| Chizpurfle
Join Date: Mar 2006 Location: underwater
Posts: 10,319
 x9
|  Stuck inside with Sirius | *Splish-Splash* | bamBAM | ☁ Spooktacular ☁
Noble rotated the blackboard, ready to start summarising their answers to his question, when he heard the definite sound of a test tube smashing on the floor. It didn’t take long to spy Cole’s confusion, and Noble was already unholstering his wand as he headed towards the Gryffindor’s desk. Did he believe it didn’t hurt? Not at all. And even if it wasn’t, it wasn’t worth the risk of not treating it appropriately. Burns weren’t to be trifled with, as evidenced by the scars on Noble’s arm. “Hand under the cold tap. Now.” Noble’s tone was serious, as he cleared the mess of the test tube and its contents from the floor with a couple of flicks of his wand. “This is why we use tongs when heating test tubes in the flame. Your hand should have been nowhere near the heat.” Either the burner or the glass. “Keep running your hand under the water for at least five minutes.”
That sorted, Noble returned to the front of class to continue. “A definite pro,” Noble nodded at Claudine. “Sometimes an indicator potion might need a short time to react, just like the Benedict’s solution needs heating, but on the whole, they’re designed to be instant.”
It seemed like Kaiser was finally getting back on track, and though his brewing was still somewhat lagging behind the rest of class, his answer was a good one. “Correct. Whilst some tests can be used in tandem, that is, performed on the same sample at the same time, most need to be performed independently. If you don’t have much of what you’re testing, you need to carefully consider which tests to run so as not to waste precious material. A good answer.”
Not such a good answer? Cole’s. And no, Noble didn’t excuse him from having burnt fingers. “Doubtful,” Noble replied. “By themselves, these solutions won’t generally diagnose an ailment quickly.” He would have explained, but someone beat him to it: Lucas. Noble’s lip curled upwards. He didn’t know what Lucas had had for breakfast that morning, but Noble was impressed. “And that is exactly why. Indicators help us identify features of the potion, rather than the potion itself. Conducting different tests…and using our senses like sight and smell like we spoke about earlier…they can all build up evidence to help us deduce what the potion is. Whilst, of course, staying cautious of how many tests we’re doing, as Kaiser said.” Noble twiddled the chalk between his fingers. “A well-reasoned answer, Lucas.”
Gunnar responded next, and Noble tilted his head at the Slytherin Prefect. “Diabetes is what you’re thinking of, I assume?” It was probably the most well-known disease related to the regulation of sugar levels. “It’s a valid suggestion, though not particularly useful for any fine scale regulation. As I’m sure you’ve all probably noticed by now…Benedict’s solution changes from blue to yellow, orange and then red, depending on the concentration of glucose. It’s somewhat hard to quantify when orange is orange versus dark yellow or orangey red though… You’d want more accuracy for a medical condition.”
And last but not least, Cecilia answered. And Noble got the sense that the young Gryffindor had been very inspired by forensics and case-solving. Fact was though, she was right. “Yes, these sorts of tests, because they’re so easy to do and don’t need much in the way of equipment, are very portable for use in the field.”
***
“As I hope you’ve all seen by now, Litmus solution turns red in the presence of acids, and blue in the presence of alkalis. In neutral liquids, such as tap water, it’s green. And following on from Cecelia’s point, Litmus can also come in the form of testing papers, that you just dip into your sample….so very easy to carry.” And he’d already covered the outcomes from the Benedict’s solution, so it was time to move on to the next experiment.
“I already mentioned that these are mundane indicators…so next we’ll move on to a magical one. The Kuznetsov indicator tests for basic toxins, turning from lime green to bright pink in the presence of toxins.” He moved to pick up the last remaining brown bottle on his desk. “By adding a known concentration of antidote to a sample of toxin and indicator one drop at a time, we can test how strong much antidote is required to neutralise the toxin. Simply put: the more antidote that is needed to change the colour, the stronger the toxin.” Which was the part they were doing today. Next lesson, they’d be doing the calculations to work out the exact concentration.
“First of all, we’re going to show that the Kuznetsov indicator is indeed an indicator for toxins.” He reached for some berries on his desk. “These are baneberries, which you should know from herbology are poisonous. Mash them up with some water with your pestle and mortar, and use a pipette to transfer some of the liquid to a vial.” He demonstrated, mashing the berries before extracting a sample of the juice into a test tube. “If I now add three drops of Kuznetsov indicator and swirl it, the solution turns bright pink due to the baneberry toxin.” Again, he showed them as he spoke. “Then add 50 ml of general purpose antidote.” He carefully opened a clear bottle with a silvery looking solution inside, and used a clean pipette to add some to the test tube. “The solution then returns to lime green.”
“Once you have seen the colour changes for yourself, retrieve a conical flask, burette and stand from the side bench.” The burette being the glass tube marked similarly to a ruler with a tap at one end.
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