"Stated another way, The number of innocent rattlers dying of alcohol poisoning from bitting (sic) drunks trying to pick them up."
Taken more seriously, and in agreement with Reptilist, I would venture to guess the answer is "None." I'll explain why. Most Viper bites, including rattlers, cottonmouths and copperheads, are what is called "subcutaneous" - just into the skin. The categories normally used in description of types of bites are:
LD50 - intramuscular
LD50 - intraperitoneal
LD50 - intravenous
LD50 - subcutaneous
The term LD-50 refers to the amount of venom it takes to kill 50 mice weighing 20 grams each injected in various portions of the body. In order to get sufficient alcohol to kill a snake, the snake would have to connect with a vein or artery, both of which are usually considerably below the subcutaneous threshold.
Also, remember, when a viper injects venom, it utilizes a very strong group of muscles to force the venom into the bite site. It does not empty its venom, keep the fangs in place, and then allow venous or arterial fluids to flow back up to the venom glands through the fangs. There is no connection between the fangs and the digestive system of a snake therefore, Rep's answer stands - "None."
OK?