Milton website says:
"Q: What is Milton Fluid?
The Milton Sterilising Fluid is a 2% aqueous solution of sodium hypochlorite that contains 16.5% salt."
I say (and so does Wikipedia):
"Sodium hypochlorite is a chemical compound with the formula NaOCl. Sodium hypochlorite solution, commonly known as bleach or clorox, is frequently used as a disinfectant or a bleaching agent." and "Sodium hypochlorite has been used for the disinfection of drinking water. A concentration equivalent to about 1 liter of household bleach per 4000 liters of water is used"
Household bleach is, in general, a solution containing 4-6% sodium hypochlorite and 0.01-0.05% sodium hydroxide; the sodium hydroxide is used to delay the breakdown of sodium hypochlorite into sodium chloride and sodium chlorate
So, Milton contains bleach, and salt (NaCl) for some reason, and presumably added water to dilute it so that it is not as strong as ordinary undiluted household bleach.
Milton says
"Q: Is Milton the same thing as bleach?
No. Bleach is an irritant and can burn the skin and corrode materials. Swallowing bleach can seriously harm human health and absolutely cannot be used to sterilise baby?s bottles or accessories.
Milton is non-corrosive and doesn?t cause irritation. It does not burn the skin, and can be used as an antiseptic in certain dilutions.
The Milton Method can also be used to treat water to make it safe to drink."
However they do not say in what way it is different, except that it also contains salt and is apparently diluted with more water.
Tell me if I'm wrong.
If it is deionised, which ions are removed? It obviously isn't just deionised water.