Loss on drying using Phosphorous pentoxide

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sivakrishna's picture
Loss on drying using Phosphorous pentoxide


Q1: I want to analyse Loss on drying in Dried Factor VIII Fraction as per IP. Here is the method suggested.
"Loss on drying determined by drying 0.5 g over phosphorus pentoxide at a pressure not exceeding 3 kPa for 24 hours."

My question is how can i dry over phosphorous pentoxide? means how to prepare the set-up for the same. I have a vacuum oven and i can create the mentioned pressure. Please suggest where i can put the P2O5 and how much and where i need to put my samples in the oven.
Q2: Can i reuse the P2O5 used for the analysis once, is there any method to regenerate P2O5.

Please help.
Siva Krishna

Dr. Analytical
Dr. Analytical's picture
Usually you will put a small

Usually you will put a small pan or tray in the bottom of the oven and put a layer of P2O5 in the tray.  I have not done this for many years, but I believe you should use several grams.

You should be able to use this for drying many samples.  When it absorbs moisture I believe it becomes a liquid, so as long as you have solid present, it should be successful.

abhigyan's picture
Phosphorus pentoxide absorbs

Phosphorus pentoxide absorbs moisture that is water, reacts to form phosphoric acid, which is a liquid. Often, the acid forms a layer on the outer side of the powder in the vessel, to reduce drying efficiency. It can be reused by scratching the upper layer to expose the dry P2O5. Can be used as long as the powder form is left.

sivakrishna's picture
Thank you very much for your

Thank you very much for your reply

nanjundappashankar's picture
Take a sample in LOD bottle

Take a sample in LOD bottle and create the vacuum in the vacuum oven , before cratinig the vacuum in the oven , take P2O5 in pertidish and sperad sufficient quantity (around 50 g of Chemical ) and carry out the Loss on drying

You cannot reused the P2O5 as the chemical is already observed the moisture content from the material .
almost the chemical will become liquid state