Is Chlorine Heavier Than Water?

Have you ever wondered comparing water and chlorine and trying to find out which one is heavier. Well, the answer to this is certainly Chlorine. If we were to get scientific and technical about it, Chlorine is about 1.5 times heavier than water. That means it packs more mass than water per unit volume and is doomed to sink

Does Chlorine Sink or Float In the Water?

If one does a small experiment, it is noticed that chlorine being the heavier one in comparison to water, sinks to the bottom. Especially if one doesn’t slowly pour it into the return jet stream or brush the bottom after adding it into water. As it is a known fact that this amber-colored liquid is more dense than water, there is no question of the case being otherwise.

Moreover gaseous chlorine which is greenish-yellow is about 2.5 times heavier than the air, so it sinks in air too.

Science Behind Flotation- Why Does Chlorine Float or Sink?

And this brings us to the science of flotation. Believe it or not, there is not one but multiple facets that affect a chemical’s, like chlorine’s ability to lie on the surface of the universal solvent (water), or to sink, or even to dissolve into it entirely.

Once chlorine gets dissolved, it doesn’t come out of the mixture itself. Chlorine has a low solubility in water which at temperatures above room temperature has a negative coefficient. At low temperatures it forms insoluble hydrates with water. Here are a few factors responsible:


The single most important factor that’s considered essential to the conversation of why chlorine sinks in water instead of floating has to do with what we’ve mentioned before: density. Density, in simple terms, is how tightly or otherwise an object is packed.

For example, a styrofoam cup has a lower density as compared to a ceramic cup, which will inevitably increase its chances of floating on top of the universal solvent, whereas a ceramic cup, which is heavier and more tightly packed, will just sink to the bottom with no assistance. Similarly, chlorine, which has a density of 3.214 g/l will drop in water and sink to the bottom because of it’s sheer mass per unit volume.


If chlorine simply dissolves into water, this whole discussion of whether it will float or sink becomes really fruitless, doesn’t it? But it doesn’t, at least completely. Chlorine itself is very mildly soluble in water, which is to say that it does not bond physically with the H2O molecules easily. Solubility also has a lot to do with the surface are to volume ratio.

When introduced as a gas during any part of the water treatment process in pools and such, it reacts with the available water at room temperature, it produces a low level of HOCl, aka hypochlorous acid and hypochlorite ions. This process is enhanced by sunlight.

In layman terms, we call the product that results from dissolving water in chlorine “chlorine water”. Some amounts of hydrochloric acid will form as well. And since neither the solubility or the acid production are colored processes, there are no visible changes to the water that gaseous chlorine is added into.

Uses of Chlorine in Water

It isn’t a hidden fact that chlorine gas itself is very poisonous but chlorine could be used to treat drinking water as well as swimming pool water. It can prove to be extremely beneficial in terms of disinfecting water by adding one part of chlorine solution to 100 parts of water being treated.

How does disinfection works? The hypochlorite ions formed – discussed above – are the main compounds responsible for the disinfection in chlorinated water. In a low pH water environment though, the hypochlorous acid will dominate and be  much more effective at disinfecting the water, assuming that is what the purpose of the chlorination is in that case.

The combination of the ions and acid make up what is called “free chlorine”, which is more effective as a disinfectant than most other types of chlorine out there. Some of the important uses are discussed in detail below.

Disinfecting Swimming Pools

Many people love to swim but since there are millions of bacteria present there has to be a disinfectant which protects the individuals who come in contact with the swimming pool from getting sick. Every individual prefers to swim in a clean pool rather than a dirty one. Chlorine has proved to be a revolutionary addition to pool hygiene regimen and continues to be the staple of the industry.

The most common pool system in use till date is the saltwater pool system which also uses salt to generate free chlorine which in turn works in a similar manner.


Apart from that, chlorination is used for ozonation. When it comes to drinking water it destroys the disease causing germs and makes the water safe for us to drink. In this process chlorine compounds such as sodium hypochlorite are added to the water in order to kill bacteria, and prevent the spread of waterborne diseases.

To Clean Water Supply Reservoirs

Not only this but it also helps eliminate slime bacteria which grow in storage tanks as well as water supply reservoirs. Looking after these reservoirs and storage tanks is extremely important if one tends to avoid the extra costs incurred for maintenance. The elimination of the risk of diseases remains the main concern here too.

The typical amount of chlorine gas required for water treatment is 1-16 mg/L of water.

Household Disinfectants

Another important use of chlorine is that it can be used to manufacture chlorine beach which is used in households. It whitens as well as disinfects clothes, kitchens and bathroom surfaces. Water solutions along with diluted bleach are extremely effective when it comes to cleaning germs which could be found on the household surfaces and can make people sick by giving them diseases like stomach bug, norovirus and seasonal flu.

And assuming you went overboard, chlorine is considered to be extremely volatile, so it will evaporate without much issue. If you don’t want to spend money to get rid of chlorine in your water, the chlorine will eventually evaporate if you simply leave the water to stand.

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