Does anyone know where one can get curing salt with sodium nitrate? I am able to find the instacure 1 (only salt and sodium nitrite), but not the 2 (same as 1, but with with sodium nitrate), but I want to air-dry a few salamis for a longer period

1) Ask your local butcher. Always good to know the local towns folk.

2) Get it from Austria https://www.kotanyi.com/at/de/produkt/poekelsalz/

3) Get Natriumnitrat from your local drugstore (Drogerie). If they object because you could also use it to make black powder ask them to mix it with regular salt. But if you an adult, do not buy kg of it and have a reasonable explanation for its use it should be no problem.

Thanks, but poekelsalz is sodium nitrite and salt only. This is what my local butcher has and I have it, but not the one with nitrate which is needed to longer drying

Do not read just the label also read the content list as well.
The linked one is with sodium nitrate not sodium nitrite. Exactly as you asked.

Yes, but I suspect it's a typo on the site. Having a mix of salt and nitrate only doesn't make sense and I haven't seen this anywhere. It's usually a higher concentration of nitrite to act immediately and a smaller concentration of nitrate which breaks down into nitrite over a longer period. Anyways, thanks!

Might be. But than it would be a typo everywhere. On the site as well as on the package. And if some one uses it for salami they would be a bit stiffled if it is not the right thing.

By law sodium nitrite can be added up to 150 mg/kg to sausages (at production time)

Sodium nitrate can be used up to 250 mg/kg (at production) in Salami and such. 150 mg/kg otherwise https://www.admin.ch/opc/de/official.../2007/2977.pdf

Someone a chemist which can tell me how I can determine if it contains nitrate or nitrite?

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You will be consuming only nitrite as the nitrate breaks into nitrite

The "unknown" content of my Kotanyi Pökel-Salz package, silly

Found a way. Sodium chloride and sodium nitrate are both pH neutral in water. Sodium chloride is not a buffer. Sodium nitrite is alkalin.

Just have to mix a bit in water, hope that the colorant is also neutral and measure the pH level. Just did and I got a nice and clean 7.
Maybe I missed something but it looks like it is indeed sodium nitrate + salt..