How can the precipitation of salicylic acid be prevented in a gel containing 15 mg clobetasol propionate, 2.4 g salicylic acid, 1.8 g Klucel GF, 18 ml propylene glycol, and 15 ml distilled water, intended for easy application to the scalp, given that adding water to the clear solution of active ingredients in propylene glycol and Klucel causes the mixture to become less viscous, white, and less homogeneous; is the salicylic acid concentration too high, and what is the maximum amount that can be successfully incorporated?

Is carbolic acid (phenol) necessary in a collodion with salicylic acid for treating warts, specifically in a prescription for 4.5 g salicylic acid powder, 4.5 g lactic acid, and 0.6 g carbolic acid in collodion with castor oil up to 30 mL to be applied once daily, considering that this concentration is too high for a preservative but may be keratolytic, whether it is required or could cause interactions, if an antioxidant is needed if included, and noting that the preparation is only reimbursed without carbolic acid?

Regarding the preparation of a euthanasia syrup consisting of 9g Pentobarbital, 16.2g (20ml) Alcohol 96%, 15g Aqua purificata, 10.4g (10ml) Propylene glycol, 250mg Saccharinum natricum, 65g Sirupus simplex, and 1g Anisi aetroleum, as mentioned on page 108 of the 2010 WZC formulary: since pentobarbital is likely insoluble in propylene glycol, alcohol 96%, and water, would it be better to use the sodium salt of pentobarbital for this formulation?

What is the best way to prepare aqua conservans, the method described in the TMF or the National Formulary, given that my course on magistral preparations always referred to water for preservation from the TMF; which formula is best, and why is propylene glycol omitted in the TMF preparation?

How can a white solid mass that forms in the following composition be dissolved: erythromycin 2%, isopropanol 40 degrees up to 200ml?

How can I prepare the following nasal drops with paraffin oil: Ephedrine HCl 300mg, Menthol and Camphor 30mg each, Chlorobutanol 150mg, liquid Paraffin 15ml, and Water up to 30ml?

What are the stability problems of a solution containing 3 grams of Phenobarbital sodium and purified water up to 300 cc?