68. An anhydride is what remains after water has been removed from an acid; or, it is the oxide of a non- metallic element, which, united with water, forms an acid.
"An Introduction to Chemical Science"
R.P. Williams
It was found that the third was by no means easy to bring about: dry phthalic anhydride is apparently only superficially affected by the dry ammonia, and it was difficult to introduce sufficient heat into the loose mass of crystals to cause the reaction to start.
"Organic-Syntheses"
Conant, James Bryant
Fowler's solution is the best-known medicinal preparation of arsenic, and contains 1 grain of arsenious anhydride in 110 minims.
"Aids to Forensic Medicine and Toxicology"
W. G. Aitchison Robertson