This story involved red and green apothecary jars in the window of a store, with different magical potions in each. Two or three inquisitive children who get involved with magic. I learned the word “widdershins” in reading this book. It may have been one of a series, possibly British. I read it/them in the early ’60s.
Maybe Bedknobs and Broomsticks by Mary Norton? The three children find the magical laboratory of the lady they know who’s studying to be a witch which contains apothecary jars, head of newt, etc.
Thanks for the suggestion but it’s something a little less mainstream, I think.
Not in an apothecary store, but in the window of a witch’s home:
Little Witch, by Anne Bennett.
Sounds like one of the Carbonel books by Barbara Sleigh, probably Carbonel, the King of Cats.
Maybe it’s The Ogre Downstairs by Diana Wynne Jones? The kids have a magical chemistry set, which might be the vials you are thinking of. I don’t remember the book well enough to know offhand if she used the word widdershins, but she has used it in other books of hers so it’s possible.
I think this is The Kingdom of Carbonel by Barbara Sleigh. The children are called John and Rosemary, and Carbonel is a magical cat, if those ring any bells!
It’s one of the Carbonel books by Barbara Sleigh – the kids’ names are Rosemary and John.
Thanks to all who responded with references to the Carbonel books. It is indeed “The Kingdom of Carbonel,” the second in the trilogy by Barbara Sleigh.