patent 4936955: http://www.google.com/patents/US4936955
   * http://www.finemech.com/Merchant2/merchant.mvc?Screen=PROD&Product_Code=A155-36&Category_Code=f516&Product_Count=5
     * Makes standard taper fluoropolymer "glassware"
+  * Good safety info: http://www.prevor.com/EN/sante/RisqueChimique/hexafluorine/fluorure.php
+  * A NaF/H2SO4 experiment: http://woelen.homescience.net/science/chem/exps/KMnO4+NaF+H2SO4/index.html
+    * Says it must be heated