How to prepare the best: Gelatin 100 mg Chloretone 70 mg boric acid 10 mg NaCl 0.9% AQUA AD INJ AD 10 GR F. collyrium

We have to do here with some kind of artificial tears for easily irritable eyes; Therefore, the addition of Chloretone or Chlorbutol. In the purchase, this substance provides us with problems because it cannot be sterilized by heat while gelatine is only sterilizable by heat. Therefore this procedure:

1. 56 mg boric acid and 500 mg NaCl are dissolved in 50 ml water for injections;
2. 100 mg gelatine is added to 9 ml of this solution, which was transferred in a pre-autoclaved collyrevial. This whole is sterilized with loose cap according to the method of Deussen with flowing water vapour for 40 minutes.
3. meanwhile, 700 mg of Chloretone is dissolved in 10 ml of propylene glycol in a pre-sterilized and dried vial (this solution can be tracked for later use);
4. after sterilization and cooling of the vial, exactly 1 ml of the Chlorbutol solution is added to the vial aseptic with a sterile syringe.