A re-post from @Stillnotsure, since it got a bit buried and it seems to again be relevant to the discussion:
"Ok, here's what I found....
1mL of 99.0-99.9 % 1,4 butanediol is equal to 1 gram of GHB the recreational drug. This is helpful because we can compare the effects of the 1,4 Butanediol to GHB. 1-2 grams of GHB is the standard dose users take for the euphoric and sedative effects. To overdose and cause death gets a bit trickier because of our individual bodies ability to break down the GHB. The same chemicals in our stomachs and blood (liver) that break down alcohol, also break down GHB.
The caveat! Many sites I found say it takes 5-10 grams of GHB to overdose, and any dose over 10 grams can be fatal. Since 1,4 butanediol has a few steps to take in the body to become GHB, it could take more than 5-10 mL to overdose or die!
The fix. Since 1,4 butanediol is broken down in the body by the same chemicals and enzymes that break down alcohol, mixing your 1,4 butanediol with alcohol has a drastically increased fatality rate because the body doesn't have enough chemicals and enzymes to break both down. In theory, you should need less 1,4 butanediol by pairing it with alcohol, but should stick to the highest purity rate available and at least 10 mL to be safe.
Now the mega downside. 1,4 butanediol is chemical and very bitter tasting. Those traits alone make a person nauseous and can cause vomiting. Real GHB tastes salty because it is a different chemical chain mixed with a salt chain. It's easier to drink real GHB. If you are going to use either to CTB you should mix it with alcohol. The best way to overcome the nausea and vomiting that are caused by GHB or 1,4 butanediol is by taking the full fatal dose of either quickly in one big swallow, not over time. That way you should fall asleep before your body has time to become nauseous.
To overcome the bodies natural response to the bitter chemical taste of 1,4 butanediol, you may have to consider the antiemetic regimen prescribed by A for Overdose on B."