[billnotgatez]

What would be the best method of preparing hydrochloric acid in the home laboratory? For the sake of argument exclude going out and buying it.

Also, for the sake of argument exclude using sulfuric acid.

[jdurg]

What would be the best method of preparing hydrochloric acid in the home laboratory? For the sake of argument exclude going out and buying it.

Also, for the sake of argument exclude using sulfuric acid.

Take some anhydrous NaCl and throw a few drops of pure phosphoric acid on there.  The vapors that come off of the salt are HCl.  Bubble that into some distilled water and you have HCl.

[woelen]

I tried it. It works, but it requires some heating. With cold H3PO4 the reaction is very slow.

Btw, this also works for KBr, making HBr, without bromine contamination and that is a good thing. In that way you can also make hydrobromic acid. I also tried with KI, but that yields impure HI. Although the reaction is not as dirty and messy as with H2SO4, it still is not 100% clean. The liquid becomes light brown/yellow and the HI apparently contains traces of iodine. If collected in water, the liquid becomes light brown. I suspect, that atmospheric oxygen is the cause of this trouble.

[billnotgatez]

Phosphoric acid
http://scifun.chem.wisc.edu/chemweek/H3PO4/H3PO4.html
http://en.wikipedia.org/wiki/H3PO4#Processed_food_use
http://en.wikipedia.org/wiki/Phosphoric_acids_and_Phosphates

Phosphoric acid and sodium chloride seems to be a good way to do create hydrochloric acid in the home laboratory. Do we get good purity this way?

[woelen]

Purity of the product will be quite good. You first, however, have to remove water from the phosphoric acid. Usually, it can be purchased at 85% concentration. It first has to be heated and boiled, until boiling stops and then the salt can be added. This gives good purity HCl. I have done this reaction myself, just to see how it works. I, however, do not need it for real production of HCl, because I can simply buy concentrated hydrochloric acid.

For making pure KBr, phosphoric acid is the ONLY acceptable alternative. With H2SO4 you get too much impurities (Br2 + SO2).

[jdurg]

Purity of the product will be quite good. You first, however, have to remove water from the phosphoric acid. Usually, it can be purchased at 85% concentration. It first has to be heated and boiled, until boiling stops and then the salt can be added. This gives good purity HCl. I have done this reaction myself, just to see how it works. I, however, do not need it for real production of HCl, because I can simply buy concentrated hydrochloric acid.

For making pure KBr, phosphoric acid is the ONLY acceptable alternative. With H2SO4 you get too much impurities (Br2 + SO2).

Pure phosphoric acid is also the only way you can make Hydroioidic Acid.  All other acids, when added to an iodide salt, would oxidize the iodide ion to iodine and you'd get a mess of iodine, some HI, and various other salts.  If you use pure phosphoric acid and add that to KI, you can distill off the HI and condense any latent iodine vapor.  (Pass the fumes through some glass tubing that is cooled down and any traces of I2 left will condense into iodine crystals and your pure HI gas will move through).