Question
Posted on: March 6 2013Menthol does not dissolve in a hydro-alcoholic lotion Menthol 1.5 g benzophenol 3g glycerol 3g spiritus 15g Aqua AD 250ml
Should we use the liquid or crystalline form for benzophenol? And there is a difference in strength and scope of application.
Answer
At my knowledge, phenol is never for 100% solid crystalline but rather a slurry. But there is also the liquid phenol or phenolum liquefactum, which contains 10% water. In the context of this regulation, the choice does not matter on condition that when you use the liquefaction you have to weigh 10% extra. The prescribed amount of benzophenol I find somewhat on the high side. Compared to an analogue preparation from NF V, I would bring the quantity to half.
In addition, you will not obtain a clear solution with the prescribed composition. I suspect a precipitate of menthol because of a too low concentration of spiritus. Of course, We have two options to solve this problem.
- Increase the amount of spiritus. This should be tried out using the method described in question 833.
- Apply the principle of solubilisation and add Tween 80. I would try with 10g. So take 10g Tween 80 + Menthol + phenol + glycerin + spiritus and then under good stirring gradually add water