was just wonder if you can salt the spice from naphtha?

Yep! Take the naphtha and add water with an acid in it. You could use fumaric acid, or acetic acid in the form of distilled white vinegar, or you could use citric acid solution... whatever salt you want to get, just use the acid form of that in the water.

The naphtha often turns cloudy. If so, this is a great indicator. Keep adding acidic solution until the naphtha layer turns un-cloudy and it should be empty of alkaloids.

This works for most any alkaloid that dissolves in naphtha in the freebase form and water when converted to a salt. For example, you could do this with DXM even though it's a completely different chemical. The steps are basically the same, down to the cloudiness acting as indicator.

Does anyone out there use a technique whereby they do naphtha pulls, and instead of freeze preciping right away and instead of reducing the pulled naphtha, they salt the naphtha with vinegar, then reduce the vinegar till it's all gone, then add only a small amount of naphtha, and then finally freeze precip it? I guess the only reason you'd do this is if you don't want to reduce the naphtha.

Sure; Coschi does it in his tek (can be found as LexTek) or as DMT Handbook. He extracts ala A/B (from some Acacia bark I remember), pulls with naphtha and salts with an acid back to water, then he basifies water and extracts with fresh naphtha.

This is quite clever, especially some time ago when defatting on bark was thought to be very important. By back-salting the alkaloids back to the acidic water one leaves the fats behind in the non-polar. By doing a "second" A/B with this alkaloid-laden water one gets a far cleaner product. This approach is still a good one in too fatty/too chlorophyl sources like chaliponga or chacruna.

Recently, my friend has become a fan of extracting the spice from MHRB with naphtha, then salting the alkaloids into vinegar. This allows him to reuse the naphtha to do another pull. Then when he's got all the alkaloids dissolved into the vinegar, he can add zinc to convert DMT N-oxide into DMT acetate. After filtering out the zinc dust, he can add clean naphtha with no plant oils, neutralize the vinegar with sodium carbonate, bump the pH up to about 13 with some NaOH, and voila! Naphtha with essentially pure spice in it. Freeze precip, and snow white crystals of weirdness appear like magic!

This isn't a great way to extract small amounts of MHRB, like 50g, because it does cause a bit of yield loss. But he's hoping to fix that with some changes to the tek.

what does the zinc do? I thought just adding basified spice with vinegar will result in dmt-acetate. What's with the zinc dust?

If you have DMT N-oxide dissolved in acidic solution and you add zinc powder, it converts the DMT N-oxide to DMT. (Since it's in vinegar, any resulting DMT freebase is immediately converted into DMT acetate just like you would expect.)

Some people don't like DMT N-oxide, such as my best friend. He says it's edgy and gratingly metallic. However, some people like DMT N-oxide just fine, like my other best friend Demetrius. He likes how long it lasts -- hyperspace for 15-20 minutes with a mix of DMT and DMT N-oxide, instead of 3-5 minutes with pure DMT.