Oakton Conductivity and TDS Standard, 1413 S; 500 mL

This is the real stuff. I had a problem with a bad mix of a 1000ppm "calibration standard" NaCl solution when trying to calibrate my EC meter for home hydroponics. Sent it back and bought this. Comes sealed. Has a temperature/EC grid on the label so with a thermometer on hand, it makes calibrating an EC meter dead on accurate. This is laboratory grade. I'll be sticking with this product for calibrations.

Does the job and arrived quickly.

I used this once to calibrate a water quality sensor we had deployed at a field site. The second time we used the solution, there were black globes of mold growing in it. The standard was wildly off when we attempted to use it (silly to try this) and the solution was within the use date (hadn't expired yet). We stored the solution according to the label and we handled the calibration solution using gloves and on a clean surface. I have used many conductivity solutions and have never had this issue. Maybe it was just a one off, but I will be using a different conductivity solution from here on out. We can't afford to use poor quality calibration solutions to calibrate thousand $$ instruments while in remote places

I just recieved the product for the second time and the expiration date is in September! That is TWO MONTHS!!!! Usually conductivity expiration is for 5 years!!! NOT ACCEPTABLE!!!!

These solutions that were shipped to me have very little date of us since they expire in January 2022, they do not come with an analysis certificate, nor with traceable calibration certificates as the reference materials should come, I am trying to contact the supplier to ask me of an explanation and it has been difficult for me. They reached a level of the liquid close to the label, I doubt that it has the 500 ml