[Koosa]

Good day all. I have the following question:

I have 98% (commercial grade) sulphuric acid and would like to make up a solution of 15% (M/V). Is the percentage listed on the MSDS (the 98%) a percentage by weight or by volume? If by weight it states as 98g sulphuric acid per 100g of solution. The SG is listed as 1.82 which means 1.82g sulphuric acid per mL of sulphuric acid. A 15% (M/V) solution is 15g sulphuric acid per 100mL of solution. I'm lost here. Any assistance will be greatly appreciated.

[Archer]

Good day all. I have the following question:

Is the percentage listed on the MSDS (the 98%) a percentage by weight or by volume?

Hi Koosa,

Usually the MSDS is by weight unless otherwise stated.

If by weight it states as 98g sulphuric acid per 100g of solution. The SG is listed as 1.82 which means 1.82g sulphuric acid per mL of sulphuric acid.

98g of acid in 100g of the reagent. The SG is unimportant.

Add approximately 15 grams of sulphuric acid slowly into about 75 ml of cold water, DO NOT add water to the acid! Then make the solution up to 100 ml (if that is the volume that you want).

Note that sulphuric acid and water get very hot when they are mixed so you may need to cool it externally if you are making a lot.

98% sulphuric is very viscous and difficult to work with accurately. Is it for something specific that it has to be standardised to 15%?

[Koosa]

Thank you Archer. The situation is such that I will use 98% sulphuric acid to make up a standard solution of 15% (M/V). The 15% solution will then be introduced in a stream of water with a flow rate of 10m3/hr. The final concentration of sulphuric acid within the stream of water will be 5ppm. This situation is specific to a process I am busy designing. This process involves pH correction as pre-treatment to reverse osmosis filtration.

[Archer]

Thank you Archer. The situation is such that I will use 98% sulphuric acid to make up a standard solution of 15% (M/V). The 15% solution will then be introduced in a stream of water with a flow rate of 10m3/hr. The final concentration of sulphuric acid within the stream of water will be 5ppm.

In that case it is worth bearing in mind that 98% sulphuric will absorb atmospheric water so 98% is not necessarily the concentration after the bottle has been open a while or the acid has been exposed to the atmosphere for a sigificant length of time (I don't know how long this is but will happen). If you need to standardise it may be worth using a crude solution of 20% M/V made in this way and titrating it to find out the exact concentration, then diluting this down to 15%.