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Mar 29, 2013 08:19 AM

Is there more than steam in steam?

I have always assumed that if I am steaming, say carrots, I can get away with using my municipal tap water, with its poisons countered by its chlorine (yuchh) because all that touches the carrrots is the pure steam, and the impurities stay below. As in steam distillation. However, if I'm cooking the carrots IN the water, I will use purified water. But now I read in "The Essence of Cookery" by Rumohr (1822) of the glories of steaming with stock, which suggests a) a kind of cooking I had never known and b) that the impurities and the chlorine are indeed getting to my steamed carrots. May I please have some comment about (a) and (b)? Thanks.

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  1. The chlorine disinfects - that is it kills bacteria that can make you sick. Most other contaminants are handled by filtration. Do you know how your 'purified water' is purified?
    says the chlorine continues to protect the water as it travels to your tap.

    14 Replies
    1. re: paulj

      Chlorine dissolved in water is in the form of chlorine ions. When you dissolve table salt in water you also add chlorine ions - along with an equal number of sodium ions. But sodium by itself is a rather nasty metal - it can burn and even explode in contact with water! So how can table salt be such an innocuous substance?

      1. re: paulj

        The same way an explosive such as Hydrogen and an oxidizer such as pure oxygen can combine to form the inert water.

        The NaCl salt bond is ionic and the salt does indeed dissociate to Na+ and Cl- ions when dissolved in water.

        1. re: travelerjjm

          Molecular ionic bonds are not "water soluble". Were that the case, our oceans would be a toxic wasteland.
          Further, the common water molecule, (not heavy water), requires considerable energy to be divided into its constituent atoms. This also is a good thing, or else our seas would have incinerated into non-life supporting silicon and ferrous compounds eons ago.

          1. re: Veggo

            True that the bonds are not "water soluble" (never said they were, btw). Salts dissociate in water due to a process called solvation. In this case sodium chloride dissociates into sodium and chlorine ions.

            Here's a great video of what happens

            1. re: travelerjjm

              But the free ions find each other and hook up again. It's like re-marrying your ex-wife. This is what keeps our oceans salty and without having to pay alimony or child support for dependent ions.

              1. re: Veggo

                Not true, Veggo. They lead perfectly happy separate lives, surrounded by younger, sexier water molecules. More Hugh Hefner than Taylor/Burton. If they did hook back up, they would precipitate out of solution and THEN our oceans would no longer be salty.

                1. re: Wahooty

                  But salt requires at a minimum a "civil union" between an acid and a base. No pre-nup required.

                  1. re: Veggo

                    Not necessarily...sometimes, as noted above, metallic sodium meets elemental wild reaction've got a bouncing baby salt on your hands.

                    I'm starting to feel like this conversation should require a permission slip. :)

                    1. re: Wahooty

                      I will concede that salt babies can be conceived outside of molecular wedlock. I wanted to protect the innocence of random atomic motions from an association of promiscuity under Heisenberg's leering microscope. It's not as though they go hang out at ionic singles' bars.

                  2. re: Wahooty

                    salt precipitation happens all the time - if the solution becomes sufficiently concentrated. All of our salt is produced by precipitation from sea water, whether in modern salt ponds, or ancient salt flats.

                    1. re: paulj

                      Yes, but my point was that it does not happen at random. Our oceans are not saturated solutions, and they do not contain NaCl molecules - they contain dissociated ions. In the circumstances to which you are referring, salt precipitates as a result of the evaporation of water. You remove the water...yes, the ions will reconnect with their long-lost loves.

                      And as much as I have enjoyed this little exchange of chemical innuendo, I'm not sure we're really helping the OP at this point. ;)

                      1. re: Wahooty

                        We are definitely getting further and further, but I think your explanations have been good about salt being dissociated in water. The way I like to think of it is that the polarity of water molecule (dipole moment) interacts with Na+ and Cl- to lower the total energy of the system. Yes, it takes energy to break that initial ionic bond of Na-Cl, but the energy gain (for the entire system) from water solvating the two ions (Na+ and Cl-) more than make up for initial energy requirement.


                        1. re: Chemicalkinetics

                          Also keep in mind that salt does not form molecules (in the usual organic sense) but crystals - a great many Na and Cl atoms arranged in a regular cubic arrangement.

                          In such a crystal, each Cl ion is surrounded by 6 Na ions, and each Na paired with 2 Cl (the Na are on the 'edges').

                          The OP was worried about chlorine in her steaming water. Here's EPA page on the use of chlorine to disinfect drinking water

          2. re: paulj

            Chlorinated water contains chloride ions as well as hypochlorite ions. It's the latter that kills wee beasties - bleach contains sodium hypochlorite. But it also contains molecular Cl2, which is volatile and will reach food that is steaming, albeit in rather small amounts. Basically, if you can smell it (either in water or in stock), it'll be in the steam when it's being heated.

            I'm not sure what the OP thinks is in his tap water, but if it's volatile, it'll be in the steam. Nonvolatile things such as heavy metal ions won't be.

        2. Chlorine has a lower boiling point than water -- it is a gas, remember. So when you heat the water, the first thing that happens is chlorine gas is released. This is why some people complain about chlorine in the shower and why you can smell it at the pool. Other impurities such as minerals and liquids with a lower boiling point will stay below for the most part.

          When you cook soup you smell the flavors before the liquid boils, right? Those odors are being released by the heat. If you steam food, the chemical compounds (some are actually called "aromatics" if I recall my college chemistry correctly) that make those odors are released and can attach to and be absorbed by the food you are steaming. I generally put celery stalks, carrot peelings and sometimes onion skins and cores in my steaming water.

          1. Might want to give your tap water a thorough boil before steaming with it -- or even let it sit out for a day or two. This (letting it sit for a few days) is what people who have fish and turtle ponds and tanks do when they need to add lots of water at once since the chlorine content of most municipal water is enough to kill smaller water animals. Most of the chlorine in a gallon of water in a wide open container will have evaporated in about 36 hrs. If you do the letting it sit method, best to use a glass vessel, because some of the metal or solvents from a steel or plastic one will have leeched into the water by then (enough that you can taste it). Don't want to trade one toxin for another.

            1. I add ginger and/or citrus when steaming vegetables. It gives them a nice hint of flavoring.

              1. In Chinese cooking, aromatics like ginger and lemon are placed on top of (or within) the food being steamed, not in the water below.