What's nitrite salt?

[Marktheghost]

I looked at the web-site with the name of the river yesterday, for sodium nitrite. The only thing that seemed likely to be it was nitrite salt. It was described as NaNo2 0.6%. Well isn't that 95% less than I actually need? It didn't mention any other ingredients.
Does that web-site sell SN? And if not, where else should I try? (I'm in Scotland, in case that makes any difference.)

 

[Wisdom3_1-9]

From what others have posted, I don't think it's legal to acquire in the UK. I'm in the US and have purchased it off that site before.