Figuring out GHB doses from a solution

[Morning Bell]

So if I had a 750 mL water-based solution that was 50% NaGHB in concentration, does that mean I have 375 milliliters of GHB? And how may I use that to figure out how many grams of GHB I have so I can safely dose it? Just trying to be extra careful is all...

[AcidConspiracy]

man you're overthinking this.
http://www.erowid.org/chemicals/ghb/ghb_dose.shtml

assuming 1g/ml concentration you have 375g of GHB, about 40 doses.

if you do not know the ratio for sure, start at ONE mL and work your way up.

[kudosdc]

[quote=AcidConspiracy;4799164]man you're overthinking this.

assuming 1g/ml concentration you have 375g of GHB, about 40 doses.
quote]

His question is not overthinking, and your assumption is confusing and could be dangerous considering the low margin of error when dosing GHB.

How is the concentration of the solution calculated? The standard method used by scientists is w/w (weight of solute/weight of solution) because you don't need to worry about the density of of the solution to know the amount of "stuff" in solution.

A lot of consumer products list concentrations as w/v (weight of solute/volume of solution) or even v/v if it is a mixture of liquids. The problem with w/v is that you can't know exactly what the final volume of a solution will be based on mixing a known weight into a known volume.

With w/w, a 50% solution of GHB in water, you must weigh the solution. Half of the weight will be GHB. In other words, 375g added to 375g of water (or 375 ml of water because it has a known density of 1) is 750g of solution.

Now, what is important to know is that you WILL NOT have 750ml of solution. 50% is a very concentrated solution and most solutions become denser as they become more concentrated. I have no idea what the density of your solution is, but it is certainly more than one, maybe even as high as 1.7. YOU must determine this by weighing solution in grams, and dividing by its volume in ml.

So, if your solution is a standard w/w, you have 750ml if it and your density is x (let's say 1.7 for this example), then your solution will weigh 1275g and it will contain 637.5g of GHB - and you have a bunch of overdoses to deal with.