[To the OP: the following is addressed to your specific questions but contains rhetoric I mean to address everyone because lots of people are going to read this as many are doubtlessly in similar positions. I don’t mean to come at you with some of this stuff on a personal level. It’s meant to make people in similar positions ask themselves some of these same questions. There are already news reports about multiple NBOMe hospitalizations in just one city where NBOMes had wider market penetration than average, so the dangers really need to be redundantly stressed.]
If your 25C/distilled water solution is in a sealed vial it won't evaporate. 25C HCl will dissolve in water, but that's what you want. I think what you're worried about is it degrading in water, right? I don't know what the stability of 25C is in water, or if it will degrade within a few months time. I thought I read it was a pretty stable molecule so my
guess is that it'd last for months without degrading. I'm no chemist, but I'd imagine if you're worried about the stability of 25C in water you might just be able to freeze it. Then just take it out of the freezer the night before so it's back to a liquid solution by the time you want to use it (can anybody confirm that this freezing and thawing process is OK for preserving the stability of a chemical like 25I or not?). If you freeze it make sure your vial is large enough so that when the solution freezes the expansion will not crack the vial. Also, you wouldn't want to liquid insufflate isopropyl alcohol so I'd scratch that idea. Jason7's method seems like it would work fine, but that's dry insufflation in a cutting agent after it’s been dried out from solution and you want liquid insufflation, right? Also, you've said you have "no way of measuring" the compound. Why can't you buy a mg scale for under $40, again? I think you're just saying you don't want to bother or you’re (effectively) saying “I’m willing to spend money to get high but not to help ensure I don’t harm others,” right? How do you know whoever you got it from measured those 10 mg correctly without your own independent confirmation?
As far as the math is concerned for liquid insufflation, remember that a dose can't be in a high volume of water because it will overflow your nasal cavity and pour down your throat (and it's not active orally). You really shouldn't use drops either. There are no consistent number of drops in 1 mL. People do use drops, yes, but that doesn’t mean it’s a good idea when more accurate methods are entirely convenient. Think about how drops would work. How are you going to get just the right number of drops in your nose or keep a really reliable count? How will you prevent not accidentally getting more drops than you want, or know that the drops are all the same volume? You really should buy syringes or some other tool for precise volumetric measurement. Not only is it safer, it's just so much easier. I know some people have a psychological block when it comes to buying syringes, but seriously if you don't have the discipline to get past something like this for the sake of responsibility it's an indication that you have no business dealing with ultra-potent chemicals and that you're more of a risk for hurting yourself or your friends (and ending up on the news, too).
You also should have a lot more confidence in your ability to do the relevant math on your own, as it is an absolutely necessary skill for dealing with this stuff. However, because I understand some people reading this are going to think "fuck you psood, you self-righteous prick" (not necessarily you OP, this goes to anybody reading this) and do it anyway out of spite and what they recklessly believe is their personal "right," I'll write it out. (Sorry people, but your going on a violent rampage or attempting to drive because you overdosed due to a basic error and are now psychotic or panicking and can't control yourself implicates OTHER PEOPLE in your decision to use these drugs. Know that doing this stuff without self-confidence and the basic knowledge needed to minimize risk is immoral and reckless. Your decision to use drugs never was just a consequence for you. The "victimless crime" idea behind drug use varies in truth value by context. This isn't me preaching my own gospel because I'm power tripping, it's a simple fact that can't be ignored with drugs like NBOMes where fucking up is extremely easy. This stuff is dangerous even taking the proper precautions, but not possessing the simple tools and acumen I’m describing is a whole different level of risk).
Anyways, if you want 500 ug per dose volume this is what I'd do (redundancies in this example are to make sure the point gets across):
Dissolve 10 mg in 2 mL of distilled water in a vial (a 1cc U-100 insulin syringe = 1 mL, as 1cc=1mL=100 units for a U-100 syringe, so that's 2 full 1 cc U-100 syringes worth of distilled water)
Since 10 mg = 10,000 ug and you have 10 mg in 2 mL of water there's 5 mg per 1mL syringe. 5 mg = 5000 ug, so since there are 100 units on the side of a 1 mL syringe, and 100/10 = 10 ten unit increments, that means every 10 unit increments of NBOMe water solution in one syringe contains 500 ug 25I-NBOMe.
To check the same math a little different way just to further illustrate we can say 2 syringes = 200 total units = 20 ten unit increments in a 1 cc U-100 syringe. Therefore, because 10 mg = 10,000 ug and in our example 10,000 ug is dissolved in 20 ten unit increments of water, 10,000ug/20 ten increment units = 500 ug per 10 unit increment.
If you don't want such a concentrated solution you can just dissolve 10 mg in 4 mL so every 10 unit increment is 250 ug. I'd also recommend shaking the solution in your vial lightly before you draw any up from it into the syringes for dosing.
This is a 1 cc U-100 syringe. There are other types of syringes that DON'T look like this (for example a 1/2 cc U-100 syringe would only have 50 units; there’s also U-40 syringes which have 40 units in 1 cc which changes the numbers above). You can use these other syringes, but for the sake of keeping things simple you should probably use a 1 cc U-100. You can see that there are 100 units on the side of the pictured U-100 syringe. So in our example above there would be 5 mg or 5000 ug of 25C in one of these, or 10 mg in 2 of these. [to be perfectly accurate the volume of the powder itself will make for more than 2 mL of water if 2 mL is added on top of it, but it won't make a huge difference so I wouldn't be too concerned about it]
), that insufflation of the dry freebase produces a much longer come-up phase than insufflation of a salt in solution. I can't remember the exact figures, but I think he said it took him at least 45 minutes to feel it, as opposed to the ~10 minute onset that I've experienced with liquid insufflation -- and he took a very high dose.
