Books published in the U.S. is in public domain if it was published before 1923.
The emulsion books written by E. J. Wall contain a lot of errors, irrelevant suggestions, misconceptions, etc. and I do not recommend them. I have a copy of 2nd edition but it's pretty bad. It's useful only as a way to search for older literatures for historical study. Same applies to Baker's book.
If you like to study the emulsion making in 1920s, I suggest to read Carroll's paper in J. Chem. Edu. Carroll was very knowledgeable at that time but that was before he worked for Eastman Kodak Company, so he could disclose much of his knowledge in published paper. Carroll's formula in that paper work reasonably well with some of photographic gelatins available today, but good results probably require some tweaking.
Originally Posted by Donald Qualls