To recipes helpdesk

Question

Posted on: March 6 2013

I have to make the following preparation for someone regularly: Ferrous sulphate. 7H20 50g Glucose 60g Aqua ad 200ml

The preparation is done as follows: Weigh everything, add the largest part water, heat under stirring until everything is dissolved and then replenish water up to 200ml.

problem is that after a while the iron sulfate crystallizes. Storing at room temperature can postpone this a time, but on the duration anyway precipitation. The solubility of ferrous sulphate is 1 in 1.5 water, 1 in 0.5 boiling water.

the concentration is quite high, but this is a kind of basic solution that is administered in drinking water à rate of 15ml per litre of water. The application is veterinary and by orally serving this solution one can provide the iron need, without injection. The occurrence of precipitation is annoying and I think it has to do with the temperature. Can I find curves of the solubility of ferrous sulphate at a decreasing temperature?

or could I add something to avoid this?

Answer

Some data could be found back from which conclusions follow.

  1. at 10 ° C, 100g saturated solution would contain 40g ferrous Sulphate 7 aq. This solution has a density = 1.24. Maybe even determine the density of your solution there, unlike others, it works volumetric and a lot of data is given gravimetric.

  2. FeSO4 7aq can lose crystal water in contact with drier air. If the raw material contains less crystal water, the solution contains more Fe.

  3. FeSO4 7aq at 38 ° C (for some at 100 ° C) would lose 6 mol of crystalline water to form the monohydrate. Besides the mono-and SEPTA hydrate there are other hydrates. In order to avoid this, very careful attention should be given to the temperature. I would take into account a limit of 35 ° C when heating. And what is the solubility of the monohydrate??? Not to be found.

  4. In contact with air, the solution takes up oxygen and after a while an insoluble alkaline iron sulfate is formed. So the water used to boil the solution out and should it be possible to saturate with nitrogen. Or even better to send nitrogen by the solution before closing the bottle. The user on the heart press the bottle to close well and keep in a cool place (15 ° C) outside the influence of the light.

  5. to avoid precipitation, it is recommended that sugars (dextrose 40%) and reducing substances. In addition, the solution must also be acid, pH = 2 à 3. This can be by adding citric acid. So maybe even additional 20g glucose dissolving.

I suppose there can be further ë xperimented.