Expert: George Maxwell - 7/31/2007

Question
I need to determine the most optimal method of lowering the freezing point of water for a consumer product our company is developing.  The product is a cool bottle with water, dye, and small particles of metal.  When shaken it looks like a cool iridescent swirling liquid.  

We've tried salt, but it makes the liquid too cloudy.  We're concerned about other substances as we need to careful if kids open them up.  I've looked up alternatives on the net (ammonium sulfate, calcium chloride, calcium magnesium acetate, magnesium chloride, potassium chloride, and sodium chloride).

Any recommendations of what would be low cost, non-toxic, and easy?  We're doing this to prevent freezing when shipping.  

Thanks -- JIm

Answer
Thank you for your question.

Any soluble salt will lower the freezing point, but (having done a quick experiment in my freezer!) I would suggest you looked at using baking soda (sodium bicarbonate) - non-toxic, cheap and it works. The only time that this would be a problem is if your product was acidic, in which case the bicarb would react with it. If all else fails, try the normal salt again, but only use a small amount: you can depress the freezing point with suprisingly little material, without clouding the solution.
Hope this helps, let me know if there's anything else I can help with. Many thanks, and best of luck with the new product.