* What was being tested? What was the experiment's goal?
* What were the contents of 1T? What substance or treatment did it contain?
* What were the contents of other test tubes? How did 1T differ from the others?
Test tube 1T might have served as a:
* Control group: A baseline for comparison. If all other test tubes received a treatment, 1T might have contained a placebo or untreated substance to show the effect of the treatment.
* Positive control: A test tube with a known positive result to ensure the experiment is working correctly. If the experiment should produce a specific outcome, 1T might contain a substance guaranteed to produce that outcome.
* Negative control: A test tube that shouldn't show a reaction to confirm the validity of the results. 1T might have contained a substance that shouldn't react to the treatment being tested.
* Calibration standard: A test tube with a known concentration or amount of a substance to calibrate the measurements taken in other test tubes.
* Duplicate or replicate: A repeat test to ensure the accuracy and reproducibility of the results.
Provide more details about the experiment, and I can give you a more specific answer.