Hard water may be used, but in that case considerable undissolved material, which, however, does not contain any arsenic, may be left after boiling.
"Special Report on Diseases of Cattle"
U.S. Department of Agriculture J.R. Mohler
If the solution does not then clear up, the caustic soda must have been very low grade, and the undissolved substance must be arsenic.
"Special Report on Diseases of Cattle"
U.S. Department of Agriculture J.R. Mohler
Heating them to about blood heat and allowing them to stand for a few hours, I filtered both liquids from the undissolved calomel.
"The History of the Medical Department of Transylvania University"
Robert Peter