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Question

Posted on: March 6 2013

Next solution discolours and crystallizes after 1 day: Resorcinol 2% erythromycin 4% isopropyl Alcohol 50% water AD 100 mL

Answer

There is one and another to say about this formula:
  1. The crystallization I suspect to occur from the erythromycin. I would suggest to boost the amount of isopropanol to 70%.

  2. The discoloration is due to the Sulpho resorcinol because of the of PH given by the erythromycin. I would suggest to add 0.1% nametabisulfite. However, I do not have the certainty that this will be sufficient. On top of that, you can also slightly lower the pH with 400 mg of anhydrous citric acid. Too low a pH is detrimental to the stability of haemoglobin!