Ok, Mees in the chapter on fixing uses Argento or Silver exclusively to describe silver salts and silver complexes.
I have looked in two chemical dictionaries, and one has no Argent- with any suffix listed, while in another it lists 'Argentous and Argentic - see Silver' in the heading of the chemical tables.
The chemistry texts I have state that the suffix 'ous' is used for salts in the lower oxidation state and the suffix 'ic' is used for salts in the higher oxidation state when there are two oxidation states, as in cuprous and cupric, or ferrous and ferric.
If there are more than two, then the lower two use these two suffixes, but the additional states are designated by the numeric state of oxidation.
If there is one oxidation state, then no suffix is used.
Therefore, the use of Argentous or Argentic implies two possible oxidation states. In addition, since the word is an adjective, there is only one real meaning such as "an argentic sheen" or a sheen pertaining to silver. Cuprous has two meanings though, as in cuprous chloride or "the stormy sky looked cuprous".
That is the best I can say regarding usage in current English language chemical texts. Argentous is a word, an adjective, but is not used in chemical terminology at the current time as far as I can find.
Lets use Natrium and Kalium and Wolfram too while we are at it.
PE