Has anyone dealt with bacteriostatic water sourcing guide?

One concrete data point for the thread. Red flags, in rough order of how much they should worry you: no verifiable address, no batch numbers, prices far under market, vendor-commissioned tests only, pressure toward irreversible payment, and shipping with no temperature control.

Following on from NurseAsh_DET — and this may be the naive question:

How much material I am losing to dead space, and whether that explains why a 10mg vial gives me nine usable draws rather than ten?

dan_philly said:

Red flags, in rough order of how much they should worry you: no verifiable address, no batch numbers, prices far under market, vendor-commissioned…

Adding the part of the answer the thread has not reached. The pattern that distinguishes a bad batch from an exit is behaviour rather than product. A bad batch comes with communication, a reshipment offer and a batch number. An exit comes with slower replies, pressure toward less reversible payment methods, sudden discounting, and the same reassurance repeated without any new information. The product tells you less than the correspondence does.

Closing the loop on my own question.

My error was treating units as a mass. Once I wrote mg/ml on the vial in marker and worked in millilitres first, the two of us got the same answer.

LibrarianMeg said:

The pattern that distinguishes a bad batch from an exit is behaviour rather than product.

LibrarianMeg has the substance of this right. The condition it depends on is worth stating. The arithmetic is right and one caveat matters: a U-40 syringe changes the markings, not the volumes. If someone hands you U-40 and you read it as U-100 you will be 2.5 times out, and that error has a direction — it is always an overdose.