You don't need to boil the vinegar.
You probably don't want to use straight vinegar.
The purpose of boiling is to get the liquid to more quickly and more completely dissolve the solids (like salt and sugar) and to more completely absorb the soluble oils from spices, etc.
A fairly strong brine is 1 cup of table salt per gallon of fluid. A fairly weak brine is 1/2 cup of table salt per gallon of water. The ratios remain the same no matter how much you scale up or down the quantities. Stronger brines faster than weaker. It also brines a little more intensely.
Thicker, bigger, denser pieces of meat take longer to brine than smaller. In the case of pork loin, already chopped, you're probably looking at about 30 minutes in a strong brine and a couple of hours in a weak one. You might be able to go overnight in a weak brine... but that's pushing it. Your chops would most likely be oversalted and their juices would be watery.
It's an extremely good idea to add some sweetness to the brine, partly to give it some extra diffusion power, and partly to mask some of the salt. It's also a good idea to use some aromatics -- mostly because it's an extremely efficient way to add both flavor and and flavor complexity. In short, "because it tastes good."
Here's an example of a moderate strength, typical and conservative brine, suitable for pork chops:
3 cups water
3 tbs salt
2 tbs sugar
1 dozen peppercorns
2 bay leaves
1 onion, cut up
1-1/2 cup ice (about)
1/2 cup rice or other very mild vinegar, or 1/4 cup cider vinegar
Add all the ingredients except the ice and vinegar to the water. Bring to the boil. Remove from heat, let cool a few minutes, then add the ice and vinegar. You may use the brine as soon as it's cool.
Add the pork chops to the brine so they are completely covered. Hold in the refrigerator for around an hour.
Remove the chops, drain them, and allow them to air dry on a rack set in a pan in the refrigerator for another hour.
Remove from the refrigerator. When the chops are dry, they will likely feel tacky, or may feel a bit dry and gritty. Either is normal and desirable. Don't clean or rinse the surface. Instead, season as desired (but NO MORE salt).
Cook as desired.
As a variation, omit the sugar, add four 1/2" thick pieces of fresh ginger to the brine before boiling, and add half a can of peach nectar and 1/4 cup of maple syrup when the brine comes off the boil. The maple/peach/onion combination goes extremely well with pork -- but... I want to give you the idea of how to experiment so you can improvise your own brines without straying too far from the basic rules.
Instead of vinegar you may want to add something like orange juice or lemonade or even a fruity liqueur like triple sec (you may even want to throw a margarita in there). Pork loves fruit, don't be afraid to play. Pork does not love vinegar. It's a meat, not a cucumber.
Brines can be a little tough to improvise, because when you stick your finger in and lick it a brine should taste BAD. Too salty, too intense, and too watery -- all at the same time. It takes a little experience to use taste as a guide, rather than someone else's recipe. While taste testing is your goal, for the first couple of times try and color within the lines.
Brining will give you a little extra leeway in how well you can cook your pork. That is, brined meat won't dry out and toughen as quickly as meat which hasn't been brined. Still, "modern" pork is extremely lean and dries out quickly. I strongly recommend not cooking it past a 165F internal temperature. There's no longer any health reason to cook pork well done. Trichina are a pest of the past, but some diners (pests of the present?) insist on well done. While a still slightly pink 145F will taste a lot better, the best practice is to please your dinner companion(s). My wife grew up on well done pork, but has learned to enjoy a compromise 155F.
Hope this helps,
Edited by boar_d_laze - 1/20/12 at 8:08am