49 CFR 172 Special Provision 39 (Numeric Codes)

These provisions are multi-modal and apply to bulk and non-bulk packagings.

Code	39
Description	This substance may be carried under provisions other than those of Class 1 only if it is so packed that the percentage of water will not fall below that stated at any time during transport. When phlegmatized with water and inorganic inert material, the content of urea nitrate must not exceed 75 percent by mass and the mixture should not be capable of being detonated by test 1(a)(i) or test 1(a)(ii) in the UN Manual of Tests and Criteria (IBR, see §171.7 of this subchapter).
HazMat with this Code	UN 1357 - Urea nitrate, wetted with not less than 20 percent water, by mass