Jenkin's Fluid:

Concentrated hydrochloric acid                   4ml
Glacial acetic acid                                      3ml
Distilled water                                          10ml
Absolute alcohol (i.e. 100%)                      73ml
Chloroform                                              10ml

Reasonably quick, haematoxylin staining quite well preserved.
For subsequent processing, it is permissible, indeed, encouraged,
that the tissue go straight into absolute alcohol, , then chloroform
and subsequent paraffin wax. (each for appropriate times, of course
and dependent upon block size, etc.)

Many years ago (wish I was too young to be able to say that!), when
working in general pathology, I used it fairly extensively with
good results, but probably not obviously better for routine work
than the 10-12% aqueous formic acid we use now.
Ref.  Jenkins, CE. J Pathology & Bacteriology, 1921;24:166.
Amusingly, according to Lillie,  the time of decalcification presumes
an ambient temperature of 17-20 degrees C in Glasgow!!
Russ Allison, Wales