Great story @panini
There is an International Standard for basic ingredients like Salt called the Codex Alimentarius (aka Food chemical codex). Almost every government refer to this standard for their regulations.
The following will brings you to a pdf: http://www.codexalimentarius.org/input/download/standards/3/CXS_150e.pdf
For those that don't want to download a file from an unknown source: use word search: "Salt specification and standard"
excerpts are below:
Food grade salt is a crystalline product consisting predominantly of sodium chloride. It is obtained from the sea, from underground rock salt deposits or from natural brine.
3.1 MINIMUM NACL CONTENT
The content of NaCl shall not be less than 97% on a dry matter basis, exclusive of additives.
3.2 NATURALLY PRESENT SECONDARY PRODUCTS AND CONTAMINANTS
The remainder comprises natural secondary products, which are present in varying amounts depending on the origin and the
method of production of the salt, and which are composed mainly of calcium, potassium, magnesium and sodium sulphates,
carbonates, bromides, and of calcium, potassium, magnesium chlorides as well. Natural contaminants may also be present in
amounts varying with the origin and the method of production of the salt. Copper shall not exceed 2 mg/kg (expressed as Cu).
For the fortification of food grade salt with iodine, use can be made of sodium and potassium iodides or iodates.
3.4.2Maximum and minimum levels
The maximum and minimum levels used for the iodisation of food grade salt are to be calculated as iodine (expressed as
mg/kg) and shall be established by the national health authorities in the light of the local iodine deficiency situation.
7.1 THE NAME OF THE PRODUCT
7.1.1 The name of the product, as declared on the label shall be "salt".
7.1.2 The name "salt" shall have in its close proximity a declaration of either "Food Grade" or "Cooking Salt" or "Table Salt".
7.1.3 Only when salt contains one or more ferrocyanide salts, added to the brine during the crystallization step, the term
"dendritic" could be included accompanying the name.
7.1.4 Where salt is used as a carrier for one or more nutrients, and sold as such for public health reasons, the name of the
product shall be declared properly on the label, for example "salt fluoridated", "salt iodated", "salt iodized", "salt fortified with
iron", "salt fortified with vitamins" and so on, as appropriate.
7.1.5 An indication of either the origin, according to the description on Section 2, or the method of production may be declared
on the label, provided such indication does not mislead or deceive the consumer.