Martina:
WineLover gives a very good description. I usually do what he suggests with a few small details.
1. if making wine with a lot of pulp, strain through a coffee filter to get rid of chunks. Strain into a small clear </span>glass
2. use a separate sample that will only be used for strict testing, and thrown away after (DO NOT TASTE THIS SAMPLE AFTER OR DURING TESTING</span>) you never know what your gonna get (imagine forest gump voice)
3. I use gloves often times in wine making because we are using chemicals, and the acid sanitizers really make my hands dry
. (plus I can be more assured they are sanitized)
Ok, onto the good stuff.
Use your titrate tube (with the bubble) and fix it onto the test vial. Be careful not to break the tip off too soon. You get air in there and your test is done.
Once you have that go ahead and turn the vial upside down (so that the part you'll be breaking is at the bottom) When you break it watch for bubbles in the solution. This will happen if you havne't gotten a good seal on the vial. If you don't, the vial will not have 'vacum' to pull juice in and will be useless (start over). If it just clicks, then you are good.
The secret I have found on this is take your time. Put a little in, swish, swish. set it on a flat surface and look to see where it's at (even if it's blue still... I'll explain later):
By filling it slowly you do two things. Give the titrates time to change the solution color and mix in the vial. By setting it down every line you fill it, you find out what point you are above. Inevitably, you will over fill the vial. (except for the rare occasion, unless you use a handle for your testing vial. which I haven't bothered to buy yet)
Keep adding liquid making mental notes what number you are at when the vial is set on a flat surface. Then fill more until the color matches your wine:
whoups, I put a little too much in. But luckily I kept track so I can deduce where it actually changed with relatively good accuracy.
Set it down and look again:
You can see it stops at 18. Since it is lighter than my sample, I could tell it was more around 20 (I just let a little too much in).
So that gives me 20 PPM of fre SO2/titrates. (how I understand it anyway).
hope that helps.
And just to let you all know. I mixed in a lot of sugar into this wine and spilled some (that's what is under the shake machine). normally it is clean except when I'm 'in the lab'.