340 g of silver nitrate are equivalent to 232 g of silver(I) oxide, so to
get 7 g of the oxide for
my recipe, you would need about 10.3 g of the nitrate, and this would
require a minimum of
2.42 g of sodium hydroxide in solution to precipitate it, but I would use an
excess of the
alkali-say 3 g. Filter off the ppt and wash it well with dist water. No need
to dry it, just let it
drain before adding to the sulphamic acid solution-it should dissolve
easily.
Mike has since added this to the revised version of the instruction sheet
published in the Alt Photo Review. It would be good if it could also be made
available in the FAQ file (Mike? Gord?), given the unweildiness of this
list's archives.
Silver oxide does have a slightly higher silver content than silver nitrate
but not nearly enough to justify the price difference of some suppliers. As
Richard Sullivan pointed out to me once before silver nitrate is the basic
product and silver oxide is a more rarely requested form, probably produced
in higher grades since it is used for analytical purposes. Many
photographers will already have silver nitrate on hand so this is another
good reason for making this modification widely available.
Good luck with argyrotype,
Philip Jackson (pjackson@nla.gov.au)