Many of the chemical solutions have a description in their name such as V/V, W/V and W/W. This blog post is an explanation of what these mean.

Each of these descriptions is a way of expressing the strength of a chemical solution. The strength of a solution can be expressed by Weight, Volume or both. It is easiest to describe each of these separately and illustrate them with an example.

**V/V
**V/V means Volume/Volume and is often used when you mix 2 liquids together. For example, a 50% v/v solution would be 50% of one solution and 50% of another – equal amounts of each in terms of Volume. Examples of these include Acetic Acid 50% v/v and Sulphuric Acid 50% v/v.

**W/W
**W/W means Weight/Weight. In a solution, it infers the percentage of substances by weight. For example, a Hydrochloric Acid 28% w/w solution means there are 280 grams of Hydrochloric Acid for every Kilogram of the solution (the remainder being water).

**W/V**

W/V means Weight/Volume . This is commonly used when a solid is dissolved in a liquid. For example, a 10% w/v solution means 100 grams of one substance is present for ever 1L of another. An example of this would be Barium Chloride 10% w/v - in this solution 100 grams of Barium Chloride is present for ever 1L of water.

**V/W**

If a solution is V/W it means Volume/Weight. This is the same as the example above but the other way around.

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Justice Chandrasekaran S

Thanks for your kind words!

I see this on hydrochloric acid solutions — 20% (v/v). Now, I can understand percent by weight but this is a puzzle to me. Does 20% (v/v) mean 20 parts by volume pure HCl per

100 parts by volume of HCl solution. How do you measure the volume of pure HCl?

Hi Alex,

Your assumption is correct that the product contains 20 parts of HCl per 100 parts of solution, however the concentration of the HCl used is not 100% (that would be a gas) but 36% w/w which is a commonly available industrial grade and generally referred to as concentrated HCl. This still gives off fumes but is a liquid product. So the answer to the question is 200mls of 36% w/w HCl in 1000mls of finished solution, this gives approximately 8.2% w/w solution.

HCl 36% w/w has an s.g. of 1.18 which means 1000mls weighs 1180g. 36% of this is pure HCl, therefore 36% of 1180 = 424.8g or 424.8 grams per litre of HCl. If we take 200mls of 36% w/w HCl we are taking 424.8 x 0.2 grams of pure HCl which equals approx. 85g pure HCl, this 85g is then diluted to 1L.

So in terms of w/w there are 200mls x 1.18 =236g plus approx. 800mls of water (s.g. of 1), giving 1036g in total. 85g of pure HCl in this total weight gives (85/1036) x 100 = 8.2% w/w.

Hope this helps!

I need a help! I am working with a polymer (PEI). Commercially it is available in solution and product say- it is 50% w/v in H2O. But, it is so viscous, that, I need to dilute it more. Now the confusion start- If I add x gm into 100 ml, what will be final concentration then?!

Please help!

Please how many grams of PEG 6000 do I need to prepare 10% and 20% of PEG and how can I prepare this!

Hi,

We don’t recommend preparing this product yourself. You should contact a chemical suppliers if you’d like to purchase PEG.

Thanks for your comment.