225 ILCS 470/23
Commodities in liquid form shall be sold only by liquid measure or by weight, and, except as otherwise provided in this Act, commodities not in liquid form shall be sold only by weight, by measure of length or area, or by count. However, liquid commodities may be sold by weight and commodities not in liquid form may be sold by count only if such methods give accurate information as to the quantity of commodity sold.
The provisions of this Section do not apply (1) to commodities sold for immediate consumption upon the premises where sold, (2) to vegetables sold by the head or bunch, (3) to commodities in containers standardized by a law of this State or by Federal law, (4) to commodities in package form when there exists a general consumer usage to express the quantity in some other manner, (5) to concrete aggregates, concrete mixtures and loose solid materials such as earth, soil, gravel, crushed stone and the like, when sold by cubic measure, or (6) to unprocessed vegetable and animal fertilizer sold by cubic measure. The Director may issue such reasonable regulations as are necessary to assure that amounts of commodity sold are determined in accordance with good commercial practice and are so determined and represented as to be accurate and informative to all parties at interest.
225 ILCS 470/23