Is purity of SN really all that important?

[Msvr]

I always see people touting absolute requirements for SN purity, specifically minimum 95%+, though often 98%+. But surely that cant really matter?
Case 1: 25g 99% pure SN contains 24.75g active SN and .25g other substance
Case 2: 28g 90% pure SN contains 25.2g active SN and 2.8g other substance

Just take 28g instead of the generally recommended 25g if your SN is a touch weak. An extra couple grams of other substance surely can't matter in the least. Even what if you took 62g of 40% pure SN, for a total of 24.8g active SN and 37.2g other substance. Maybe in this extreme of an example there's an argument for such dillution cause slower absorbtion, but even still... 62g is like 1 bite of food. You'd still absorb the SN pretty readily.

 

[un.exist]

Your math is correct but the biology is different.

You're assuming the impurity is inert. In technical-grade SN, the impurity is often sodium nitrate. At 2.8g, that is a clinically significant dose of sodium nitrate, which could cause delayed methemoglobinemia and it is not peaceful or quick. Even if the impurity is just table salt, 2.8g in 50ml of water is a hypertonic solution.

62g is about 12 teaspoons of powder. A highly concentrated or overly dilute solution = pylorospasm = delayed absorption. Your body will likely metabolise the SN before it enters the bloodstream.

The 95%+ rule is about getting all that active ingredient into your blood within a 5 minute window before your body's detox systems and vomiting reflex can stop it. More grams of impurity work against that window by increasing volume, adding secondary toxins, delaying emtying.