Edinburgh etch

I have been doing some research on using Edinburgh Etch for copper.
I am a bit puzzled at some conflicting

In some of the articles that I have read, one is told to combine the
citric acid in water and to add it to the Ferric chloride.

Other articles say to add the Ferric Chloride to the the citric acid

Knowing full well that one adds the acid to the water, and not the
reverse I am a bit puzzled as to the proper proceedure of combining
two acids to each other.

I certainly don’t want an explosion caused by the improper combining
of the two acids. Thanks for your help.

Alma Rands