All liquid chemicals have different refractive indices, so such a device will, in theory, work. However, the rub is in the details. When I was a boyscout we would estimate the height of trees by moving to a point where, when we pointed at the top of the tree our arms were at an estimated 45 degree angle to the ground. We then paced off the distance to the tree to get the height.
In theory, 100% accurate. In practice a given tree could be estimated at 30 to 60 feet tall, depending on who did the estimate.
With $1000 worth of surveying tools I'm sure we could have gotten to within an inch of the actual height. With just a Mark 1 Mod 0 eyeball and a pair of Mark 1 Mod 0 legs, not so close.
I'm sure that with a multi-$1000 lab refractometer a pretty accurate measurement can be made. With a $5 instrument, not so much.