If a 30% solution means 30 grams CaCl2 per 100 ml of solution, then 30 ml of 30% solution would contain 9 grams of CaCl2.

So how much does 37 gallons of milk weigh in kilograms? Peter Dixon says 1 gallon of cow or goat milk weighs 8.6 pounds. So 37 gallons weighs 318.2 pounds = 144.33 kilograms.

~~9 grams in 144.33 kg of milk is .063% (rounded), so you are under .1%~~

Assuming my math and assumptions (weight of a gallon of milk, meaning of 30% solution) are correct.

EDIT: Nope, my math is wrong. 144.33 kg is 144,330 grams. 9 grams is .0062% of 144330 grams.